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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
Showing 1 - 30 of 30 Journals sorted alphabetically
Acta Astronautica     Hybrid Journal   (Followers: 234)
Advances in Aerospace Engineering     Open Access   (Followers: 77)
Advances in Aerospace Science and Technology     Open Access   (Followers: 16)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 3)
Advances in Space Research     Hybrid Journal   (Followers: 301)
Aeronautical Journal, The     Hybrid Journal   (Followers: 12)
Aerospace     Open Access   (Followers: 68)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 25)
Aerospace Science and Technology     Hybrid Journal   (Followers: 318)
Aerospace Systems     Hybrid Journal   (Followers: 11)
Aerospace technic and technology     Open Access   (Followers: 8)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 7)
AIAA Journal     Hybrid Journal   (Followers: 1020)
Air Medical Journal     Hybrid Journal   (Followers: 7)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 149)
Artificial Satellites     Open Access   (Followers: 22)
ASTRA Proceedings     Open Access   (Followers: 3)
Astrodynamics     Hybrid Journal   (Followers: 5)
Aviation     Open Access   (Followers: 13)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 7)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 27)
Aviation Week     Full-text available via subscription   (Followers: 423)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 32)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 31)
Chinese Journal of Aeronautics     Open Access   (Followers: 20)
Ciencia y Poder Aéreo     Open Access   (Followers: 4)
Civil Aviation High Technologies     Open Access   (Followers: 7)
Control Systems     Hybrid Journal   (Followers: 244)
Cosmic Research     Hybrid Journal   (Followers: 6)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 26)
Fatigue of Aircraft Structures     Open Access   (Followers: 22)
Frontiers in Aerospace Engineering     Open Access   (Followers: 21)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 16)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 189)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 262)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 3)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 292)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 44)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 38)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 47)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 5)
International Journal of Aerospace Engineering     Open Access   (Followers: 88)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 24)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 23)
International Journal of Aerospace Sciences     Open Access   (Followers: 38)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 8)
International Journal of Aviation Management     Hybrid Journal   (Followers: 6)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 8)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 10)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 11)
International Journal of Micro Air Vehicles     Open Access   (Followers: 12)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 16)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
International Journal of Space Structures     Full-text available via subscription   (Followers: 20)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 11)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 6)
Investigación Pecuaria     Open Access   (Followers: 2)
Journal of Aerodynamics     Open Access   (Followers: 27)
Journal of Aeronautical Materials     Open Access   (Followers: 10)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 67)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 23)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 28)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 57)
Journal of Aerospace Technology and Management     Open Access   (Followers: 11)
Journal of Aircraft     Hybrid Journal   (Followers: 275)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 17)
Journal of Airline and Airport Management     Open Access   (Followers: 12)
Journal of Astrobiology & Outreach     Open Access   (Followers: 6)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 3)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 3)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 176)
Journal of KONBiN     Open Access   (Followers: 5)
Journal of Navigation     Hybrid Journal   (Followers: 185)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 579)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 9)
Journal of Space Weather and Space Climate     Open Access   (Followers: 31)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 711)
Journal of Spatial Science     Hybrid Journal   (Followers: 5)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 10)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 12)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 3)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 22)
Life Sciences in Space Research     Hybrid Journal   (Followers: 6)
MAD - Magazine of Aviation Development     Open Access   (Followers: 3)
Mekanika : Jurnal Teknik Mesin i     Open Access   (Followers: 1)
Microgravity Science and Technology     Hybrid Journal   (Followers: 4)
New Space     Hybrid Journal   (Followers: 7)
Nonlinear Dynamics     Hybrid Journal   (Followers: 20)
npj Microgravity     Open Access   (Followers: 4)
Open Aerospace Engineering Journal     Open Access   (Followers: 4)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 2)
Population Space and Place     Hybrid Journal   (Followers: 11)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 4)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 19)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 43)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 83)
Propulsion and Power Research     Open Access   (Followers: 90)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 21)
RocketSTEM     Free   (Followers: 7)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 24)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 2)
Space and Polity     Hybrid Journal   (Followers: 7)
Space Policy     Hybrid Journal   (Followers: 31)
Space Research Today     Full-text available via subscription   (Followers: 44)
Space Safety Magazine     Free   (Followers: 51)
Space Science International     Open Access   (Followers: 127)
Space Science Reviews     Hybrid Journal   (Followers: 93)
SpaceNews     Free   (Followers: 791)
Spatial Information Research     Hybrid Journal   (Followers: 2)
Transactions on Aerospace Research     Open Access   (Followers: 2)
Transport and Aerospace Engineering     Open Access   (Followers: 4)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 8)
Unmanned Systems     Hybrid Journal   (Followers: 5)
Xibei Gongye Daxue Xuebao / Journal of Northwestern Polytechnical University     Open Access   (Followers: 1)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)

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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: 43  
 
  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]
  • Numerical solution for elliptical orbit pursuit-evasion game via deep
           neural networks and pseudospectral method

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      Authors: Cheng-ming Zhang, Yan-wei Zhu, Le-ping Yang, Xin Zeng, Run-de Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents an efficient and stable DNNs-based Radau pseudospectral method for the free-time elliptical orbit pursuit-evasion game based on the equivalent reconstruction of the game model. Firstly, the relative dynamics equations are established by adding the nonlinear terms caused by the eccentricity to the Hill–Clohessy–Wilshire equations. Then the original pursuit-evasion problem is deduced to a 4-dimensional one-sided optimal control problem (OCP) based on the equivalent reconstruction. Secondly, in order to apply the deep neural networks (DNNs) to map the relationship between the OCP and the solution, the normalization of costates is introduced to eliminate the non-uniqueness of solutions when generating samples for training DNNs. Thirdly, the DNNs-based Radau pseudospectral method is proposed where the DNNs output the guesses of solutions to the derived OCP and the Radau pseudospectral method optimizes the histories of controls obtained by the guesses to the convergence. The simulation results demonstrate that the proposed method converges more stably and decreases the calculation time greatly compared with the traditional indirect method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-23T02:34:38Z
      DOI: 10.1177/09544100221109980
       
  • A unified in-time correction-based testability growth model and its
           application on test planning

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      Authors: Xiaohua Li, Chenxu Zhao, Bo Lu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Test management is a critical problem for in-time correction-based testability growth test. For the existing testability growth model, they are either too complex to be implemented in practice, or do not have the ability to draw a smooth test planning/projecting curve. This paper proposes a unified model for in-time correction-based testability growth test and presents its application on the test planning. Firstly, a simple model with only three parameters is developed, and its compatibility with the original Markov model is proved. The revised model only has three parameters, which can reduce the complexity of parameters estimation and increase the certainty of the test planning. Secondly, the paper incorporates the simplified transition probability model with the test cost model and studies the optimal test planning method with the minimum test cost criterion. To illustrate the efficacy of the proposed model, an application of the model to an attitude control system of a helicopter available in the open literature is given. The simulation demonstrates that the model and the method proposed in this paper are reasonable, and they are useful for effectively managing the testability growth test planning problem during system maturation.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-22T09:51:48Z
      DOI: 10.1177/09544100221108612
       
