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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
Showing 1 - 30 of 30 Journals sorted by number of followers
AIAA Journal     Hybrid Journal   (Followers: 1002)
SpaceNews     Free   (Followers: 779)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 702)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 569)
Aviation Week     Full-text available via subscription   (Followers: 411)
Aerospace Science and Technology     Hybrid Journal   (Followers: 305)
Advances in Space Research     Hybrid Journal   (Followers: 295)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 281)
Journal of Aircraft     Hybrid Journal   (Followers: 262)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 251)
Control Systems     Hybrid Journal   (Followers: 235)
Acta Astronautica     Hybrid Journal   (Followers: 220)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 177)
Journal of Navigation     Hybrid Journal   (Followers: 176)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 165)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 139)
Space Science International     Open Access   (Followers: 117)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Propulsion and Power Research     Open Access   (Followers: 89)
International Journal of Aerospace Engineering     Open Access   (Followers: 86)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 82)
Advances in Aerospace Engineering     Open Access   (Followers: 74)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 66)
Aerospace     Open Access   (Followers: 64)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 57)
Space Safety Magazine     Free   (Followers: 50)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 46)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 43)
Space Research Today     Full-text available via subscription   (Followers: 43)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 42)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 37)
International Journal of Aerospace Sciences     Open Access   (Followers: 36)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 31)
Space Policy     Hybrid Journal   (Followers: 30)
Journal of Space Weather and Space Climate     Open Access   (Followers: 30)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 30)
Journal of Aerodynamics     Open Access   (Followers: 27)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 27)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 25)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 23)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 23)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 23)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 22)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 22)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 22)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 21)
Artificial Satellites     Open Access   (Followers: 21)
Fatigue of Aircraft Structures     Open Access   (Followers: 21)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Frontiers in Aerospace Engineering     Open Access   (Followers: 20)
International Journal of Space Structures     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
Chinese Journal of Aeronautics     Open Access   (Followers: 19)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 15)
Advances in Aerospace Science and Technology     Open Access   (Followers: 14)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
Aviation     Open Access   (Followers: 12)
International Journal of Micro Air Vehicles     Open Access   (Followers: 11)
Journal of Airline and Airport Management     Open Access   (Followers: 11)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 11)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 11)
Population Space and Place     Hybrid Journal   (Followers: 10)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 10)
Journal of Aeronautical Materials     Open Access   (Followers: 10)
Aerospace Systems     Hybrid Journal   (Followers: 10)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 10)
Journal of Aerospace Technology and Management     Open Access   (Followers: 10)
Aeronautical Journal, The     Hybrid Journal   (Followers: 9)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 9)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 9)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 8)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 8)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 7)
Aerospace technic and technology     Open Access   (Followers: 7)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 7)
New Space     Hybrid Journal   (Followers: 6)
Space and Polity     Hybrid Journal   (Followers: 6)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 6)
Civil Aviation High Technologies     Open Access   (Followers: 6)
Air Medical Journal     Hybrid Journal   (Followers: 6)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
RocketSTEM     Free   (Followers: 5)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Life Sciences in Space Research     Hybrid Journal   (Followers: 5)
International Journal of Aviation Management     Hybrid Journal   (Followers: 5)
Cosmic Research     Hybrid Journal   (Followers: 5)
Journal of Spatial Science     Hybrid Journal   (Followers: 4)
Journal of KONBiN     Open Access   (Followers: 4)
Astrodynamics     Hybrid Journal   (Followers: 4)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 4)
Unmanned Systems     Hybrid Journal   (Followers: 4)
Transport and Aerospace Engineering     Open Access   (Followers: 4)
Open Aerospace Engineering Journal     Open Access   (Followers: 4)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Microgravity Science and Technology     Hybrid Journal   (Followers: 3)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 3)
npj Microgravity     Open Access   (Followers: 3)
ASTRA Proceedings     Open Access   (Followers: 3)
MAD - Magazine of Aviation Development     Open Access   (Followers: 3)
Ciencia y Poder Aéreo     Open Access   (Followers: 3)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 2)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 1)
Investigación Pecuaria     Open Access   (Followers: 1)
Transactions on Aerospace Research     Open Access   (Followers: 1)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Xibei Gongye Daxue Xuebao / Journal of Northwestern Polytechnical University     Open Access  
Mekanika : Jurnal Teknik Mesin i     Open Access  

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Similar Journals
Journal Cover
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering
Journal Prestige (SJR): 0.422
Citation Impact (citeScore): 1
Number of Followers: 42  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0954-4100 - ISSN (Online) 2041-3025
Published by Sage Publications Homepage  [1174 journals]
  • Study on aerodynamic features of rod thrust vector control for physical
           applications

    • Free pre-print version: Loading...

      Authors: Kexin Wu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Mechanical thrust vector control is a classical and important branch in the vectoring control field, offering an extremely reliable control effect. In this article, a simple technology using a cylindrical rod has been numerically investigated to achieve jet controls for three-dimensional conical axisymmetric nozzles. Complex flow phenomena caused by the cylindrical rod on a flat plate and in a converging–diverging nozzle are elucidated with the purpose of a profound understanding of this technique for physical applications. Published experimental data are used to validate the dependability of current CFD results. A grid sensitivity study is carried through and analyzed. The result section discusses the impacts of three factors on performance, involving the rod penetration height, rod location, and nozzle pressure ratio. Significant vectoring performance variations and flow topologies descriptions are illuminated in full detail. When the rod penetration height changes, this technique has an effective control range, namely H/Rt ≤ 0.4. In this effective control range, the vectoring angle and efficiency increase and the thrust coefficient decreases with a deeper rod insertion. As the rod location moves downstream towards the nozzle exit, the vectoring angle increases and the thrust coefficient decays. Moreover, the direction of jet deflection remarkably varies for diverse rod locations. While the nozzle pressure ratio increases, the vectoring angle initially increases to reach the maximum level and then decays slightly. Meanwhile, the thrust coefficient continuously increases.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-16T03:29:22Z
      DOI: 10.1177/09544100221095363
       
  • High-efficiency hybrid trim method for CFD simulation of rigid coaxial
           rotor

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      Authors: Haotian Qi, Ping Wang, Linsong Jiang, Yang Zhang, Liangquan Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to solve the trim problem of computational fluid dynamics (CFD) simulation for rigid coaxial rotor, a hybrid trim model coupling CFD method and high-efficiency model (blade element theory) is established. In the trim process, the Jacobian matrix is solved by the high-efficiency model, while the CFD solver is only called for rotor performances modifying after each trimming step. The influences of pseudo time step, number of CFD revolution, and inflow model are investigated. Validation cases of AH-1G and Harrington-1 rotors are carried out, and good agreements are obtained. Results show that the trim efficiency can be significantly improved by saving the calculation of CFD for the Jacobian matrix. The trim accuracy is guaranteed by the correction operation with the CFD solver at each step. Moreover, as only time-averaged rotor performances are useful for trim, the efficiency can be further improved by adopting appropriately small pseudo time step and CFD revolution. The hybrid trim model has high robustness. The accuracy of inflow model for the coaxial rotor affects the convergence speed, but the final convergence can be achieved generally.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-15T03:24:13Z
      DOI: 10.1177/09544100221095369
       
  • Mean value-based collaborative method for structural optimization of
           aircraft family

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      Authors: Xu Chao, Yao Weixing
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to improve the efficiency of the general platform optimization, a new mean value-based collaborative method (MVCM) for structural optimization of general platform is proposed. The key idea of this method is to decompose the general platform optimization problem into a system-level optimization problem and several independent subsystem-level optimization problems by introducing coordination variables. While meeting the design requirements and performance requirements, the subsystem optimizes each aircraft so that the design variables of each aircraft are as close as possible to coordination variables. The system-level coordination adjusts the coordination variables according to the results of each subsystem. With the continuous iteration between the system and the subsystems, the coordination variables that can maximize the generality of the product family are finally found. The numerical test results show that the MVCM can greatly improve the efficiency of the general platform optimization.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-12T11:07:39Z
      DOI: 10.1177/09544100221086324
       
  • Robust adaptive sliding mode control strategy of uncertain nonlinear
           systems

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      Authors: Yassine Soukkou, Mohamed Tadjine, Quan Min Zhu, Mokhtar Nibouche
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a robust adaptive sliding mode controller scheme as applied to a class of uncertain nonlinear systems with parametric uncertainties and external disturbances. First, a sliding mode control technique is designed. Then, the proposed robust adaptive control schemes are applied to estimate the parametric uncertainties and the upper bound value of the external disturbances by using adaptive laws, ensure robustness in presence of parametric uncertainties and external disturbances, and reduce chattering problem by introducing an hyperbolic tangent function. Lyapunov stability theory is used to analyze the stability of the closed-loop system. As an exemplar, the schemes have been applied to a quadrotor unmanned aerial vehicle (QUAV) model. Simulation results for the control of the QUAV model are provided to illustrate the performance of the proposed robust adaptive sliding mode control scheme and demonstrate that the proposed method has good tracking performance. The simulation results clearly prove the effectiveness of our approach.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-12T09:13:35Z
      DOI: 10.1177/09544100221091325
       
  • Aerodynamic effects of surface deformities on aerofoils for low-speed
           stratospheric flight

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      Authors: Jeremy Kimmons, Peter Thomas, Simone Colonia
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      High-altitude pseudo-satellites are an expanding focal area of the aerospace industry which require new technologies and manufacturing processes to reduce weight and increase efficiency with the aim of increasing endurance. One such process has resulted in the occurrence of small deformities along the leading edge of a lightweight unmanned aerial vehicle structure with the application of its skin, which may have a detrimental impact on its performance and efficiency. This paper focuses on the effects of these manufacturing deformities on the aerodynamic performance of the vehicle’s aerofoil when operating in low Reynolds number flow with the intention of identifying any detrimental flow variation. This analysis is achieved by comparing the lift curve, drag polar and pressure coefficient of both the deformed and undeformed cases of two aerofoils: a SG6042 and a GOE 523. This is accompanied with an examination of the local flow conditions scrutinising the near-wall y+ and turbulent kinetic energy calculations. The investigation finds that in two-dimensional flow, the deformities replicate the effects of transition trips in the shrinking or elimination of laminar separation bubbles. At Reynolds numbers below 250,000, the deformities reduce the net drag while leaving the lift largely unaffected. However, as a result, there is a slight shift in the minimum power condition in the order of 8% which would produce some performance loss for power efficiency and endurance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-11T07:22:04Z
      DOI: 10.1177/09544100221093210
       
  • Research on the flow field and film cooling effectiveness of the endwall
           with swirling film cooling

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      Authors: Jian Zhang, Qun Zheng, Zhaolin Li, Guoqiang Yue, Yuting Jiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to obtain the effect of endwall secondary flow on the swirling film cooling, a geometric model of cascade is established to research the endwall swirling film cooling and swirling flow induced by prismatic jet impingement configurations. Numerical simulation is applied to investigate three jet flow configurations on the endwall film cooling performance at the compound angles of film hole γ = 0° and 30° and blowing ratios M = 0.5–2.0. The influence of complex vortex structures near endwall for jet flow is analyzed in detail; the strong transverse cross flow near the endwall is the main reason affecting the film cooling effectiveness. The variation laws of endwall film cooling effectiveness with the compound angle of film hole, jet flow configuration, and the blowing ratio are obtained. As the blowing ratio increases, the spanwise average film cooling effectiveness increases first and then decreases. While the blowing ratio is M =1.0, the endwall film cooling effectiveness is the best. Increasing the compound angle of the film hole leads to a decrease in the endwall cooling effectiveness. The spanwise average cooling effectiveness of γ = 30° decreases by 35% compared to the γ = 0°.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-11T05:33:22Z
      DOI: 10.1177/09544100221097527
       
  • Active nonlinear vibration control of a membrane solar array structure

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      Authors: Xiang Liu, Lianglinag Lv, Guoping Cai
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Membrane solar array has attracted a lot of attentions in recent years because of the advantage of light-weight, low-cost, and high-folding-ratio. Meanwhile, the membrane solar array structure also pose challenging large-amplitude vibration issue which will impact the performance of the spacecraft significantly. In this paper, active nonlinear vibration control of a membrane solar array structure is studied. Based on the nonlinear finite element method, a nonlinear dynamic model of the structure is established. The optimal positions of piezoelectric actuators are determined by optimizing a controllability optimization criterion with Particle Swarm Optimizer algorithm. An active controller is designed to suppress the undesired nonlinear vibration based on the linearized dynamic model by using the LQR control method. Simulation results show that the designed active controller can suppress the nonlinear vibration of the membrane solar array structure effectively, and the optimally placed actuators can produce better control effect with smaller control inputs.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-10T11:06:20Z
      DOI: 10.1177/09544100221081518
       
  • Effects of circular and non-circular nozzle exit geometries on subsonic
           and supersonic jet propagations

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      Authors: Thillaikumar Thangaraj, Mrinal Kaushik, Thanigaiarasu S
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The mixing enhancement and core length reduction of a jet without significant loss of thrust are essential for reducing infrared radiation, mitigating aeroacoustic noise, improving combustion characteristics, and thrust vectoring. The jet mixing can be improved by manipulating the flow behavior. In subsonic and sonic jets, the flow manipulation may be achieved by utilizing nozzles with non-circular geometries that shed vortices of varying size due to their non-uniform azimuth curvatures. Non-uniform vortices generate differential spreading along the nozzle’s perimeter, causing axis switching and improving entrainment characteristics. Therefore, the present study examines the effects of two non-circular nozzle exit shapes (elliptic and square) on the mixing augmenting efficacy at subsonic and sonic flow conditions. The circular nozzle is tested for comparison. Both quantitative and qualitative analyses evaluate the efficacy of nozzles with non-circular exit geometries. Among the configurations investigated, the elliptic nozzle is superior in shortening the potential core length and enhancing the jet spread. A maximum reduction of 18.75% in core length with rapid jet decay was accomplished with the elliptic nozzle. The measurement of pressure profiles at different streamwise locations reveals that the spread rate is greater for elliptic and square jets than their circular counterpart. The elliptic jet exhibits the highest spread along the minor-axis direction compared to the major-axis direction. The differential jet spread rate in the elliptical jet causes an early axis-switching––direct evidence of mixing augmentation. Shadowgraph images show the asymmetric pattern of shock cell structures and differential spreading in elliptic and square jets.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-10T06:26:38Z
      DOI: 10.1177/09544100221097537
       
  • Initial weight estimation of twin-fuselage configuration in aircraft
           conceptual design

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      Authors: Yiyuan Ma, Jin Yan, Ali Elham
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The Ultra-High Aspect Ratio Wing (UHARW) concept can improve the aircraft’s aerodynamic efficiency and reduce fuel consumption. The Twin-Fuselage (TF) configuration is one of the promising concepts for the UHARW design to reduce the wing bending moments and shear forces. This paper presents the development of a semi-empirical method for the weight estimation of TF aircraft in the initial sizing stage. A physics-based wing weight estimation method is improved for higher fidelity aerodynamic analysis and modified for composite material structures of TF aircraft. This method is used in the design of experiments and the results are applied for regression analysis to establish a semi-empirical method. Eventually, the established semi-empirical weight estimation method is integrated into a TF aircraft conceptual design and performance analysis framework. A mid-range TF aircraft and a long-range TF aircraft are designed and sized to illustrate its application and efficiency in rapidly estimating the TF aircraft weight breakdown.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-07T01:49:30Z
      DOI: 10.1177/09544100221095370
       
  • Nonlinear analysis and control of an underactuated 3-DOF control moment
           gyroscope with experimental validation

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      Authors: Gobiha D, Rohith G
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Nonlinear controllers have been extensively abstracted in recent times. Nevertheless, real time implementation for underactuated MIMO physical systems is rarely attempted. This work proposes a nonlinear framework based on dynamical analysis and the sliding mode based control technique to control a highly coupled and nonlinear MIMO underactuated control moment gyroscope. First, an analytical formulation based on dynamic characterization is proposed to understand both the unactuated dynamics and the performance constraints of the gyroscope. This characterization helps in designing a feasible nonlinear sliding mode controller which helps in a simple and straightforward control of the system through the entire operating regime. The effectiveness of the proposed nonlinear control and analytical framework is established by successful implementation on the experimental gyroscope setup.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-04T06:34:35Z
      DOI: 10.1177/09544100221081820
       
  • A general real-time optimization framework for polynomial-based trajectory
           planning of autonomous flying robots

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      Authors: Yunes Sh. Alqudsi, Ayman H Kassem, Gamal El-Bayoumi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a general real-time, numerically stable optimization framework for time polynomial-based trajectory generation of autonomous aerial robots. The proposed general optimization framework (GOF) allows various optimization criteria for trajectory generation cost-function, such as minimizing the trajectory total length, time, and position derivatives. Minimizing position derivatives includes velocity, acceleration, jerk, and snap, or any combination of them. This study considers the quadrotor as the test platform. By exploiting tools from the calculus of variations, differential flatness property, and polynomial-based trajectories, the developed algorithm finds feasible trajectories without extensive computational sampling and iterative searching in the high-dimensional state space of quadrotor dynamics. The GOF includes a segment-wise gradient descent-like algorithm to iteratively decrease the allowed time of each segment individually so as to avoid getting stuck at a local minimum. The comparison analysis with existing methods validated the numerical stability and computational speed advantages of the proposed approach. It also shows that the algorithm is suitable for the real-time generation of high-performance long-range trajectories consisting of a large number of waypoints and high-order piecewise polynomials. An animated simulation of this work is available at https://youtu.be/E1AC1vyPqOE
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-04T06:23:39Z
      DOI: 10.1177/09544100221090690
       
  • Effects of fusion height of tip winglet on the clearance flow in a
           compressor cascade

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      Authors: Wenfeng Xu, Peng Sun, Jingjun Zhong, Shaobing Han, Guogang Yang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The leakage flow generated by rotor clearance seriously affects efficiency and stability of a compressor. In order to reduce the effect of leakage flow, the tip winglet has been applied at the tip of a transonic compressor cascade. Numerical simulation has been used to investigate the influence of tip winglets with different fusion heights on the flow field structure. Furthermore, the effect of winglets was analyzed under different clearance heights and incidence angles. Results reveal that the winglet can weaken the kinetic energy of the leakage flow. The development of the leakage vortex along the pitchwise is suppressed, and the total pressure loss is decreased near the tip. The increase in the tip separation vortex scale leads to a remarkable decrease in the leakage flow rate. With the increase in fusion height, the scale of tip separation vortex decreases gradually, and the suppression effect on the leakage flow rate is weakened. The optimal scheme can reduce the loss by 3.3% and leakage flow rate by 13.4%. The suppression effect of the winglet on flow loss increases gradually with the increase in incidence angle. Moreover, the suppression effect of the winglet on leakage flow and flow loss increases first and then decreases with the increase in tip clearance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-04T05:29:05Z
      DOI: 10.1177/09544100221083346
       
  • Maneuvering penetration strategies of ballistic missiles based on deep
           reinforcement learning

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      Authors: Xiaoqi Qiu, Changsheng Gao, Wuxing Jing
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a ballistic missile terminal penetration scenario is studied, which contains three participants: target, missile, and defender. The ballistic missile attempts to hit the target while evading the defender. A maneuvering penetration guidance strategy that balances both the guidance accuracy and penetration capability is proposed through deep reinforcement learning. Reward shaping and random initialization are applied to improve training speed and generalization, respectively. The proposed strategy is developed based on the twin delayed deep deterministic policy gradient algorithm. It directly maps observations to actions and is an end-to-end guidance scheme that does not require an accurate model. The simulation results show that the proposed strategy has higher penetration probabilities than conventional strategies for different initial heading errors and even for defenders with different guidance laws, which indicates its good robustness and generalization. For different initial heading errors, it has learned different maneuvering modes and has certain intelligence. In addition, it is computationally small, does not consume much memory, and can be easily applied on modern flight computers.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-28T05:53:23Z
      DOI: 10.1177/09544100221088361
       
  • Performance analysis and optimization of a radiating fin array

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      Authors: Kübra Solak, Cihat Arslantürk
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Space radiators are used to reject waste heat from power units, electronic devices, and various equipment in space vehicles. It is important that radiators can achieve the heat desired to be dissipated into space with the least mass. With a view to ensuring this aim, the heat transfer calculations that must be performed must be highly accurate. Therefore, the variation of conductivity with temperature should also be taken into account in the mathematical model. This paper presents heat transfer performance and optimization of a fin array consisting of straight fins put axially on a tube and radiating heat into deep space. The mathematical model yields the governing equation as a highly nonlinear integro-differential equation which is solved by the variation of parameters method (VPM). By applying an appropriate optimization procedure, the conduction–radiation parameter, Nc, providing maximum heat transfer is obtained for a given fixed fin profile emissivity, ε, opening angle among the fins, γ, and thermal conductivity parameter describing the variation of thermal conductivity, β. For the range of suitable problem parameters, optimum values of the dimensionless conduction–radiation parameter Nc, which is a combination of thermal and geometric quantities, are expressed in ε and γ for a given β. The correlation equations are expected to provide remarkable benefits to the designer.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-27T09:49:31Z
      DOI: 10.1177/09544100221088362
       
  • A novel solution methodology for longitudinal flight characterization of a
           Flying-Wing Micro Aerial Vehicle

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      Authors: Taimur Ali Shams, Syed Irtiza Ali Shah, Aamer Shahzad, Muzaffar Habib, Farhat Asim, Mohtashim Mansoor
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A longitudinal flight dynamic study of a low mass moment of inertia vehicle is presented. Aerodynamic and stability derivatives of a flying-wing microaerial vehicle (FWMAV) were obtained through detailed subsonic wind tunnel tests at a Reynolds Number of 1.87 × 105. Rate and acceleration derivatives were obtained using the potential flow solver, Tornado®. A novel methodology for the estimation of dimensional derivatives is proposed, and results are compared with the conventional linear time-invariant systems (LTI) approach. Free response for natural frequency, damping coefficient, and time constant as well as forced response upon a unit step and a unit impulse elevon input has been calculated and analyzed. The proposed methodology predicted two pairs of complex conjugates for the longitudinal flight up to a pitch angle of 89° whereas the conventional methodology predicted the same up to 57°. Longitudinal modes sensitivity in terms of stability with the variation of mass, velocity, and pitch angle has also been analyzed. The flying-wing microaerial vehicle was able to sustain straight and level flight during flight trials; however, higher frequencies of phugoid and short period modes were observed. These high frequencies were the consequence of large magnitude of [math] (ratio of Z-force derivative with the angle of attack and cruise velocity) and [math] (ratio of Z-force derivative with the axial velocity and cruise velocity). It is concluded that the proposed methodology presented a more realistic representation of longitudinal flight modes since classical flight modes are captured till 89° which conventional LTI methodology failed to do so.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-27T08:19:57Z
      DOI: 10.1177/09544100221081845
       
  • Obstruction of infrared signature with cold gases

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      Authors: Onur Bas
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The idea of infrared signature reduction by injecting cold gas between the source and observer has been investigated. Statistical narrow band coefficients of ethylene have been generated from HITRAN spectroscopic database and proposed to attenuate radiation on the 8–14 μm spectral region whereas CO2 is employed for 3–5 μm wavelength band suppression. Dilution of ethylene with CO2 also suppresses the flammability and guarantees safe operation. Several 1-D test cases are solved to validate the developed solver, and the proposed method is tested on 1-D and 3-D problems. The results satisfactorily show that a significant and safe radiance reduction can be achieved with cold CO2 diluted ethylene injection between the exhaust and observer on the whole spectrum.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-26T10:59:36Z
      DOI: 10.1177/09544100221089054
       
  • Experimental research on operation performance and acoustic behavior of
           two-phase dual-tube pulse detonation engine

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      Authors: Xiaolong Huang, Ning Li, Chunsheng Weng, Yang Kang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to research the operation synchronous of dual-tube pulse detonation engine, the operation performance and acoustic behavior of dual-tube pulse detonation engine under different fill fractions are studied experimentally. The results show that the instability of deflagration to detonation transition is the main reason for the non-synchronous work of the two tubes. With the increase of fill fraction, the detonation sound pressure increases gradually. In the region near the tube exit, the pressure and velocity of the shock wave attenuate rapidly, and the attenuation speed gradually slows down while the propagation distance increases. The time interval of detonation waves arriving at the tube exit of the two tubes can significantly affect the peak sound pressure and the duration of the sound wave outside the tube. With the increase of time interval, the peak sound pressure decreases and the total duration as well as the duration of the positive pressure increase. The synchronization of the working process of the dual-tube pulse detonation engine can be diagnosed by analyzing the pressure and duration of the sound wave outside the tube. The research results in this paper have certain reference significance for improving the synchronous of multi-tube pulse detonation engine and will be useful for the application of multi-tube pulse detonation engine in aircraft power system.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-26T04:00:47Z
      DOI: 10.1177/09544100211072920
       
  • Linear parameter-varying-based transition flight control design for a
           tilt-rotor aircraft

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      Authors: Shen Qu, Guoming Zhu, Weihua Su, Sean Shan-Min Swei
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents the development of novel transition flight controllers for a class of urban air mobility aircrafts configured with a fixed-wing and six distributed electric rotor assemblies. Only the two tilt-rotors are utilized for thrust vectoring during transition flight from hovering to steady-level flight, while the four lift-rotors are modulated with aerodynamic lift induced by fixed-wing to maintain stable altitude-hold. Three tractable tilt-rotor articulation profiles are proposed by taking into account of various aircraft and hardware constraints. Given a predefined nominal tilting profile, a family of linear models is obtained by linearizing the nonlinear aircraft model at multiple tilt-rotor angular positions along the tilting profile. Using tilt-rotor angular position as a scheduling parameter, a discrete-time linear parameter-varying model can be constructed, which is then used to develop a novel transition flight control architecture that integrates the adaptive model predictive control law with feedforward effect of the dynamic reference compensation. The simulation results demonstrate the effectiveness of proposed transition flight controllers and its robustness subject to external disturbance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-25T12:29:02Z
      DOI: 10.1177/09544100221083713
       
  • Dynamic manipulability measure for on-orbit manipulation by frictional
           contacts

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      Authors: Li Chen, Zixuan Zheng, Jianping Yuan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Due to unilateral constraints of frictional contacts and the dynamic coupling phenomenon, the study on the unfixed manipulation through frictional contacts for multi-arm space robots is few carried out. This paper proposes a new measure method to assess the dynamic manipulability of the unfixed manipulation through frictional contacts. In particular, the explicit map from the base actuation and joint torques to the object acceleration, the base acceleration, and the internal force is formulated under unilateral constraints of frictional contacts. Considering typical control scenarios of both free-floating and free-flying systems, dynamic manipulabilities are derived separately. As an illustrative example, the dynamic manipulability of a planar dual-arm space robot is computed and reported, which visualizes the influence of different system parameters.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-24T04:25:30Z
      DOI: 10.1177/09544100221086588
       
