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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 86 journals)
Acta Astronautica     Hybrid Journal   (Followers: 267)
Advances in Space Research     Full-text available via subscription   (Followers: 281)
Aeronautica     Open Access   (Followers: 4)
Aerospace     Open Access   (Followers: 3)
Aerospace and Electronic Systems, IEEE Transactions on     Hybrid Journal   (Followers: 50)
Aerospace Science and Technology     Hybrid Journal   (Followers: 295)
Affective Computing, IEEE Transactions on     Hybrid Journal   (Followers: 6)
AIAA Journal     Full-text available via subscription   (Followers: 453)
Air Force Magazine     Full-text available via subscription   (Followers: 3)
Air Medical Journal     Hybrid Journal   (Followers: 2)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 115)
American Journal of Space Science     Open Access   (Followers: 32)
Artificial Satellites     Open Access   (Followers: 13)
Aviation     Hybrid Journal   (Followers: 3)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 1)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 5)
Aviation Week     Full-text available via subscription   (Followers: 8)
Aviation, Space, and Environmental Medicine     Full-text available via subscription   (Followers: 5)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 12)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 20)
Chinese Journal of Aeronautics     Open Access   (Followers: 10)
Control Systems     Hybrid Journal   (Followers: 18)
Cosmic Research     Hybrid Journal   (Followers: 2)
COSPAR Colloquia Series     Full-text available via subscription  
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 4)
Elsevier Astrodynamics Series     Full-text available via subscription   (Followers: 1)
Fatigue of Aircraft Structures     Open Access   (Followers: 4)
Frontiers in Aerospace Engineering     Open Access   (Followers: 3)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 10)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 33)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 9)
International Journal of Aeroacoustics     Full-text available via subscription   (Followers: 6)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 11)
International Journal of Aerospace Engineering     Open Access   (Followers: 38)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 10)
International Journal of Applied Geospatial Research     Full-text available via subscription   (Followers: 4)
International Journal of Aviation Management     Hybrid Journal  
International Journal of Aviation Psychology     Hybrid Journal   (Followers: 4)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription  
International Journal of Crashworthiness     Hybrid Journal   (Followers: 5)
International Journal of Flow Control     Full-text available via subscription   (Followers: 2)
International Journal of Hypersonics     Full-text available via subscription   (Followers: 3)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 3)
International Journal of Satellite Communications Policy and Management     Hybrid Journal  
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 2)
International Journal of Space Structures     Full-text available via subscription   (Followers: 2)
International Journal of Sustainable Aviation     Hybrid Journal  
International Journal of Turbo & Jet-Engines     Full-text available via subscription  
ISRN Astronomy and Astrophysics     Open Access   (Followers: 11)
Journal of Aerospace Computing, Information, and Communication     Full-text available via subscription   (Followers: 12)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 111)
Journal of Aerospace Engineering & Technology     Full-text available via subscription  
Journal of Aerospace Operations     Hybrid Journal   (Followers: 3)
Journal of Aerospace Technology and Management     Open Access   (Followers: 1)
Journal of Aircraft     Full-text available via subscription   (Followers: 255)
Journal of Airline and Airport Management     Open Access   (Followers: 2)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 6)
Journal of Guidance, Control, and Dynamics     Full-text available via subscription   (Followers: 49)
Journal of Konbin     Open Access  
Journal of Navigation     Hybrid Journal   (Followers: 18)
Journal of Propulsion and Power     Full-text available via subscription   (Followers: 204)
Journal of Space Weather and Space Climate     Open Access   (Followers: 3)
Journal of Spacecraft and Rockets     Full-text available via subscription   (Followers: 304)
Journal of Spatial Science     Hybrid Journal   (Followers: 1)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 1)
Journal of the Astronautical Sciences     Hybrid Journal  
Microgravity Science and Technology     Hybrid Journal  
New Space     Hybrid Journal   (Followers: 2)
Nonlinear Dynamics     Hybrid Journal   (Followers: 5)
Population Space and Place     Hybrid Journal   (Followers: 2)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal  