  • Comparison of the Newton–Raphson Method and genetic algorithm solutions
           for nonlinear aircraft trim analysis

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      Authors: Ugur Ozdemir
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      As the number of unknowns in trim analysis increases, the problem becomes more complicated, and traditional methods begin to fail. Common problems with conventional methods may be an ill-conditioned matrix, rounding errors, and division by zero. Furthermore, these methods are likely to find the local optimum, not the global optimum. In such cases, hybrid use with intelligent methods such as genetic algorithms is recommended. In this study, a flight situation that the Newton–Raphson method has for difficulty in solving is selected for a six-degree-of-freedom nonlinear trim analysis. Trim analysis was performed using the Newton–Raphson method, genetic algorithm, and by their hybrid use, respectively. The Newton–Raphson method had convergence problems despite very good initial guesses. The genetic algorithm was able to solve the same problem by itself. The unknowns in trim analysis, such as deflection angles of an elevator, a rudder, and an aileron, have physical limits, whereas the constraints make conventional methods more complicated, and the ability to use these limits in the genetic algorithm narrows the solution space and reduces the computation time. The hybrid use of the GA and Newton–Raphson method significantly increased the performance of the Newton–Raphson method and eliminated the convergence problem. It has been shown that a 6-degree-of-freedom trim problem, which traditional numerical methods such as the Newton–Raphson method have for difficulty in solving, can be solved easily and effectively with the hybrid use of the GA and the Newton–Raphson method. The strength of the proposed hybrid method to solve a highly nonlinear trim problem was demonstrated.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-20T03:51:26Z
      DOI: 10.1177/09544100221107726
       
  • Numerical study on detonation initiation process in the chamber with
           characteristic structures of the dual-mode scramjet combustor

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      Authors: Lisi Wei, Zhiwu Wang, Weifeng Qin, Longfei Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to improve the performance of traditional ramjet, a ramjet based on pulse detonation (PD-Ramjet) instead of isobaric combustion was proposed. Several special-shaped detonation chambers which retained the characteristic structures of the dual-mode scramjet combustor were designed. Characteristic structures included the expansion channel and the cavity. The filling process and detonation initiation process of the stoichiometric hydrogen/air mixture under the incoming flow condition of the sub-combustion mode were studied in the detonation chambers with characteristic structures by two-dimensional numerical simulation method, and the influences of the characteristic structures on the filling process and detonation initiation process were analyzed. The simulation and analysis results indicated that the hydrogen concentration at both sides of the chamber near the outlet was low due to the structure of the expansion channel, and the pressure and velocity of the detonation wave decreased gradually after the expansion channel. The cavity had a significant influence on the filling process, which resulted in the uneven hydrogen concentration downstream the cavity, especially near the outlet of the chamber. The intensity of the detonation wave attenuated to a certain extent by reason of the cavity, where the peak pressure first decayed due to the sudden expansion of the flow path and then rose owing to the reflection at the cavity aft wall.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-15T02:46:50Z
      DOI: 10.1177/09544100221107508
       
  • Turbine inlet temperature effects on the start process of an expansion
           cycle liquid propellant rocket engine

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      Authors: Mohammad Amin Eskandari, Hassan Karimi, Ali Sarvari, Mahyar Naderi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The main objective of this study is to investigate the effect of turbine inlet temperature on the transient phase of expansion cycle liquid propellant rocket engines during start. For this purpose, the non-linear differential mathematical model for 15 main components of the engine is derived, and the corresponding interaction between them is established. Afterward, the model is simulated using MATLAB Simulink, and 150 equations are solved with the Newton–Raphson method. The RL10 expansion cycle liquid propellant rocket engine is selected as a case study, and its dynamic behavior is simulated, and the results are compared with the experimental data. The simulation results showed that the present model for engine dynamic parameters, including thrust-chamber pressure, fuel, oxidizer mass flow rate, and turbo-pump speed, has less than 5% error compared to previous literatures. Using the prepared modeling software, the effect of turbine inlet temperature is studied on the engine start process. The obtained results demonstrated that inappropriate temperature profile during start transient might cause an engine malfunction while entering the nominal working regime.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-15T01:02:34Z
      DOI: 10.1177/09544100221090797
       
  • Effect of hexagonal stringer design on bulging factor and stress intensity
           factor of cracks in the skin of pressurized aircraft fuselage

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      Authors: Ahmed F Zayati, Tarek Lazghab, Mohamed Soula
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Aircraft structural fatigue is a serious issue. Untreated, it could lead to failure. Several aircraft accidents were caused by widespread fatigue damage. For cracks in the fuselage, the stress state is due to the bulging around the crack caused by applied internal pressure. This condition is characterized by a parameter called the bulging factor; it compares the stress intensity factor of a crack in curved shell to its counterpart in a plate. Bulging factor expressions are available for longitudinal and circumferential cracks but less for slanted cracks.The underlying structure that stiffens the skin of the fuselage has a direct impact on the stress intensity factor and the bulging factor of the crack. A hexagonal grid stiffening pattern has been shown to provide sufficient stiffening to the fuselage skin while using a lesser amount of material compared to the traditional orthogonal grid design. However, the response of this grid pattern in the presence of a cracked fuselage has not been studied.The current paper aims to estimate the effect of the hexagonal grid pattern on the bulging factor and stress intensity factor of cracks of various lengths and orientations in the skin of the fuselage. Results obtained are compared to the conventional orthogonal grid stiffening pattern of a fuselage structure. Several patterns were considered.Resultsshow that cracks of different lengths and orientations in hexagonal grid stiffened panels had stress intensity factors and bulging factors that are comparable to the base case within a margin of 2%–8%.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T11:37:37Z
      DOI: 10.1177/09544100221107724
       
  • Strain energy form coefficients for bending of short beams having full and
           

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      Authors: Toufik Yahiaoui, Toufik Zebbiche
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The aim of this work is to develop a new generalized formula and a numerical computation program for evaluating the energy form coefficient of a complex and arbitrary cross section for full and thin-walled cross section with respect to any central axis, for the bending of beams of small lengths in comparison with the transverse dimension of the section. This coefficient plays a very important role in the calculation of the deformation energy of beams subjected to bending under the effect of a shearing force for short beams. It also enters in the formulation of FEM bending model, in order to calculate the stresses and the strains due to the external forces. The application is made for complex sections used in various fields of construction and in particular for airfoils designed for aerospace construction. A method is developed to calculate this coefficient as a function of the rotation of the central axes. The calculation of the area, the moments, and the product of inertias with respect to the central axes is necessary. The formula for calculating this coefficient is presented as a definite integral of a non-analytical function determined point by point along the direction of the application of the shear force. This function is based on the calculation of the partial static moments. The calculation of the latter is based on the development of a technique by subdividing the upper part of the section into adjacent common triangles at one point for the full solid section or by segments on the boundary for the thin-walled section. To speed up the process of numerically calculating this integral with high precision and reduced time, Gauss Legendre quadrature of order 40 is used. The calculation of the distribution of the tangential stress as well as its maximum value is determined. A shear shape coefficient is therefore determined. In the second part of this work, an application is made for the static calculation by the FEM of a hyper static beam with a view to determining the influence of this coefficient on all the parameters of resistance and bending stiffness as a correction of the classical model of bending by the FEM. A study of the error made by the classical bending model on our shear effect model is presented. A coefficient of efficiency of a section is presented.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T11:01:24Z
      DOI: 10.1177/09544100221107247
       