  • Uncertainty quantification of aeroelastic wings flutter using an optimized
           machine learning approach

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      Authors: Mohsen Rezaei, Kourosh H Shirazi, Hamed H Khodaparast
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study outlines the flutter characteristics of aeroelastic wings under unsteady aerodynamic loading based on an efficient support vector machine assisted k-method. First, the aeroelastic wing flutter speed and flutter frequency are obtained using k-method. Then, the uncertain input parameters distribution is modeled by probability density functions. These parameters are propagated to the aeroelastic wing equations. The Monte Carlo simulation using 12 parallel logical threads is carried out to obtain the flutter speed and the flutter frequency distribution. An optimal robust surrogate model is trained by limited numbers of input and output using support vector machine. Monte Carlo simulation is also carried out in conjunction with the machine learning based k-method computational framework for obtaining the complete probabilistic description of flutter speed and flutter frequency. The coupled support vector regression based k-method is a novel approach that is first used in the aeroelastic wings flutter. The present method is found to reduce the computational time and cost significantly without compromising the accuracy of results.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-23T12:47:52Z
      DOI: 10.1177/09544100221080765
       
  • High-altitude airship propulsion system optimal design and experiment
           based on energy balance

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      Authors: Wang Dongchen, Song Bifeng, Jiao Jun, Wang Haifeng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes a propulsion optimization method with the surrogate modeling technique based on the coupling relationship between the propulsion and energy subsystem to achieve high-altitude airship weight reduction and figure out key factors. Propeller and motor surrogate models were constructed based on an inhouse fluid-structure solver and validated by the wind tunnel experiment. Solar intensity variation, solar cell distribution, and energy balance were modeled for the calculation of energy system weight. By minimizing the total weight of propulsion end energy subsystem as the goal and energy balance as the constraint, an optimization architecture was built. And a typical high-altitude airship is optimized as an example. Propulsion design variables were analyzed to figure out the influence on the airship’s overall performance. The results show that introducing energy balance into propulsion system optimal design can effectively reduce the total weight of the propulsion and energy system.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-23T09:22:12Z
      DOI: 10.1177/09544100221089700
       
  • Combined application of passive and active boundary layer aspiration in a
           transonic compressor rotor for shock wave/boundary layer interaction
           control

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      Authors: Xiaoxiao Zhou, Qingjun Zhao, Ben Zhao, Qiangren Xu, Wei Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Shock wave/boundary layer interaction (SWBLI) is one of the key factors that limits the improvement of aerodynamic performance and stability for supersonic/transonic compressors. In this research, a combined flow control device (CFCD) was designed for controlling SWBLI in the NASA transonic compressor Rotor 35. The original flow fields for Rotor 35 were numerically analyzed first. The results show that the SWBLI is severe, resulting in much flow loss and partly leading to the compressor instability. Based on this phenomenon, the CFCD was designed with a novel three-dimensional passive self-recirculation flow channel and an active suction slot. The flow channel is mounted on the rotor blade suction surface to connect the low- and high-pressure regions ahead of and behind the shock, respectively. The effect of the CFCD on the rotor performance and corresponding working mechanism are then researched as well. With the help of CFCD, the rotor-achieved total pressure ratio (TPR) is maximally increased by 3.0%, and the stall margin (SM) is improved by 4.1% as well. But the rotor isentropic efficiency (IE) considering additional energy expenditure caused by active suction flow has the maximum increment at choke point of 0.27% and highest reduction at near-stall point of 0.54%. The working mechanisms of CFCD include two aspects: one is forming a stable and low-entropy generated lambda shock wave and the other one is reducing the magnitude of flow separation. The dominant mechanism varies with the rotor working condition and depends on whether the leading-edge shock moves upstream of the passive bleed slot.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-21T12:51:31Z
      DOI: 10.1177/09544100221082332
       
  • Loss evaluation and aerodynamics investigation of an aggressive
           intermediate turbine duct under off-design conditions

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      Authors: Kaihe Geng, Chenxing Hu, Ce Yang, Yanzhao Li, Changmao Yang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To maximize the performance of the intermediate turbine duct (ITD) under off-design conditions, the loss generation in a one-half stage turbine was quantified using entropy generation and the global entropy generation rate. The numerical results solved by the unsteady Reynolds-averaged Navier–Strokes equations were first verified. Then, the aerodynamic losses within the high-pressure turbine stage were evaluated by efficiency loss under nine operating conditions composed of three rotor speeds and three rotor tip gaps. Finally, the disturbance modes caused by the upstream wake were captured by the dynamic mode decomposition method. Different from the influence of tip gaps, losses of the high-pressure turbine and the ITD are due to the swirl angle display an opposite trend. Under the influence of the interaction between the tip leakage flow and the shroud flow of the ITD, the viscous dissipation and turbulent dissipation increase with a larger tip gap owing to the dominant counter-rotating vortices and secondary flow occurring near the upstream of the ITD shroud. In addition, a large gap seems to enlarge the swirl component of the inflow angle, especially over 80% passage height, leading to greater dissipation losses in these areas. At the ITD inlet, two pairs of counter-rotating vortices at the shroud and the hub are, respectively, captured by the axial velocity mode. Large tip gaps enhance endwall vortices near the shroud and make the up vortex pairs merge into one pair.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-20T11:09:25Z
      DOI: 10.1177/09544100221085330
       
  • Data-driven fault-tolerant control for unmanned aerial vehicles without
           using identification model

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      Authors: Duo Zheng, Xinghua Xu, Defu Lin
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Unmanned aerial vehicle (UAV)’s fault-control problem was studied in this paper, and data-driven fault-tolerant control scheme was developed for acceleration tracking control of UAV in order to cope with the uncertainties induced by aerodynamic damage. A linear UAV dynamic model was given with reasonable assumptions, and the acceleration tracking control for UAV was converted to solving an infinite-horizon optimal control problem. The augmented algebraic Riccati equation (ARE) is derived, and its solution stability is proved based on Lyapunov theory. The data-driven control algorithm is further derived for online solving of the augmented ARE with only using flight data. The proposed algorithm is based on experience replay of flight data rather than model knowledge, so it greatly reduces the effect of uncertainties induced by aerodynamic damage on the flight control system for UAVs. Finally, the effectiveness of developed algorithm is verified through the numerical simulations under different uncertainties induced by aerodynamic damage.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-19T01:12:26Z
      DOI: 10.1177/09544100221084385
       
  • Adaptive Kalman filter based on multiple fading factors for fast in-motion
           initial alignment with rotation modulation technique

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      Authors: Jianguo Liu, Xiyuan Chen
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a novel fast fine alignment method is proposed on the basis of micro electro mechanical systems (MEMS) for unmanned aerial vehicle (UAV) under mooring conditions. Firstly, the model of single-axis rotation modulation with extended angular rate measurement is built to improve the speed of convergence, especially the azimuth misalignment angle and the constant error of gyroscope along the rotation axis. Both model mismatch and noise uncertainty of the extended measurement will arise for the difficulty to obtain the exact angular velocity of the carrier without auxiliary sensors. To address this problem, the adaptive Kalman filter based on multiple fading factors is proposed. Besides, the meta-heuristic beetle antennae search (BAS) algorithm is applied for the first time to optimize the fading factors in real time. Then, the effectiveness of the proposed method is verified by means of singular value decomposition and error covariance matrix analysis. Finally, the result of comparative simulations and experiments show that the observability degree and convergence speed of misalignment angles improve significantly compared to those conventional methods and the estimated values can satisfy the requirements of fine alignment. More importantly, the constant error of gyroscope along the rotation axis is estimated accurately and can be compensated in the subsequent navigation process.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-18T12:20:05Z
      DOI: 10.1177/09544100221082802
       
  • Effects of confinement and curvature on a jet in a supersonic cross-flow

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      Authors: Dapeng Xiong, Mingbo Sun, Jiangfei Yu, Zhiwei Hu, Yixin Yang, Hongbo Wang, Zhengguo Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To reveal the effects of confinement and curvature on the jet mixing in a supersonic cross-flow, large eddy simulations were conducted to study the jet in supersonic cross-flow in a channel and a pipe at a Mach number of 2.7. The comparison was based on an equal friction Mach number, friction Reynolds number, and Prandtl number. The synthetic eddy model was utilized to generate the inflow turbulent boundary layer. Our study shows the major counter-rotating vortex pair (CVP) was higher in the pipe than in the channel, while the trailing CVP was larger and appeared within the recirculating flow. The pipe had a stronger shock train than the channel due to the confinement and curvature of the pipe. The jet penetration of the pipe is 18.4% larger than that of the channel at x/D = 10, and the stream velocity of the pipe is much more reduced behind the jet than in the channel. Three reasons for the higher mixing efficiency of the pipe are revealed according to our findings, including the larger and higher major CVP, the higher penetration, the stronger shock. The mixing efficiency of the pipe is 4.68% higher than that of the channel due to the above reasons at x/D = 10.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-18T10:10:08Z
      DOI: 10.1177/09544100221089067
       
  • Aerodynamic design and evaluation of an open-nose supersonic drone

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      Authors: Eiman B. Saheby, Anthony P. Hays, Shen Xing
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The objective of this paper is to investigate the efficiency of a proposed supersonic drone configuration, in terms of drag, ram recovery, and fundamental flight performance factors. Sustainable supersonic cruise at Mach 1.6 is the major segment of the mission profile which affects the overall geometry resulting from the conceptual design phase, a tailless delta drone with an open-nose forebody, lofted around the inlet which consists of an analytical compression surface and a S-duct diffuser. Because the aerodynamics of this unconventional configuration is unknown, a series of CFD simulations using the ANSYS Fluent solver is coupled to the design process to predict both internal and external aerodynamics as a proof of the concept. The simulations indicate that the drone’s overall drag is significantly lower than the other configurations with side or underside integrated inlets while the inlet pressure recovery is adjusted to maximize the engine thrust. The parasite drag at design speed is about 0.022 which is considerably lower than conventional configurations and the pressure recovery more than 0.96 is possible by applying the boundary layer bypass. A comparative study, with a developed thrust model, shows that the configuration satisfies mission requirements and exceeds them at transonic and supersonic flight phases.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-16T03:26:20Z
      DOI: 10.1177/09544100221084389
       
  • Numerical estimation of longitudinal damping derivatives of a flying wing
           micro aerial vehicle

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      Authors: Taimur A Shams, Syed Irtiza Ali Shah, Aamer Shahzad, Kashif Mehmood
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Longitudinal damping derivatives, [math], of an aerial vehicle is important from an aerodynamic stability point of view. Experimental calculation of longitudinal damping derivatives using wind tunnel is not a cost-effective method; therefore, researchers have developed numerical solutions as an alternative. In this research, the longitudinal damping derivatives of a flying wing micro aerial vehicle (FWMAV) were calculated using numerical simulations by adopting pull-up maneuver and forced harmonic motion in pitch axis. Pull-up maneuver with four steady rotational rates was simulated to obtain pitch rate derivative, Cmq. Combined derivative, [math], was obtained by simulating forced harmonic motion of FWMAV around a mean angle of attack of 0° with amplitude of oscillation of ± 3° using four reduced frequencies (0.02, 0.03, 0.04, and 0.05). Unstructured surface and volume mesh was used in a spherical domain engulfed inside a large cuboid domain for moving reference frame strategy. Reynolds number taking mean aerodynamic chord as a reference length was 2.33 × 105. Spalart–Allmaras turbulence model was used. Pitch rate derivative, combined derivative, and acceleration derivative were found as − 0.03/rad, − 7.39/rad, and − 7.36/rad, respectively, by the use of a phase method at a reduced frequency of 0.03. During flight dynamic analysis, it was found that [math] has a significant contribution on damping in short period mode with no effect on Phugoid mode. The research concluded that for tailless configurations, acceleration derivative [math] can exist and can provide necessary damping in the longitudinal flight mode.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T12:14:10Z
      DOI: 10.1177/09544100221082856
       
  • Fault-tolerant consensus of nonlinear agents considering switching
           topology in the presence of communication noise

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      Authors: Sabyasachi Mondal, Antonios Tsourdos
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, the consensus of nonlinear multi-agent systems (MASs) is discussed, considering actuator fault and switching topology in the presence of communication noise. The actuator fault and communication noise are both considered to be random. The switching of the topologies is considered random as well. These issues are handled by Distributed Nonlinear Dynamic Inversion (DNDI), which is designed for Multi-Agent Systems (MASs) operation. The convergence proof with actuator fault is provided, which shows the robustness of the controller. The simulation results show that DNDI successfully dealt with the actuator fault and communication events simultaneously.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T03:46:37Z
      DOI: 10.1177/09544100211069179
       
  • Numerical investigation of an aggressive s-shaped compressor transition
           duct with boundary layer suction

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      Authors: Song Huang, Chengwu Yang, Ge Han, Shengfeng Zhao, Hongzhi Cheng, Xingen Lu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Aggressive s-shaped compressor transition ducts are important components in the connection between upstream boosters and downstream high-pressure compressors. The flow path is an s-shaped channel with struts and a large radial drop length ratio, which breaks through the limitations of traditional design and has a large aerodynamic loss. Therefore, this paper considers an aggressive s-shaped compressor transition duct in a geared turbofan engine and creatively proposes a method for controlling the flow separation through boundary layer suction. The results show that hub suction reduces the losses of the aggressive s-shape transition duct. As the mass flow rate of hub suction increases, the total pressure loss coefficient decreases and the rate of reduction in the total pressure loss slows down. Combined boundary layer suction reduces the total pressure loss to a greater extent. On the premise that the location of blade suction remains unchanged, the optimal location for the circumferential slot of hub suction is at 20% of the axial chord length of the strut, whereby the total pressure loss coefficient decreases by about 30% compared with the case of no suction. When the mass flow rate of suction is fixed at 3% of the inlet mass flow rate, a distribution of 0.5% from blade suction and 2.5% from hub suction reduces the total pressure loss by 1.6% compared with the case where all 3% comes from hub suction. The distribution of the mass flow rate for combined boundary layer suction has an optimal ratio.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T02:30:57Z
      DOI: 10.1177/09544100221084384
       
  • Efficiency of rocket engine thrust vector control by solid obstacle on the
           nozzle wall

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      Authors: Genadii Strelnikov, Oleksandr Ihnatiev, Nataliya Pryadko, Katerina Ternova
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The thrust vector control of a rocket engine by disturbing the supersonic flow in its nozzle is used for missile development for various purposes in different countries. Disturbance of the supersonic flow in the jet engine nozzle can be caused by various obstacles on the nozzle wall: solid obstacle, liquid or gas jet, combinations of solid obstacle with injected jets. The simplest and most effective way to create a disturbance is to disturb it by setting a solid cylindrical obstacle on the nozzle wall. The high efficiency is explained by the lack of the working fluid consumption on board the aircraft to create a control force, or its minimum amount necessary to protect the obstacle from the high-temperature oncoming gas flow in the rocket engine nozzle. This paper presents the study results of gas flow simulation with cylindrical obstacle perturbation on the wall of the Laval rocket engine nozzle in its subsonic and supersonic parts. The optimal placement in the nozzle is determined to obtain the maximum lateral control force. As a result of research, it was found that the perturbation of a supersonic flow in a rocket engine nozzle by a cylindrical obstacle has practically the same character when its position changes along the length of the nozzle. In the subsonic part of the nozzle in the median plane, the perturbed pressure on the wall has a positive sign, and on the obstacle wall its sign-alternating. When an obstacle is in the subsonic part of the nozzle, the integral value of the lateral force is negative in comparison with positive for the supersonic part.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T01:53:41Z
      DOI: 10.1177/09544100221083714
       
  • Effects of different structural parameters on the 7075-T651 aluminum alloy
           lug structure fatigue life

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      Authors: Li Hui, Hongda Wang, Yanqing Huang, Wenjun Yang, Song Zhou
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Lug structure is an important connection structure in aviation aircraft. However, fatigue cracks are easily generated during the service of the aircraft. Therefore, this study aims to explore the influence of different structural parameters on the fatigue life of the 7075-T651 aluminum alloy lug, using experimental and numerical methods to determine the effects of these structural parameters. Scanning electron microscopy was employed for fracture analysis, and three-dimensional finite element models were used to solve the holes edge stress distributions under peak load and stress concentration factor. The results indicate that the fatigue life of the lug increases with the increase in the extrusion projection area and the included angle of the outer edge, and the impact of the extrusion projection area on the fatigue life of the lug is greater than the angle of the outer edge, and the fatigue life of the lug does not change with the change of the chamfer at the bottom. The peak stress at the root of the lug hole becomes the main factor affecting the fatigue life of the lug, and the crack always expands along the net cross-section of each parameter lug.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T01:14:28Z
      DOI: 10.1177/09544100221083354
       
  • A new strategy for solving store separation problems using OpenFOAM

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      Authors: Saleh Abuhanieh, Hasan U. Akay, Barış Bicer
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The ability of OpenFOAM to solve the problem of a store separating from an air vehicle (store separation problem) has been evaluated using a dynamic mesh (Overset/Chimera) technique for an industry-class (transonic and generic) benchmark test case. The major limitations of the standard libraries have been determined. To tackle these challenges, a new strategy has been proposed and implemented using only open-source libraries and tools. The strategy combines porting, modifying, and adapting an overset library from the OpenFOAM fork platform (foam-extend) to the standard OpenFOAM platform (ESI). Furthermore, in order to overcome the well-known weakness of the standard OpenFOAM compressible solvers, the newly adapted overset library was integrated with an open-source, density-based, and coupled solver (HiSA), which uses the OpenFOAM technology. Additionally, a force restrained model was developed to consider the externally applied forces on the store by the store ejectors. The accuracy of the developed strategy has been compared with wind tunnel tests and the solutions of two well-known commercial codes, showing good agreements with them. While the study has focused on simulations with inviscid Euler equations (typical of the test case considered here), the viscosity effect on the solution has also been studied with Navier–Stokes equations and compared with other results in the literature, showing minor differences. To the best of the authors’ knowledge, this is the first work which studies and validates the store separation problem in transonic regime with OpenFOAM.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-11T08:12:56Z
      DOI: 10.1177/09544100221080771
       
  • Effects of canard oscillations on the unsteady flowfield over the wing in
           supersonic flow

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      Authors: Ali R Davari, Mohammad R Soltani
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Few studies have been devoted to effects of canard oscillations on the flowfield over the wing in supersonic flow and the associated time lags. In this article, an in-depth experimental study on a closely coupled canard-wing-body configuration in supersonic flow has been undertaken to mark the zone of influence of the oscillatory canard on the wing. Surface pressure measurements have been performed on the wing downstream of canard in both static and oscillatory cases at various wing angles of attack and canard deflection angles as well as the canard oscillation amplitudes and frequencies. The results show that the upwash and downwash flowfields due to an oscillatory canard periodically change the effective angle of attack seen by the wing and have different effects on various regions. In supersonic flow, the pressure rise due to the oblique shock waves causes the primary flow separation and the vortex break down onsets to occur at higher angles of attack, comparing to those in the lower speed regimes. According to the results, the mid-span region on the wing, which is directly in the shadow of the oscillating canard, receives more disturbances. During upstroke, the canard induces a downwash field to the front half of the wing, while in downstroke motion, the front regions of the wing experience upwash flow, giving rise to the effective angle of attack seen by the wing. Among various oscillation parameters, the pitching amplitude was observed to have a strong impact on the time lag in flowfield over the wing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-09T02:20:55Z
      DOI: 10.1177/09544100221083348
       
  • Risk identification of civil aviation engine control system based on
           particle swarm optimization-mean impact value-support vector machine

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      Authors: Jing Cai, Han Bao, Yan Huang, Di Zhou
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The actual risk of the engine control system in operation is often higher than expected risk level, which brings hidden dangers to the safe operation of aircraft. Therefore, a PSO-MIV-SVM (particle swarm optimization-mean impact value-support vector machine) model is proposed to identify the risk of engine control system. Firstly, seven characteristic variables are extracted through the analysis of engine unsafe information, and 810 typical engine event samples were selected and normalized. Secondly, the SVM-based engine control system risk identification model is established and optimal kernel function of the SVM model is selected. Thirdly, the SVM-MIV method is used to sort the importance of the seven characteristic variables, and the identification accuracies of different characteristic variable groups are calculated to obtain the optimal combination of characteristic variables. Finally, the parameters of the SVM model are optimized by using the PSO algorithm and the accuracy of the PSO-MIV-SVM model for the risk identification of the engine control system reaches 93.58%.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-06T04:10:29Z
      DOI: 10.1177/09544100221080767
       
  • Gravity-compensated guidance for impact-angle interception of a moving
           target

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      Authors: Hyeong-Geun Kim, Jun-Yong Lee, Pyojin Kim
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes an impact-angle control guidance (IACG) law for anti-ship and anti-tank missiles in which the command converges to zero at the point of interception, even in a gravity field. The desired line-of-sight (LoS) angle that satisfies the terminal impact-angle and acceleration constraints is first defined. The guidance command is then derived as a solution that realizes the convergence of the actual LoS angle to the desired LoS angle during the terminal stage of homing in on a target. Gravity is considered when designing the guidance law such that the desired terminal constraints are accurately satisfied, even under realistic pitch-axis engagement. We also investigated whether the proposed law is optimal for minimizing the total expense of maneuvering while performing IACG in a gravity field. The results of the numerical simulations included in this study demonstrate that the proposed guidance law achieves accurate impact-angle interception with the command converging to zero at the end of homing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-04T10:03:50Z
      DOI: 10.1177/09544100221082101
       
  • Adaptive super-twisting control for deployment of space-tethered system
           with unknown boundary disturbances

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      Authors: Zhe Dong, Lei Zhang, Aijun Li, Changqing Wang, QingSheng Shi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes an adaptive super-twisting control (ASTC) for the deployment of space-tethered systems with the consideration of uncertainty of external and internal disturbances with unknown boundaries. The main advantage of the ASTC scheme is that it can deal with the unknown bounds of uncertainties and disturbances. The proposed control law consists of two adaptive control gains that ensure the establishment, in a finite time, of a real second-order sliding mode. This, in turn, guarantees a convergence to a small domain and without overestimating the control gains. The stability of the control law is demonstrated theoretically. Compared with the sliding mode control algorithm with power reaching law, the newly proposed adaptive super-twisting control method performs better in the settling time, the maximum in-plane angle, and angular velocity control and suppressing oscillations. Numerical simulations are presented to validate the effectiveness and robustness of the proposed ASTC scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-31T05:55:17Z
      DOI: 10.1177/09544100211068909
       
  • A structural design approach for a droop nose morphing demonstrator with
           shape memory alloy patches

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      Authors: Dimitrios G Stamatelos, Vassilios Kappatos
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An innovative concept has been devised for assisting an actuator to morph a Droop Nose (DN) structure, which is comprised from the skin and three longitudinal omega stringers. The concept is based on the development of a suitable composite patch, with embedded shape memory alloy (SMA) wires, and the appropriate design of a DN configuration for morphing purposes. The integration of composite patches, to the DN structure, has a dual innovative role: (a) it can either provide/extend the morphing capabilities of the structure, in terms of displacement or (b) it can reduce the required actuation forces for obtaining morphing of the DN structure. For determining the most suitable DN configuration, for the application, a sensitivity analysis, with the aid of ANSYS finite element (FE) software and a design of experiments (DoE) approach, has been carried out. The investigated parameters (geometrical and lamination characteristics) are selected to vary the stiffness of the DN structure. Additionally, a numerical parametric FE model, of the SMA patch and its configuration, is developed and analysed. The developed FE models simulated the shape memory effect of SMA wires considering their activation temperature and hence their thermo-mechanical behaviour. Eventually, a possible integration of the SMA patches to the DN structure is proposed and the respective remarks are highlighted.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-29T10:07:10Z
      DOI: 10.1177/09544100221080116
       
  • Nonlinear aeroelastic stability analysis of a two-stage axially moving
           telescopic wing by using fully intrinsic equations

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      Authors: Sayed Hossein Moravej Barzani, Hossein Shahverdi, Mohammadreza Amoozgar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      During the process of span extension for an aircraft wing equipped with a telescopic morphing mechanism, the wing aspect ratio increases, and hence, the geometrical nonlinearities might become more significant. In this regard, this paper aims to investigate the effect of structural nonlinearity on the aeroelasticity of span morphing wings using the exact fully intrinsic equations for the first time. Furthermore, the effects of various parameters such as thrust force, engine location, chord size, flight altitude, initial angle of attack, and overlapping mass on the aeroelasticity of the wing are studied. The applied aerodynamic loads in an incompressible flow regime are determined using Peters’ unsteady aerodynamic model. In order to check the stability of the system, first the resulting nonlinear partial differential equations are discretized by using the central finite difference method and then linearized about the static equilibrium. Finally, by obtaining the eigenvalues of the linearized system, the stability of the wing is evaluated. It is observed that by using the fully intrinsic equations, the instability of the axially moving telescopic wing can be determined more accurately. Moreover, the results show that the morphing length and overlapping mass have significant effects on the aeroelastic stability of the telescopic wing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-28T09:13:41Z
      DOI: 10.1177/09544100221080117
       
  • Coordinated control of free-floating dual-arm space robots based on hybrid
           task-priority approach

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      Authors: Mengqing Hong, Hui Zhou, Liaoxue Liu, Yu Guo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper addresses the problem of the coordinated control of the free-floating dual-arm space robots, in the case of multiple conflict tasks. Taking the dynamic coupling effect into consideration, a relative Jacobian matrix is presented to establish the kinematic model of the free-floating dual-arm space robot. Then, an adaptive coordinated controller is elaborately developed for three conflict tasks, including position tracking of the master arm, relative motion of dual arms, and obstacle avoidance. Owing to the hybrid task-priority approach, the proposed controller can effectively ensure the execution of the obstacle avoidance task without sacrificing the performance of the first two tasks. In addition, the singularity problem is settled via introducing an adaptive damping factor based damped least-squares inverse. Meanwhile, a novel hyperbolic tangent function is designed to handle the discontinuity in performing the null space task. Finally, numerical simulations were constructed to compare the performance of the proposed coordinated controller based on hybrid task-priority approach with the controller based on task-priority approach. The simulation results show that the proposed controller has an improved tracking performance of the master arm and safety performance, compared with single task-priority approach.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-27T01:03:52Z
      DOI: 10.1177/09544100211053537
       
  • Effects of Coanda jet direction on the aerodynamics and flow physics of
           the swept circulation control wing