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 19)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 42)
Propulsion and Power Research     Open Access   (Followers: 1)
Recent Patents on Space Technology     Full-text available via subscription  
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 12)
Space and Polity     Hybrid Journal   (Followers: 2)
Space Communications     Hybrid Journal   (Followers: 2)
Space Policy     Hybrid Journal   (Followers: 15)
Space Research Today     Full-text available via subscription   (Followers: 24)
Space Safety Magazine     Free   (Followers: 3)
Space Science Reviews     Hybrid Journal   (Followers: 9)
SpaceNews     Free   (Followers: 198)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 1)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 2)
Вестник УГАТУ     Open Access  
Journal Cover CEAS Aeronautical Journal
   [22 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1869-5582
     Published by Springer-Verlag Homepage  [2209 journals]
  • Enhancement of aircraft wake vortex decay in ground proximity
    • Abstract: Abstract Aircraft wake vortex evolution in ground proximity is investigated experimentally in a water towing tank, as well as numerically with wall-resolved large eddy simulation (LES). With these complementary instruments the enhancement of wake vortex decay by obstacles, introduced at the ground surface, is analyzed. The experimental methods include time-resolved stereo particle image velocimetry and vortex core visualization. For comparison with the experiment, the LES considers the turbulent wake of the strut, holding the towed aircraft model. Wake vortex trajectories and circulation decay are compared at different distances from the obstacle. Tracers are employed to visualize the obstacle’s effects on the vortex core, in LES and experiment. The experimentally obtained trajectories and decay characteristics are reproduced qualitatively by simulations, whereas the agreement is degraded at later times. Beyond that, the vortex dynamics, deduced from the LES results, help to understand the experimental observations. The obstacles trigger helical secondary vortex structures, propagating along the primary vortices. The observed propagation speed of the helical disturbance is fairly well predicted by the suggested simple model. It is shown that the obstacles significantly modify the vortex interaction with the ground and substantially accelerate vortex decay. Two neighboring obstacles lead to colliding disturbances that further enhance vortex decay rates.
      PubDate: 2014-06-01
  • A reduced-order model for the investigation of the aeroelasticity of
           circulation-controlled wings
    • Abstract: Abstract The application of active circulation control allows shortening of runways which can be significant in particular cases. The goal of the present paper is to study the influence of the circulation control on the aeroelastic behaviour of wings. For numerical analyses, a simplified computational model is presented, which allows for systematic parameter variations. The model is based on model reduction using modal analysis, so that an efficient performance of numerical studies is possible as well as the integration of the aeroelasticity into a flight dynamics model.
      PubDate: 2014-06-01
  • System architecture of HALAS—a helicopter slung load stabilisation
           and positioning system
    • Abstract: Abstract To support helicopter pilots during slung load operations currently a pilot assistance system called Hubschrauber-Außenlast-Assistenzsystem (HALAS) is being developed within a cooperation of the German Aerospace Centre (DLR) and iMAR Navigation GmbH. The objective of this research is the demonstration of an automatic slung load stabilisation and positioning system during the flight test with DLR’s research helicopter Active Control Technology/Flying Helicopter Simulator (ACT/FHS). The automatic slung load control system is being designed to extend the functionalities of the helicopter’s stability, control and augmentation system. The control system will be able to handle the challenges of rescue hoist operations. This means compensation of additional roll, pitch and yaw moments created by a significant distance of the load suspension point to the helicopter’s centre of gravity and the handling of a variable cable length. To measure the slung load motion, an optical-inertial sensor is being developed by iMAR Navigation GmbH. In this paper, the overall system architecture of HALAS as well as the hardware integration into the ACT/FHS is explained. The optical-inertial sensor used for the slung load dynamics measurement and estimation is described in detail. Furthermore, a first system analysis of a simulation model used for the later controller design is presented. The focus of the stability analysis is laid on variations of cable length, load mass and load suspension point position. The control law development process itself is not part of this paper but will be published later.