  • A modified unsteady-nonlinear aeroelastic model for flapping wings

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      Authors: Seid H Pourtakdoust, Hadi Zare, Arian Bighashdel
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is produced via a servo motor whose dynamics is also considered for the analysis. A special case study is also performed whose combined aeroelastic solution is determined and validated under a sinusoidal flapping motion. To this end, an experimental setup is designed and tested in order to validate the proposed integrated approach for aeroelastic modeling of FWs. There is very good agreement between the numerical and experimental results for elastic FW aerodynamics. It should be noted that the proposed integrated aeroelastic approach is readily adaptable to all kinds of elastic wings with arbitrary geometry and various combination of structural elements.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T05:03:01Z
      DOI: 10.1177/09544100221108316
       
  • Optimal flight trajectory synthesis for an anti-collision maneouvre
           performed within environment of moving obstacles

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      Authors: Jerzy Graffstein
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      For solving the airplane-to-obstacle collision avoidance problem, two methods are necessary, that is, one for detecting a collision threat and the other one for synthesizing a safe manoeuvre avoiding threating obstacles. In the article, a method for detecting a threat of collision to obstacle was presented for the case of many obstacles moving within the neighbourhood of the airplane. Methods for optimal anti-collision trajectory synthesis and for proving the workability of such a result were proposed too. A solution of an optimisation problem, obtained by the swarm of particles optimization (PSO) was used for trajectory synthesis. A form of quality index was proposed for this task and the analyses of its behaviour for several values of weighting factors were presented. Results of simulations of flight along an optimal, anti-collision manoeuvre trajectory proved that such a manoeuvre is workable.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T02:25:48Z
      DOI: 10.1177/09544100221107725
       
  • Helicopter flight dynamics with simulated rainfall

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      Authors: Guozhi Li, Yihua Cao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Sustaining flight operation that encounters with rainfall might be a challenge to a pilot due to lacking of understanding flight dynamics in the rain conditions. This paper, combined with a computational fluid dynamics (CFD) technique, develops a nonlinear flight dynamics model in the rain conditions that can be capable of exploring UH-60A single-rotor helicopter flight dynamics in the rain conditions, including trim, stability, and controllability. Firstly, in order to obtain a data-driven basis relating to multiple working conditions of the blades, a CFD-based method of simulation of the blade airfoil in the conditions of the angles of attack ranging from −26° to 26° and under a thunderstorm heavy rain scenario when the rate of rainfall is 1500 mm/h is developed. Then, these data are incorporated into a nonlinear flight dynamics model in the form of coefficient increments. Numerical simulations are conducted in the range of the flight velocities from 0 knots to 160 knots. The quantitative results indicate that rainfall degrades the blade airfoil aerodynamic performance and increases the rotor torque and required power, affecting the helicopter trim, stability, and controllability. More importantly, helicopter that flies in a small or moderate flight velocity and that encounters rainfall might be a relative serious case, which should be paid attention to.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T02:14:27Z
      DOI: 10.1177/09544100221107255
       
  • Investigation on flame characteristics approaching thermal chocking in a
           cavity-based supersonic combustor

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      Authors: Zun Cai, Jianbin Li, Taiyu Wang, Yanan Wang, Jiajian Zhu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study experimentally investigated the combustion process in a cavity-based supersonic combustor at the inflow condition of Mach 2.92 with stagnation pressure 2.6 MPa and stagnation temperature 1530 K. Time-averaged flame distribution and oscillation characteristics were revealed by post-processing CH* chemiluminescence images. Wall pressures along the combustor bottom wall were also measured to provide quantitative information. Representative cascaded injection set-ups upstreaming the cavity were selected to compare ethylene flame characteristics. It is found that the combustion process is approaching thermal chocking when increasing the equivalence ratio to 0.8 according to the one-dimensional analysis of the Mach number distribution. At the same equivalence ratio, increasing the number of the cascaded injectors by lowering the injection pressure is not beneficial for the combustion enhancement, indicating that the injection pressure is also a key factor affecting the combustion heat release. However, increasing the injection pressure can cause obvious flame oscillations above the cavity as well as increasing the axis distance of the injectors. As a result, the injection scheme with two cascaded injectors which have the injection distance of 0.1 and 0.4 time the length of the cavity floor, respectively, upstreaming the cavity is suggested as a favorable scheme for scramjet applications.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T01:32:22Z
      DOI: 10.1177/09544100221107248
       
  • Extended aeroacoustic spanwise correction method for the aerodynamic noise
           prediction of large-span objects

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      Authors: Weijie Chen, Kangshen Xiang, Liangfeng Wang, Fan Tong, Weiyang Qiao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In a numerical study, a shorter span extent than experiment is often used to save the computational resource. The predicted sound pressure level should be corrected before compared with the experimental results. This study concerns the extended aeroacoustic spanwise correction method for the noise prediction radiated from large-span objects. Four new types of spanwise correction models are derived based on the assumption of the spanwise coherence function taking the form of a rectangular function, a trigonometric function, a Laplacian function and a Gaussian function, respectively. The large eddy simulation (LES) combined with the acoustic analogy theory is used for the aerodynamic noise prediction. The predicted far-field sound levels are then corrected by the proposed spanwise correction methods for the large-span objects. Far-field acoustic measurements and near-field hot-wire measurements are also performed in an anechoic wind tunnel for validation purpose. The predicted aerodynamic and aeroacoustic results are found in good agreement with the experiments with the proposed spanwise correction method. The present models based on the Laplacian function and Gaussian function are unified models taking the advantage of that there is no need to compare the relative extent of the numerical length, experimental length, and coherence length. The results also indicate that although there is no significant difference between the various functions, corrections based on the Gaussian profile seem to perform better compared with other functions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-12T11:53:29Z
      DOI: 10.1177/09544100221107251
       
  • A hybrid trim strategy for coaxial compound helicopter

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      Authors: Yuan Su, Zeyuan Wang, Yihua Cao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Interest in the coaxial compound helicopter (CCH) has been increasing in the civil aviation and engineering community for its high-speed and high-maneuverability features, and is likely to continue to do so for the foreseeable future. Since the control in CCH is totally different from the conventional helicopter, the redundant control strategy design is one of the biggest challenges. In this study, the CCH model based on XH-59A is built to investigate the impact of the propeller and the elevator on the flight performance. Four trim strategies with different objectives are proposed and then compared to find the optimal control allocation. A heuristic descent search method is applied to search the optimal velocity at which the propeller and the elevator are engaged. A significant improvement of power required at medium- and high-speed with acceptable rotor airloads increment was found by using the Hybrid Trim strategy in the speed range of 0–100 m/s, with regard to a pre-configured pitch angle schedule. The corresponding control variables obtained located in a reasonable control range, with a maximum power reduced of 13% at 100 m/s, which showcase the potential of the Hybrid Trim strategy.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-12T08:20:46Z
      DOI: 10.1177/09544100221103021
       