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      Authors: Shuai Shao, Zheng Guo, Zhongxi Hou, Gaowei Jia, Laiping Zhang, Xianzhong Gao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Over the last decade, many flight tests of the conventional/canard/flying-wing layout UAVs (unmanned aerial vehicle) have proven that the trailing-edge circulation control (CC) is an effective method to generate a significant rolling moment for the rolling control. However, the Coanda jet’s three-dimensional effects, especially the Coanda jet direction, on the design of UCAVs (unmanned combat air vehicle) have not been revealed and discussed clearly yet. In order to solve this problem, the effects of the Coanda jet direction on the swept wing’s aerodynamics and flow physics are investigated in detail in this paper. An in-house CFD(computational fluid dynamics) solver HyperFLOW with the Spalart–Allmaras for Rotation and Curvature turbulence model and the velocity inlet boundary has been validated by 2-D and 3-D CC cases and is used in this work. The research reveals that compared with the Coanda jet in the freestream direction (FJ jet), the Coanda jet perpendicular to the trailing edge (PJ jet) has a more significant impact on the aerodynamic loads and flow structures for swept wings, including increasing lift, drag, and nose-down moment, enhancing the wingtip vortex and weakening the thickness vortex. In contrast, the FJ jet performs better in improving the lift-to-drag ratio of swept wings. On a typical UCAV, the generalizability of the conclusion about the Coanda jet direction effects on the aerodynamic characteristics is verified. The current research gets an insight into the three-dimensional effects of the trailing-edge CC and provides solid support for implementing the CC technology into practical aircraft concepts.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-26T03:41:58Z
      DOI: 10.1177/09544100211068728
       
  • Orbital perturbation analysis and generation of nominal near rectilinear
           halo orbits using low-thrust propulsion

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      Authors: Chongrui Du, Olga L Starinova
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The near rectilinear halo orbit (NRHO) is a potential orbit for the establishment of lunar space station. This research is focused on the analysis of major orbital perturbations on NRHOs and the generation of nominal orbit using a low-thrust engine in the ephemeris model. First, the NRHO family is defined in the circular restricted three-body problem (CRTBP). Then, different perturbations are performed to integrate the spacecraft motion along the NRHOs; meanwhile, a modified momentum integral is employed to calculate the orbit deviation in the case of each perturbation examined independently. By this way, these perturbations are classified according to the magnitude of impact on NRHOs. Finally, combined with a fuel-optimal control, a target-point strategy generating the nominal-controlled NRHO in the real Earth–Moon system is proposed using low-thrust technology. By selecting a fixed point from the original NRHO, the spacecraft is forced to depart from this point and then return to it, thereby forming a controlled closed trajectory. This provides an alternative nominal orbit for the future application of the low-thrust engine to lunar exploration missions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-26T02:30:03Z
      DOI: 10.1177/09544100211072318
       
  • Flight performance of helicopter tail rotors with extendable chord

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      Authors: Kelong Yang, Dong Han
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To investigate the potential of Statically and Dynamically Extendable Chord (SEC/DEC) in performance improvement of helicopter tail rotors, a prediction model of helicopter flight performance is developed and validated. It is suitable to deploy the SEC and DEC close to the blade tip for power reduction of tail rotor in hover and high-speed flight. The deployment locations of SEC and DEC for tail rotors are similar to that of main rotors. In hover, the deployment of the SEC and DEC results in little power reduction. From low to medium speed flight, the deployment of the DEC and SEC increases the power. In high-speed flight, the SEC and DEC can significantly decrease the power, especially at a large take-off weight. At 300 km/h, when the chord extension is 20% of blade chord, the SEC and DEC with 1/rev input decrease the power by 14.44% and 20.47% at a take-off weight coefficient of 0.0091. The DEC shows greater potential in power reduction than the SEC. There is an optimal phase input for the maximum power reduction, which does not vary with forward speed. For the DEC with 1/rev input, the optimal phase is [math]. The optimal phase input for the maximum power reduction of tail rotors is different from that of main rotors.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-26T02:23:35Z
      DOI: 10.1177/09544100221080142
       
  • Soft one-class extreme learning machine for turboshaft engine fault
           detection

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      Authors: Yong-Ping Zhao, Gong Huang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      One-class extreme learning machine (OC-ELM) is a very common one-class classification algorithm. In the process of constructing the OC-ELM, a part of training samples will be removed by the algorithm, which leads to inconsistency between its constraint condition and decision function, and is also known as the problem of hard margin flaw. In order to solve this problem, a soft one-class extreme learning machine (SOC-ELM) is proposed by assigning an appropriate margin to each training sample. Experimental results on benchmark data sets show that SOC-ELM has a strong classification performance. When the SOC-ELM is used for fault detection of a turboshaft engine, it can achieve good detection effectiveness and has strong robustness.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-25T09:19:17Z
      DOI: 10.1177/09544100211068906
       
  • Sliding mode controller based aircraft automatic landing for alternate
           profiles

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      Authors: Salahudden Salahudden, Akash T Das, Jitu Sanwale, Dipak K Giri, Ajoy K Ghosh
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In the present paper, different autonomous landing profiles are formulated and simulated. Generic landing is modelled first, wherein, approach and acquired runway heading is considered as same. The second-landing profile involves altitude hold when runway is not clear to land the aircraft. Expedited landing is the third profile modelled with a glide slope-maintained descent to reduce the ground distance required pre-touchdown. In either of the landing profiles, flare is kept the same. The merits and demerits with respect to the practicality of implementation of these profiles are then discussed. Each landing profile has been demonstrated using sliding mode controller (SMC). The asymptotic stability and finite-time proofs of the designed controller are shown using Lyapunov function. F-18 HARV aircraft is considered to test the efficacy of the formulated landing profiles. Expedited landing profile proposed here is a novel approach in which altitude descent gradient is maintained with helical descent path. Additionally, results of this approach show significant improvement in terms of possibility of initiating an unconventional and yet safe as well as economical method much nearer to the runway.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-25T09:06:59Z
      DOI: 10.1177/09544100211068903
       
  • An approach of Proper Orthogonal Decomposition-aided Free-form Deformation
           with application in compressor blade design

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      Authors: Shuyue Wang, Kaidi Wang, Sheng Qin, Zizhao Yuan, Gang Sun, Zhong Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Compressor blade design influences aero-engine performance mainly through its total pressure ratio and efficiency. As a volume-based geometric parameterization, Free-form Deformation (FFD) brings three-dimensionality that is essential to blade design. However, the manipulation of control points with respect to simple numeric parametric perturbation renders the use of design space low-efficient. Therefore, an improved FFD with ‘wiser’ control point lay-out is expected to identify those more important design variables. This paper proposes novel design variables that are assigned to grouping of control points’ displacement in FFD lay-out. In short, the approach is realized as: (i) establish a library of sufficient blade shape samples; (ii) filter the database with geometric constraints; (iii) extract dominant modes via (POD) Proper Orthogonal Decomposition; (iv) construct new design variables and apply them in optimization. With geometric constraint filtering, problem-oriented information is injected. With POD, the dominance of new selected geometric parameters in problem description is assured. Perfunctory details of displacement data of each control point in the lay-out can be replaced by grouped data as new design variable candidates. As a proof-of-concept study of the new approach, compressor blade Rotor 37 is selected to be the good platform of testing the feasibility of POD-aided FFD as a global and flexible yet economic geometric parameterization. Result demonstrates the feasibility of proposed POD-aided FFD approach that helps conduct an optimization involving displacement of 6 × 4 × 3 control points with as few as five new design variables, while still being capable of bringing optimization effect in three test cases.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-25T07:41:37Z
      DOI: 10.1177/09544100221075071
       
  • Removing adverse effect of measurement process in flotation method

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      Authors: Rui Zhu, Qingguo Fei, Dong Jiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Ground simulation of space quasi-zero gravity environment is essential in modal testing of space structures. The air flotation method is widely used, in which the air cushion unit is attached to the measured structure. This inevitably increases the total mass of the structure to be tested and leads to the incorrect prediction of modal parameters. And irregular airflow disturbances of the air cushion unit also have negative effects on the test. The fast elimination method is presented to remove the adverse impact in the test data based on measured frequency response functions. Numerical simulations are performed employing the magnetometer structure. Results show that this method effectively removes the adverse mass and the airflow effect.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-25T02:55:32Z
      DOI: 10.1177/09544100211068218
       
  • Reducing helicopter 1/rev vibration using extendable trailing-edge plate

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      Authors: Xiaomiao Ji, Mao Yang, Chenxi Ning
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Due to manufacturing errors and wear, helicopter rotor blades are not completely similar resulting in significant 1/rev fuselage vibration. In practice, rotor track and balance (RTB) based on neural network is used to eliminate the 1/rev vibration. This greatly increases the maintenance workload and cannot adjust the 1/rev vibration in flight. In view of this, a new RTB approach, namely, extendable trailing-edge plate (TEP), is studied in the present paper. Since TEP extension changes the profile of the baseline airfoil, the computational fluid dynamics (CFD) calculation is performed to study the aerodynamic characteristics of the airfoil with the extendable TEP under different extension amounts. Combined with the aerodynamic characteristics of the extendable TEP airfoil, a comprehensive helicopter aeromechanic analysis program adapted to the extendable TEP mechanism is used to explore the effects of the extendable TEP on the 1/rev fuselage vibration and hub loads. In addition, by analyzing the hub loads and the acceleration of the fuselage caused by the extendable TEP device, the mechanism of action is studied. Results show that the adjustment method based on extendable TEP is able to reduce the 1/rev acceleration of the fuselage by up to 85%–95%, which is about 8% higher than that of neural network-based algorithm. Therefore, the extendable TEP has great potential in RTB (i.e., eliminating rotor inherent dissimilarity). In addition, the factors that affect the 1/rev vertical vibration level of the airframe under different flight conditions are different.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-25T02:35:40Z
      DOI: 10.1177/09544100221080106
       
  • Optimization of low-thrust multi-debris removal mission via an efficient
           approximation model of orbit rendezvous

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      Authors: An-yi Huang, Ya-zhong Luo, Heng-nian Li, Sheng-gang Wu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An efficient iterative approximation model for low-thrust rendezvous in low-earth orbit is proposed to be applied in optimization of multi-debris removal missions. Based on an existing method for impulsive orbit rendezvous and a novel iteration process, the propellant cost and thrust time of a low-thrust rendezvous can be quickly evaluated. Moreover, another iterative method is also designed to help find the minimal transfer duration required for orbit rendezvous. Then, its application in the max-reward optimization of debris removal mission with a large-scale targets to be selected is studied. In the three-steps optimization including target selection, sequence optimization, and low-thrust trajectory optimization, the iterative approximation model is used to deal with the constraints and evaluate the objective functions more efficiently. The problem of the eighth Chinese trajectory optimization competition was used to test the performance, and a leading solution including 93 targets was found. Comparisons with previous results were made to prove the advantages of the method in this paper.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-24T07:58:11Z
      DOI: 10.1177/09544100221074746
       
  • Research on the dual-channel electro-impulse de-icing system of aircrafts

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      Authors: Yusong Wang, Tao Guo, Kai Li, Chunling Zhu, Qian Du
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The electro-impulse de-icing system (EIDI) is a mechanical de-icing system that guarantees the safe flight of the aircraft under icing weather conditions. It owns many merits such as high reliability and low energy consumption. To solve the problem of the small de-icing area under single-channel, a dual-channel EIDI system model is proposed. The electro-magnetic field and de-icing results of the dual-channel EIDI system are investigated. Comparisons of de-icing results between simulations and experiments on the flat aluminum plate are also made. Furthermore, the de-icing research is carried out with a real wing structure by varying the excitation time and magnitude of impulse load. Simulation results of the electro-magnetic field show that the maximum of the density of electro-magnetic force always appears at the midpoint of the inner and outer radius of coils. The excitation of the two coils is independent and can be decoupled. The de-icing results illustrate that the de-icing rate increases with the striking intervals and impulse load. The load multiple (LM) should be selected between 1.5 and 3 for the dual-channel EIDI system for energy optimization. In addition, it is advisable to distribute the impulse loads with the largest possible difference on both sides when the LM is 1–3.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-24T05:56:59Z
      DOI: 10.1177/09544100211060604
       
  • Macroscopical contact pressure and microscopic leakage performance
           analysis of rubber seal considering thermal oxygen aging effect

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      Authors: Heng-Chao Sun, Yan-Yan Hao, Li-Na Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Leakage performance of rubber seal is a key factor of spacecraft system, which is required long life. But the degradation law of the rubber seal performance in long service period is limited to qualitative analysis for its macro contact performance, and the quantitative research of rubber seal leakage performance is rarely involved considering thermal oxygen aging effect. Therefore, the thermal oxygen aging mathematical model is firstly established to predict the life of rubber material by aging tests. Secondly, the finite element model (FEM) of rubber seal performance analysis considering thermal oxygen aging effect is built to obtain the degradation law of its macroscopic contact performance with the increase of service time. Thirdly, the micro-leakage model of rubber seal considering thermal oxygen aging effect is established based on the material surface microstructure, contact pressure, and contact width, and the leakage rate of rubber seal is calculated by the model. Finally, the micro-leakage model of rubber seal is modified based on the experimental results, so the calculation accuracy of leakage rate is improved.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-24T05:24:26Z
      DOI: 10.1177/09544100221080504
       
  • Dynamics and adaptive backstepping control of multibody spacecraft
           connected with active magnetic bearing

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      Authors: Xian Zhao, Yunhai Geng, Tao Yi, Chao Yuan, Baolin Wu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, to realize the high-resolution observation mission, a new type of multibody optical spacecraft connected with active magnetic bearing (AMB) is introduced. Then, to address the attitude control problem facing high-precision observation for multibody spacecraft, the dynamic model of the multibody system is developed and an adaptive backstepping controller (ABC) is subsequently proposed. First, a high-precision electromagnetic force model of AMB is developed. Different from traditional models that only consider rotor position and current, the relative attitude between rotor and platform is considered. Then, based on the AMB model, the dynamic and kinematic model of multibody spacecraft is derived. Additionally, considering the electromagnetic bearing is unstable statically, an ABC method is proposed. The stability of the closed-loop system is guaranteed by the Lyapunov theorem. Finally, to indicate the effectiveness of the proposed method, some numerical simulations of comparison with the iterative learning control (ILC) method are performed. As indicated by the simulation results, the ABC is capable of eliminating periodic deviation, and it is more effective than the ILC in solving the control problem caused by periodic disturbance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-23T08:03:54Z
      DOI: 10.1177/09544100211064470
       
  • Vector field guidance for standoff target tracking

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      Authors: Tammineni Harinarayana, Sikha Hota, Rahul Kushwaha
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This work presents a guidance algorithm for standoff target tracking by unmanned aerial vehicles using the traditional Lyapunov guidance vector field framework. Unlike the past work, this guidance law is the function of the minimum radius of curvature, and, hence, it can act more flexibly for different maneuverable vehicles. Moreover, normalized even and odd functions are proposed here as circulation and convergence terms to improve performance in terms of optimality. The presence of wind is also considered for real world applications. As the proposed guidance law generates paths of continuous curvature, the designed path is flyable by fixed-wing unmanned vehicles. Simulation results are presented to validate the proposed guidance law.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-23T04:52:33Z
      DOI: 10.1177/09544100211072320
       
  • Unacknowledged fatal error in expressions for shear strains in 3-D theory
           of elasticity in curvilinear co-ordinates and the consequences

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      Authors: L. J. Hart-Smith
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An undetected fatal error has existed in the 3-D theory of elasticity in curvilinear co-ordinates since its formulation in the 19th century, whereby the linear expressions for shear strains as functions of the three orthogonal displacements fail to satisfy St. Venant’s compatibility equations. This error has, consequently, invalidated all thin-shell theories and finite-elements (other than those in Cartesian co-ordinates). The error is shown to have been caused by defining all six strain components mathematically to fit a single strain tensor as if they were independent quantities not constrained by any need for compatibility, instead of calculating what they really were. With six strain components (three direct and three shear) and six compatibility equations, this procedure was always scientifically unacceptable. It is further shown that the three real shear-strain components satisfying compatibility are fully defined derivative functions of the three direct strains. The correct shear-strain characterizations are established here by two totally independent methods, the first by analysis, and the second by revealing that St. Venant’s compatibility equations actually specify mathematically what the three shear strains must be. The article includes the correct specific strain components for thin cylindrical shells and exposes the bogus compatibility equations that were derived decades ago from the incompatible classical strain components, which concealed the existence of this error for cylindrical and spherical shells. This “fix,” universally accepted, whereby the compatibility equations were made to fit a set of independent strain components, defeats the purpose of compatibility requirements constraining the options for possible strains that cannot all be independent if they are to be compatible. It is recommended that the several related malpractices in the analysis and design of thin-shell structures be discontinued—and that new shell theories and new finite-elements and structural analysis computer codes be developed to replace them.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-22T09:00:19Z
      DOI: 10.1177/09544100211060600
       
  • Numerical simulation of the quadcopter flow field in the vertical descent
           state

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      Authors: Junjie Wang, Renliang Chen, Jiaxin Lu, Yanqin Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Quadcopters will possibly enter the vortex ring state (VRS), which may jeopardize flight safety of the aircraft, in descending as helicopters do. But aerodynamic characteristics of the quadcopter in the VRS are quite different with the helicopter due to the aerodynamic interference between the rotors, and they were hardly studied. In this paper, the flow fields of a quadcopter and a single rotor in vertical descending are studied through CFD simulation, and the variation laws of lift and power are analyzed. The results show that the single rotor and the quadcopter will enter the VRS like helicopters. Compared with the single rotor, the quadcopter enters the VRS at a smaller decent speed (0.65 vh vs. 0.785 vh). The single rotor reaches its largest lift loss at 19.6% in the middle stage of the VRS, while the rotor of the quadcopter reaches it at 10.6% in the late stage. When the quadcopter enters the late stage of the VRS, its lift variation between rotors is up to 5%. For flight safety, the maximum speed of the quadcopter in vertical descending should be limited to a safe speed (Vc = 0.65 vh). This study can provide a reference for the safety of quadcopter flight.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-18T08:12:42Z
      DOI: 10.1177/09544100211073372
       
  • Performance deterioration of axial compressor rotor due to uniform and
           non-uniform surface roughness

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      Authors: Ashima Malhotra, Shraman Goswami, Pradeep Amboor Madathil
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Surface roughness is a significant source of performance loss in gas turbine engines. The fan and compressor, being the initial components of the gas turbine engine, are more prone to surface roughness effects due to the ingestion of debris at low atmospheric conditions. This paper attempts to numerically study the impact of uniform and non-uniform surface roughness on axial compressor rotor performance. NASA rotor 37 is used as the validation test case for the numerical methodology, and the results show a good match between the experimental and computational fluid dynamics data. Detailed flow field analysis indicates that there is a reduction in rough blade performance and the overall flow turning that reduces the work done by the rotor. The location sensitivity studies shock location is the major contributor to the overall loss in the performance. Also, the study of non-uniform roughness on blade performance shows that roughness on the leading edge is the major contributor to the loss as compared to the trailing edge and so does roughness on the shroud as compared to the roughness on the hub. An interesting observation is that for the given configuration and roughness height, near the shroud, the role of the tip vortex is more pronounced than the role of surface roughness on the performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-14T09:30:53Z
      DOI: 10.1177/09544100211068912
       
  • Review of wave drag reduction techniques: Advances in active, passive, and
           hybrid flow control

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      Authors: Shagufta Rashid, Fahad Nawaz, Adnan Maqsood, Shuaib Salamat, Rizwan Riaz
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Typical challenges of supersonic flight include wave drag, acoustic signature, and aerodynamic heating due to the formation of shock waves ahead of the vehicle. Efforts in the form of sleek aerodynamic designs, better propulsion systems, and the implementation of passive and active techniques are generally adopted to achieve a weaker shock wave system. Shock reduction can improve flight range, reduce fuel consumption, and provide thermal protection of the forebody region. This paper briefly reviews shock reduction techniques, including passive, active, and hybrid flow control. Airfoil shape optimization, mechanical spike, and forebody cavities are studied as passive flow control approaches. For active flow control, developments in the area of opposing jets and energy deposition are explored. The combination of active and passive flow control and the hybrid flow techniques are discussed in the end. The discussions include the principle of operation, physics of fluid behavior, and overall contribution to flight stability characteristics. The implications in the usage of these technologies, along with potential gaps, are also identified. This comprehensive review can serve as the basis for contemporary solutions to realize sustainable supersonic travel for the aviation industry.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-12T10:47:34Z
      DOI: 10.1177/09544100211069796
       
  • Integrated design of adaptive fault-tolerant control for non-minimum phase
           hypersonic flight vehicle system with input saturation and state
           constraints

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      Authors: Le Wang, Ruiyun Qi, Zhiyu Peng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, for the six-degree-of-freedom (six-DOF) model of hypersonic flight vehicle (HFV) subject to actuator faults, state constraints, parametric uncertainties, and external disturbances, an adaptive fault tolerant control (FTC) scheme is proposed based on barrier Lyapunov functions (BLFs). The study is begun with a series of control-oriented manipulations: at first, due to the high complexity of the six-DOF model, the corresponding simplified model is proposed under reasonable assumptions; then, through the stability analysis of the internal dynamics, we can conclude that the vehicle model is a non-minimum phase system, namely, having unacceptable zero-dynamics. In order to solve the non-minimum phase problem, the elevator-to-lift coupling term is regarded as uncertainty of the model. Subsequently, in consideration of the insufficient control torque caused by the fault of the rudder or elevators, an adaptive fault-tolerant controller is designed based on BLFs, backstepping method, and Nussbaum gains. In the control law, the uncertain parameters are replaced by their estimates updated by adaptive laws. And the angle of attack and the roll angle of the aircraft are constrained in the preset range. Additionally, the convergence of the proposed FTC algorithm and the boundedness of all the signals of the closed system is proved by Lyapunov stability theory. At last, the numerical simulation results of the six-DOF model are carried out to manifest the effective tracking performance of the proposed FTC scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-10T04:12:38Z
      DOI: 10.1177/09544100211057985
       
  • A fast matrix generation method for solving entry trajectory optimization
           problems under the pseudospectral method

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      Authors: Zhaoting Li, Xiangji Tang, Hongbo Zhang, Guojian Tang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A fast matrix generation method based on correlations is proposed for the pseudospectral method (PSM) to solve the entry trajectory optimization problem. First, the optimization problem is analyzed to obtain some assumptions of performance indicators and constraints. Then, the chain rule and correlations among the variables are used to simplify the gradient calculations, resulting in a fast generation method for the gradient vector. Meanwhile, based on the previous assumptions, a fast generation method for the Jacobi matrix is derived semi-analytically using the correlation information among the variables. Finally, the trajectory optimization problem is studied using a typical aircraft. The results are verified via comparisons with the well-known GPOPS II software. Furthermore, the superiority of the proposed method in terms of the computational efficiency is demonstrated by comparing the relevant time indexes. The performance of the proposed method in calculating the Jacobian matrix and gradient matches that of the GPOPS, combined with a relatively short solution time.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-09T12:13:45Z
      DOI: 10.1177/09544100211066271
       
  • Numerical study of unsteady shock/mixing interaction in confined space

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      Authors: Zhangming Zha, Zhengyin Ye
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Unsteady shock wave enhancement is an effective technical approach to achieve air/fuel mixing under high speed and compressible conditions. However, unsteady shock/mixing interactions are always accompanied by complex wave structures, so the height of the combustion chamber will inevitably have a significant impact on shock waves and engine performance. In this regard, shock/mixing interactions in confined space are studied in this article by direct numerical simulation to investigate the effect of wall constraint on shock wave enhancement. Shock wave structure, total pressure loss, thickness of mixing layer, and turbulence intensity of flow field with different confinement degrees are calculated and compared. The results show that the unsteady shock wave can dramatically enhance the thickness of the mixing layer and the turbulence intensity, thus improving the mixing efficiency. In addition, as the wall constraint increases, the intensity of the shock wave and the total pressure loss increase; the flow field is more prone to Mach reflection. The average total pressure loss caused by steady shock wave and unsteady shock wave is essentially the same for an identical wall height, but the total pressure distortion caused by the unsteady shock wave is more substantial. Furthermore, the enhancements of mixing efficiency by the shock wave are also affected significantly by the degree of wall constraint; therefore, a suitable wall height needs to be determined in order to achieve the highest mixing efficiency.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-09T05:50:21Z
      DOI: 10.1177/09544100211043042
       
  • Improving experiment data process accuracy for axial compressors:
           Converting inter-stage data into meridional flow fields

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      Authors: Chenghua Zhou, Zixuan Yue, Donghai Jin, Jun Zhang, Liping An, Faxiang Lan, Xingmin Gui
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The total temperature and pressure are measured as inter-stage data in axial compressor experiments. Traditional diagnosing methods of 0-dimension (0D) or 1-dimension (1D) could lead to higher errors at hub sections without the presence of the radial equilibrium equation at stator leading edges, and 3-dimensional computational fluid dynamics can hardly provide reliable results for multistage compressors. In this paper, a fast method called “Diagnosis Using Inter-stage Data” (DUID) was developed to convert experiment data into meridional flow fields, which automatically satisfies the radial equilibrium equation and provides more accurate results for axial compressors. An aeroengine fan, a 3-stage compressor and a 6-stage compressor were used to validate the DUID. Their meridional flow fields, which cannot be observed directly in test rigs, were rebuilt. Results reveal facts that hub static pressures are approximately 15% lower than the traditional 0D/1D constant assumption. Though the stator models determine the loss ratio in a single stage, the DUID can avoid the model error amplification and be robustious for multistage compressors. And the generated flow field is sensitive to changes in the total temperature. Analyses of the experiment flow fields provide more quantitative and accurate references for subsequent modifications. In conclusion, using experiment inter-stage data, the DUID can rebuild meridional flow fields, which help to improve data processing accuracy.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-08T09:48:43Z
      DOI: 10.1177/09544100211063686
       
  • Effect of different radial skewed angles of reversed blade-angle slot
           casing treatment on transonic axial flow compressor stability

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      Authors: Haoguang Zhang, Feiyang Dong, Enhao Wang, Wenhao Liu, Wuli Chu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Single-channel unsteady numerical simulation was carried out on NASA Rotor 35 to study the influence of radial skewed angle of reversed blade-angle slot casing treatment (RBSCT) on the aerodynamic performance and stall margin of a transonic compressor. Moreover, the influence mechanism is explained by detailed flow field analysis. The radial skewed angles were set to +0°, +30°, +60°, and +75° in the research. The calculated result shows that stall margin improvement (SMI) generated by the slots is increased when the radial skewed angle is gradually increased. The SMI of 17.47% for the slots with +75° radial skewed angle is the biggest among the four RBSCTs. As for the design efficiency improvement (DEI), it is increased first and then decreased with the radial skewed angle increasing. RBSCT with +60°radial skewed angle achieves the greatest DEI of 1.11%. The flow field analysis shows that the radial momentum of the injected and sucked flows is improved with the increasing of radial skewed angle. The improvement can reduce the relative airflow angle of mainstream near the stall condition. Furthermore, the excessive radial skewed angle will increase the flow losses in the slots. Consequently, the design efficiency is reduced at +75°.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-04T07:34:31Z
      DOI: 10.1177/09544100211042322
       