      PubDate: 2014-06-01
  • Data parser approaches for (online) parameter estimation
    • Abstract: Abstract Finding maneuvers for parameter estimation in flight data records is a laborious task and traditionally performed post-flight on ground. Two different data parser approaches to automatically detect these maneuvers in flight are presented. Both methods search the control input signals for significant changes that correspond to test maneuvers. The first algorithm is based on the signal time derivative of the input signal whereas the second method uses a fast orthogonal wavelet transform. Both algorithms are tested with flight test data recorded with the DLR research aircraft ATTAS. Performance results are compared and potential problems when applying the parsers to other data are discussed. Results indicate that both methods are applicable in an online parameter estimation tool. The intention of the work in this paper is to develop an algorithm with a high level of automation for in-flight use, but both approaches could also be applied to offline flight data mining problems.
      PubDate: 2014-05-17
  • Conceptual aircraft design with hybrid laminar flow control
    • Abstract: Abstract This paper describes a methodology for conceptual design and optimization of aircraft with hybrid laminar flow control (HLFC) systems integrated into wing and tails. An existing conceptual aircraft design platform is enhanced by the necessary methods for sizing of HLFC system architecture and prediction of aerodynamic drag polars. These include transonic drag characteristics as well as transition prediction by analysing boundary layer instability mechanisms. The implemented methods are described and its sensitivities against relevant aircraft design parameters are discussed. The integrated sizing methodology allows to assess the net benefit of HLFC system integration on overall aircraft level and to minimize aircraft fuel consumption by variation of aircraft design parameters, cruise conditions and HLFC system parameters. To demonstrate the applicability of the developed methodology in conceptual aircraft design it is used for design and assessment of an HLFC long-range passenger aircraft. The influence of the HLFC main drivers Mach number and wing sweep angle on aerodynamics, systems and aircraft design characteristics is investigated. Further, aircraft component resizing is analysed to further exploit the fuel reduction potential of the HLFC technology.
      PubDate: 2014-05-15
  • Comparing explicit and implicit modeling of rotor flapping dynamics for
           the EC 135
    • Abstract: Abstract To be valid up to higher frequencies, state space models derived by system identification methods have to include rotor states describing the dynamics of flapping and sometimes even downwash and regressive lag motion. In the case of flapping, the rigid body equations are usually augmented by the explicit differential equations for the longitudinal and lateral flapping angles which are then coupled to the rigid body equations through the corresponding force and moment terms. Alternatively, an implicit formulation can be used that includes the pitch and roll acceleration as model states. The paper compares the two modeling approaches for the EC 135 helicopter. For this helicopter, the formulation with flapping angles in its classical hybrid form shows some higher order deficiency in the match of the longitudinal and lateral accelerations, which are not apparent in the implicit model. After ruling out other effects, the discrepancies can be attributed to a vertical offset of the center of gravity from its assumed position. Once this offset is accounted for in the data, results from the two modeling approaches can be compared to each other and to theoretical predictions.
      PubDate: 2014-05-07
  • Aerodynamic performance of an over-the-wing propeller configuration at
           increasing Mach number
    • Abstract: Abstract Over-the-wing propeller configurations and particularly channel wing concepts show increased climb performance, and through effective acoustic shielding, reduced noise emissions when compared to a conventional tractor configuration. The main aerodynamic mechanisms could be identified by steady flow simulations of a simplified wing geometry and actuator disk. At take-off, where the thrust coefficient is very high, the drag of the wing decreases much stronger than the thrust of the propeller. This paper investigates the cruise conditions where the thrust coefficient is by one order of magnitude lower. The numerical results give evidence that, even at a moderate flight Mach number of 0.6, the beneficial influence of the over-the-wing propeller on the drag coefficient of the wing is negligibly small. On the other hand, the amount of propeller efficiency that is lost through high inflow velocity above the wing increases with Ma due to compressibility effects. As a result, the propulsive efficiency of an over-the-wing configuration is 16 % smaller than the reference (tractor). Semi-empirical correlations show that even at very low Mach numbers a drawback of at least 5 % remains. Although repositioning the propeller at the wing trailing edge may recover 4 % of the propulsive efficiency at Ma = 0.6, it is not advisable to give up most of the noise-shielding effect at take-off which is an important advantage of the channel wing.