  • Feature extraction of rotor-stator rubbing faults based on harmonic fusion
           vector bispectrum, ITD and Hjorth parameters

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      Authors: Mingyue Yu, Haonan Cong, Wangying Chen, Minghe Fang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To solve the difficulty in extracting the characteristics of rotor–stator rubbing faults, the paper has proposed the combined method of Complexity parameter, the harmonic fusion vector bispectrum (HFVB), and intrinsic time-scale decomposition (ITD). First, to fully embody the characteristic information of fault, the HFVB is used to blend the information of signals collected from sensors installed in different positions. Second, taking in mind that the ITD algorithm can embody the effective separation of nonstationary and nonlinear signals, the ITD algorithm makes the separation of blended signals. Third, regarding the important influence of signal complexity on fault characteristic extraction, the complexity parameter of Hjorth parameters can provide very great embodiment of signal complexity. Complexity parameter of Hjorth parameters is introduced as a characteristic parameter index to make a option of proper rotation component (PRC) which can show the characteristics of rubbing fault better. Fourth, signals are reconstructed based on chosen signal components. Meanwhile, to reduce the influence of noise, reconstructed signals are denoised accordingly. Finally, implement the characteristic extraction and fault identification of rubbing faults according to the square demodulation spectrum (SDF) of denoised signals. The result indicates that the harmonic fusion vector bispectrum method can embody the effective blending of fault information; the complexity parameter in Hjorth parameter can serve as the index parameter for option of sensitive characteristic components of rubbing faults. Based on the proposed method, in the square demodulation spectrum of reconstructed signals, it can effectively and precisely provide the characteristics of rotor–stator rubbing fault and successfully identify a fault type.8714542030
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-11T05:38:16Z
      DOI: 10.1177/09544100221107256
       
  • Multi-objective nozzle design optimization for maximum thrust vectoring
           performance

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      Authors: Saadia Afridi, Tariq Amin Khan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Thrust vectoring is a promising technology that offers the potential for improved maneuverability, control efficiency, and stealth characteristics of aircraft. Optimized nozzle design over a range of operating conditions is one of the most crucial factors for maximum thrust vectoring operation. Our goal was to investigate the optimal design of bypass dual throat nozzle to maximize thrust vectoring. We performed a multi-objective optimization study by varying the nozzle bypass angle, convergence angle, and bypass width to see what impact these parameters had on the performance of the bypass dual throat nozzle. A steady numerical simulation has been performed on 55 different nozzle configurations to compare their thrust vectoring performance and losses. In all simulations, the k-ϵ turbulence model is used to determine the vectoring states of the nozzle. The computational fluid dynamics analysis was followed by a multi-objective optimization process using the Response Surface Methodology within the ModeFrontier software. The testing of the optimized nozzle shapes using ANSYS FLUENT verified the accuracy and reliability of the multi-objective optimization algorithm. These findings suggest that nozzle convergence does not significantly affect thrust vectoring. In contrast, bypass width and bypass angle significantly affected thrust vectoring.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-09T10:42:37Z
      DOI: 10.1177/09544100221106656
       
  • Three-dimensional continuous-time integrated guidance and control design
           using model predictive control

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      Authors: Reza Sheikhbahaei, Saeed Khankalantary
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this study, a novel three-dimensional continuous-time integrated guidance and control (IGC) scheme is presented. The proposed method is developed on the basis of generalized model predictive control (GMPC) approach and super-twisting extended state observer (STESO). The GMPC is used to generate the optimal closed form control law for the interceptor and the STESO is applied to estimate the maneuvering target lateral accelerations as well as the lumped disturbances. To the aim of IGC design, a six-degrees-of-freedom model based on the interceptor-target kinematics and interceptor dynamics is constructed. Afterward, the GMPC control law formulation for a nonlinear system exposed to disturbances is extracted. Finally, the effectiveness of the proposed IGC system is studied by numerical simulations. The simulation results reveal satisfactory interception performance including less energy consumption in comparison to a recently proposed successful IGC method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-07T06:23:59Z
      DOI: 10.1177/09544100221103320
       
  • Adaptive neural tracking control of constrained waverider vehicles via
           single-network adaptive dynamic programming

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      Authors: Qiang Qi, Xiangwei Bu, Baoxu Jiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The approximate optimization is considered though adaptive dynamic programming (ADP) method for waverider vehicles (WVs). This method can achieve the stability, robustness, and near optimization of the tracking problem for WVs. First, baseline controllers are designed for both velocity subsystem and altitude subsystem via neural network approximation. Meantime, novel auxiliary systems are implemented to compensate the desired control law with actuator saturation. Then, transient optimal controllers are developed using single-network adaptive critic method. Moreover, the stability of closed-loop systems, and the convergence of both the tracking error and the auxiliary system are theoretically proved. Finally, the superiority of the proposed method is proved via compared simulation results.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-06T06:30:34Z
      DOI: 10.1177/09544100221097531
       
  • Aerodynamic performance characterization of bio-inspired wings with
           leading edge tubercles at low Reynolds number

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      Authors: V T Gopinathan, J Bruce Ralphin Rose
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      On the observation of biomimetic Humpback Whale (HW) flippers, the airfoil aerodynamic performance characteristics are explored. The Leading Edge (LE) tubercle geometry was inspired by the flipper of HW that has rounded LE protuberances and tapered trailing edge configurations. The tubercles have excellent flow control characteristics at the post-stall region. Aerodynamic characteristics of airfoils such as NACA0015 and NACA4415 with LE tubercles are experimentally and numerically investigated at the low Reynolds number about Re = 1.83 × 105. The bio-inspired modified airfoils (HUMP 0015 and 4415) are designed with the amplitude to wavelength ratio [math] of 0.05. The numerical simulation over the modified airfoils shows that, at higher Angle of Attack the flow separation is delayed in the peak region whereas the early flow separation is observed in the trough region adjacent to the LE. The boundary layer flow separation analysis is done extensively through numerical simulations and the velocity vector profiles are captured at different chordwise positions. The stall delay phenomenon is observed through the outcome of this research that specifically insists at the peak region of tubercles. Computation of Coefficient of pressure [math] distribution is also done by both numerical and wind tunnel experiments. Analysis of [math] distribution allows the identification of critical regions that initiate the adverse pressure gradient and region of flow separation. It is a novel effort to predict the Coefficients of Lift [math] and Drag [math] concerning the bio-inspired airfoils through [math] distribution such that the influence of flow separation and vortex distribution are characterized for the modified and baseline airfoils. Comparison of [math], [math], and [math] between the baseline and modified airfoils reveal the enhanced momentum transfer characteristics of bio-inspired tubercles.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-04T04:12:35Z
      DOI: 10.1177/09544100221103737
       
  • Robust attitude estimation for an unmanned aerial vehicle using multiple
           GPS receivers