  • Mean line aerodynamic design of an axial compressor using a novel design
           approach based on reinforcement learning

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      Authors: Yi Liu, Jiang Chen, Jinxin Cheng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper develops a novel design approach based on reinforcement learning, which can independently complete the mean line aerodynamic design process of the axial compressor. The approach combines Deep Deterministic Policy Gradient (DDPG) algorithm with mean line aerodynamic predicting program HARIKA to acquire the design experiences of the axial compressor. DDPG combines basic reinforcement learning algorithm with artificial neural networks to get continuous observation and give corresponding actions. After the specific modification of the DDPG, multi-objective optimization can be integrated into the design process. Under the guidance of this approach, the design and optimization processes of a 9-stage high-pressure axial compressor were completed without expert experiences. At the design point, the isentropic efficiency was 88.5% and the surge margin was 25%, which meets the requirement of the compressor’s efficiency and stability. And there was an increase of 13.4% and 22%, respectively, compared to the initial design. Moreover, through the analysis of the design results, the distributions of aerodynamic parameters conform to expert experiences. To verify the approach, traditional optimization methods, multi-island genetic optimization algorithm (GA), and multi-objective particle swarm optimization algorithm (MOPSO) were used to solve the same optimization problem. The DDPG optimized efficiency was 0.2% lower than the traditional optimization method, and the pressure ratio at the work point was, respectively, 0.6% and 2% higher than that of the MOPSO and GA, which proved the effectiveness of the new design approach. Furthermore, after training, this approach can give design results immediately near the specific design requirements, which is different from the traditional optimization methods. The new approach saved 93% evaluation steps compared to the GA in the −3% design point and finished the design process in 8 steps in the +3% design point, where GA failed to complete.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-04T06:47:20Z
      DOI: 10.1177/09544100211063115
       
  • Three-dimensional prescribed performance sliding mode guidance law for
           intercepting maneuvering target

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      Authors: Meng-chen Ma, Li-Guo Tan, Shen-Min Song, Yang-Liu Zhou, Ye-Jun Xu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article describes three-dimensional sliding mode guidance laws with prescribed performance. The proposed guidance laws can ensure that the line of sight (LOS) angle converges according to the prescribed performance, and the convergence rate, the steady-state error and the maximum overshoot can be preset in advance. By combining the LOS tracking error with the performance constraint function, a new error variable function is designed, and then the prescribed performance control problem is transformed into that of the boundedness of the error variable function. The key concept in this approach is to design a new sliding mode surface to ensure that the error variable function is bounded, so as to ensure that the system state converges according to the prescribed performance. Additionally, this article discusses the problem whereby the upper bound of the aggregate uncertainty, including the target information, is unavailable. An adaptive guidance law is presented for this scenario. Finally, simulations comparisons are conducted with other forms of guidance laws. Simulation results show that the guidance laws proposed in this article achieve effective performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-04T06:33:35Z
      DOI: 10.1177/09544100211044949
       
  • Numerical investigation of the influence of aerothermoelastic dynamic
           response on the performance of the three-dimensional hypersonic inlet

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      Authors: Kun Ye, Zhenghao Feng, Xiran Liu, Zhengyin Ye
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The influence of aerothermoelastic dynamic response on the performance of the three-dimensional hypersonic inlet is investigated in this paper. A dynamic aerothermoelastic analysis framework is developed. The reliability of the framework is verified. The effects of aerodynamic heating on the dynamic response, the effects of the aerothermoelastic dynamic response of the inlet on the flow field structure, and the performance parameters are studied. The results indicate that the static deformation of the leading edge structure is large while the vibration amplitude is small. Meanwhile, the vibration amplitude of the trailing edge structure is larger. The aerothermoelastic dynamic response changes the shock wave structure near the exit, strengthens the shock wave intensity, increases the length of the separated region, and changes the flow field of the exit. Simultaneously, the flow field structure also experiences obvious dynamic changes at different moments. The dynamic response increases the time-averaged flow coefficient, reduces the time-averaged total pressure recovery coefficient, and improves the time-averaged reverse pressure ratio. At the same time, the dynamic response leads to the fluctuation of performance parameters, especially the large fluctuation range of the reverse pressure ratio at the exit.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-04T05:38:00Z
      DOI: 10.1177/09544100211050754
       
  • Duffing–van der Pol nonlinear reduced-order model for explaining the
           phenomena and mechanism in pulsed jet flow separation control

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      Authors: Weiyu Lu, Guoping Huang, Yuxuan Yang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A two-equation nonlinear reduced-order model is established to describe the interaction between external periodic excitation from a pulsed jet and unsteady flow separation. This model, which is based on a 2D Navier–Stokes equation, the Stuart vortex row model, and the Stuart–Landau model, can approximately describe the typical phenomena occurring in pulsed jet flow separation control. These phenomena include the frequency-dependent, threshold, and lock-on effects, which are related to the frequency, intensity, and phase of excitation. Two indices, namely, the maximum Lyapunov exponent and the entrainment degree, are introduced to identify the mechanism of flow control via external periodic excitation. These indices are used to reflect the order degree and momentum transfer of the flow field. A comparison of the results of the model and those of a numerical simulation in a curved diffuser shows that the nonlinear reduced-order model is effective for qualitatively featuring the behavior of pulsed jet flow separation control. Moreover, the mechanism of pulsed jet flow separation control is explained via the model. Three aspects (i.e., flow instability, flow field ordering, and momentum transfer) are assumed to function together, resulting in an efficient flow control performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-03T02:59:21Z
      DOI: 10.1177/09544100211068911
       
  • Uncertain trajectory planning integrating polynomial chaos and convex
           programming

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      Authors: Yiting Tan, Wuxing Jing, Changsheng Gao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The present work explores the robust trajectory optimization scheme considering both the initial state disturbance and multiple constraints. An uncertain multi-constraint optimization model has been first established. Due to the existence of the stochastic disturbance, standard numerical trajectory planning algorithms cannot be directly applied to address the considered issue. Hence, based on the intrusive polynomial chaos expansion, we present a deterministic quantification for the stochastic state and constraints, so that the transformed optimization model becomes solvable for standard numerical optimization methods. To obtain the enhanced computational performance, an hp pseudo-spectral sequential convex programming procedure combined with a penalty function and backtracking search is proposed. This is achieved by discretizing and convexifying the nonlinear dynamics/constraints using hp quadrature collocation and successive linearization, respectively, and by adjusting the confidence region manually in the iteration. The simulation of a three-dimensional interception with the specific impact angle is conducted to verify the effectiveness. The simulation results show that the initial solutions are insensitive to the convex optimization, and the control commands generated by the proposed algorithm are effective against the initial state disturbance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-02T04:15:31Z
      DOI: 10.1177/09544100211065284
       
  • Robust adaptive attitude control of flexible spacecraft using a sliding
           mode disturbance observer

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      Authors: Umair Javaid, Ziyang Zhen, Yixuan Xue, Salman Ijaz
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A composite control scheme based on a disturbance observer is presented in this paper to deal with the attitude control problem of flexible spacecraft. Specifically, a sliding mode disturbance observer (SMDO) is developed to attenuate the unmodeled system dynamics, parameter uncertainties, and multiple external disturbances. The key feature of this approach is to relax the assumption imposed on disturbance to be constant or changing at a slow rate, which is a typical assumption in this class of problems involving a disturbance observer. Then, an exclusive adaptive integral sliding mode controller is combined with the SMDO to get the improved closed-loop control performance of the system. The underlying benefit of the proposed control scheme is improved robustness against time-dependent external disturbances and system model uncertainties. The stability analysis of the closed-loop system is provided using Lyapunov’s stability theory. Simulation results are provided to show the effectiveness of the proposed control scheme, especially in comparison with existing results.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-02T02:56:08Z
      DOI: 10.1177/09544100211055318
       
  • A novel quasi-dynamic guidance law for a dynamic dual-spin projectile with
           non-conventional, asymmetric roll constraints

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      Authors: James Norris, John Economou, Amer Hameed
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A novel quasi-dynamic guidance law (QDGL) is presented for a dual-spin projectile (DSP) with unconventional constraints on roll direction. A 7 degree-of-freedom (DOF) dynamic model is established and the projectile operational mechanism is presented with a description of how it is used to enact control. The QDGL is presented and a parametric study is conducted to show how the QDGL parameters affect the system response. A procedure of using batches of Monte Carlo simulations is described, to numerically compare the system response with different QDGL configurations. A genetic algorithm is then used to optimise both the innate system parameters and PID controller gains. The disturbance rejection capabilities of the optimal QDGL are then evaluated along with the performance against different target profiles. It was found that the GA optimised QDGL is able to provide satisfactory control capabilities against static and dynamic targets.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-01T08:08:11Z
      DOI: 10.1177/09544100211062021
       
  • Flight dynamics analysis of a small tandem helicopter considering
           aerodynamic interference

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      Authors: Dengyan Duan, Yujun Li, Zhiwei Ding, Jianbo Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The interference calculation is essential to the flight dynamic analysis especially for multi-rotors configurations. To analyze the flight dynamic characteristics of a small tandem helicopter precisely, a vortex method is utilized to obtain the aerodynamic interaction between the tandem rotors and the fuselage. Specially, the unsteady air loads and the wake of the rotors are developed using a lifting surface method and the viscous vortex particle theory, respectively, and the fuselage is modeled by the panel method to simulate the blocking effect on the rotors. Then the aerodynamic interference of the small tandem helicopter is analyzed under the conditions of different vertical or horizontal distance between the rear and front rotors. Subsequently, to save calculation time during flight dynamic analysis, a hybrid optimization trimming method combining the equilibrium optimizer and the improved delta method is proposed. At last, the flight dynamic analysis for the small tandem helicopter with different configurations are carried out and the results indicate that configuration in which the rear rotor is located higher than the front rotor and the one with larger longitudinal distance between tandem rotors are beneficial to increase the stability in lateral and longitudinal directions, respectively.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-28T10:41:41Z
      DOI: 10.1177/09544100211069418
       
  • An analytical investigation of transient imperfectly expanded turbulent
           jet

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      Authors: Amirreza Ghahremani, Mohammad Aramfard, Mohammad Hassan Saidi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Supersonic turbulent high-pressure jet flows, which are discharging in low-pressure quiescent ambient, are recognized as imperfectly expanded turbulent jet. Steady-state imperfectly expanded jet flow has been already studied analytically; however, the transient flow has not been thoroughly studied. In the present study, the transient imperfectly expanded jet flow with focus on fuel spray in combustion is investigated analytically employing two-step separation of variables method and Fourier-Bessel expansion. The results are validated using available experimental data. The effects of different parameters such as eddy viscosity and pressure ratio on the behavior of the jet are studied. Results show that increasing the eddy viscosity decreases the velocity magnitude and required time to reach fully developed jet. Increasing the pressure ratio almost linearly increases the required time to reach steady state. The density distribution which affects the combustion performance is reported for different axial and radial positions. In the transient region, tip penetration is obtained and validated with the experimental results in the literature, and the velocity profile at different times is presented. The simplicity and accuracy are key advantages of the developed method compared with the experimental and numerical methods. The analytical method proposed in the present research helps to understand the behavior of jet flows from transient to steady state condition without using expensive and time-consuming numerical or experimental techniques.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-26T11:36:12Z
      DOI: 10.1177/09544100221077465
       
  • Intake grille design for an embedded ventilation-and-cooling system in an
           aircraft

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      Authors: Bai-gang Mi, Heyuan Huang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An inlet grille typically needs to be installed at the inlet of the air intake of the ventilation-and-cooling system embedded in airborne electronic equipment to improve pneumatic stealth performance. Here, a typical flying wing model is used as a case study, and a computational fluid dynamics (CFD) simulation is performed. The flow resistance characteristics of the air intake of the opening of the ventilation-and-cooling system on a flat fuselage surface with and without an inlet grille are analyzed at different flow rates and Mach 0.25. The effects of the grille opening shape, diversion angle, thickness, aperture size, and hole shape on the flow resistance characteristics are investigated in detail. The grille is found to effectively guide airflow entry: although the flow resistance at the inlet is increased, the flow resistance at the inlet and outlet of the air intake is significantly reduced. The optimal developments of the outflow and flow resistance characteristics are obtained for a quadrilateral opening. The smaller the diversion angle is, the smoother the airflow entry, and the higher the quality of the internal airflow. The rectification, viscous resistance, and weight exhibit opposing trends with increasing thickness and must be comprehensively considered in designing an optimal scheme. A large-aperture grille ensures good flow patency at low flow rates, whereas a small-aperture grille can reduce flow perturbations and separation at high flow rates by smoothly guiding air into the intake. A grille with round holes has a better spanwise and chordwise balancing effect on the airflow and better flow resistance characteristics than a grille with diamond-shaped holes.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-26T09:24:58Z
      DOI: 10.1177/09544100211062810
       
  • A flexible method for geometric design of axial compressor blades

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      Authors: Jiong Yang, Bifu Hu, Yuan Tao, Jixing Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes a method for the geometric design of axial compressor blades. First, a novel approach for creating 2D blade sections is proposed, where each 2D blade section is obtained by imposing the defined thickness distribution along the camber line. The camber line of each 2D blade section is defined by specifying the angle change of each point on the camber line. In order to make this method applicable to a wider range of blade section design, the camber line of each section can be designed in several (usually 2 or 3) segments. It takes into account the change rule of blade section along the flow channel, which is the most concerned in the aerodynamic design, rather than the specific curve form of blade section. Then, the 2D blade sections are mapped to the corresponding arbitrary rotational flow surface. Finally, the 3D blade model is generated by lofting the blade sections in the flow surfaces. Some typical examples are presented. It shows that this method has good applicability and flexibility to realize the geometric design of multiple types of blades.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-24T06:56:46Z
      DOI: 10.1177/09544100211063078
       
  • Base drag estimation in suddenly expanded supersonic flows using
           backpropagation genetic and recurrent neural networks

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      Authors: Jaimon D Quadros, Thalambeti Prashanth, Sher A Khan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In recent years, base pressure management has gained a lot of industrial importance due to its applications in missiles and projectiles. For certain aerodynamic vehicles, the base pressure becomes a critical factor in regulating the base drag. That prompted the current work to develop input–output relationships for a suddenly expanded flow process using experiments and neural network-based forward and reverse mapping. The objective of forward mapping (FM) is to predict the responses, namely base pressure (β), base pressure with cavity (βcav), and base pressure with rib (βrib), for a known combination of flow and geometric parameters, namely Mach number (M), nozzle pressure ratio (η), area ratio (α), and length to diameter ratio (ψ). On the other hand, an effort is made to decide the optimal set of flow and geometric parameters for achieving the desired base pressure by reverse mapping (RM). Neural network-controlled backpropagation and recurrent and genetic algorithms have been employed to carry out the forward and reverse mapping trials. A batch mode of training was employed to conduct a parametric study for adjusting and optimizing the neural network parameters. Due to the requirement of massive data for batch mode training, the data required for training was achieved using the response equations developed through response surface methodology. Further, the forecasting performances of the neural network algorithms are compared with the regression models (FM) and among themselves (RM) through random test cases. The findings indicate that all evolved neural network (NN) models could make accurate predictions in both forward and reverse mappings. The results obtained would help aerodynamic engineers control various parameters and their values that affect base drag.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-24T03:15:24Z
      DOI: 10.1177/09544100211072594
       
  • Numerical simulation on interaction process between impact penetrator and
           lunar soil particles for lunar subsurface exploration

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      Authors: He Li, Yi Shen, Zongquan Deng, Qingliang Zeng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Unmanned in-situ exploration is an important technique to study the physical and mechanical parameters of lunar composition and evolution. The impact penetrator is an effective device for in-situ detection of the lunar soil profile at predetermined depth. Because of the lack of real lunar soil samples, it is very difficult to study and evaluate the performance of the impact penetrator. In order to truly reflect the interaction between the impact penetrator and lunar soil particles, a simulation model of the lunar soil body was established by means of discrete-element analysis, and the model parameters were matched and verified by the experimental method. Based on this model, the interaction behaviors between the penetrators with different head configurations and the lunar soil body were simulated. The stress field distribution in the lunar soil body and particle movement patterns during the penetrating process were revealed, which reflects the working principle and performance of the penetrator. The numerical simulation on the interaction process between the impact penetrator and lunar soil particles provides a feasible and effective method for the design and optimization of the penetrator, which will contribute to the development of lunar subsurface in-situ exploration technologies.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-23T06:51:23Z
      DOI: 10.1177/09544100211070866
       
  • Three-dimensional impact angles constrained integral sliding mode guidance
           law for missiles with input saturation

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      Authors: Tong Li, Hua-ming Qian
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes the three-dimensional impact angles constrained integral sliding mode guidance laws for the missile with the constraint of the input saturation. To solve the problem of the input constraint, an integral sliding mode surface is given for the first time by using the saturation function. The first three-dimensional integral sliding mode guidance law can solve the impact angle constraint and the target accelerations with known upper bound, while the second one can solve the impact angle constraint, input saturation, and the target accelerations with unknown upper bound simultaneously. Finally, numerical simulations are used to verify the effectiveness of the guidance laws.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-23T06:39:25Z
      DOI: 10.1177/09544100211072323
       
  • Disturbance observer backstepping sliding mode agile attitude control of
           satellite based on the anti-saturation hybrid actuator of the magnetorquer
           and magnetically suspended wheel

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      Authors: Javad Tayebi, Chao Han, Yuanjin Yu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a new anti-saturation strategy to avoid external singularity, improve reliability, and fast maneuvers of a satellite by combining the novel three-dimensional magnetically suspended wheel (3-D MSW) actuator and magnetorquer. The MSW is the preferred actuator for agile maneuvering compared to the traditional control moment gyro due to frictionlessness, low vibration, and long lifetime. The anti-saturation strategy includes 3-D MSW arrangement with pyramid configuration and three orthogonal magnetorquers. A steering law is designed to distribute control torque between actuators by calculating command tilt angles of the 3-D MSW and magnetic dipoles of the magnetorquer. A nonlinear disturbance observer backstepping sliding mode controller is designed to control the rotor shaft of 3-D MSW for agile maneuvers and desaturate it with the magnetorquer despite high-frequency disturbances. Finally, simulation results of attitude control based on anti-saturation hybrid actuators demonstrate the effectiveness and accuracy of agile maneuvers. Compared with usual steering laws, simulation outcomes confirm the proposed method and desaturate the 3-D MSW system when it experiences a maximum workspace and does not have extra angular momentum.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-23T03:48:19Z
      DOI: 10.1177/09544100211069699
       
  • Time-delay-locked dynamic mode decomposition for extracting flow patterns
           of compressor in experiment

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      Authors: Jiaqi Wang, Jin Chen, Moru Song, Guangming Dong
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Dynamic mode decomposition (DMD) is widely used in extracting the main features of high-dimensional nonlinear systems in computational fluid dynamics. However, it cannot be directly applied to real compressors due to the limitations of data acquisition over the entire flow field. In order to overcome this limitation, our paper proposes a time-delay-locked DMD algorithm. It combines the idea of phase locking, Hankel time-delay method, and DMD method. Based on it, the flow patterns are successfully extracted and the unsteady flow phenomena including rotating stall and rotating instability are explained as modal waves. Multi-peak spectrum nearly 1/2 BPF observed under off-design RI conditions is explained. In addition, multi-scale of rotating stall is analyzed and shock wave is captured.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-23T02:51:48Z
      DOI: 10.1177/09544100211069252
       
  • Modelling, analysis and experimental study of the prop-rotor of
           vertical/short-take-off and landing aircraft

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      Authors: Xiao Yang, Xiangyang Wang, Jihong Zhu, Wenhui Yan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The main objective of this work is to characterise the prop-rotor of V/STOL (Vertical/short-take-off and landing) aircraft in various operating conditions, especially in transition flight. To this end, a BET (Blade element theory) based analytic model/tool with a low computational cost has been built to predict the aerodynamic performance of the prop-rotor. This BET-based model can predict prop-rotor thrust, torque, normal force, and yaw moment as well as their corresponding 1P load (once-per-revolution load on the single blade) regarding oblique flow. This model is verified and shows good consistency with the wind tunnel experimental data and CFD simulation results. Furthermore, by using this BET model/tool, the effects of axial advance ratio, tilt angle and collective pitch angle on these component loads on the prop-rotor are explored. Moreover, the effects of these variables on the vibratory amplitudes of the 1P load on the single blade and 3P harmonic loads on the prop-rotor due to inclined flow are presented as well.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-23T01:35:18Z
      DOI: 10.1177/09544100211070157
       
  • Development of a novel autonomous space debris collision avoidance system
           for uncrewed spacecraft

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      Authors: Mayukh Sarkar, Shreya Barad, Ashray Mohit, Malaikannan G
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The objective of the study is to model a system which can effectively prevent the collision between space debris and spacecraft by robust design and algorithms of the system. The location and trajectory of the debris field at each and every instant are tracked with the help of image processing. The Voronoi diagram and Dijkstra’s algorithm are utilized to determine the alternate orbits for the spacecraft in order to avert the collision. The discrete subsystem, namely, orbit determination system, orbit maneuvering system, and reaction control system, is modeled and simulated using the Simulink platform. The collision avoidance system employs the most energy-efficient Hohmann maneuver to find the alternate orbits for spacecraft between circular orbits. The simulation results shown from the present work clearly evidences the effectiveness of collision avoidance. The present collision avoidance system always determines the safe and fuel economic trajectory for spacecraft independent of human interference.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-22T12:00:32Z
      DOI: 10.1177/09544100211072321
       
  • Sensitivity study of fiducial-aided navigation of Unmanned Aerial Vehicles

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      Authors: Amanda J Strate, Randall Christensen
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The possible applications and benefits of autonomous Unmanned Aerial Vehicle (UAV) use in urban areas are gaining considerable attention. Before these possibilities can be realized, it is essential that UAVs be able to navigate reliably and precisely in urban environments. The most common means of determining the location of a UAV is to utilize position measurements from Global Navigation Satellite Systems (GNSS). In urban environments, however, GNSS measurements are significantly degraded due to occlusions and multipath. This research analyzes the use of camera Line-of-Sight (LOS) measurements to self-describing fiducials as a replacement for conventional GNSS measurements. An extended Kalman filter (EKF) is developed and validated for the purpose of combining continuous measurements from an Inertial Measurement Unit (IMU) with the discrete LOS measurements to accurately estimate the states of a UAV. The sensitivity of the estimation error covariance to various system parameters is assessed, including IMU grade, fiducial placement, vehicle altitude, and image processing frequency.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-22T11:35:24Z
      DOI: 10.1177/09544100211067715
       
  • Research on the stability enhancement mechanism of multi-parameter
           interaction of casing treatment in an axial compressor rotor

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      Authors: Zhidong Chi, Wuli Chu, Ziyun Zhang, Haoguang Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The research on geometric parameters of casing treatment (CT) has always been a hot topic, yet the multi-parameter interaction is rarely studied. In order to gain better knowledge of the interaction mechanism of geometric parameters of CT, the experimental and numerical study based on the response surface method has been carried out in an axial compressor rotor. First of all, the statistical analysis based on the database of experimental and numerical results is presented to summarize the influence law of varied parameters on the stability enhancement. It was found that axial overlap, open area ratio, and their interaction had the most significant influence on the stability enhancement of CT. Subsequently, the interaction between axial overlap and open area ratio was analyzed by visualization flow field in details, which provided a deeper insight into stability enhancement mechanism of CT. It indicated that the mass flow and momentum dominated by injection and the suction effect played a key role for extending stability. With smaller open area ratio, it was difficult for the slots to manipulate and control the tip leakage flow or secondary tip leakage flow, resulting in the weak effect of CT on compressor performance. Finally, the underlying flow physics in the tip region and dominant region of CT has also been discussed to penetrate the essential reason of multi-parameter interaction.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-08T10:31:07Z
      DOI: 10.1177/09544100211063079
       
  • Effect of circumferential non-uniform tip clearance on the dynamic stall
           

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      Authors: Haoyang Xu, Jun Hu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, the single-stage compressor with circumferential non-uniform tip clearance is experimentally investigated under 180° total pressure distortion for the compressor characteristics and the dynamic stall process. In the special structure of the circumferential non-uniform tip clearance, different circumferential distortion areas are adopted to actively induce the stall. The maximum or minimum flow coefficient near the stall point occurs when the location where the rotor departs the distortion area is at the average tip clearance rather than the maximum or minimum tip clearance. Based on the time-frequency analysis regarding the dynamic stall process at different correspondences between the inlet distortion and the tip clearance, it is found that the rotating frequency of the stall cell that is independent of the location of the distortion area is slightly less than 50% rotor rotating frequency and the large-scale stall inception whose frequency is 4–8 times the rotor rotating frequency occurs. Besides the circumferential phase difference from 90° to 180° between the location where the disturbance occurs and the location where the rotor departs, the distortion area exists. According to the dynamic stall process, the stall interpretation model of circumferential total pressure distortion under the circumferential non-uniform tip clearance is established.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-08T05:54:08Z
      DOI: 10.1177/09544100211063164
       
  • Three-dimensional cooperative guidance law to control impact time and
           angle with fixed-time convergence

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      Authors: Hong-Xia Li, Hui-Jie Li, Yuan-Li Cai
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article proposes a new terminal cooperative guidance law to control both impact time and impact angle in three-dimensional engagement. The presented guidance law employs on and normal line-of-sight accelerations to control the impact time and angle together. Two parts are included in this guidance law, that is, the guidance laws with impact time constraint and impact angle constraint. The first is designed based on fixed-time consensus theory to fulfill the salvo attack of the target, and the second is developed based on fixed-time nonsingular fast terminal sliding mode control method to achieve the desired impact angles. The stability analysis of this guidance law based on Lyapunov theory is also presented in detail. Moreover, the maneuvering target can be intercepted successfully with the presented guidance law, and the fixed-time stability and less control energy are well ensured. Additionally, the effectiveness and applicability of the proposed guidance scheme are explicitly verified through simulation tests.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-05T05:30:11Z
      DOI: 10.1177/09544100211043093
       
  • Multi-objective surrogate model-based optimization of a small aircraft
           engine air-intake duct