      PubDate: 2014-04-10
  • On the use of a steerable main landing gear for crosswind landing
    • Abstract: Abstract Several crosswind-related incidents show that landing under heavy crosswind conditions can be challenging for pilots and may pose a threat to aviation or at least lead to higher pilot workload and/or irregularities in operations. For transport aircraft the common approach technique for crosswind landings is the so-called crabbed approach with wings level and a windward heading correction. This technique requires alignment of the aircraft with the runway prior to touchdown in order to keep lateral loads of the landing gear and tyres as low as possible and to maintain the controllability on ground after touchdown. The German Aerospace Center Institute of Flight Systems has used the idea of steerable main gears and developed a crosswind landing assistance system. During approach all gear struts are automatically aligned with the runway so that no decrab manoeuvre is required. On ground the assistance system uses each steerable landing gear, differential braking, and the aerodynamic control surfaces to control and stabilise the aircraft. After touchdown the aircraft is automatically aligned with the runway centreline and the still existing crab angle is slowly reduced. A simulator study with pilots in the loop using a model of a typical medium range transport aircraft was conducted in order to evaluate the benefits of such a landing technique. The study revealed that not only the aircraft controllability could be improved by landing in crabbed motion under strong crosswind conditions, but that the side forces acting on the landing gear can be reduced significantly as well. It was also shown that the use of steerable main landing gears is able to enlarge the spectrum of autoland operations, which is relatively limited at present in terms of maximum allowable crosswinds. All together the system has shown to be able to improve flight safety, lower the risk of weather-related delays due to go-arounds or diversions, and it also reduces structural loads on the landing gear during touchdown and landing.
      PubDate: 2014-03-30
  • Aerodynamic and structural investigation of an active back-flow flap for
           dynamic stall control
    • Abstract: Abstract The design and experimental investigation of a back-flow flap for helicopter dynamic stall control is described. A spoiler-type flap is designed, and shown by CFD to reduce the pitching moment peak during dynamic stall by 34 %. Initial experiments with a passively actuated flap in a low-speed wind tunnel showed that the opening and closing times for the flap due to the aerodynamic forces are sufficiently short and that the flap is not affected by the inertial forces of the model pitching. The experiments showed the need for a flap restraint, and that an active actuation is needed so that the flap angle is sufficient at the time of stall to have a control effect. Initial demonstrators for the structural concept of the active back-flow flap using glass fiber reinforced polymer and a solid state hinge are presented, showing the possibility of fabrication as an after-market add-on.
      PubDate: 2014-03-29
  • Multidisciplinary analysis of CROR propulsion systems: DLR activities in
           the JTI SFWA project
    • Abstract: Abstract In the frame of the EU 7th Framework Joint Technology Initiative Smart Fixed Wing Aircraft project, the DLR Institute of Aerodynamics and Flow Technology (DLR-AS) is participating as an associated partner in the Airbus-led studies of the Contra-Rotating Open Rotor (CROR) as possible powerplant for future transport aircraft. Due to significant technical challenges in terms of noise emissions, installation effects and certification that still need to be addressed for this novel propulsion system, the numerical activities require the use of sophisticated multidisciplinary analysis tools and approaches covering aerodynamics, aeroacoustics and aeroelastics. In this paper an overview of the DLR-AS work in the project is given, which covers the numerical assessment of a novel noise reduction technology, an initial study of blade aeroelasticity as well as some in-depth studies on isolated and installed pusher-configuration CROR engine configurations. The first results of a validation of the numerical simulations using experimental test data that is being generated in Airbus-led low-speed wind tunnel tests are also presented.