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      Authors: Djamel DHAHBANE, Abdelkrim NEMRA, Samir SAKHI
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Estimation of the system state is an important task in the field of control, localization, and navigation. Many sensors are used to extract the attitude information. GPS (Global Positioning System) is widely used to provide position and velocity for ground and aerial vehicles. However, only a few research works have addressed the problem of attitude estimation using multiple GPS receivers. The main contribution of this paper consists on proposing a robust algorithm for attitude estimation of an unmanned aerial vehicle using INS/3GPS integration. First, we propose two alternative methods for attitude determination with three GPS receivers: Direct Computing Method (DCM) and Least Square Method (LSM) based on Singular Value Decomposition (SVD). Second, the attitude given by GPS receivers is fused with the measurement of a three-axis gyroscope using a robust Smooth Variable Structure Filter (SVSF). The optimal geometric configuration of GPS antennas is determined based on a deep performance analysis of the proposed system. Then, robustness analysis is assessed against measurement noise and parameters uncertainties. Simulation results are presented to demonstrate the robustness of the proposed approach. A more realistic evaluation of the proposed solution is obtained using an aerial vehicle type “Helicopter” from the Virtual Robot Experimentation Platform (VREP simulator). The proposed filter is compared with an Extended Kalman Filter (EKF). The obtained results have confirmed how much the SVSF is robust for attitude estimation in presence of the considered disturbances.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-03T08:03:34Z
      DOI: 10.1177/09544100221089220
       
  • Fixed time output feedback control for quadrotor unmanned aerial vehicle
           under disturbances

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      Authors: Shikai Shao, Shu Wang, Yuanjie Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper designs a fixed time output feedback trajectory tracking control scheme for quadrotor Unmanned Aerial Vehicle with unmeasurable velocity and external disturbances. Firstly, a fixed time extend state observer (ESO) is devised to accurately observe the unknown velocity and estimate unknown total disturbances within a fixed time. Especially, the convergence time of system is independent of system initial states. Secondly, considering control accuracy and convergence rate, robust fixed time controllers are respectively designed for position and attitude system. Thirdly, the tracking errors of controller is capable of converging to zero according to homogeneous theory and Lyapunov theory, and superior results can be achieved under the proposed control scheme. Finally, simulations and comparison studies are verified to demonstrate the effectiveness of the designed fixed time output feedback control scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-28T10:36:16Z
      DOI: 10.1177/09544100221089068
       
  • Integrated control scheme for a large membrane diffractive space telescope

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      Authors: Liang Tang, Zixi Guo, Xiao Feng, Xin Guan, Kebei Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      For higher resolution, next-generation space telescopes would be equipped with 10–20 m scale membrane diffractive primary lenses, and would have 100 m scale focal length. The large and flexible structure makes high-accuracy and high-stability control a great challenge. Specifically, both high-frequency and low-frequency disturbances must be attenuated, and the relative motion between the primary lens and the receiver (composed of the correcting optics and the imaging sensor) must be controlled. This paper presents a novel integrated control scheme to achieve the strict control goals. The dynamic model of a membrane diffractive space telescope is presented, where both high-frequency and low-frequency disturbances are considered. Nonlinear deformation of the flexible structure is also taken into account. The integrated control scheme consists of 3 parts: (1) an Agile Stable Precision platform (ASP), which can not only reduce the high-frequency vibrations for the receiver but also act as the actuator in the receiver control system; (2) a neural network controller for the spacecraft bus, which control the attitude of the spacecraft bus under uncertain low-frequency disturbances; (3) a finite-time neural network controller for the receiver to make the relative position and attitude of the receiver track on the expected state as fast as possible. Numerical simulations were carried out to verify the superiority of the integrated control scheme. Compared with traditional single stage spacecraft control (i.e., without the ASP), the accuracy and stability of the relative position and attitude are improved by at least one order of magnitude, and the settling time is greatly reduced.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-28T10:06:12Z
      DOI: 10.1177/09544100221100049
       
  • High-speed rarefied gas flow simulations using Quasi-Gas Dynamic equations
           with slip and jump boundary conditions

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      Authors: Nam TP Le, Phuc T Huynh
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The high-speed rarefied gas flow simulation is essential for the aerothermodynamic design of high-altitude vehicles. Recently, the Quasi-Gas Dynamic (QGD) equations have been implemented in OpenFOAM as a CFD solver named QGDFoam. In computational fluid dynamics (CFD), the accuracy of the prediction of the surface quantities depends on the slip and jump boundary conditions applied to the surfaces. In the present work, various first-order and second-order slip and jump boundary conditions have been numerically implemented into the solver QGDFoam in OpenFOAM to obtain a completed solver for simulating the rarefied gas flows. It then captures the surface quantities of the gas flows, such as the surface gas pressure, the slip velocity, and surface gas temperature. This completed solver is validated for the sharp-leading-edge wedge, the compression ramp, and the NACA 0012 micro-airfoil cases. Using the QGD model with the slip and jump conditions extends its application and enhances it to simulate high-speed rarefied gas flows. The simulation results show that the slip and jump conditions have been successfully employed with the QGD equations and give good results for predicting the surface quantities compared with the DSMC data.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-28T04:44:03Z
      DOI: 10.1177/09544100221103752
       
  • Toward the feasible solution of a long-lasting dynamic similitude problem

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      Authors: Pedram Hajipourzadeh, Afshin Banazadeh
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Dynamic similar models are designed to study the flight behavior of the full-scale aircraft in early design stages. Due to physical and operational constraints, full dynamic similarity between the scaled-down model and full-scale aircraft is not feasible. Thus, the scale model would be flying at different Reynolds number and Mach number. A given aircraft configuration with specific aerodynamic characteristics will have different performance if Mach number and Reynolds number are changed considerably, which results in different dynamic behavior of the scale model. To compensate for these dissimilarities, it is proposed to modify the airfoil geometry of the scale model to preserve aerodynamic similarity. In this study, based on the flight regime and design requirements, maximum thickness of the airfoil, maximum camber, and their respective location are modified to preserve aerodynamic characteristics at different Mach and Reynolds numbers. Geometry optimization was performed using Particle Swarm Optimization and the geometry optimization results show that it is possible to mitigate the change in Reynolds and Mach number in various flight conditions. It has been shown that optimized geometries of all test cases had airfoils with lower maximum thickness and slightly higher maximum camber.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-27T07:30:20Z
      DOI: 10.1177/09544100221103007
       
  • Unsteady aerodynamic analysis and effectiveness of bio-inspired flapping
           wings in V-formation flight

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      Authors: Ethan Billingsley, Mehdi Ghommem, Rui Vasconcellos, Abdessattar Abdelkefi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Several bird species have been observed to fly in V-formation, an arrangement which exploits aerodynamic features to allow the group to conserve energy when migrating over long distances without stopping and feeding. The use of such grouping arrangement and organized pattern has demonstrated longer endurance and less power consumption in comparison with single flights. In this work, a computationally efficient potential flow solver based on the unsteady vortex lattice method (UVLM) is employed to assess the aerodynamic performance of flapping wings in forward flight in terms of lift and thrust generation along with the propulsive efficiency. The UVLM has the capability to simulate incompressible and inviscid flows over moving thin wings where the separation lines are known a priori. A bio-inspired, albatross wing shape is considered and its aerodynamic performance in formation flights is compared against conventional elliptical and rectangular wing shapes. The aerodynamic analysis is carried out for different wing arrangements of 3-body and 5-body V-formations to determine the optimal spacing parameters leading to maximum propulsive efficiency. The simulation results reveal that, at the optimal formation angle and separation distance, the albatross-inspired wing shape produces the most lift over the flapping cycle, while the rectangular wing shape generates the most thrust over the flapping cycle. Furthermore, the optimal configuration in terms of propulsive efficiency is found to be a 5-body V-formation utilizing the albatross wing shape with a separation distance set to one-third of the span and a formation angle set to 139°. The present study provides guidance for the design of multi-flapping wing air vehicles based on the expected flight mission. The albatross wing shape is found to have superior capability in producing lift, while the elliptical wing shape is observed to consume less power. The rectangular wing shape is found to produce higher thrust and then can achieve faster forward motion.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-27T07:10:05Z
      DOI: 10.1177/09544100221103020
       