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      Authors: Przemysław S Drężek, Sławomir Kubacki, Jerzy Żółtak
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Aviation industry is constantly striving for more efficient design processes in respect to optimal time, human and computational resources utilization. This implies a need for application of an approximation techniques enabling for fast responses generation with maintained level of results quality. This study focuses on an advancement of aerodynamic shape optimization process of a small aircraft engine intake system by introduction of a surrogate modelling step into the design loop. The multi-objective metamodel assisted optimization is carried out in order to reduce pressure losses along the engine intake duct and increase flow homogeneity at the engine compressor intake plane. Latin Hypercube Design method is utilized in order to sample the design space. A set of initial objective function evaluations is generated with application of Reynolds-averaged Navier–Stokes solver. The ensemble of samples is further used to train a Kriging-based surrogate model. The Efficient Global Optimization algorithm basing on the Expected Improvement function is employed to gradually increase the metamodel prediction quality by usage of sequential sampling technique. Finally, the optimal point predicted by the Kriging surrogate is validated against the high-fidelity model with usage of the Computational Fluid Dynamics code. The paper presents an application of the abovementioned methodology to the design process of the I-31T aircraft turboprop engine intake system. Proposed Kriging-based optimization workflow is utilized in order to reduce pressure losses and improve flow homogeneity in the engine air-intake duct.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-03T04:34:28Z
      DOI: 10.1177/09544100211070868
       
  • A multi-parameter stable-distribution-based protection levels calculation
           method for ground-based augmentation systems integrity assessment

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      Authors: Haiying Liu, Xiaozhu Shi, Hao Sun, Xiaolin Meng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The Protection Levels (PL) of Ground-Based Augmentation Systems (GBAS) are bounds of the positioning errors associated with given integrity levels. However, the practical Gaussian Overbounding Method (GOM) cannot describe the non-Gaussian nature of the error model such as “thick tail,” which makes PL tend to be overestimated. To overcome this problem, an error overbounding model based on stable distribution is proposed in this paper. Four stable distribution parameters are involved to accurately describe the GBAS ranging error. The weighted summation feature of the stable distribution is combined with the maximum likelihood estimation when calculating PL. Thus, it is possible to achieve a higher accuracy of PL under similar calculation complexity. In addition, this paper puts forward the Concept of Tightness (CoT) to describe the overbounding effect intuitively and quantitatively. In order to verify the effect of this method, multiple receivers are set to simulate the GBAS system, theyn the Stable Overbounding Method (SOM) is used to calculate the PL in two directions (Vertical and Lateral) under the hypotheses of H0 and H1. The CoT convincingly proves that the SOM has a better overbounding effect and improves the continuity of GBAS. It is evident that the multi-parameter SOM makes the overbounding of the protection level tighter and reduces the probability that the protection level is close to the Alarm Limit (AL), thus improving the accuracy of PL computing and the availability of GBAS systems.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-02T07:14:54Z
      DOI: 10.1177/09544100211063678
       
  • Simulation model for analysis and evaluation of selected measures of the
           helicopter’s readiness

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      Authors: Jarosław Ziółkowski, Jerzy Małachowski, Mateusz Oszczypała, Joanna Szkutnik-Rogoż, Jakub Konwerski
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A methodology of analysis and evaluation of the selected indices of the helicopter readiness used in the Polish Navy is presented in this paper. These objects are the multi-purpose helicopters of the Polish and Russian production, performing mainly the rescue tasks. A mathematical model was based on the source databases covering a period of 2 years, which were developed in the form of the multi-format MS Excel spreadsheets. While considering the operating environment and a specificity of the performed tasks, an event-based model of the operation process was proposed in this paper, which enables to evaluate selected indices of readiness. Due to the specificity of the individual types of renovations and repairs, the calculated measures of the readiness were enabled in a multi-faceted manner, that is, they were referred to three separate operating periods covering the current operating period, the entire (i.e. two-year) studying period including extended renovations and the entire studying period including extended renovations and repairs. A broader approach enabled to calculate the functional and technical indices of the readiness of the helicopter.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-31T12:05:47Z
      DOI: 10.1177/09544100211069180
       
  • Preliminary design and technology forecast synthesis for solar-powered
           high altitude aircraft

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      Authors: Petr Mukhachev, Daniil Padalitsa, Anton Ivanov
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      High altitude long endurance solar aircraft is a very attractive platform for applications ranging from remote sensing to telecommunication. In contrast to conventional aircraft, the operation of solar-powered one is highly dependent on available solar enengy, which imposes strong constraints on total takeoff mass, and, thus, energy balance becomes dependent on the season and latitude of planned operations. Despite tremendous success in many projects from Helios to Zephyr, energy balance at high altitudes is still not favorable in a range of latitudes and seasons. In this study, a design space for a solar-powered aircraft mission, constrained by its energy balance is explored. It is found that the tradeoff that should be made between seasonal and spatial capabilities for continuous flight of a solar-powered aircraft. The influence of key technologies on solar aircraft perpetual flight capabilities in different regions and seasons is identified. To do that, solar cell efficiency and energy storage specific energy are considered as design parameters in range of available forecasts. In the end, available technology forecasts are synthesized on the precision agriculture case to show which technological level is required to make 6 moths mission possible.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-27T11:20:15Z
      DOI: 10.1177/09544100211053753
       
  • High-precision numerical calculation method of solar radiation pressure
           force for wrinkled solar sails

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      Authors: Jie Zou, Dongxu Li, Jie Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Due to small magnitude of solar radiation pressure (SRP), the area-mass ratio of the solar sail should be large enough to obtain adequate thrust acceleration. Therefore, the membrane structure is usually adopted for solar sails. However, the membrane barely has out-of-plane stiffness; thus, it is necessary to apply in-plane tension on the membrane for maintaining the plane, which may result in wrinkles. The wrinkle will influence SRP force of solar sails. On the one hand, wrinkled regions of the sail are no longer flat, so the angle between the normal vector of the surface in wrinkled regions and the direction of sunlight differ from a flat sail. On the other hand, wrinkles may cause shadow when the solar sail is almost parallel to sunlight and the shadow region cannot generate SRP force. In this paper, the nonlinear buckling theory is used to propose a numerical calculation method to solve the problem of wrinkling analysis of solar sails with complex boundary. Then, a high-precision method for calculating SRP force of wrinkled solar sails is proposed, consisting of two parts: the infinitesimal element SRP force model and the wrinkle shading model. Numerical simulation result verifies the effectiveness of the wrinkling analysis method and the SRP force calculation method. Furthermore, according to calculation result, wrinkles have a certain influence on the SRP force of the solar sail, which will become significant when the solar sail gets parallel to sunlight.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-21T07:59:52Z
      DOI: 10.1177/09544100211063681
       
  • Propulsive and combustion behavior of hydrocarbon fuels containing boron
           nanoparticles in a liquid rocket combustor

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      Authors: Yushu Jin, Xu Xu, Xu Wang, Suyi Dou, Qingchun Yang, Lun Pan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Nano-sized energetic particle as fuel additives is of great significance for liquid hydrocarbon fuels that will exhibit high-density and high-calorific value in high-speed propulsion systems. An experimental investigation has been conducted to determine the propulsive and combustion behavior of hydrocarbon fuels containing boron nanoparticles. In this study, nano-sized boron particles with average diameter of 20 nm are added into the basic fuel JP-10 and quadricyclane, respectively. They are then referred as slurry fuels and burned in the rocket combustor using pure oxygen as the oxidizer. With a wide range of excess oxidizer coefficients, three parameters characterizing the propulsion performance are employed to evaluate the effect of boron nanoparticles on hydrocarbon fuels. It is found that the boron-based slurry fuel showed superior density specific impulse. It is increased by 1.18% and 1.44% when the addition of boron particles with 10% mass fraction are added into the basic fuel JP-10 and quadricyclane, respectively. Combustion depositions of the boron-based slurry fuel located at different positions are then collected for deep analysis by means of the energy dispersive spectrometer, X-ray diffractometer, and scanning electron microscope. Comprehensive microanalysis results demonstrate that boron particles first combine with the C-element in the hydrocarbon fuel to form the boron carbide with a reticular structure, and then the boron carbide oxidizes to form block-shaped boron oxide. However, the surface boron oxide hindered the further reaction of the internal boron carbide, which limits the energy release of the boron particles and ultimately leads to the unsatisfactory combustion efficiency of the slurry fuel.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-21T07:18:30Z
      DOI: 10.1177/09544100211066358
       
  • Accommodating the multi-state constraint Kalman filter for visual-inertial
           navigation in a moving and stationary flight

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      Authors: Arshiya Mahmoudi, Mahdi Mortazavi, Mehdi Sabzehparvar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      For more than a decade, the multi-state constraint Kalman filter is used for visual-inertial navigation. Its advantages are the light-weight calculations, consistency, and similarity to the current mature GPS/INS Kalman filters. For using it in an airborne platform, an important deficiency exists. It diverges while the object stops moving. In this work, this deficiency is accounted for, by changing the state augmentation and measurement update policy from a time-based to horizontal travel-based scheme, and by reusing the oldest tracked point over and over. Besides the computational savings, it works infinitely with no extra errors in full-stops and with minor error build up in very low speeds.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-14T06:35:08Z
      DOI: 10.1177/09544100211029742
       
  • Attitude-pendulum-sloshing coupled dynamics of quadrotors slung liquid
           containers

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      Authors: Kuo Zhu, Jie Huang, Sergey Gnezdilov
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Quadrotors suspended water containers may be used for fire-fighting services. Unfortunately, the complicated dynamics in this type of system degrade the flight safety because of coupling effects among the quadrotor attitude, container swing, and liquid sloshing. However, few effects have been directed at the attitude-pendulum-sloshing dynamics in this type of aerial cranes. A novel planar model of a quadrotor carrying a liquid tank under dual-hoist mechanisms is presented. The model includes vehicle-attitude dynamics, load-swing dynamics, and fluid-sloshing dynamics. Resulting from the model, a new method is proposed to control coupled oscillations among the vehicle attitude, load swing, and fluid sloshing. Numerous simulations on the nonlinear model demonstrate that the control method can reduce the undesirable oscillations, stabilize the quadrotor’s attitude, and reject the external disturbances. The theoretical findings may also extend to the three-dimensional dynamics of quadrotors slung liquid tanks, and other types of aerial vehicles transporting liquid containers including helicopters or tiltrotors.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-13T09:28:44Z
      DOI: 10.1177/09544100211068907
       
  • Study on the test load for the structural test of the flight-load
           condition of the external fuel tank for fixed-wing aircraft

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      Authors: Hyun-gi Kim, Sungchan Kim, Byung-Geun Ha
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this study, for the purpose of conducting the structural tests for the verification of structural soundness of the flight-load conditions of the external fuel tank for the fixed-wing aircraft, the flight load acting on the external fuel tank was converted to test load and the suitability of the converted loads was verified. The loads imposed on the external fuel tank were expressed as the combination of the inertial load (based on the acceleration in the translational direction) and the tangential direction inertial load (based on the angular acceleration of the moment). To calculate the test load, the transfer function table was generated by calculating the shear load and moment based on the unit load. For this purpose, a transfer function table was established by dividing the external fuel tank into a few sections and calculating the shear load and moment generated by the unit shear load and unit moment in each section. In addition, the test load for each section was calculated by computing the established transfer function table and flight-load conditions. However, in actual structural tests, it is often not possible to impose a load in the same position as the point at which the shear load and moment are calculated. For this reason, the actual test-load positions had to be determined and the calculated test loads were redistributed to those positions. Then, the final test load plan was established by applying a whiffle tree to increase the efficiency of the test while also making it easier to apply the actuators. Finally, the suitability of the established test load plan was confirmed by comparison with the flight-load conditions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-11T10:11:05Z
      DOI: 10.1177/09544100211062809
       
  • Suboptimal control law for a near-space hypersonic vehicle based on
           Koopman operator and algebraic Riccati equation

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      Authors: Peichao Mi, Qingxian Wu, Yuhui Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a novel suboptimal attitude tracking controller based on the algebraic Riccati equation for a near-space hypersonic vehicle (NSHV). Since the NSHV’s attitude dynamics is complexly nonlinear, it is hard to directly construct an appropriate algebraic Riccati equation. We design the construction based on the Chebyshev series and the Koopman operator theory, which includes three steps. First, the Chebyshev series are considered to transform the error dynamics of the NSHV’s attitude into a polynomial system. Second, the Koopman operator is used to obtain a series of high-dimensional linear dynamics to approximate each of the polynomial system’s vector fields. In this step, our contribution is to determine a well-posed linear dynamics with the minimal dimension to approximate the original nonlinear vector field, which helps to design the control law and analyze the control performance. Third, based on the high-dimensional dynamics, the NSHV’s attitude error dynamics is separated into the linear part and the nonlinear part, such that the algebraic Riccati equation can be constructed according to the linear part. Then, the suboptimal error feedback control law is derived from the algebraic Riccati equation. The closed-loop control system is proved to be locally exponentially stable. Finally, the numerical simulation demonstrates the effectiveness of the suboptimal control law.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-11T09:44:45Z
      DOI: 10.1177/09544100211045594
       
  • Experimental study on the aerodynamic influence of purge flow in a turbine
           cascade with different mainstream incidence angles

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      Authors: Zhao Lianpeng, Ma Hongwei
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Demand for high reliability and long life of modern turbine requires that turbine components should be cooled adequately. The cooling flow purged into the rotor-stator disk cavity will inevitably interact with the mainstream. The current paper mainly focuses on the aerodynamic influence of cooling flow on the secondary flows in the mainstream. Both particle image velocimetry and blade wall pressure measurement were utilized to study the flow field within the turbine blade passage under different mainstream incidence angles and purge flow rates. The purge flow was found to promote the development of the passage vortex by inducing vortices which can enhance the vorticity of the passage vortex. In addition, the mainstream incidence angle also has an impact on the development of the passage vortex through affecting the blade loading and the horseshoe vortex. Furthermore, the transient results demonstrate that the time-averaged vortex is the superposition of large number of transient vortices, and the purge flow causes more transient vortices with large size and high strength.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-11T09:16:59Z
      DOI: 10.1177/09544100211063685
       
  • Research on compact propulsion system dynamic model based on deep neural
           network

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      Authors: Juan Fang, Qiangang Zheng, Haibo Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The on-board dynamic model is the basis of numerous advanced control technologies for modern aero-engine, and its accuracy and real-time performance are two crucial indicators. Since the simulation accuracy declines with the deviation from the ground point of the conventional compact propulsion system dynamic model (CPSDM), an improved CPSDM (ICPSDM) based on deep neural network is proposed in this paper. First, the K-means algorithm is utilized to get the sampling point, and the engine simulation data is collected in the cluster centers. Then, the batch normalize deep neural network (BN-DNN) is applied to build the ICPSDM, which can shorten the training time tremendously. The simulation results show that, in the same simulation environment, the accuracy of turbine inlet temperature T4, fan surge margin SMc, thrust F, and specific fuel consumption SFC calculated by ICPSDM are 11.04, 3.17, 1.89, and 1.98 times of CPSDM, respectively, at off-design point, and the real-time performance of ICPSDM is more than 30 times faster than the component-level model.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-04T02:46:11Z
      DOI: 10.1177/09544100211064387
       
  • Numerical studies on modeling the near- and far-field wake vortex of a
           quadrotor in forward flight

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      Authors: Joshua C Nathanael, Chung-Hung John Wang, Kin Huat Low
      First page: 1166
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The operation of Unmanned Aerial Systems (UAS) is expected to keep increasing in the future with its rapid advancement and ever-expanding applications. One of the safety measures that need to be put into place for safe UAS operations is separation requirements. This article presents the results from flow simulations of quadrotor propellers using the Overset method in ANSYS Fluent 19.2 and the Virtual Blade Model (VBM) method in OpenFOAM as part of ongoing work to establish a wake vortex–based safe separation distance for UAS operations. The near-field flow simulation using the Reynolds-averaged Navier–Stokes turbulence model was validated with mesh convergence and turbulence model studies and verified with simulation and experimental data in the literature to ensure that the propeller simulation methods could generate a realistic near-field flow of multi-rotor UAS in forward flight. The far-field flow simulation using the Large Eddy Simulation turbulence model was validated with a mesh convergence study by calculating and comparing the circulation strength of the vortices in the far-field flow of each mesh setup but not verified due to a lack of existing experimental data.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-01-25T11:09:24Z
      DOI: 10.1177/09544100211029074
       
  • Effect of upper surface shape on waverider performances

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      Authors: Chuanzhen Liu, Junwu Tian, Peng Bai, Qing Shang
      First page: 1239
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Waveriders are of high lift-to-drag (L/D) ratio in hypersonic states; however, low volume of loading limits its application in practical engineering significantly. Raising the upper surface is a method to increase the volume space for waveriders, and this article studies the effect of the upper surface shape on the aerodynamic performances based on a single swept waverider configuration. Cubic polynomials were employed to construct the upper surface to replace the freestream-traced surface, and 2 parameters, the trailing edge thickness and inclination angle of head, were extracted as design variables. Analyzing the flow field using computational fluid dynamics techniques, raising the upper surface only had effect on the aerodynamic performance from the upper surface, but nearly no effect on the lower surface, and thus the design of upper and lower surfaces can be decoupled. As the trailing edge thickness and inclination angle of head increase, the volume of waveriders grows rapidly, while the loss in L/D ratio is limited. Compared with expanding the lower surface, raising the upper surface yielded better aerodynamic performances. The results indicate that raising the upper surface is a feasible and efficient approach to increase the loading volume of the waverider and hence promote its application in engineering.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-02-24T03:53:50Z
      DOI: 10.1177/09544100211029454
       
  • New methodology for flight control system sizing and hinge moment
           estimation

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      Authors: Carlos Cabaleiro de la Hoz, Marco Fioriti
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Flight control surfaces guarantee a safe and precise control of the aircraft. As a result, hinge moments are generated. These moments need to be estimated in order to properly size the aircraft actuators. Control surfaces include the ailerons, rudder, elevator, flaps, slats, and spoilers, and they are moved by electric or hydraulic actuators. Actuator sizing is the key when comparing different flight control system architectures. This fact becomes even more important when developing more-electric aircraft. Hinge moments need to be estimated so that the actuators can be properly sized and their effects on the overall aircraft design are measured. Hinge moments are difficult to estimate on the early stages of the design process due to the large number of required input. Detailed information about the airfoil, wing surfaces, control surfaces, and actuators is needed but yet not known on early design phases. The objective of this paper is to propose a new methodology for flight control system sizing, including mass and power estimation. A surrogate model for the hinge moment estimation is also proposed and used. The main advantage of this new methodology is that all the components and actuators can be properly sized instead of just having overall system results. The whole system can now be sized more in detail during the preliminary design process, which allows to have a more reliable estimation and to perform systems installation analysis. Results show a reliable system mass estimation similar to the results obtained with other known methods and also providing the weight for each component individually.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-29T03:13:33Z
      DOI: 10.1177/09544100211063110
       
  • Research on rolling stability of the flexible waverider based on
           computational fluid dynamics/computational structural dynamics/rigid body
           dynamics coupling methodology

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      Authors: Shang Yiming, Hua Ruhao, Yuan Xianxu, Tang Zhigong, Wang Zhongwei
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The shape of hypersonic aircrafts represented by waveriders is becoming more slender and flatter, thereby greatly reducing the structural rigidity. This innovation is applied to satisfy the demand of long-range flight. The rolling stability of the waveriders is poor due to the slender shape. Therefore, the effect of the elastic deformation on the rolling stability cannot be ignored. The effect of the elastic deformation on the stability of rolling and forced pitching/free rolling coupling motions of the waveriders is studied through computational fluid dynamics (CFD)/computational structural dynamics (CSD)/rigid body dynamics (RBD) coupling methodology. Comparison results of numerical simulation indicate that the elastic deformation of the structure increases the local angle of attack, thereby enhancing the static stability of the waveriders. The rolling motion of the waveriders changes from point attractor to periodic attractor when the vibration velocity due to elastic deformation is considered. The rolling oscillation frequency of the flexible model is higher than that of the rigid model. For the forced pitching/free rolling motion, stability theory based on the rigid body hypothesis is unsuitable when the elastic effect is taken into consideration.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-28T05:54:17Z
      DOI: 10.1177/09544100211059630
       
  • Recent advances in active fault tolerant flight control systems

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      Authors: Muhammad Sohail Khan Raja, Qasim Ali
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The Flight Control System (FCS) is considered as the brain of an aerial vehicle. It is a mechanism through which pilot’s commands are transferred to the actuators of the aircraft control surfaces. In order to ensure safety and increase reliability of aerial vehicles, development of fault tolerant FCSs has been the focus of research community for past few decades. Fault tolerant ability enables an aircraft to maintain satisfactory performance even in the state of a fault. Fault Tolerant Control Systems (FTCS) are categorized as passive and active control systems. Passive FTCS are designed to mitigate the effects of certain known faults. These faults can be related to sensor failure, actuator failure, or system component failure. On the other hand, active FTCS contain a controller reconfiguration mechanism, whereby, they can adjust the controller input online to mitigate the effects of the faults. In this way, they can accommodate complicated and versatile faults as compared to their passive counterparts. This paper presents a review of significant research during last decade in active fault tolerant control with applications to FCSs. A review of state-of-the-art works in this domain has also been presented. Upon review, these state-of-the-art research interests have been categorized into respective categories. Furthermore, research works have been cataloged based on their technology readiness levels. Based on these reviews, future research directions have also been highlighted.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-28T05:52:03Z
      DOI: 10.1177/09544100211062812
       
  • An improved prognostics model with its application to the remaining useful
           life of turbofan engine

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      Authors: Jia-Jun He, Yong-Ping Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Machinery prognostics play a crucial role in upgrading machinery service and optimizing machinery operation and maintenance schedule by forecasting the remaining useful life (RUL) of the monitored equipment, which has become more and more popular in recent years. The safety of aviation is one of the issues that people are most concerned about in the field of transportation, since it might cause disastrous loss of life and property once accident happened. The turbofan engine is an important part of the aircraft that provides thrust for plane. With aging, the turbofan engine becomes prone to failures. As a result, it would be worth studying prognostics in turbofan engine to improve the reliability of machinery and reduce unnecessary maintenance cost. Recently, a data-driven prognostics modeling strategy called the classification of predictions strategy (CPS) was proposed, in which the continuous signal and the discrete modes of an actual system come together to achieve RUL estimation. However, machine health states measured from classification rarely have just one potential situation, and this strategy cannot determine whether the fault occurs or not by a certain probability which comes closer to reality. Moreover, since there is no information and prior knowledge of prognostics application, it is hard to obtain the probability of various situations from raw measured data. Hence, based on previous work, this paper proposes an improved prognostics modeling method named the classification of predictions strategy with decision probability (CPS-DP), whose key innovations mainly include three parts: (1) decision probability process (DPP) where each step of multi-step prediction obeys geometric distribution and can judge whether the failure state occurs using the decision probability; (2) decision probability calculation (DPC) algorithm, which is first proposed by this paper and can calculate the values of decision probability without prior knowledge of prognostics application; and (3) withdrawal mechanism optimizer (WMO), which is specially designed to compensate for the shortcomings of DPP and further enhance the performance of the prognostics model. In brief, first, CPS is used to build a basic prognostics model to acquire RUL estimation results, in which the information applied to find the probability has been contained. Later, the mean of RUL estimation errors is figured from the results, which is further employed to calculate the probability using DPC algorithm. Then, CPS-DP can be achieved by means of integrating two parts: DPP and CPS. Furthermore, to further improve the performance, WMO is utilized to optimize CPS-DP with rolling back predictions. Ultimately, an enhanced prognostic model based on CPS-DP is set up through uniting CPS, DPP, and WMO. To validate the proposed method, experimental results on the turbofan engine in 2008 prognostics and health management competition are investigated.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-24T11:52:13Z
      DOI: 10.1177/09544100211050432
       
  • Manuscript title: Effect of spanwise groove on the dynamic stall
           characteristics of an airfoil

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      Authors: Rajesh Yadav, Aslesha Bodavula
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Numerical simulations are conducted to investigate the effect of triangular groove on the dynamic stall characteristics of a NACA 0012 airfoil at a Reynolds number of 135,000. The right-angled triangular grooves are placed at either 10%, 25%, or 50% chord locations on the suction and have depths of 0.025c and 0.05c, measured normal to the surface of the airfoil. The solutions that are second order accurate in time and space are obtained using pressure-based finite volume solver and the 4-equation transition SST turbulence model viz. γ- Reθt is used to predict transition and viscous stresses accurately. The airfoil is in harmonic pitch motion about its quarter-chord with a maximum circular frequency of 18.67 rad/s. The results suggest that the presence of a groove, except for the deeper grove at 0.5c, quickens the dynamic stall, but with smaller rise in Cl,max and a less severe fall in lift at the stall. The mean Cl value during the downstroke is improved by up to 8% for the deeper groove at 0.25c, reducing the hysteresis in lift significantly. The grooves at 0.1c, 0.25c, and 0.5c also reduce the drag by 4%, 7%, and 9% during a complete cycle, with subsequent improvements of 54%, 69%, and 63% in the l/d ratio. The current finding can be thus used to enhance the performance of flapping wing MAVs, helicopter rotors, and wind turbine blades as these applications encounter the dynamic stall phenomena frequently.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-22T10:16:42Z
      DOI: 10.1177/09544100211065277
       
  • Nonlinear combustion instability analysis of a bluff body burner based on
           the flame describing function

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      Authors: Yipin Lu, Yinli Xiao, Juan Wu, Liang Chen
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Lean premixed combustion is a common form of combustion organization in power equipment and propulsion systems. In order to understand the dynamic characteristics of lean premixed flame and predict and control its combustion instability, it is necessary to obtain its flame describing function (FDF). Based on the open source CFD toolbox, OpenFOAM, the dynamic K-equation model, and the finite rate Partially Stirred Reactor (PaSR) model were used to perform large eddy simulations (LES) of lean premixed combustion, and the response of the unsteady heat release rate to single-frequency harmonic disturbances was studied. The response of the unsteady heat release rate was characterized by the FDF, and the response of the unsteady heat release rate to the two-frequency harmonic disturbance was studied. The results show that the quantitative heat release rate response and flame dynamics have very proper accuracy. In the single-frequency harmonic disturbance, as the forcing frequency increases, the curling behavior of the flame surface and the instantaneous vortex structure change; the nonlinear kinematics effect is manifested by the entrainment of the vortex. At lower forcing frequencies, the heat release response changes linearly with the increase of forcing amplitude; at intermediate frequencies, the heat release response exhibits obvious nonlinear behavior; at high frequencies, the heat release response to amplitude changes decreases. The introduction of the second harmonic disturbance will significantly reduce the response range of the total heat release rate and make the combustion more stable.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-10T03:16:07Z
      DOI: 10.1177/09544100211044021
       
  • Effect of flat wall length on decay and shock structure of a supersonic
           square wall jet