      PubDate: 2014-03-26
  • Aerodynamic power and mechanical efficiency of bat airframes using a
           quasi-steady model
    • Abstract: Abstract Previous bat aerodynamic power models are refined by (1) varying the value of wing profile drag with lift coefficient, which varies with both flight speed and Reynolds number, (2) allowing for the aerodynamic cleanliness of head, body, ears and tail in calculating parasitic drag values at various speeds and according to airframe type, (3) incorporating models of wingbeat amplitude and frequency in the power calculations, and, (4) upgrading the allometric, phylogenetically corrected relationship between basal metabolic rate and body mass using data from 98 bat species. The fidelity of the aerodynamic power model is assessed using published wind tunnel data on a bat in steady glide. By comparing empirical published metabolic power (P met) values with values derived using the new aerodynamic model, we update estimates of in-flight musculoskeletal mechanical efficiency (η) for the airframes of eight bat species at steady level flight speeds. Furthermore, we calculate the increase in η at high speeds. The bats assessed range in body mass from 0.01 to 1 kg, and the comparison covers the speed range normally used by free-flying bats during their excursions. At their best endurance flight speeds (V end), η = 1.52 Ln (m bat) + 11.44 (%). At speeds > V end, η = η@ Vend + 1.3 (V−V end) (%). These equations yield accurate P met estimates for flight speeds within the range used for the steady level flight.
      PubDate: 2014-03-26
  • SFB 880: fundamentals of high lift for future commercial aircraft
    • Abstract: Abstract The recently founded Collaborative Research Centre SFB 880 of the Technische Universität Braunschweig, “Fundamentals of High-Lift for Future Commercial Aircraft”, develops new knowledge in aircraft noise, advanced approaches towards active high lift, and in the dynamics of flight with active high lift during short takeoff and landing operations. The research centre has therefore devised a range of research projects that aim at integrated aeroacoustic and aerodynamic design capabilities for drastic noise reductions and the generation of active high lift with an extremely high efficiency of the used onboard power. Flight dynamics of commercial aircraft with increased lift capabilities for takeoff and landing by means of active control and including the effects of aeroelasticity and engine failure modes are also investigated. The research centre has developed a joint strategy for technology assessment using high-quality conceptual design data of a reference aircraft that represents the state of the art in CO2 reductions, low noise, and short takeoff and landing for point-to-point air connections within Europe. The paper describes the overall strategy of the coordinated research work and gives examples of recent results.
      PubDate: 2014-03-19
  • Analysis of a multi-functional high-lift system driven by an active
           differential gear box
    • Abstract: Abstract A flight dynamics evaluation was performed to analyse the ability to use the outer flap for roll control as well. Based on the Airbus A350 flap system architecture, where the outer flap can be deployed independently from the inner flap using a so-called active differential gear box (ADGB), two different concepts were identified as potentially beneficial for the desired purpose. In both concepts, the inner ailerons were removed to save weight and system complexity and the outer flap performs (all speed) roll control together with the outer (low speed) aileron. Concept 1 comprises the usual flap geometry and the outer aileron, whereas concept 2 comprises an outer flap, which is extended in spanwise direction by the length of the inner aileron. Roll spoilers were not considered in the presented analyses. The flight dynamics evaluation revealed that a flap deflection rate of at least 16°/s is necessary to fulfil requirements from certification specification CS-25 and handling quality criteria. A system analysis showed that the existing ADGB is only able to deflect the flap with a maximum rate of 0.43°/s or 1.4°/s with slight modifications of the existing ADGB. These values showed to be insufficient for regular roll control. Nevertheless, in case of a dual loss of hydraulic power, the only available roll control could be performed by one remaining pair of ailerons, which are driven by an electrical back-up hydraulic actuator at the A350. In order to enable roll control, if these electrical back-up hydraulic actuators fail additionally, it was analysed whether the outer flap could be used as emergency roll control with the aforementioned feasible flap dynamics. The results showed that the handling qualities with this flap system ensuring roll control are barely controllable. However, it appears feasible to reach degraded but acceptable handling qualities if the system dynamics could be slightly increased.