  • Performance evaluation of a novel adaptive variable structure state
           estimator

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      Authors: Nilanjan Patra, Smita Sadhu, Tapan Kumar Ghoshal
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An improved nonlinear adaptive state estimator called Adaptive Smooth Variable Structure Filter ASVSF has been proposed and its algorithm described. ASVSF extends the functionality and performance of a previously reported robust smooth variable structure filter (SVSF) with optimal boundary layer (SVSF-OBL). Improvement in performance includes the provision for accommodating unknown and time varying process noise covariance, which generally characterizes modelling uncertainty. The novelty of this proposed ASVSF estimator, which inherits the features of the SVSF, is that it adaptively provides an estimate of the unknown time varying process noise covariance (and hence called adaptive SVSF or ASVSF) which is required for determining the optimal boundary layer width of SVSF-OBL thus obviating the need of the prior knowledge of the process noise covariance. This makes the proposed estimator performance to be insensitive to (and therefore robust with respect to) unknown time varying process noise covariance while retaining the optimality of SVSF-OBL. The performance of the proposed ASVSF estimator is evaluated using Monte Carlo simulation and is compared with previously reported state estimators using a case of maneuvering civilian aircraft where a simplified and grossly approximate process model is used in the estimator/filter for tracking and thereby generating a time varying and unknown process noise covariance situation. Three different measures of Root Mean Square (RMS) error over the trajectory have been used for comparison which demonstrates the strengths of the proposed ASVSF estimator.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-26T07:53:04Z
      DOI: 10.1177/09544100221103328
       
  • Neural longitudinal control of hypersonic vehicles with constrained
           aerodynamic surfaces

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      Authors: Guan Wang, Hao An, Ziyi Guo, Hongwei Xia, Weinan Xie, Guangcheng Ma
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a neural adaptive flight control for longitudinal dynamics of air-breathing hypersonic vehicles (AHVs) with constrained aerodynamic surfaces. Multiple actuator constraints including magnitude, rate, and first-order dynamic model in both the elevator and canard are transformed into a specific control allocation problem, which can be readily solved using the standard model predictive control (MPC) technique. Furthermore, an adaptive control scheme is developed combining with the above control allocation and the recurrent cerebellar model articulation controller (RCMAC), which well handles actuator constraints and uncertain factors including aerodynamic coefficients, external disturbances, and flexible dynamics. Numerous simulation results verify performance and robustness of the proposed neural adaptive control.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-26T07:06:19Z
      DOI: 10.1177/09544100211069181
       
  • A composite controller design using an adaptive internal type-2 fuzzy
           logic system and the fixed-time disturbance observer for an air-breathing
           hypersonic vehicle with a variable geometry inlet

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      Authors: Liqian Dou, Yiqun Li, Miaomiao Du, Xiuyun Zhang, Zhiyu Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a novel composite controller design technique is addressed for using an adaptive interval type-2 fuzzy logic system (FLS) with the fixed-time disturbance observer (FTDO) such that the enhanced tracking performance is achieved for an air-breathing hypersonic vehicle with a variable geometry inlet (AHV-VGI). First, introducing the variable geometry inlet to take proper mass flow into the engine without any flow spillage ensures enough thrust for acceleration and maneuvering flight. The interval type-2 FLS integrated with an adaptive control algorithm is derived to approximate the complicated nonlinear items in the control strategy online, which assures that the tracking error are semi-globally uniformly bounded. After that, the fixed-time disturbance observer that is constructed to provide the estimations of uncertainty including external disturbance leads to a more practical and robust flight control system for AHV-VGI. The uniform stability of the whole system is proved under the framework of Lyapunov theory. Finally, simulation results and analysis are presented to demonstrate the effectiveness of the proposed composite control scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-26T03:21:24Z
      DOI: 10.1177/09544100221086051
       
  • Effects of asymmetric stroke deviation on the aerodynamic performance of
           flapping wing

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      Authors: Fujia Hu, Yuanying Wang, Dian Li, Xiaomin Liu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The kinematics of insect flapping flight are complex and asymmetric, which are contributed to their superior flying capabilities, and the design of novel flapping micro air vehicles can draw inspiration from relevant researches. Previous studies usually focus on the wing with asymmetric stroke or pitch motions. A trajectory with asymmetric deviation motion, named as “pear-shaped” pattern, is proposed in current work. The hovering aerodynamics and vortex dynamics of a rigid flapping wing have been numerically investigated by comparing with that of “line-shaped” pattern with no deviation. In order to have a better insight into the influences of the asymmetric deviation, we change the kinematic parameters, that is, stroke amplitude, pitching amplitude, deviation amplitude, and phase lag between stroke and pitch angles. The results show that the wing with asymmetric deviation exhibits superior capability in lift enhancement for most of the cases analyzed, which is accompanied by the extra power cost and slight reduction in efficiency. The asymmetric deviation in cases with high stroke amplitude or low pitching amplitude may be considered as a cost-saving strategy, subject to slight damage on lift generation (if acceptable). Additionally, the asymmetric deviation brings a strong asymmetry into the instantaneous forces during one flapping cycle. The underlying lift-enhancing mechanism is explored by examining the dominant vortex structures in the adjacent flow field of the wing, which is mainly attributed to the changes in the effective angle of attack, increasing with downward deviation and decreasing with upward deviation.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-25T07:33:25Z
      DOI: 10.1177/09544100221103477
       
  • S-duct flow distortion with non-uniform inlet conditions

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      Authors: Matteo Migliorini, Pavlos K Zachos, David G MacManus, Pierre Haladuda
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Convoluted aero-engine intakes are often required to enable closer integration between engine and airframe. Although the majority of previous research focused on the distortion of S-duct intakes with undistorted inlet conditions, there is a need to investigate the impact of more challenging inlet conditions at which the intake duct is expected to operate. The impact of inlet vortices and total pressure profiles on the inherent unsteady flow distortion of an S-duct intake was assessed with stereo particle image velocimetry. Inlet vortices disrupted the characteristic flow switching mode but had a modest impact on the peak levels and unsteady fluctuations. Non-uniform inlet total pressure profiles increased the peak swirl intensity and its unsteadiness. The frequency of swirl angle fluctuations was sensitive to the azimuthal orientation of the non-uniform total pressure distribution. The modelling of peak distortion with the extreme value theory revealed that although for some inlet configurations the measured peak swirl intensity was similar, the growth rate of the peak values beyond the experimental observations was substantially different and it was related with the measured flow unsteadiness. This highlights the need of unsteady swirl distortion measurements and the use of statistical models to assess the time-invariant peak distortion levels. Overall, the work shows it is vital to include the effect of the inlet flow conditions as it substantially alters the characteristics of the complex intake flow distortion.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-24T11:05:35Z
      DOI: 10.1177/09544100221101669
       