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      Authors: Venkata Satya Manikanta Tammabathula, Venkata Sai Krishna Ghanta, Tharaka Narendra Sridhar Bandla
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Experiments were conducted to find the effect of wall length on the decay behaviour and shock structure of a supersonic wall jet issuing from c-d nozzle of the square-shaped exit. A straight flat wall of width same as the side length of the square was attached to the lip of the nozzle such that the leading edge of the wall and the side of the square aligned properly which allowed the supersonic jet to graze past the flat wall. Experiments were conducted with five different wall lengths, that is, [math] = 0.5, 1, 2, 4 and 8. Wall pressure measurements were made from leading edge to the trailing edge of the wall along its centreline. Schlieren flow visualization of the jet flow over the wall for the different wall lengths revealed the shock pattern and the effect of the wall length on the shock structure. The shock structure and jet deflection were significantly affected due to the presence of the wall. There was an upward jet deflection for [math] up to [math] whereas a downward jet deflection was observed for [math]. Noticeable changes in the shock structure were observed for the wall lengths up to 2Dh. The wall length also significantly affected the jet decay characteristics and supersonic core length. Maximum enhancement in jet decay and maximum reduction in supersonic core length resulted when the wall length was [math]. However, when the wall length was increased to [math], there was a significant reduction in jet decay and a recovery of [math]. Presence of wall always resulted a reduction in Lsc irrespective of wall length. The wall effect was to induce a more precipitous pressure drop closer to the nozzle exit, and a more gradual drop farther from it for [math]> [math].
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-06T03:27:39Z
      DOI: 10.1177/09544100211058016
       
  • Kalman filter identification method for micro-vibration transfer paths of
           satellites

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      Authors: Yan Shen, Yang Xu, Xiaowei Sheng, Xianbo Yin
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Micro-vibrations on-board a satellite have degrading effects on the performance of certain payloads like observation cameras. The major sources of vibrations include momentum wheels, solar array drives, other rotary mechanical equipment, etc. These vibrations result in loss of the pointing precision and image quality of the payload through intricate transfer paths. To improve the accuracy of a satellite system with many vibration sources and complex transfer paths, it is necessary to determine the main transfer path of vibration. In this study, a path identification method is proposed and applied to the transfer system from the momentum wheel to the camera mount. First, the observer/Kalman filter identification (OKID) algorithm is used to acquire the state-space equation of each path subsystem. Then, the subsystem order is obtained based on the slope of the singular entropy increment. In the next phase, combined with the measured disturbance force of the momentum wheel, the displacement response of the target point is predicted. Finally, the dominant transfer path of vibration is achieved by calculating the vibration contribution of each path to the response point. The results indicate that the dominant transfer path is the axial path of the horizontal momentum wheel, which contributes to the vibration of the camera mount at most. Effective vibration reduction measures should be taken to this path to suppress the vibration signal. In comparing the identified displacement response with the finite element response of the camera mount under different noise conditions, the correlation coefficients are>0.85, which proves the accuracy and anti-noise capability of the identification method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-06T03:19:59Z
      DOI: 10.1177/09544100211053306
       
  • Impact angle guidance law to prevent the detection degradation of a seeker

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      Authors: Jun-Yong Lee, H Jin Kim
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An impact angle control guidance (IACG) law applicable to a homing missile equipped with a strapdown imaging seeker is investigated against a stationary target. Given an impact angle constraint, usually a detour is generated and the change of the look angle is inevitable. A rapid change of the look angle can cause a fast relative target motion in the seeker’s image plane, which can lead to a motion blur effect. The main contribution of the paper is that an IACG law is designed to minimize the look angle rate to prevent the loss of the target signal. Based on the variational approach, the optimal look angle rate that satisfies the impact angle constraint is derived, and the guidance law is designed to follow the optimal look angle rate. Using various weighting functions, a guidance law that has low sensitivity to the initial condition is also developed. Numerical simulation supports the performance of the guidance law. The result illustrates that the proposed guidance law reduces the rate of look angle in comparison with other IACG laws.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-06T01:53:13Z
      DOI: 10.1177/09544100211044036
       
  • Static roughness element effects on protuberance full-span wing at micro
           aerial vehicle application

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      Authors: Hossein Jabbari, Mohammad Hassan Djavareshkian, Ali Esmaeili
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Although the tubercle wings provide good maneuverability at post-stall conditions, the aerodynamic performance at pre-stall angles is threatened by forming a laminar separation bubble at the trough section of the tubercle wing; consequently, the flight endurance and range are reduced. In the present study, the idea of passive flow control is introduced by using the distribution of static roughness elements on a full-span wing with a sinusoidal leading edge. Initially, the effect of roughness element length, height, and its location are studied at a pre-stall angle (16-degree). Their effect on the laminar separation bubble and vortex shedding formed behind the wing are also investigated. The Reynolds number is assumed to be equal to [math] which is in the range of critical Reynolds number and matches to the micro aerial vehicles application. An improved hybrid model, improved delay detached eddy simulation IDDES, has been used to model the flow turbulence structure. In the extended transition region at low Reynolds numbers, the roughness bypassed the instability. Consequently, roughening the surface of the aerofoil increased the boundary layer’s flow momentum, making it more resistible to adverse pressure gradients. By suppressing the bubble, the static roughness element led to pre-stall flow control, which saw an increase in lift coefficient, [math], and a decrease in drag coefficient, [math]. The results have been demonstrated that the aerodynamic performance, [math], has been improved approximately 22.7%, 38%, and 45% for [math], and [math], respectively. The optimal arrangement of static roughness elements could decline the size of the vortices and strengthen the cores associated with them. This claim can be interpreted with the vortex shedding frequency.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-05T03:57:52Z
      DOI: 10.1177/09544100211049932
       
  • Severity assessment of aircraft engine fan blades under airborne collision
           of unmanned aerial vehicles comparable to bird strike certification
           standards

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      Authors: Mohd Hasrizam Che Man, Hu Liu, Kin Huat Low
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Airborne drone collision on commercial manned aircraft has received extensive awareness due to the increasing drone operations in the restricted airspace. In addition, the bird strike certification for aircraft engines is likely to be inadequate for a drone collision with identical kinetic energy due to the difference in damage levels. Thus, it is important to understand and compare the risk between drones and bird strikes. This study aims to understand the damage severity from bird and drone strikes on the manned commercial aircraft engine. The finite element method (FEM) simulation is adopted to obtain the damage of engine fan blades under the drone collision and bird strikes at different collision positions. The Lagrangian and smoothed-particle hydrodynamics approaches are employed for the drone and bird simulations, respectively. In addition, three different drone and bird weight categories were considered in this study, namely, small, medium, and large, to investigate the effect of kinetic energy on the damage of fan blades. Results from the FEM simulation demonstrated that the damage of the engine fan blades due to drone collisions were more severe when comparing bird strikes of the same weight category. The damage severity level was proposed based on the damage of engine fan blades. In the event of a drone ingestion, the damage severity level assists in the identification of potential damage to engine fan blades and its performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-12-01T10:06:23Z
      DOI: 10.1177/09544100211044909
       
  • Online collision avoidance trajectory planning for spacecraft proximity
           operations with uncertain obstacle

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      Authors: Run-de Zhang, Wei-wei Cai, Le-ping Yang, Cheng Si
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The spacecraft relative motion trajectory planning is one of the enabling techniques for autonomous proximity operations, especially in the increasingly complicated mission environments. Most traditional trajectory planning methods focus on improving the performance criteria in the deterministic conditions, whereas various uncertain elements in practice would significantly degrade the trajectory performance. Considering the uncertainties underlying the collision avoidance constraints, this paper suggests a model predictive control based online trajectory planning framework in which the obstacle information in higher-precision would be consistently updated by the onboard sensor. To improve the computational efficiency of the online planning framework, the rotating hyperplane (RH) technique is utilized to transform the nonlinear ellipsoidal keep-out zone constraints into convex formulations. And the concept of rotation window is introduced to eliminate the unexpected mismatch between the spacecraft motion and hyperplane rotation in the conventional RH method, which in sequence improves the RH method’s capability for multiple obstacle avoidance problem. Moreover, a three-dimensional (3-D) extension strategy is proposed to simplify the computation procedure when applying the RH method for a 3-D collision avoidance problem. Numerical simulations are carried out to validate the performance of the proposed online trajectory planning framework in addressing the uncertain collision avoidance constraints.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-11-29T03:39:08Z
      DOI: 10.1177/09544100211056164
       
  • Smith predictor compensation and fuzzy incremental control for delay of
           space docking hardware-in-the-loop simulation system

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      Authors: Simiao Yu, Junwei Han, Wenming Zhang, Dongmei Xu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Hardware-in-the-loop (HIL) simulation for space manipulator docking is an important means to simulate real space docking on the ground. The HIL simulation system in this paper utilizes the contact force measured by force sensor to calculate the dynamics of the mechanisms, and the docking process is simulated by the parallel robot. The measurement delay of force sensor and dynamic response delay of the parallel robot are inevitable, which not only affect the accuracy of simulation but also lead to the instability of the HIL simulation system. The traditional first-order phase compensation is the most commonly used force sensor compensator; but when the force changes with a high frequency, its compensation effect becomes bad, which will lead to the divergence of the HIL simulation system. Most control methods of the parallel robot are based on the model of the parallel robot, but the forces of the parallel robot are complex during the docking process, and the system parameters, motion frequency, and dynamic response characteristics are time-varying; thus, it is difficult to design the controller based on the model. In this paper, the Smith predictor compensation (SPC) method and fuzzy incremental control (FIC) method are utilized to decrease the delays of the force sensor and parallel robot, respectively. The effectiveness of the Smith predictor compensation and fuzzy incremental control method in reducing the delay of the HIL system and in improving the stability of the system is verified by simulation and experiment; compared with the traditional first-order phase compensation and proportional-integral-differential control methods, the advantages of the proposed methods are illustrated. The research in this paper provides an important technical means for accurately simulating the real docking process.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-11-25T06:10:50Z
      DOI: 10.1177/09544100211053305
       
  • Straight-line path-following control for roll-out phase of the
           equipped-skid aircraft

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      Authors: Taotao Liang, Qiaozhi Yin, Xiaohui Wei
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The paper deals with straight-line path-following control design for the aircraft equipped with skid landing gears. First, a simple yet accurate on-ground aircraft model is established, which takes into account the effects of the aerodynamic and ground forces. To improve the directional stability of the aircraft during the roll-out phase, a novel skid with variable friction coefficients is proposed. Second, the path-following problem is converted to the attitude control problem by constructing a guiding vector field that generates the commanded course, and then an improved error function is proposed to manage the trade-off between the convergence rate and the strong lateral maneuvers. To achieve a good performance in path following, the incremental nonlinear control allocation is applied to make full use of three available actuators (nose wheel, variable friction skid, and rudder). The expected path here is the runway centerline so as to avoid runway excursions. Finally, the effectiveness and robustness of the path-following control are validated on different initial conditions. Results show that the proposed skid structure and control scheme are propitious to enhancing the resistance to crosswind. Moreover, the maximum lateral displacement during the path-following process decreases, especially in the low-speed region.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-11-23T07:07:08Z
      DOI: 10.1177/09544100211050129
       
  • Robust UKF-based filtering for tracking a maneuvering hypersonic glide
           vehicle

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      Authors: Jingshuai Huang, Hongbo Zhang, Guojian Tang, Weimin Bao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To track a non-cooperative hypersonic glide vehicle (HGV) without any precise information, an approach to the state estimation is presented based on a robust UKF-based filter (RUKFBF) in this paper. The HGV has an uncertain reentry motion because of unknown maneuvers which is a primary factor leading to degradation of tracking accuracy. Aiming at enhancing accuracy, the strong tracking algorithm (STA) is introduced to addressing the model error caused by a bank-reversal maneuver of HGV. Furthermore, the Huber technique is employed to deal with possible measurement model errors. In the RUKFBF, mutual interferences are suppressed between the STA and the Huber technique via two strategies. The one is that the calculation of the fading factor in the STA adopts an unmodified measurement noise covariance, and the other one is that two judgment criteria are proposed to limit large fading factors in the presence of measurement model errors. To simulate real tracking scenarios, the RUKFBF is tested through tracking a HGV trajectory considering a practical guidance strategy. Simulation results demonstrate the effectiveness of the RUKFBF in the presence of model errors and the observability of the estimated state.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-11-20T07:21:50Z
      DOI: 10.1177/09544100211051106
       
  • Parametric study on active flow control of a transonic axial compressor
           rotor using endwall synthetic jet

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      Authors: Guang Wang, Wuli Chu, Haoguang Zhang, Zhentao Guo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      High-load axial compressor is the mainstream of current compressor design and development. In order to improve the aerodynamic performance of high-load axial compressor, an active flow control method in which a synthetic jet is applied to the endwall is proposed. Taking the transonic axial compressor NASA Rotor 35 as the research object, using a single factor analysis method, the influence of five different excitation positions, three different excitation frequencies, and three different jet peak velocities on the aerodynamic performance of the compressor was studied in turn, and obtained the influence law of the endwall synthetic jet excitation parameters. The results show that all three parameters have important effects on the performance of the compressor. Among the excitation parameters studied in this paper, there is an optimal excitation position of 25% Ca. When excited at this position, the flow margin of the compressor is expanded the most. On the basis of maintaining the optimal excitation position and the maximum jet peak velocity, the calculation results found that the jet frequency has little effect on the compressor’s near stall flow rate, but has a great impact on the total pressure ratio and efficiency. The pressure ratio and efficiency increase with the increase of the excitation frequency. However, there seems to be a threshold of the excitation frequency. Only when the excitation frequency is greater than the threshold can the total pressure ratio and efficiency be higher than the prototype compressor. The jet peak velocity has the smallest impact on the compressor performance. Based on the optimal excitation position and the excitation frequency exceeding the threshold, even if the jet peak velocity is small, the compressor can obtain a higher flow margin, total pressure ratio, and efficiency than the prototype compressor. As the jet peak velocity increases, the performance of compressor can be further improved.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-11-10T10:49:03Z
      DOI: 10.1177/09544100211049026
       
  • Insight into the factors affecting the safety of take-off and landing of
           the ship-borne helicopter

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      Authors: Yihua Cao, Yihao Qin
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Despite the important role and highly frequent appearance of the helicopter in modern ship operations, the flight mission with take-off and landing of helicopters to ships, especially ships with small-sized decks, could be very challenging and potentially hazardous. Many researches on ship-helicopter dynamic interface (DI) have been conducted, and significant progress has been made. In this paper, a comprehensive and systematical review of the factors affecting the flying qualities of ship-borne helicopter and pilot workload during taking off and landing is derived from these efforts to date. The factors from two aspects, including the ship environment and the pilot-helicopter interface, are covered to address how these factors affect the helicopter handling qualities and pilot workload, primarily focusing on aerodynamic issues. The insight into these factors is not only of great significance for conducting take-off and landing tasks safely but also helpful to establish suitable fidelity criteria and guidelines for the modelling and simulation of the ship-helicopter DI environment.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-11-03T02:18:48Z
      DOI: 10.1177/09544100211050452
       
  • Optimization study on the influence of little blades’ spatial position
           on a compressor cascade performance

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      Authors: Shan Ma, Xiaolin Sun
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To reveal the importance of little blades’ spatial position to improve the cascade performance at different condition, the pitchwise and axial direction of the little blades on the end-wall are adopted as the optimization variables to complete a double-objective optimization. Meanwhile, the three-dimensional flow field characteristics of the cascade with and without little blades are analyzed comparatively. The study found that as the optimal solutions are obtained at the three bigger incidences (3°, 5°, and 7°), the optimal position is always close to the leading edge of blade and far away from the blade suction surface, and the more intuitive design suggestions are given in this article. Moreover, at the near design conditions (−1°, 0°, and 1°), little blades increase the total pressure loss and reduce the static pressure, which are considered unsuitable for improving the cascade performance. If the stable operation range are the main performance indicators, the optimization of the little blades’ spatial position should be completed at the near stall condition (7° incidence). If the conditions with mid-range incidences (2°< i
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-31T08:45:00Z
      DOI: 10.1177/09544100211044327
       
  • On the subsonic and low transonic aerodynamic performance of the land
           speed record car, Bloodhound LSR

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      Authors: Ben Evans, Jack Townsend, Oubay Hassan, Kenneth Morgan, Ron Ayers, Mark Chapman, Andy Green
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The land speed record vehicle, Bloodhound, undertook testing at subsonic and low transonic speeds (up to Mach 0.8) at Hakskeen Pan, South Africa, during October and November of 2019. A decade of CFD-led aerodynamic design had been undertaken to produce a vehicle with the aim of minimised Mach number aerodynamic dependencies and minimised overall drag. This paper sets out and explains the measured pressure distributions with a focus on the highest speed run of Bloodhound up to a peak speed of 628 mile/h. It compares the measured aerodynamic performance with the various CFD model predictions used throughout the design process showing that, whilst localised discrepancies between CFD model and real behaviour exist, overall the Reynolds-averaged Navier–Stokes (RANS)-based CFD tools used to design the car did result in sufficiently accurate aerodynamic data to predict the overall vehicle performance to a high degree of accuracy. The work outlined in this paper, and the conclusions and recommendations drawn, form the basis for a future record attempt and the understanding of what will be required in principle to extend the World Land Speed Record to 1000 mile/h. It also provides guidance on how to effectively make use of RANS-based CFD modelling predictions for other complex, ground-interacting high-speed applications.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-29T06:54:22Z
      DOI: 10.1177/09544100211046159
       
  • Numerical research on the performance of solid fuel rocket scramjet
           combustor

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      Authors: Hao Huang, Zhiwei Feng, Likun Ma, Tao Yang, Chaolong Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Combustion efficiency is the main factor affecting the performance of solid fuel rocket scramjet. To reveal the influence of combustor configuration on performance and further improve combustion efficiency, the influence of the width-height ratio of the rectangle-section combustor on the performance of solid fuel rocket scramjet is investigated numerically in this article. Three-dimensional compressible Reynolds-averaged Navier-Stokes equations coupled with shear stress transport k–ω turbulence model are employed to simulate the aerodynamics. The Euler–Lagrange approach is used to calculate the multiphase flow. Combustion of carbon particles is modeled by the improved Moving Flame Front model. Accuracy of the present numerical model is validated by the experimental data of a rectangle-section combustor from literature. Results show that as the width-height ratio increases, the combustion efficiency increases first and then decreases. The influence of cavity and its position on the performance are also investigated. Results show that cavity can significantly improve combustion efficiency. The effect of cavity position on performance is related to the distribution of particles.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-28T10:40:46Z
      DOI: 10.1177/09544100211037226
       
  • Attitude control of the low earth orbit CubeSat using a moving mass
           actuator

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      Authors: Zhengliang Lu, Yuandong Hu, Wenhe Liao, Xiang Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper investigates an attitude control method for the CubeSat using a moving mass actuator to solve the problem of the strong aerodynamic disturbance in low Earth orbit. The rotational and translational equations are derived for the CubeSat with three moving masses, and their dynamic effects are analyzed. A magnetorquer is used to prevent the underactuation of the attitude control system. The movement of moving masses is slowed down by using a discrete double-loop Proportion Integral Differential control method, thereby reducing the fast time-varying additional disturbance. A nonlinear observer is used for the precise estimation of the slow time-varying disturbance. Notably, the ideal attitude control torque is allocated to two actuators by using the proposed control allocation algorithm. Numerical simulation indicates that the attitude convergence accuracy is up to ±0.1° despite the uncertain dynamics, unknown disturbances, and dynamic effects. The results verify the feasibility of the proposed control method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-26T11:51:41Z
      DOI: 10.1177/09544100211048275
       
  • Distributed attitude consensus tracking control for spacecraft formation
           flying via adaptive nonsingular fast terminal sliding mode control

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      Authors: Xiong Xie, Tao Sheng, Liang He, Zhijun Chen, Yong Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article investigates the distributed attitude consensus tracking control for spacecraft formation flying with unknown external disturbances and model uncertainties. First, a terminal sliding mode disturbance observer (TSMDO) is constructed to estimate the generalized disturbances including external disturbances and model uncertainties. The finite-time convergence of the estimation errors using TSMDO is analyzed. Second, a variable structure control law is developed to avoid introducing initial errors of the TSMDO. Third, a novel adaptive nonsingular fast terminal sliding mode (ANFTSM) control law based on TSMDO is proposed to ensure the convergence of attitude tracking errors to zero. Based on theoretical analysis, the finite-time stability can be guaranteed by Lyapunov theory. Finally, the effectiveness of the developed control law is verified via numerical simulations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-25T02:28:26Z
      DOI: 10.1177/09544100211042243
       
  • Multi-label learning using label-specific features for simultaneous fault
           diagnosis of aircraft engine

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      Authors: Bing Li, Yong-Ping Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Lacking of the management of simultaneous fault is one of the limitations of condition monitoring for a gas turbine, which is critical for the safety and decision-making of aircraft operation. To this end, this paper employed a multi-label (ML) learning strategy to address the simultaneous fault issues. Moreover, a feature selection algorithm is proposed, which is based on the viewpoint that different class labels might be distinguished by certain specific characteristics of their own. The proposed algorithm achieves the goal of label-specific feature selection by iteratively optimizing the weight reconstruction matrix, and the learned label-specific features for the corresponding label can be used for multi-label classification. As thus, sensor data for different components of aircraft engines can be determined by the proposed algorithm to deal with the simultaneous fault diagnosis. Finally, comprehensive experiments on the benchmark data sets of multi-label learning validate the advantages and feasibility of the presented approaches, and the effectiveness of their application to simultaneous fault diagnosis of aircraft engines is also proved by extensive experiments.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-22T01:44:15Z
      DOI: 10.1177/09544100211049935
       
  • The response of the solid fuel ramjet combustor to the inflow excitations

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      Authors: AmirMahdi Tahsini, Seyed Saeid Nabavi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The response of the solid fuel ramjet to the imposed excitations of the ambient pressure is investigated using full part computation of the system including the intake, combustion chamber, and exhaust nozzle. The finite volume solver of the turbulent reacting compressible flow is used to simulate the flow field, where two grid blocks are considered for discretizing the computational domain. Both impulsive and oscillatory excitations are imposed to predict the response of the solid fuel mass flow rate. The results demonstrate that strong fuel flow overshoot occurs in the case of sudden impulsive excitation which is omitted for gradual impulsive excitations. In addition, the oscillatory excitations eventually lead to regular oscillatory response with frequencies similar to the imposed excitations and decrease the average fuel mass flow rate independent of the excitation frequency. But the amplitude of the response depends on the excitation frequency and amplification occurs in some frequencies. This behavior is not related to the combustion instabilities and is similar to the L-star instability in the solid rocket motors. In the design and analysis of the solid fuel ramjets, the coupling of the flight dynamics and the engine performance must be considered, and this study is the first step of such complete methodology to have more accurate predictions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-21T01:23:08Z
      DOI: 10.1177/09544100211053405
       
  • Effect of three non-axisymmetric stator schemes on compressor performance
           with distorted inlet

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      Authors: Wenguang Fu, Peng Sun
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In the boundary layer ingesting propulsion system, the compressor suffers from a non-uniform flow field. The compressor operating with distorted inflow continuously results in the loss of aerodynamic performance and stability margin. In this paper, three non-axisymmetric configurations are described for the stator of a transonic compressor to match the non-uniform flow field. The flow fields with distorted inflow at near stall condition are obtained and analyzed, the effects of the prototype stator and the three non-axisymmetric stators on aerodynamic performance are compared in detail. Results show that the non-axisymmetric stator schemes can effectively improve the stability margin of the transonic compressor and the maximum stability margin is relatively increased by 22.3% in all the three non-axisymmetric stators. The non-axisymmetric stator design is effective on decreasing the aerodynamic losses and improving the performance of the compressor operating with distorted inflow. Overall, the results show that in the design of the non-axisymmetric stator, the adoption of a curved-twisted blade and the increase of cascade solidity have the potential to reduce loss sources caused by distorted inflow.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-14T07:38:24Z
      DOI: 10.1177/09544100211049877
       
  • Design of sliding mode flight control system for a flexible aircraft

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      Authors: Majeed Mohamed, Madhavan Gopakumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The evolution of large transport aircraft is characterized by longer fuselages and larger wingspans, while efforts to decrease the structural weight reduce the structural stiffness. Both effects lead to more flexible aircraft structures with significant aeroelastic coupling between flight mechanics and structural dynamics, especially at high speed, high altitude cruise. The lesser frequency separation between rigid body and flexible modes of flexible aircraft results in a stronger interaction between the flight control system and its structural modes, with higher flexibility effects on aircraft dynamics. Therefore, the design of a flight control law based on the assumption that the aircraft dynamics are rigid is no longer valid for the flexible aircraft. This paper focuses on the design of a flight control system for flexible aircraft described in terms of a rigid body mode and four flexible body modes and whose parameters are assumed to be varying. In this paper, a conditional integral based sliding mode control (SMC) is used for robust tracking control of the pitch angle of the flexible aircraft. The performance of the proposed nonlinear flight control system has been shown through the numerical simulations of the flexible aircraft. Good transient and steady-state performance of a control system are also ensured without suffering from the drawback of control chattering in SMC.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-13T09:41:59Z
      DOI: 10.1177/09544100211045592
       
  • Fixed-time cooperative guidance for multiple missiles with impact angle
           constraint

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      Authors: Xinghe Zhou, Weihong Wang, Zhenghua Liu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      For the guidance problem of multiple missiles attacking a maneuvering target simultaneously in plane, a novel fixed-time distributed cooperative guidance law with impact angle constraint is designed in this paper. The design process of distributed cooperative guidance law can be roughly divided into two parts. First, based on the nonsingular terminal sliding mode control, a cooperative guidance law on the line-of-sight (LOS) direction is developed, which can guarantee that all missiles hit the maneuvering target simultaneously. Second, another guidance law in normal direction of the LOS direction is designed to achieve the fixed-time convergence of LOS angular rate and LOS angle. Finally, numerical simulations verify the effectiveness of the proposed cooperative guidance law for different engagement scenarios.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-12T03:54:47Z
      DOI: 10.1177/09544100211048043
       
  • Investigation of variable geometry orifice design for improving
           centrifugal compressor low-end performance and stable operating range

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      Authors: Ben Zhao, Qingjun Zhao, Xiaorong Xiang, Wei Zhao, Jianzhong Xu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Active control of the inlet flow area in a centrifugal compressor is a method to improve compressor aerodynamic performance and stall margin. As a core part of the area control device, the variable geometry orifice is investigated and its two key design parameters are analyzed in detail, the setting angle of the orifice with respect to the shroud casing and the radial height of the orifice to the shroud casing from the orifice inner rim. This paper proposes a physics-based equation that describes the relationship of the two parameters with compressor mass flow rate and then validates the equation using numerical simulations. As far as the setting angle, the physics-based equation suggests not to be larger than 90°. The numerical results not only validate the physics-based equation but also show the most optimal angle of 78°. In terms of the orifice height, both the physics-based equation and the numerical simulations suggest an active height control of orifice in the compressor inlet duct.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-11T02:19:48Z
      DOI: 10.1177/09544100211047678
       