      PubDate: 2014-03-08
  • A parametric model for probabilistic analysis of turbine blades
           considering real geometric effects
    • Abstract: Abstract This paper addresses the consideration of manufacturing effects of gas turbine blades in a probabilistic setting. Currently, during design these effects are covered by safety factors and conservative assumptions. The probabilistic investigation, on the other hand, will enable us to calculate the effect of variability on stresses and relevant aerodynamic quantities such as efficiency, thus providing the foundation for robust blade design. A set of 500 new and used turbine blades, provided by Rolls-Royce Deutschland, was digitised with an optical scan system. Cooling holes and abrasion effects were statistically analysed and removed from the scanned data set. Classical turbine parameters were identified. Finally, the variability (probability density functions and corresponding parameters) of the geometric parameters can be calculated according to the digitised geometries and the manufacturing process can be statistically analysed. The presented parametric model will provide the basis for upcoming numerical probabilistic assessment of the real geometric effects.
      PubDate: 2014-03-01
  • Comparative assessment of transient characteristics of conventional and
           hybrid gas turbine engine
    • Abstract: Abstract Reduction of CO2 emission of future aircraft is the main objective of agreements like Flightpath 2050 from the European Commission and the Vision 2020 from the ACARE. For achieving these emission reduction goals, hybrid propulsion systems are considered as a meantime solution on the way to universally electric propulsion systems and are hence the subject of numerous investigations. These studies, however, almost exclusively focus on steady-state behaviour and energy analysis and leave out the benefit on transient performance that comes from hybridisation. To assess the benefit of the hybridisation on a gas turbine engine, multiple simulations of conventional engines and their hybrid versions are performed with a Matlab Simulink® model and the results are compared with time response diagrams and commonly used metrics. It could be shown that the acceleration time of a hybrid gas turbine engine can be reduced by half compared when the shaft power share of the electric motor is 25 %. Furthermore, the study shows that the primary benefit of the hybridisation comes from the larger torque range of the electric motor compared to the turbine.
      PubDate: 2014-02-27
  • Development of a tunnel-in-the-sky display for helicopter noise abatement
    • Abstract: Abstract Research on helicopter noise abatement at DLR has led to the development of a pilot assistant display for following prescribed noise-optimised landing procedures. An intuitive tunnel-in-the-sky display was chosen in order to reduce pilot workload during complex manoeuvres. The tunnel representation allows the pilot to anticipate the coming flight path. This has led to improvements in flight path accuracy compared to flights with a standard primary flight display with target indicators only. Trajectory generation is performed partly during flight which allows the update of the displayed trajectory relative to the current helicopter position. After selecting the desired noise abatement procedure, landing place and approach direction, a transition trajectory is generated that leads the pilot to the entrance point of the actual procedure. Performance of the tunnel-in-the-sky display has successfully been demonstrated during ground-based simulator tests with two pilots and in first airborne test flights. The display will be used for upcoming flight test campaigns with DLR’s research helicopter ACT/FHS.
      PubDate: 2014-02-26
  • Experimental investigation of high-pressure pulsed blowing for dynamic
           stall control
    • Abstract: Abstract Dynamic stall control using pulsed blowing is compared with control by constant blowing for an OA209 airfoil. Flow control was by blowing from 42 portholes, flush with the airfoil surface, of diameter 1 % chord positioned at 10 % chord and with separation 6.7 % chord. Light stall at Mach 0.3 could be fully suppressed by constant blowing, and for deep stall a pitching moment peak reduction of 65% was seen. For the jet configuration and test cases investigated in this paper, pulsed blowing at 100–500 Hz was found to be at best as effective as constant blowing with the same mass flux for the control of dynamic stall.