  • Long short-term memory neural network with scoring loss function for
           aero-engine remaining useful life estimation

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      Authors: Li-Hua Ren, Zhi-Feng Ye, Yong-Ping Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Estimation of the aero-engine remaining useful life (RUL) is a significant part of prognostics and health management (PHM) and the basis of condition-based maintenance (CBM) which can improve the reliability and economy. Multiple operating conditions, nonlinear degradation, and early prediction are significant and distinctive issues compared with other prognostics problems. While these issues do not get enough attention and researches in aero-engine RUL estimation. In view of these points, three specific data preparation approaches and a novel loss function are introduced. The data preparation approaches can extract high-quality data for the long short-term memory (LSTM) neural network according to the characteristic of aero-engine degradation data. Among these approaches, operating condition normalization is an effective method to handle the multiple operating conditions problems, and RUL limitation identification is a novel method to identify the turning point of the nonlinear degradation process. The scoring function is an innovative loss function used to replace the mean square error (MSE) loss function which has a preference for early prediction. The comparisons with the original LSTM and some other approaches indicate that the combination of the data preparations and the scoring loss function is an effective solution for the above issues, and can achieve the best performance among the approaches.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-24T09:09:24Z
      DOI: 10.1177/09544100221103731
       
  • Objective comparison of numerical spin study with aircraft model
           free-flight spin tests

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      Authors: Bilal Malik, Jehanzeb Masud, Suhail Akhtar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper reports on the results of a research project that investigated the spin and recovery characteristics of a multirole fighter aircraft. In the first phase, numerical/computational methods were used to predict full scale aircraft spin and recovery characteristics. The aerodynamic data used in the numerical study was obtained from rotary balance steady coning and oscillatory coning motion dynamic wind tunnel tests conducted on 1/13th scale aircraft dynamic model. All the possible steady spin modes were numerically computed, a complete set of dynamic modes of the spinning aircraft were evaluated and six degree of freedom simulations of predicted flat spins were performed to investigate their dynamic stability and recovery characteristics. In the second phase, free-flight spin trials were conducted using 1/5th scale dynamic model of the understudy aircraft to validate the results of the analytical spin studies. Dynamic characteristics of the analytically predicted flat spins were objectively compared with flat spins found in free-flight spin trials as a validation process. Our results reveal that the numerically predicted full scale aircraft spin and recovery dynamic characteristics correlate well with those estimated from model test flights. The present study is an important step toward objective comparison of numerical spin studies based on dynamic wind tunnel tests data with free-flight spin trials, yielding important guidelines and results for future aircraft spin studies.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-23T02:09:48Z
      DOI: 10.1177/09544100221103011
       
  • 4-degrees of freedom attitude equations of motion: A new approach for
           simulating flexible satellite dynamics with time-varying payload despite
           time delay and disturbances

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      Authors: Shayesteh Nikpay, Mahdi Fakoor, Ahmad Kalhor
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A new approach for the pointing of satellite’s payload is improving the dynamics of satellites to more than 3-DOF. In this approach, there would be no requirement for satellite complete rotations to perform the payload’s mission. The purpose of this study is to derive Four Degrees of Freedom (4-DOF) equations of motion of a satellite and its payload. Therefore, the payload can observe an area of the earth, and simultaneously, the satellite can transfer data to the earth station. Lagrange dynamics are utilized to derive 4-DOF dynamic equations of the system. Then, the system of payload-satellite is controlled by the sliding mode control method with three different sliding functions. Environmental disturbances and appropriate time delay for Low Earth Orbit are applied to the nonlinear attitude equations. Numerical simulations demonstrate the effectiveness of the 4-DOF nonlinear dynamics of the payload-satellite system and indicate that the controller negates the effects of the nonlinear external disturbances and time delay. According to the results, the attitude states attain the reference targets of Euler angles and the time-varying payload with excellent precision and high convergence speed.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-21T05:34:41Z
      DOI: 10.1177/09544100221092189
       
  • Transonic flutter suppression with tuned mass damper by model-based
           stability analysis method

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      Authors: Luo Fuqing, Gao Chuanqiang, Lyu Zhen, Zhang Weiwei, Xu Qiannan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Flutter as a self-excited oscillation can cause catastrophic damage to the aircraft structure. Tuned mass damper (TMD) is one of the vibration suppression methods widely used in engineering. However, traditional linear aerodynamic methods are not accurate in transonic flow. In this study, we first establish an unsteady aerodynamic model of the NACA0012 airfoil using the system identification method based on the Auto-Regressive with eXogenous input (ARX) model. Then, a flutter suppression model is constructed by coupling the TMD with the aeroelastic system. The parameters of the TMD are investigated using the model-based aeroelastic stability analysis. It is found that the flutter instability mode of the original system has changed due to the participation of the TMD in the system modal coupling. The proposed reduced-order model (ROM) provides a fast stability analysis method for flutter suppression with TMD as well as significant guidance for TMD design and optimization.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-20T03:37:44Z
      DOI: 10.1177/09544100221089704
       
  • Real-time prediction for the surge of turboshaft engine using multi-branch
           feature fusion neural network

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      Authors: Xing-Long Zhang, Tian-Hong Zhang, Ling-Wei Li, Jia-Ming Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The existing aeroengine instability precursor detection methods can be summarized as applying advanced signal processing technologies to various signals from the compressor test rig rather than the whole engine. Besides, these methods seriously depend on the artificial designed feature and threshold and also ignore the limit on the sensors onboard. Thus, with the help of the powerful feature extraction ability of the deep neural network, a real-time surge prediction method based on the multi-branch feature fusion neural network (MBFFNN) is proposed. First, the dataset can be obtained by using overlapping slices to divide surge test data into a sample sequence and using complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to label each sample precisely. Second, for each sample, the time-domain statistical parameters are calculated and the recurrence plot is obtained by using phase space reconstruction. Finally, the MBFFNN with mixed data type input is designed, and its performance is evaluated by the generated dataset. The experimental results show that compared with multilayer perceptron (MLP), long short-term memory (LSTM), and deep residual network (DRN), MBFFNN has the best performance on two datasets for different surge tests, which demonstrates that the proposed method for surge prediction can accurately judge the state of the aeroengine, identify the instability precursor before the surge, and give an early warning in advance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-19T07:33:18Z
      DOI: 10.1177/09544100221097586
       
  • Integrated impact time guidance and control against non-maneuvering
           targets