  • Aero-engine acceleration control using deep reinforcement learning with
           phase-based reward function

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      Authors: Qian-Kun Hu, Yong-Ping Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, the conventional aero-engine acceleration control task is formulated into a Markov Decision Process (MDP) problem. Then, a novel phase-based reward function is proposed to enhance the performance of deep reinforcement learning (DRL) in solving feedback control tasks. With that reward function, an aero-engine controller based on Trust Region Policy Optimization (TRPO) is developed to improve the aero-engine acceleration performance. Four comparison simulations were conducted to verify the effectiveness of the proposed methods. The simulation results show that the phase-based reward function helps to eliminate the oscillation problem of the aero-engine control system, which is caused by the traditional goal-based reward function when DRL is applied to the aero-engine control. And the TRPO controller outperforms deep Q-learning (DQN) and the proportional-integral-derivative (PID) in the aero-engine acceleration control task. Compared to DQN and PID controller, the acceleration time of aero-engine is decreased by 0.6 and 2.58 s, respectively, and the aero-engine acceleration performance is improved by 16.8 and 46.4% each.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-09T07:35:14Z
      DOI: 10.1177/09544100211046225
       
  • Trajectory planning with mid-air collision avoidance for quadrotor
           unmanned aerial vehicles

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      Authors: Yuhang Jiang, Shiqiang Hu, Christopher J Damaren
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Flight collision between unmanned aerial vehicles (UAVs) in mid-air poses a potential risk to flight safety in low-altitude airspace. This article transforms the problem of collision avoidance between quadrotor UAVs into a trajectory-planning problem using optimal control algorithms, therefore achieving both robustness and efficiency. Specifically, the pseudospectral method is introduced to solve the raised optimal control problem, while the generated optimal trajectory is precisely followed by a feedback controller. It is worth noting that the contributions of this article also include the introduction of the normalized relative coordinate, so that UAVs can obtain collision-free trajectories more conveniently in real time. The collision-free trajectories for a classical scenario of collision avoidance between two UAVs are given in the simulation part by both solving the optimal control problem and querying the prior results. The scalability of the proposed method is also verified in the simulation part by solving a collision avoidance problem among multiple UAVs.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-09T02:44:17Z
      DOI: 10.1177/09544100211044046
       
  • Vibration fault identification of a turbojet engine based on cepstrum
           analysis

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      Authors: Jingjing Huang, Xijun Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A vibration fault identification method based on vibration state characteristics of a turbojet engine and cepstrum analysis technology was proposed in this paper, and the application of cepstrum in vibration analysis of an aero-engine was also discussed. The vibration data of the turbojet engine in three different test cases of 0.8 rated state, max power state, and afterburning state were analyzed using the cepstrum analysis method. The periodic components and the characteristics of multi-component side-frequency complex signals in the dense overtone vibration signals were separated and extracted, which reflected the sensitivity of the positions of the compressor casing and the turbine casing to the harmonic vibration components of high- and low-pressure rotors and the characteristic difference of different vibration parts. Thus, effective identification of vibration faults was achieved. The results shows that the cepstrum analysis technique applied to the vibration analysis of the turbojet engine can better identify the sideband components of the frequency domain modulated signal and enhance the recognition capability of the fault frequency component, which is helpful to identify the engine vibration fault quickly and accurately.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-08T11:49:53Z
      DOI: 10.1177/09544100211047788
       
  • Research on color coding of fighter jet head-up display key information
           

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      Authors: Yafeng Niu, Tianyu Zhou, Ling Bai
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      HUD is currently the main flight status display commonly used in modern fighter jets. Color coding is an important method in HUD visual information display. Different weather, terrain, climate, time, season, and other environmental phenomena will affect the HUD. The HUD’s multi-color display mode has become a key method to solve the overload display of dynamic and static information in complex flight environments. This paper discusses the use of eye-tracking equipment to record eye movement experimental data using different HUD color schemes, as well as the correct rate and response time to complete the task, in order to evaluate the color combinations of different characters in different high-altitude and sea flight background conditions. Cognitive status was obtained by seven key eye movement indicators (average fixation time, first fixation duration, fixation ratio, fixation time ratio, fixation track length and lookback times, and pupil diameter) designed by color-coded dimensions to evaluate the key element information of the HUD: discernibility, which is related to average fixation time, duration of first fixation, and pupil diameter; perceptibility, which is related to gaze ratio, fixation time ratio, and other indicators; and accessibility, which is related to fixation track length and number of lookbacks. At the same time, the background color brightness interval that affects color matching was obtained, and five key information colors (K1(0, 100, 100), K2(30, 100, 100), K3(300, 100, 100), K4(330, 100, 100), and K5(60, 100, 100)) were selected for experimental exploration to obtain the best matching scheme for color coding of key elements of the HUD against different lightness backgrounds. The results indicate that against a flight background with ocean brightness, ranges are [1–20], [21–40], [41–60], and [61–99] and colors with hues of 30, 300, 60, and 300 are selected for the key information. Finally, the results give an improvement and optimization plan for the HUD. The research conclusion provides some guidance for HUD design and improvement for different flight backgrounds, and a reference for improving pilots' cognitive performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-08T10:38:29Z
      DOI: 10.1177/09544100211049025
       
  • Guidance and control with fixed-time convergence for an interception
           missile

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      Authors: Lei Cui, Nan Jin, Yantao Zong
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article deals with the problem of partial integrated guidance and control (IGC) design with fixed-time convergence. First of all, two new fixed-time stability systems are proposed, and a novel nonsingular terminal sliding mode with fixed-time convergence is constructed by switching the exponential term of system state variables, which can realize the transition from finite-time convergence to fixed-time convergence. Concurrently, in order to solve the singular problem of terminal sliding mode, a continuous piecewise function is used in the sliding mode surface design. Then, a novel nonsingular terminal sliding mode control with fixed-time convergence is proposed for partial IGC design; that is, the upper-bound of convergence time is independent of the initial states of both missile and target and can be set in advance. In addition, a radial basis function neural network (RBFNN) is used to adaptively estimate and compensate for the uncertainties caused by the target’s maneuvering, so that the design of fixed-time sliding mode controller does not need to know any information about the target maneuver in advance, which enables the proposed controller to be better with robustness. Finally, the effectiveness and merits of the proposed control strategy are shown by the numerical simulation results based on the nonlinear longitudinal model of missile.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-08T06:05:29Z
      DOI: 10.1177/09544100211044052
       
  • FOV constrained guidance law for nonstationary nonmaneuvering target
           interception with any impact angle

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      Authors: Nikhil Kumar Singh, Sikha Hota
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents the nonstationary nonmaneuvering target interception with all possible desired impact angles in a two-dimensional (2D) aerial engagement scenario, where the target can move in any direction. The paper also considers the field-of-view (FOV) constraint for designing the guidance law so that the target is always visible while following the missile trajectory in the entire engagement time, which makes it feasible for real world applications. The guidance law is based on the pure proportional navigation (PPN) to achieve any impact angle of the entire angular spectrum. The proposed guidance law is then simulated for intercepting a nonstationary nonmaneuvering target using a kinematic model of a missile to demonstrate the efficacy of the presented scheme. A comparison with the related work existing in the literature has also been added to establish the superiority of the present work.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-06T11:15:04Z
      DOI: 10.1177/09544100211046867
       
  • Acoustic and phase portrait analysis of leading-edge roughness element on
           laminar separation bubbles at low Reynolds number flow

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      Authors: Hossein Jabbari, Esmaeili Ali, Mohammad Hasan Djavareshkian
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Since laminar separation bubbles are neutrally shaped on the suction side of full-span wings in low Reynolds number flows, a roughness element can be used to improve the performance of micro aerial vehicles. The purpose of this article was to investigate the leading-edge roughness element’s effect and its location on upstream of the laminar separation bubble from phase portrait point of view. Therefore, passive control might have an acoustic side effect, especially when the bubble might burst and increase noise. Consequently, the effect of the leading-edge roughness element features on the bubble’s behavior is considered on the acoustic pressure field and the vortices behind the NASA-LS0417 cross-section. The consequences express that the distribution of roughness in the appropriate dimensions and location could contribute to increasing the performance of the airfoil and the interaction of vortices produced by roughness elements with shear layers on the suction side has increased the sound frequency in the relevant sound pressure level (SPL). The results have demonstrated that vortex shedding frequency was increased in the presence of roughness compared to the smooth airfoil. Also, more complexity of the phase portrait circuits was found, retrieved from velocity gradient limitation. Likewise, the highest SPL is related to the state where the separation bubble phenomenon is on the surface versus placing roughness elements on the leading edge leads to a negative amount of SPL.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-04T12:16:17Z
      DOI: 10.1177/09544100211044316
       
  • Indirect low-thrust trajectory optimization with gridded ion thruster
           model

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      Authors: Zhemin Chi, Yang Wang, Lin Cheng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The work deals with indirect optimization of minimum-time and minimum-fuel interplanetary trajectories when gridded ion thruster models are considered. Using an accurate model of solar electric propulsion is beneficial in preliminary mission design, and allows including operational constraints. The maximum thrust and the specific impulse are expressed as a function of thruster input power, which is achieved by means of point-fitting lines that match the performance capabilities of the thrusters. Minimum-time and minimum-fuel problems are formulated to be solved by indirect optimization. In order to increase the accuracy and robustness of the shooting procedure, analytic Jacobians are derived, and a hybrid switching detection technique is used to improve the integration accuracy for minimum-fuel problems. Two examples of Earth-to-Mars transfer and Near-Earth rendezvous mission using the realistic NASA’s Evolutionary Xenon Thruster (NEXT) are given to substantiate the feasibility and effectiveness of the proposed method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-10-01T10:29:00Z
      DOI: 10.1177/09544100211043846
       
  • Progress on error propagation and correction of long-range rockets in
           disturbing gravity field

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      Authors: Lei Wang, Zhiqiang Lin, Yongjun Peng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Disturbing gravity field is becoming an important factor leading to impact error of long-range rockets. In this paper, the influence mechanism of deflection of the vertical and spatial disturbing gravity on inertial navigation and guidance system are firstly introduced, respectively. Then, the navigation error propagation methods due to disturbing gravity field are reviewed. The fast assignment models of disturbing gravity field, which are available for compensating navigation errors in engineering, are also summarized. After that, the unpowered trajectory error propagation methods and the corresponding guidance correction strategies, as well as potential directions for future efforts, are discussed.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-09-29T10:31:56Z
      DOI: 10.1177/09544100211046109
       
  • Prescribed performance-based adaptive sliding mode control for the
           autopilot design of missile with lateral jets

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      Authors: Zhihong Zhang, Kemao Ma
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A novel prescribed performance-based adaptive sliding mode control is investigated for the autopilot design of missile with lateral reaction jets. An integral sliding mode surface is designed for a class of nonlinear systems such that the prescribed output-tracking behavior is incorporated into the sliding mode dynamics. An adaptive algorithm is developed using the concept of equivalent control to attenuate the chattering effect. Then, the method is applied to the autopilot design where the sliding mode control law is allocated to two sets of actuators according to their respective characteristics. The proposed integral sliding surface guarantees that the missile output can track the given reference command with the prescribed performance indices from the very beginning of the time. Moreover, the adaptation laws allow the reduction of the jets consumption. Several simulations conducted at different set-points show the efficacy of the proposed methods.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-09-29T08:18:46Z
      DOI: 10.1177/09544100211044387
       
  • Mechanism analysis of magnetohydrodynamic shock control in hypersonic flow

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      Authors: Shichao Luo, Jun Liu, Hao Jiang, Junyuan Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The effects of external magnetic fields on the shock-wave configuration at hypersonic plasma flow field are investigated in this paper. A series of numerical simulations over various geometry configurations, namely, a blunt body and a fixed-geometry inlet forebody, have been conducted by varying the applied magnetic field under different freestream conditions. Results show that magnetohydrodynamic shock control capabilities under three types of magnetic field are ranked from weak to strong as dipole magnet, solenoid magnet, and uniform magnet field. Under the same applied magnetic field, it is easier to deflect the shock at a relatively high altitude condition, compared with the low altitude case. The bow shock standoff distance is dependent on the distribution of counter-flow Lorentz force right after shock in the stagnation region. For the oblique shock control, the function of two components of Lorentz force is different that the counter-flow one decelerates the flow and increases the shock-wave angle, while the normal one squeezes the oblique shock and deflects the streamlines.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-09-25T05:52:08Z
      DOI: 10.1177/09544100211042536
       
  • Velocity-free attitude tracking for rigid spacecraft via bounded control

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      Authors: Jian Zhang, Wen-Jie Wu, Long Liu, Dai Liu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article investigates the attitude tracking control problem for a rigid spacecraft without angular velocity feedback, in which external disturbances, parametric uncertainties, and input saturation are considered. Initially, an angular velocity observer is developed incorporated with adaptive technique, which could tackle the unmeasurable angular velocity and system uncertainties simultaneously. By introducing adaptive updating law into the proposed observer, the synchronized uncertainties are handled such that robustness of the observer is enhanced, even in the presence of external disturbances. Further, for solving the input constraints problem, command filter and backstepping method are utilized; thus, a bounded attitude tracking control law is derived. Finally, the attitude tracking performance is evaluated by numerical examples.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-09-06T05:10:04Z
      DOI: 10.1177/09544100211042348
       
  • Planning of refracted starlight observation based on observability
           analysis

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      Authors: Chengzhen Wu, Xueying An, Dingjie Wang, Hongbo Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In traditional observation schemes of stellar refraction navigation, the accuracy was limited due to unreasonable observation directions. In order to ameliorate this situation, a method of refracted starlight observation based on observability analysis is proposed. The function of this method is optimally generating an observation attitude sequence according to standard trajectories of spacecraft so that the selection of a refracted starlight observation sequence can be realized. Specifically, the improvement of Fisher information matrix calculation enables this method to be qualified for the navigation problem with unsteady measurement quantities as well as the non-fully observability which is defined as the capability of estimating the system state through measurements in finite time. Here, we construct a quantitative relationship between refracted starlight measurements and system observability by means of Fisher information index (FII). Next, the observation scheme is retrieved by searching the maximum value of the optimized variable, which includes the (FII). Finally, we resort to the extended Kalman filter to accomplish typical trajectory navigation simulations of the observation scheme. The results indicate that our method brings more accuracy than traditional ones in estimation of position and velocity of the optimal observation scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-09-01T10:53:44Z
      DOI: 10.1177/09544100211030111
       
  • Robust fault-tolerant control design for hypersonic vehicle with input
           saturation and actuator faults

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      Authors: Zhong-Zhe Yue, Jing-Guang Sun
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study investigates the flight longitudinal tracking control problem of hypersonic vehicle in presence of the input saturation, external disturbances, model parametric uncertainties, and actuator faults. First, the velocity and altitude subsystem are established with disturbances based on the feedback linearization model. Second, two robust anti-saturation fault-tolerant controllers are designed for the velocity subsystem and altitude subsystem by the utilization of the tangent function, Nussbaum function, and adaptive nonlinear filter. Finally, Lyapunov stability theory is used to prove that the states of the closed-loop system are bounded. And, the effectiveness and robustness of the control strategy are proved by numerical simulations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-28T12:24:23Z
      DOI: 10.1177/09544100211041255
       
  • Loss prediction of axial compressors using genetic algorithm–back
           propagation neural network in throughflow method

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      Authors: Jian Li, Jinfang Teng, Mingmin Zhu, Xiaoqing Qiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      While the consistent advance in computational power has enabled the Computational Fluid Dynamics (CFD) an effective tool for compressor performance characterization, the need for quick performance estimates at initial design phase of compressor still requires the use of low order models. Thus, the throughflow method remains the backbone of compressors design process. The accuracy of the throughflow calculation mainly depends on the adopted empirical correlations. However, the traditional empirical models are just accurate for the conventionally loaded compressor at normal working conditions. In this article, the mechanism of blade profile loss generation and the formation mode of existing empirical correlation are studied, and the reason why the traditional diffusion factor based empirical models are not applicable for modern high-loading compressors or conventional-loading blades at negative incidence is also discussed. Then, the Genetic Algorithm assisted Back Propagation Neural Network (GA-BPNN) is used to train the surrogate model for the design and off-design loss prediction along the blade span of the compressor. Based on the test data of four transonic compressor stages, a database containing 72 sets of blade element geometry and about 1400 sets of blade element performance data is established. Considering the different mechanisms of rotor and stator losses at different working conditions, the entire database and surrogate model are divided into four components according to the rotor and stator at positive incidence and negative incidence. Comparing the prediction results of the surrogate model with the traditional empirical correlations and experimental data, the results show that the GA-BPNN is an alternative solution for developing the empirical model.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-28T08:28:45Z
      DOI: 10.1177/09544100211041490
       
  • Calibration and data reduction for X-hotwires using cross validation

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      Authors: Mohan Vijaya Anoop, Budda Thiagarajan Kannan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A strategy for calibration of X-wire probes and data inversion is described in this article. The approach used has elements of full velocity vs yaw-angle calibration with robust curve fitting. The responses of an X-wire probe placed in a calibration jet are recorded for a set of velocity and yaw inputs followed by fitting cross-validated splines. These spline functions trained from calibration data are evaluated for the probe responses during measurement. X-wire probes are calibrated for low to moderate velocities (0.65 m/s to 32 m/s) and yaw angles in the range −40° to 40° and comparisons with conventional interpolation schemes are made. The proposed algorithm can be extended to calibration of other multiple wire probes and for higher velocities. Some measurements in a single round turbulent jet flow at high Reynolds number using the proposed inversion algorithm are also presented. The present scheme is found to perform better particularly at low flow magnitudes and/or extreme flow angles than the schemes used previously.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-28T03:55:00Z
      DOI: 10.1177/09544100211040305
       
  • Model predictive tracking control of uncertain moving structures with
           nonaffine saturated actuation: Rotating control force

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      Authors: Sadeq Yaqubi, Mohammad Reza Homaeinezhad
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article presents a novel scheme for model-based control of multi-input–multi-output (MIMO) systems considering input nonaffinity, nonlinear dynamical effects, and bounded modeling uncertainty. Commonly, model-based control of a nonaffine system is conducted based on an equivalent pseudo-affine expression. However, validity of this approximation necessitates boundedness of inputs and states. Furthermore, existence of truncation errors is inevitable when obtaining the pseudo-affine model. Therefore, robustness to bounded uncertainty should be ensured even in cases where the original system is deterministic. To address the expressed issues, in this study the boundedness assumptions are incorporated in a constrained robust model predictive control (MPC) algorithm. The corresponding MPC scheme is based on construction of cost according to predicted sliding functions over a finite prediction horizon. It should be noted that for the considered class of uncertain nonlinear nonaffine system, obtaining the perquisite robust stability and feasibility conditions is non-trivial. To attain the aforementioned qualities, it is proposed that sliding functions can be expressed as the sum of input-based terms (using pseudo-affine approximation of input gains based on Taylor expansion) and dynamical variation terms. Subsequently, robust stability is ensured by constructing a Lyapunov-based terminal cost. Constraints satisfaction conditions are determined based on calculation of the corresponding feasible region. Numerical simulations for a nonlinear nonaffine mechanical system indicate efficiency of the presented control model. Comparisons with other applicable schemes highlight significant features of the presented algorithm and the attained improvements regarding stability and control feasibility are discussed.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-27T08:04:54Z
      DOI: 10.1177/09544100211041224
       
  • Effective strategy of non-axisymmetric endwall contouring in a linear
           compressor cascade

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      Authors: Yuchen Ma, Jinfang Teng, Mingmin Zhu, Xiaoqing Qiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The corner separation and the related secondary flow have great impact on the compressor performance, and non-axisymmetric endwall contouring is proved effective in improving compressor efficiency. The aim of the study is to improve the compressor performance by two local endwall contouring strategies at the design and off-design conditions. The endwall is parameterized and the Bezier curve is used to loft the endwall surface. The design of the contoured endwall is based on a multi-point optimization method to minimize the aerodynamic pressure loss. In order to identify the influence of the contoured endwall, a detailed flow analysis is conducted on four effective contoured endwall designs. The selected endwall geometries exhibit great control ability on the corner separation and significantly reduce the pressure loss at the two operating conditions. The directional concave near the leading edge can induce strong streamwise pressure gradient and accelerate the endwall flow, greatly reducing the cross-passage pressure gradient. The convex structures near the concave edge and at the outlet can block the cross-flow and prevent the interaction between the cross-flow and the suction corner flow. The benefit of the contoured endwall is mainly due to the re-distributed endwall static pressure and blocking of the cross-flow movement. In terms of the control effect, the shape of the concave also matters and better control effect is observed on the deep and wide concave. The flow will be guided by the concave, and the best suppression on corner separation is observed on the concave which follows the suction side. The results also indicate that the relief of the hub corner separation slightly increases the shroud pressure loss.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-14T03:18:39Z
      DOI: 10.1177/09544100211037518
       
  • Airfoil lift calculation using wind tunnel wall pressures

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      Authors: Sreevishnu Oruganti, Shreyas Narsipur
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An experimental method to calculate lift using static pressure ports on the wind tunnel walls and its associated limits has been explored in this article. While the wall-pressure measurement (WPM) technique for lift calculation has been implemented by other researchers, there is a lack of literature on the sensitivity of the WPM method to airfoil chord length, model thickness, surface roughness, and freestream conditions. Chord sensitivity studies showed that the airfoil chord to test section length ratio plays an important role in the accuracy of the measurements. Models need to be appropriately sized for optimum performance of the WPM method. Additionally, choosing the correct scaling ratio also ensures independence of lift measurements from freestream Reynolds number conditions. Finally, a combination of symmetric and cambered airfoils with thicknesses varying from 6% − 21% were tested and successfully validated against reference data for a freestream chord Reynolds number range of 100,000 to 550,000. The WPM method was found to be sensitive to varying surface flow conditions and airfoil thickness and has been shown to be a viable replacement to traditional lift measurement techniques using load balances or airfoils with surface pressure ports.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-14T02:58:54Z
      DOI: 10.1177/09544100211038253
       
  • Experimental investigation on fluid structure and full-cone spray
           characteristics of a jet-swirl atomizer using shadowgraph technique

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      Authors: Mazyar Shafaee, Abbas Elkaie, Mohammad Amin Hassani
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Full-cone spray is quite important in spray cooling and catalytic combustion applications; however, it is not extensively studied. Besides, the liquid spray is relatively a non-uniform structure especially along longitudinal axis which includes different sizes and distribution of droplets. The few published experimental studies are limited to calculate some of the spray characteristics on a certain plane located downstream of the nozzle exit. Therefore, the spray parameters representing fluid structure, droplets mean diameter, and their distribution in different cross sections from nozzle exit are considered in this study. Accordingly, a jet-swirl atomizer with pressure-swirl full-cone spray is investigated where all important full-cone spray characteristics are considered at different planes from nozzle exit. The spray images are obtained with a shadowgraph technique and are analyzed to obtain the Sauter mean diameter (SMD), D10, and droplet size distribution along with the spray structure, spray cone angle, and discharge coefficient. The experimental results are verified based on the pre-published numerical studies on the same atomizer. The experimental and numerical results show good agreement. Moreover, the results show that the SMD is increased by moving away from center of spray to its edges, and the droplets number density is increased in central regions. The increased droplets number density leads to the greater external forces which create smaller droplets. In contrast, larger particles exist in peripheral parts due to the less droplets concentration. Furthermore, and far away from the exit nozzle, the SMD values are decreased due to the increased aerodynamic forces and oscillations. The droplets dispersion including spray density in radial and axial directions is also observed using spray density images.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-12T02:50:33Z
      DOI: 10.1177/09544100211037633
       
  • Effects of tip air injection on the aerodynamic stability of an axial flow
           compressor with total pressure distortion

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      Authors: Baofeng Tu, Xinyu Zhang, Liang Li, Jun Hu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The compressor is a critical component that determines the aerodynamic stability of an aero-engine. Total pressure inlet distortion decreases the thrust and shrinks the stability margin, thus inducing severe performance degradation or even flameout. Generally, tip air injection is used to reduce the adverse influence of total pressure inlet distortion on the aerodynamic stability. In the present work, an experimental investigation on the effects of tip air injection on the stability of a two-stage low-speed axial compressor with total pressure inlet distortion was carried out. A flat baffle generated the total pressure distortion at the inlet of the compressor. The stall margin of the compressor was reduced significantly by the total pressure distortion. When the dimensionless insertion depth of the flat baffle was 0.45, the stall margin decreased to 11.4%. Under the total pressure inlet distortion, tip air injection effectively improved the distortion resistance capability of the compressor. The circumferential layout of the nozzle played a critical role in the stability expansion effect of tip air injection under the inlet flow condition of the total pressure distortion. The modal wave disturbance was likely to occur in the distortion-affected region (the low-pressure region and the mixing region). Tip air injection did not inhibit the generation of the modal wave but restrained the development of the modal wave into the stall cell. It improved the low-speed compressor’s tolerance to the modal wave and allowed a higher amplitude modal wave to occur.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-10T01:23:29Z
      DOI: 10.1177/09544100211037522
       
  • Evaporation and combustion of n-heptane droplets in supersonic combustor

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      Authors: Amir Mahdi Tahsini, Seyed Saeid Nabavi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The purpose of the present study is to investigate the combustion of the n-heptane droplet cloud in the supersonic combustor. The finite volume solver is developed to simulate the two-phase reacting compressible flow using single step reaction mechanism as finite rate chemistry. The focus is on the impacts of droplet size and cloud density on the performance of the scramjet. For the considered physical situation, the upper limit of the droplet size is determined to have higher combustion efficiency, and it is shown that the combustion mode is kinetic-controlled for small sizes and is evaporation-controlled for large droplet sizes. The variation of combustor’s exit total pressure and temperature is also investigated for different droplet cloud densities, demonstrating their apparent opposite behavior that must be considered to get optimum propulsion efficiency. In addition, it is illustrated that thermal choking is another criterion which should be avoided by controlling the fuel mass flow rate for intended flight conditions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-05T08:04:26Z
      DOI: 10.1177/09544100211037627
       
  • Analysis of the free-space acoustic signature of a BBMF Rolls-Royce Merlin
           engine from 842 rpm to 2740 rpm