      PubDate: 2014-02-20
  • Numerical and experimental investigation of an impeller tip clearance
           variation in an aero-engine centrifugal compressor with close-coupled
    • Abstract: Abstract The subject of this paper is the experimental and numerical investigation of the influence of impeller tip clearance on the aerodynamics of a high-pressure transonic centrifugal compressor used in an aero-engine application. The overall change in aerodynamic performance of the stage, the isolated impeller and the isolated diffuser is analyzed. Local flow phenomena, responsible for the change in performance, are examined in closer detail. Experimental data from a state-of-the-art test rig, containing detailed 2D particle-image-velocimetry measurements, are used. 3D Reynolds-averaged Navier–Stokes simulations are conducted with the CFD solver turbo-machinery research aerodynamics computational environment to get a detailed insight into the flow field. This study contributes towards a better understanding of the principal flow phenomena of a centrifugal compressor with a close-coupled pipe-diffuser and the additional losses introduced in the individual compressor components by an increased impeller tip clearance.
      PubDate: 2014-02-12
  • Optimum number of engines for transport aircraft employing electrically
           powered distributed propulsion
    • Abstract: Abstract Realizing a significant reduction of enroute emissions with respect to greenhouse gases is one major challenge in aircraft design today. Conventional kerosene propulsion systems are going to reach their efficiency limits in near future and it will be very ambitious to fulfill the requirements for future aircraft transportation using conventional engines. Consequently, new approaches for propulsion system design and integration are required to further improve aircraft efficiency through synergy effects. In this paper, a universally electric, short-haul, medium-capacity aircraft utilizing electric motors and battery for motive power is used as datum. The focus lies on the impact of a distributed propulsion system on the aircraft design and flight performance and will not discuss the advantages and disadvantages of the used reference aircraft configuration. Initial studies were performed identifying that the critical design cases for electric motor sizing are the one-engine-inoperative (OEI) flight segments, i.e., the climb gradients required at take-off and landing as well as field length requirements. By increasing the number of installed engines (i.e., motor–fan combinations) the OEI performance requirements may be satisfied with a reduced amount of installed motor and battery system power. An integrated aircraft performance analysis is conducted to estimate the possible net benefit in terms of increased aircraft range when increasing the number of installed engines. Aerodynamic efficiency degradation is considered as well as weight impacts due to electric motor scaling and necessary system architecture modifications. The analysis shows that a 6 % increase in aircraft design range can be achieved when going from 2 to 4 installed propulsive devices.
      PubDate: 2014-01-15
  • Manufacturing of CFRP specimens with controlled out-of-plane waviness
    • Abstract: Abstract In this paper, the manufacturing of carbon fibre reinforced plastic laminates with intentionally, reproducibly and mathematically defined high quality out-of-plane waviness made from unidirectional prepreg material is described. This methodology is employed to manufacture tension test specimens with included controlled out-of-plane ply waviness. The waviness ratio is A/L = 0.09, where A and L denote the wave amplitude and the wavelength, respectively. A number of quality assurance verifications is carried out on these specimens before the tension test. These verifications are to corroborate that the realised graded waviness is consistent with the theoretically defined waviness function. The manufacturing process of these specimens is described in detail. The tension test of the specimens is performed by means of a hydraulic testing device. The force–displacement curves of the tension test are plotted to analyse the material behaviours. Experimental investigations are carried out in conjunction with non-destructive 3D optical measurement methodology to identify the failure mechanisms. The results of quality assurance verifications on the specimens exhibit a perfect matching between the geometrically graded shapes and the theoretical function. Furthermore, the results of tension qualification tests show that all specimens have very similar damage behaviour and the failure events have occurred in the waviness area.
      PubDate: 2013-10-04
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