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      Authors: Aditya Patil, Shashi Ranjan Kumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes integrated guidance and control for skid-to-turn cruciform canard-controlled interceptors for controlling impact time along with interception of non-maneuvering targets. This approach circumvents the possible difficulties associated with designing guidance and control subsystems independently. An interceptor control surface deflection for achieving appropriate lateral acceleration to achieve the guidance objectives are derived using sliding-mode control considering nonlinear engagement dynamics, thereby remaining effective even for engagement with large initial heading errors. The switching surface is chosen to be a function of time-to-go and its rate with different time-to-go estimates against stationary and moving targets. The time-to-go estimate for stationary target accounts for the heading angle errors, while that for constant velocity target provides an exact value. Unlike many of the existing strategies, the proposed approaches enable the interceptor to achieve an impact time, even less than its initial estimates. The efficacy of the proposed guidance strategies is validated through numerical simulations for various initial engagement geometries. Furthermore, the performance of the proposed integrated guidance and control approach is also compared with the separate design of guidance and control subsystems, and shown to be superior.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-19T06:41:37Z
      DOI: 10.1177/09544100221083427
       
  • Flow characteristics and separation control in a transitional twin
           air-intake

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      Authors: KrishnaKumar R Yadav, Anuj Jain, Akshoy Ranjan Paul
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Ambient air is ingested into the engine of military aircrafts using the air-intake system within a limited space. The flow non-uniformity produced in the air-intake creates flow separation and total pressure loss due to the centerline curvature and area diffusion which eventually affects its performance. The current work discusses the performance of a transitional twin air-intake without and in presence of slotted synthetic jets. The synthetic jet is employed just before the inflection at a range of velocity ratio from 1 to 10 and found that for a velocity ratio of 4.0, the pressure distortion at the aerodynamic interface plane is found minimum. Hence, the other performance parameters are computed at that optimized flow condition. The outcome of the study reveal that the static pressure is recovered by 4.61%–6.64% while the total pressure loss is decreased by 59.28%–89.95% using optimized synthetic jets for a range of Reynolds numbers.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-18T08:00:33Z
      DOI: 10.1177/09544100221103652
       
  • Research on aero-engine performance seeking control based on the NN-PSM
           on-board model

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      Authors: Qiangang Zheng, Dewei Xiang, Cheng Chen, Haibo Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to improve the real-time performance of performance seeking control (PSC), a neural network-propulsion system matrix(NN-PSM) on-board model is proposed and applied to PSC. First, based on NN-PSM, a large-envelope, multi-variable on-board adaptive model is established. The PSM is extracted through a small deviation linearization method. The neural network is used to map the relationship between the flight conditions, engine control parameters, and the engine performance parameters, and designed a Kalman filter to estimate engine health parameters in real-time. Then, four PSC mode of maximum thrust, minimum fuel consumption, minimum high-pressure turbine inlet temperature, and minimum infrared radiation intensity are designed using LP optimization algorithm as optimize algorithm. Finally, the simulation results show that NN-PSM has much higher precision than Compact Propulsion System Model (CPSM). The PSC simulations show that compared with the PSC based on the conventional CPSM, the proposed method has much better real-time performance and get better engine performance, such as more thrust, less specific fuel consumption, and less turbine inlet temperature.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-17T07:55:34Z
      DOI: 10.1177/09544100221088360
       
  • Unsteady and nonlinear aerodynamic prediction of airfoil undergoing
           large-amplitude pitching oscillation based on gated recurrent unit network
           

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      Authors: You Wu, Yuting Dai, Chao Yang, Guangjing Huang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a reduced-order model (ROM) based on data-driven machine learning algorithm is constructed to identify the aerodynamic forces of airfoil undergoing large-amplitude pitching oscillation. Strong nonlinearity and unsteadiness in aerodynamics is a major challenge in the prediction of aerodynamic forces. To deal with this problem, the recurrent neural network (RNN) with gated recurrent unit (GRU) is applied for nonlinear and unsteady aerodynamic identification. A motion input signal which covers a wide range of frequency and amplitude is designed to enable the ROM with generalization capability. Shear stress transport (SST) model with low-Reynolds number modification is introduced into the computational fluid dynamics (CFD) method to calculate the aerodynamic forces as the training data. The time step size and lag order of the model are determined by the frequency domain characteristics of the training data. The results suggest that the proposed ROM has a high identification precision on nonlinear unsteady aerodynamics. The well-trained ROM could accurately predict the aerodynamic forces of airfoil undergoing sinusoidal oscillations with various frequencies and amplitudes. The proposed ROM shows advantages in accuracy over other ROM techniques. The calculation speed of ROM is 69 times faster than that of CFD method on the premise of accuracy, which can be expected a good application in engineering.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-17T01:44:18Z
      DOI: 10.1177/09544100221097521
       
  • Supersonic inlet flow recognition by hybrid-mutation non-dominated sorting
           genetic algorithm with support vector machines

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      Authors: Tian-Lin Yang, Huan Wu, Yong-Ping Zhao, Hui-Jun Tan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The recognition of supersonic inlet flow pattern has become a research hotspot in recent years. In this paper, the dual external pressure supersonic inlet is taken as the research object. To explore the flow characteristics of the inlet, time-mean processing on the inlet pressure signal collected by sensors is conducted first, and the features of the inlet pressure data in time domain and frequency domain are extracted, respectively. As feature selection (FS) plays an important role in classification tasks and has been recently studied as a multi-objective optimization problem, two objectives of FS are considered and an improved non-dominated sorting genetic algorithm NSGA2 with hybrid mutation operators using support vector machines (SVM) as classifiers is proposed, aiming to simultaneously select feature subsets and optimize SVMs hyper-parameters. In addition, a way to deal with variation transgression is proposed to make the mutation operator of the single-objective evolution fit well in the multi-objective evolution algorithm. Experimental results on 31 sensor datasets demonstrate that our proposed algorithm can achieve competitive classification accuracy while obtaining a smaller size of feature subset compared with particle swarm optimization algorithm and some multi-objective optimization algorithms using single-objective evolution mutation operators.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-16T06:50:03Z
      DOI: 10.1177/09544100221097538
       
  • Study on aerodynamic features of rod thrust vector control for physical
           applications

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      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
       
  • Vertical thrust-based effective flat-spin recovery of aircraft restricting
           altitude loss

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      Authors: Salahudden Salahudden, Ajoy K Ghosh
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Among the various modes of aircraft spin, flat-spin being the most ruthless form, the severity and the flight parameters govern the recovery success rate. This paper presents a novel approach for utilizing vertical thrust to reduce the fatality of the flat-spin in terms of excessive altitude loss regulating the survivability post aircraft recovery. F-18 High Alpha Research Vehicle is considered for the present study to demonstrate effectiveness of the proposed method. The dynamics of vertical thrust add-on is conceptualized and incorporated to the standard aircraft. Subsequently, to validate the effectiveness of this mode of recovery as compared to the conventional primary control based method, standard sliding-mode control technique is adopted. Closed-loop simulation shows that vertical thrust restricts altitude loss and minimizes spin recovery time compared to the conventional mode of recovery from flat-spin. The outcome of the present study ensures the use of vertical thrust as a potential solution for minimizing aircraft flat-spin-related fatal accidents.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-16T02:22:17Z
      DOI: 10.1177/09544100221089055
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
      First page: 1836
      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
       
  • 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
      First page: 1861
      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
       
 
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