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      Authors: John C Bennett
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A technique has been developed to analyse the free-space acoustic signature of the Rolls-Royce Merlin engine in order to provide diagnostic information relating to its performance. The work is motivated by a need to maintain the reliability and maximise the lifetime of this historic engine which is an important component of the aircraft operated by the UK Battle of Britain Memorial Flight (BBMF). For convenience, the data were extracted from the soundtrack of a video recording made whilst the aircraft was undergoing a full-power ground-run. The aim of the work is to generate information relating the individual firings of each cylinder and this is presented as a multi-level colour image. Here, the ignition time history for two revolutions (six ignitions) is shown vertically and corresponds to the bank of exhaust ports facing the microphone. Subsequent similar histories are presented along the horizontal time axis. The results are sensitive to engine speed variations, and a correlation between successive vertical columns is carried out to quantify this drift and adjust the data accordingly. Seven engine speeds from 842 to 2740 rpm are examined. The processed data illustrate that some speeds exhibit well-defined, single ignitions whereas others show varying degrees of after-firing type effects. At the higher engine speeds, it would seem that the cylinder ignition amplitudes become much more irregular, and the results for 2740 rpm indicate a breakdown in engine performance. The coefficient of variation (Cv) has been demonstrated as a measure of these factors. Finally, a technique has been proposed and demonstrated for the identification of individual cylinders in the firing sequence. The data acquisition process is relatively straight-forward and should not demand excessive time to cover a full range of engine speeds. With further investigations, it could be possible to readily relate the imaging results to specific engine faults.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-04T03:33:28Z
      DOI: 10.1177/09544100211033403
       
  • New approach of inverse design of transonic compressor rotor blade via
           prescribed isentropic Mach distributions without modification of governing
           equations

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      Authors: Sheng Qin, Shuyue Wang, Gang Sun, Yongjian Zhong, Bochao Cao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Shock loss is the primary source of total pressure loss of transonic axial compressors. Reducing the shock by redesigning the geometry of rotor is of great interest for turbomachinery designers. However, the complex flow field involving shock waves, shock-boundary interaction, intense secondary flows, etc., in the compressor makes the design of rotor difficult. The conventional method of design and optimization is computationally intensive and time-costly. This study introduces an inverse design method to design rotor blades corresponding to prescribed isentropic Mach number distributions with no modification of flow-governing equations. An artificial neural network is trained to predict the isentropic Mach number distributions of any deformed blades. Then, with the pattern search optimization, the blade corresponding to the prescribed isentropic Mach number distributions can be achieved. When the aerodynamic parameter database is calculated and the neural network is obtained, this method can design large numbers of blades of changed isentropic Mach number distributions immediately, without modifying the computational fluid dynamics (CFD) flow solver. The design process is fully automatic and efficient. In this study, NASA Rotor 37 is redesigned and optimized as test cases. Some analysis on the influence of blade shape on aerodynamic characteristics of the rotor is represented in this study.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-20T03:22:03Z
      DOI: 10.1177/09544100211032489
       
  • Composite attitude fault tolerant tracking control for flexible satellite
           with time delay

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      Authors: Xiaofeng Xu, Mou Chen, Tao Li, Shuyi Shao, Qingxian Wu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article deals with the problem of attitude tracking control for flexible satellite under flexible vibration disturbance, actuator fault and time delay. Based on disturbance observer and fault tolerant control techniques, the flexible vibration disturbance and actuator fault are effectively estimated by disturbance observer and fault estimation observer, respectively. Meanwhile, a delay-dependent attitude tracking feedback controller is designed to ensure that the reference attitude is stably tracked. To reduce the conservatism of the designed algorithm, a time delay correlative decomposition factor is introduced to make the flexible satellite have a better performance for attitude tracking control. Finally, the effectiveness of the proposed method is illustrated by numerical simulations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-17T12:59:23Z
      DOI: 10.1177/09544100211030151
       
  • Position and velocity estimation with a low Earth orbit regional
           navigation satellite constellation

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      Authors: Tomer Shtark, Pini Gurfil
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Position and velocity estimation using Global Navigation Satellite Systems (GNSS) has been widely studied and implemented. In contrast to existing GNSS, the idea of using low Earth orbit (LEO) satellites for position and velocity determination is relatively new. On one hand, the launch to LEO is more affordable compared to GNSS orbits. On the other hand, LEO satellites provide reduced coverage and suffer from orbit determination uncertainties. In this article, we study position and velocity estimation for an aerial platform using signals from a LEO satellite constellation, designed to produce a relatively long coverage duration, while minimizing the geometric dilution of precision. We determine the receiver’s position by using the trilateration method and the velocity by using Doppler estimation, and improve the accuracy thereof by utilizing an Extended Kalman Filter (EKF). We suggest a solution for the trilateration initialization problem, which arises for LEO navigation satellites, which relies on averaging the Earth projection of all the satellites within sight. We examine two scenarios, one wherein the EKF’s dynamical model matches the reference dynamical model, and another with a model mismatch. When the dynamical model is approximated, the EKF reduces the position and velocity errors considerably. When the dynamical model is known, the position and velocity errors can be reduced by an order of magnitude.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-17T02:47:33Z
      DOI: 10.1177/09544100211031348
       
  • Tracking and vibration control of a free-floating space manipulator system
           with flexible links and joints

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      Authors: Yuming Huang, Weidong Chen, Minqiang Shao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The problem of modeling and controlling of a free-floating space manipulator with flexures in both links and joints is addressed in this study. A mathematical model of the system is developed by combining Lagrange’s equations and momentum conservation. The finite element method is introduced to discretize multi-links with complex cross-sections. In order to reduce the dimensions and maintain the precision of a rigid-flexible coupled system, an iterated improved reduction system method is adopted. Then, a novel composite control scheme for the reduced system is presented that uses the concept of integral manifolds and singular perturbation theory. Finally, an augmented computed torque controller is applied to the under-actuated slow subsystem to realize trajectory tracking in joint space, while a linear-quadratic controller is designed to damp out the vibration of joints and links. Numerical simulation results verified that the proposed hybrid controller can successfully suppress vibration and track trajectory at the same time.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-17T01:42:14Z
      DOI: 10.1177/09544100211031118
       
  • An exploitation-enhanced multi-objective efficient global optimization
           algorithm for expensive aerodynamic shape optimizations

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      Authors: Feng Deng, Ning Qin
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The traditional multi-objective efficient global optimization (EGO) algorithms have been hybridized and adapted to solving the expensive aerodynamic shape optimization problems based on high-fidelity numerical simulations. Although the traditional EGO algorithms are highly efficient in solving some of the optimization problems with very complex landscape, it is not preferred to solve most of the aerodynamic shape optimization problems with relatively low-degree multi-modal design spaces. A new infill criterion encouraging more local exploitation has been proposed by hybridizing two traditional multi-objective expected improvements (EIs), namely, statistical multi-objective EI and expected hypervolume improvement, in order to improve their robustness and efficiency in aerodynamic shape optimization. Different analytical test problems and aerodynamic shape optimization problems have been investigated. In comparison with traditional multi-objective EI algorithms and a standard evolutionary multi-objective optimization algorithm, the proposed method is shown to be more robust and efficient in the tests due to its hybrid characteristics, easier handling of sub-optimization problems, and enhanced exploitation capability.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-17T01:19:50Z
      DOI: 10.1177/09544100211032432
       
  • Adaptive model predictive control of a six-rotor electric vertical
           take-off and landing urban air mobility aircraft subject to motor failure
           during hovering

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      Authors: Shen Qu, Guoming Zhu, Weihua Su, Sean Shan-Min Swei, Mariko Hashimoto, Tao Zeng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this article, motor failure control of a six-rotor electric vertical take-off and landing (eVTOL) urban air mobility aircraft is investigated using adaptive model predictive control (MPC) based on the linear parameter-varying (LPV) model developed using the nonlinear rigid-body aircraft model. For capturing the aircraft dynamics under motor failure conditions, a family of linearized models are obtained by trimming the nonlinear aircraft model at multiple equilibrium conditions and the LPV model is obtained by linking the linear models using the failed rotor speed, where the system transition from healthy to failure is modeled by a scheduling parameter calculated based on failed rotor speed caused by available motor peak power after failure. The proposed adaptive MPC is developed to optimize the system output performance, including the rigid-body aircraft velocity and altitude, by using quadratic programming optimization with reference compensation subject to a set of time-varying constraints representing the current available propeller acceleration calculated based on the motor power. Simulation study is conducted based on the developed LPV control design and original nonlinear rigid-body model, and the simulation results demonstrate that the designed adaptive MPC controller is able to recover and maintain the aircraft at desired stable condition after motor failure.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-16T11:02:29Z
      DOI: 10.1177/09544100211032434
       
  • Design and co-simulation of a nose wheel steering system for a civil
           aircraft

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      Authors: Dawei Li, Mingxing Lin, Tao Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to automate the ground maneuvering of a civil regional aircraft and improve the efficiency of the air transport system, a fly-by-wire nose wheel steering system (NWSS) was designed. A rack and pinion steering mechanism integrated with a single actuator mechanism was proposed. The basic control circuit diagram with integrated test, the electro-hydraulic system diagram, and the mathematical model of the steering system were established and analyzed. A co-simulation model of the system was built to verify the control law. The results show that the properties of the prototype meet the design requirements. Given the importance of the NWSS, the simulation results can be used to optimize the basic design parameters. This methodology can also be used for other types of aircraft.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-15T05:40:02Z
      DOI: 10.1177/09544100211031717
       
  • Investigation of the stability of transverse hydrogen injection combustion
           caused by plate vibration using the dynamic mode decomposition method

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      Authors: Kun Ye, Liuzhen Qin, Zhenghao Feng, Zhengyin Ye
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article investigated the stability of transverse hydrogen injection combustion caused by the plate vibration. The finite-rate method is used to simulate the combustion. The unsteady flow field in the unstable phase of combustion is extracted. The unstable mode of the shock wave structure and the flame structure during the stage of combustion instability, the spatial and temporal characteristics of the dominant modes, as well as their stability are analyzed based on the dynamic mode decomposition (DMD) method. The results indicate that, according to the sequence of energy, the extracted first six orders modes of the shock wave structure and the flame structure have relatively low frequency with a negative growth rate and small numerical value, which presents a trend of weak convergence. The characteristics of the dominant structure of DMD modes show that the plate vibration has great effects on the reflected shock wave structure near the plate and on the upper wall surface, as well as the flame structure near the plate. According to the sequence of the mode energy and the growth rate, respectively, the extracted first six orders modes have relatively high frequency. Simultaneously, the structures of the modes extracted by the sequence of mode energy are more regular, while those extracted by the sequence of growth rate are more disorderly. The unstable shock wave structure is mainly manifested by the reflected shock wave in the vibration region and the shock wave structure reflected by the upper wall surface. The unstable flame structure is mainly concentrated near the vibration region and downstream areas.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-14T06:56:31Z
      DOI: 10.1177/09544100211030115
       
  • Sliding mode–based simultaneous control of impact angle and impact
           time

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      Authors: Kakoli Majumder, Shashi Ranjan Kumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this article, a sliding mode control–based nonlinear guidance scheme for controlling both impact angle and impact time simultaneously is proposed. The problem of impact angle control is first transformed to that of controlling line-of-sight angle and its rate, while the requirement of impact time is achieved by tracking the desired time-to-go. The chosen time-to-go estimate accounts for the curvature required to meet the impact angle requirements toward the target interception. In order to satisfy both of these terminal constraints, the sliding surface is defined as a combination of impact time error and the variable pertaining to the errors in line-of-sight angle and its rate, with appropriate gains assigned to them. The interceptor first performs necessary maneuvers to meet the impact time requirements and then steers its course to achieve the target interception at a desired impact angle. The guidance law is initially derived using nonlinear engagement kinematics against stationary targets and then extended to cater to constant velocity targets using the concept of predicted interception point. Numerical simulations are performed to validate the efficacy of the proposed guidance scheme for various initial engagement geometries. The performance of the proposed guidance scheme is also compared with those of the existing guidance laws and shown to be superior.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-05T10:08:15Z
      DOI: 10.1177/09544100211029817
       
  • Iterative learning NARMA-L2 control for turbofan engine with dynamic
           uncertainty in flight envelope

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      Authors: Feng Lu, Zhaohong Yan, Jie Tang, Jinquan Huang, Xiaojie Qiu, Yahui Gao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Nonlinear control of turbofan engines in the flight envelope has attracted much attention in consideration of the inherent nonlinearity of the engine dynamics. Most nonlinear control design techniques rely on the correction theory of reference model parameter to extend the typical flight operations from ground operation. However, dynamic uncertainties in flight envelope lead to the deviation of operating state, and it is negative to control performance. This article is to develop online correction neural network–based speed control approaches for the turbofan engine with dynamic uncertainty in the flight envelope. Two improved online correction nonlinear ways combined with nonlinear autoregressive moving average (NARMA) are proposed, such as gradient search nonlinear autoregressive moving average with feedback linearization (NARMA-L2) control and iterative learning NARMA-L2 control. The contribution of this article is to provide better control quality of fast regulation and less steady errors of engine speed by the proposed methodology in comparison to the conventional NARMA-L2 control. Some important results are reached on both turbofan engine controller design and dynamic uncertainty tolerance at the typical flight operations, and the numerical examples demonstrate the superiority of the proposed control in the flight envelope.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-05T06:46:43Z
      DOI: 10.1177/09544100211029814
       
  • Optimization investigation of vacuum air-intake for atmosphere-breathing
           electric propulsion system

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      Authors: Peng Zheng, Jianjun Wu, Yu Zhang, Biqi Wu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An atmosphere-breathing electric propulsion system uses the rarefied atmospheric molecules as the propellant for the electric thruster. In the best case, it can allow spacecraft complete a long-time mission in the lower Earth orbit without carrying any propellant. In this article, the intake geometry is designed, analysed and optimized to improve the performance of atmospheric particles capture, including collection efficiency and compression ratio. The orthogonal method is used in the simulation test to analyse the sensitivities of main parameters, including the configuration of grid ducts, the configuration of tapered chamber, the length-to-diameter ratio of tapered chamber and the diameter of tube. The results show that the performance of air-intake can be optimized with different parameter combinations. Compared with different intake designs of previous studies, the optimal design in this article shows the better particle capture performance under the same boundary conditions. The particles compression ratio is over 100, and the collection efficiency can reach 81.08%.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-01T02:10:48Z
      DOI: 10.1177/09544100211029829
       
  • Numerical analysis on evolution process of multiple rotating detonation
           waves with ethylene–oxygen–nitrogen mixture

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      Authors: Haolong Meng, ChunSheng Weng, Qiang Xiao, Quan Zheng, Yuwen Wu, Fang Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Two-dimensional numerical simulations of a rotating detonation combustor (RDC) fueled by ethylene–oxygen–nitrogen were performed to investigate the evolution process of multiple rotating detonation waves (RDWs), that is, initial chaotic stage, self-adjustment stage, and the final stable stage. The number of stable RDWs corresponding to the initial conditions was in good agreement with that predicted by an empirical model proposed by Daniau et al. from Lavrenty’ev Institute of Hydrodynamics (LIH). From the simulation results, the spontaneous formation of a reverse RDW and the transition of trailing waves to detonation waves contribute to the emergence of the chaotic stage. The self-adjustment stage comprises three distinctive parts, which are the self-adjustment of the propagation direction, the number, and the propagation characteristics of RDWs. Furthermore, the double-wave collision was found to play a significant role in modulating the propagation direction as well as the number of RDWs. The same self-adjusting trend of different instantaneous propagation characteristics (e.g., peak pressure, propagation velocity, and wave front height) of the RDWs was observed, suggesting the self-similarity property of the adjusting mechanism demonstrated in the evolution of rotating detonation dynamics.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-01T01:34:05Z
      DOI: 10.1177/09544100211030153
       
  • Parameterization and optimization design of a two-dimensional axisymmetric
           hypersonic inlet

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      Authors: Shangcheng Xu, Yi Wang, Zhenguo Wang, Xiaoqiang Fan, Bing Xiong
      First page: 1035
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Optimization method, as a promising way to improve inlet aerodynamic performance, has received increasing attention. The present research is undertaken to design a two-dimensional axisymmetric hypersonic inlet using parametric optimization. The inlet configuration is parameterized and optimized in consideration of total pressure recovery and starting performance. A Pareto front is obtained by solving the multi-objective optimization problem. Then, the flow structures of the optimized inlets are analyzed and the starting performances are evaluated. Results show that the total pressure loss mainly occurs in the internal contraction section, especially near the inlet entrance, and therefore the total pressure recovery coefficient can be greatly improved by decreasing external compression. As a result, the guidance for designing high-performance inlets is concluded. Besides, it is found that as the internal contraction ratio increases, the inlet starting ability becomes worse, which attributes to the larger separation bubble at the inlet entrance. Finally, the total pressure recovery coefficient and the starting Mach number of the optimized inlets are obtained, which can be a reference for engineering design.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-06-30T02:19:37Z
      DOI: 10.1177/09544100211029535
       
  • Generating and storing power on the moon using in situ resources

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      Authors: Alex Ellery
      First page: 1045
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The Moon Village and similar concepts are strongly reliant on in situ resource utilisation (ISRU). There is great interest in harvesting solar power using locally leveraged in situ resources as an essential facet of in situ infrastructure. Traditionally, silicon-based photovoltaic cells have been assumed, preferably manufactured in situ using a 3D printing rover, but there are major difficulties with such scenarios. Solar cells require pre-processing of regolith and solar cell manufacture. We present an alternative lunar resource leveraged-solar power production system on the Moon which can yield high conversion efficiencies – solar Fresnel lens-thermionic conversion. The thermionic vacuum tube is constructed from lunar-derived materials and NiFe asteroidal ores on the Moon. Given that the majority of energy required for ISRU is thermal, thermionic conversion exploits this energy source directly. Silicates such as anorthite can be treated with acid to yield alumina and silicic acid in solution from which pure silica can be precipitated. Pure silica when heated to high temperature yields fused silica glass which is transparent – fused silica glass may be employed to manufacture Fresnel lenses and/or mirrors. Both silica and alumina may be input to the Metalysis Fray Farthing Chen Cambridge electrolytic process to yield near pure Si and near pure Al, respectively.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-05T10:00:03Z
      DOI: 10.1177/09544100211029433
       
  • Numerical investigation of the effect of triangular cavity on the unsteady
           aerodynamics of NACA 0012 at a low Reynolds number

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      Authors: Rajesh Yadav, Aslesha Bodavula
      First page: 1064
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Time accurate numerical simulations were conducted to investigate the effect of triangular cavities on the unsteady aerodynamic characteristics of NACA 0012 airfoil at a Reynolds number of 50,000. Right-angled triangular cavities are placed at 10%, 25% and 50% chord location on the suction and have depths of 0.025c and 0.05c, measured normal to the surface of the airfoil. The second-order accurate solution to the RANS equations is obtained using a pressure-based finite volume solver with a four-equation transition turbulence model, γ–Reθt, to model the effect of turbulence. The two-dimensional results suggest that the cavity of depth 0.025c at 10% chord improves the aerodynamic efficiency (l/d ratio) by 52%, at an angle of attack of α = 8°, wherein the flow is steady. The shallower triangular cavity when placed at 25%c and 50%c enhances the l/d ratio by only 10% and 17%, respectively, in the steady-state regime of angles of attack between α = 6° and 10°. The deeper cavity also enhances the l/d ratio by up to 13%, 22% and 14% at angles of attack between α = 6° and 10°. Even in the unsteady vortex shedding regime, at α =12° and higher, significant improvements in the time-averaged l/d ratios are observed for both cavity depths. The improvements in l/d ratio in the steady-state, pre-stall regime are primarily because of drag reduction while in the post-stall, unsteady regime, the improvements are because of enhancements in time-averaged Cl values. The current finding can thus be used to enhance the aerodynamic performance of MAVs and UAVs that fly at low Reynolds numbers.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-06-18T12:23:02Z
      DOI: 10.1177/09544100211027042
       
  • Aerodynamic surrogate model based on deep long short-term memory network:
           An application on high-lift device control

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      Authors: Yi Zhang, Shuyue Wang, Gang Sun, Jun Mao
      First page: 1081
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An unsteady aerodynamic surrogate model based on the deep LSTM (long short-term memory) network is proposed for predicting unsteady aerodynamic coefficients. Deflection angles and deflection velocities of control surfaces are introduced to input values of the surrogate model to enhance the capability of identifying different motion states so that accumulative error can be controlled. Longitudinal stability is extremely important for flight safety while few studies have worked on unsteady aerodynamics of airfoils/wings with moving high-lift device (HLD) motion. Longitudinal static margin sequence of the HLD extending process is studied, and nonlinearity and hysteresis of coefficients in HLD motion are validated. The surrogate model is then applied in HLD motion control with the particle swarm optimization (PSO) method. Additionally, the results are then performed in three-dimensional aircraft HLD control. Validation computations show that longitudinal stability of optimized configuration is promoted with lift coefficient unchanged.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-06-21T11:15:24Z
      DOI: 10.1177/09544100211027023
       
  • Experimental and numerical study on cavitation performances of a turbopump
           with and without an inducer

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      Authors: Yanxia Fu, Jiangfeng Xie, Yang Shen, Giovanni Pace, Dario Valentini, Angelo Pasini, Luca D’Agostino
      First page: 1098
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The cavitation performances and its internal flows in a centrifugal turbopump with and without a three-bladed axial inducer have been studied both experimentally and numerically. A 3D steady numerical model has been applied to simulate the cavitating flow from the inlet to the outlet ducts of the turbopump with and without an inducer by using ANSYS CFX code. In the present work, to clarify this relationship, we conducted experiments in both cold water (T = 20°C) and hot water (T = 80°C) with a focus on the development of vapor volume fraction and head degradation by gradually reducing the inlet pressure from atmospheric conditions to the minimum allowable value at a constant rate of about 3 mbar/s. The measured and predicted cavitation performances of the turbopump with and without an inducer have been compared under different operating conditions and the temperature of the operating fluid.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-15T06:12:30Z
      DOI: 10.1177/09544100211027045
       
  • A novel hybrid aircraft propulsion based on the DEA compressor—part
           B: Performance

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      Authors: Babak Aryana
      First page: 1112
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This two-parts article introduces a novel hybrid propulsion system based on the DEA compressor. The system encompasses a Pulse Detonation TurboDEA as the master engine that supplies several full-electric ancillary thrusters called DEAThruster. The system, called the propulsion set, can be categorized as a distributed propulsion system based on the design mission and number of ancillary thrusters. Part B of this article explains the performance sizing of the propulsion set designed in part A. Evaluating the performance of the propulsion, computer programs are written for all major components of the both master engine and ancillary thruster. The intake, compressor, detonation process, diffusers, axial turbine, and exit nozzle are modeled under certain flight conditions, and their performances are revealed and analyzed. The flight conditions are considered from the static condition at the sea level up to flight Mach number 5 at an altitude of 20,000 m. The performance of the propulsion set is also compared with some aircraft propulsions modeled by similar studies in all important aspects.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-09T05:01:19Z
      DOI: 10.1177/09544100211028725
       
  • Integral terminal sliding-mode robust vibration control of large space
           intelligent truss structures using a disturbance observer

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      Authors: Dalong Tian, Jianguo Guo
      First page: 1155
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study aims to develop an advanced integral terminal sliding-mode robust control method using a disturbance observer (DO) to suppress the forced vibration of a large space intelligent truss structure (LSITS). First, the dynamics of the electromechanical coupling of the piezoelectric stack actuator and the LSITS, based on finite element and Lagrangian methods, are established. Subsequently, to constrict the vibration of the structure, a novel integral terminal sliding-mode control (ITSMC) law for the DO is used to estimate the parameter perturbation of the LSITS based on a continuous external disturbance. Simulation results show that, under a forced vibration and compared with the ITSMC system without a DO, the displacement amplitude of the ITSMC system with the DO is effectively reduced. In the case where the model parameters of the LSITS deviate by ±50%, and an unknown continuous external disturbance exists, the control system with the DO can adequately attenuate the structural vibration and realize robust control. Concurrently, the voltage of the employed piezoelectric stack actuator is reduced, and voltage jitter is alleviated.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-06-30T02:26:04Z
      DOI: 10.1177/09544100211029084
       
  • Vertical tail sizing of propeller-driven aircraft considering the
           asymmetric blade effect

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      Authors: Mohsen Rostami, Joon Chung, Daniel Neufeld
      First page: 1184
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An engineering approach is presented to analyse the asymmetric blade thrust effect with the help of analytical and semi-empirical methods. It is shown that the contribution of the asymmetric blade thrust effect in the lateral-directional stability of multi-engine propeller-driven aircraft is significant particularly in critical flight conditions with one engine out of service. Also, in some cases where the engines are rotating in one direction, the asymmetric blade effect has substantial effects on the handling qualities of the aircraft even in normal flight conditions. Overall, due to the significant contribution of this phenomenon in the lateral-directional stability of propeller-driven airplanes, it is important to consider it in the design of the vertical stabilizer and rudder. The resulting analytical method has been used to determine the vertical tail incident angle and desired rudder deflection in accordance with the most critical flight condition for two different cases and validated to ensure the accuracy of the result. In this work, the aerodynamic coefficients as well as the stability and control derivatives have been predicted using analytical and semi-empirical methods validated for light aircraft.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-05T10:13:35Z
      DOI: 10.1177/09544100211029450
       
  • A novel full-electric aircraft propulsion based on the DEA compressor

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      Authors: Babak Aryana
      First page: 1196
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article introduces a novel full-electric aircraft propulsion designed based on the DEA compressor, named DEAThruster that is supplied by a PEMFC. The thruster designed and modeled in this study is a compact DEAThruster to operate in altitudes up to 15,000 m and in the subsonic/transonic region with a specific thrust around 8300 N s/kg. The results show the thruster can satisfy all expectations, and it can generate up to 8300 N s/kg specific thrust for flight conditions encompassing static condition at sea level up to flight Mach number 0.95 in altitude 15,000 m. The DEAThruster can potentially be a practical alternative for gas turbine propulsions in all aspects when all available options for full-electric propulsions are not competitive for conventional aircraft propulsions in performance, size, and weight.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-07-06T01:21:00Z
      DOI: 10.1177/09544100211029437
       
  • Fault-tolerant control of flexible satellite with magnetic actuation and
           reaction wheel

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      Authors: Mohammad H Hajkarim, Nima Assadian
      First page: 1222
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The attitude fault-tolerant control of a flexible satellite actuated by reaction wheels and magnetic torquer bars is investigated in this article. A low earth orbit is considered for moment perturbations such as drag and gravity gradient. Furthermore, the flexible panels attached to a rigid central body are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using Lagrange’s equation, and the resulting dynamical model is validated by comparing its simulation results to the NX Siemens software results. Finally, a fault-tolerant controller based on sliding mode control is suggested and tested in different scenarios. It is showed that the proposed control method tolerates the actuators’ faults and controls the satellite’s attitude while desaturating the reaction wheels.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2021-08-24T10:24:07Z
      DOI: 10.1177/09544100211029497
       
 
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