The First Aircraft Institute
The First Aircraft Institute
Gao X.,The First Aircraft Institute |
Yang S.,Beihang University |
Chai J.,The First Aircraft Institute |
Zhao J.,Beihang University
Beijing Hangkong Hangtian Daxue Xuebao/Journal of Beijing University of Aeronautics and Astronautics | Year: 2017
For stealth aircraft, the scattering contribution of discontinuous targets becomes considerable. The common method is based on low scattering carrier and compares measurement results of carrier with discontinuity and that without discontinuity. The scattering increase of target with discontinuity is obtained to analyze its electromagnetic scattering characteristic. This method has disadvantages of low efficiency, small-size target and high cost. An improved method is presented based on vector cancellation, which regards carrier as part of target background and separates carrier scattering from result. The scattering characteristic of discontinuous target in whole angle region which is independent of carrier is obtained, and the result is more integrative and more accurate. By comparing with literature and validation analysis, the vector cancellation method can get scattering characteristic of discontinuous target in whole angle region. The test results and target size are unrelated to carrier, so that this method has advantages of high precision and low cost. © 2017, Editorial Board of JBUAA. All right reserved.
Guo S.,Cranfield University |
Jing Z.W.,Cranfield University |
Jing Z.W.,The First Aircraft Institute |
Li H.,Cranfield University |
And 2 more authors.
Aerospace Science and Technology | Year: 2017
The effectiveness of a passive gust alleviation device (PGAD) mounted at the wingtip of aircraft in conventional and flying-wing configurations have been studied in previous research. However the PGAD influence on the aeroelastic stability in particular the body freedom flutter (BFF) of a flying-wing aircraft remains as a concern. This present investigation is focused on evaluating the beneficial effect of PGAD on both gust load alleviation and BFF of a small flying-wing aircraft of high aspect ratio wing made of composite. A small range of (1-cos) type of gust load has been considered to select a representative critical gust load case for the study. A parametric study indicates that there is a narrow band of optimal key parameters for the PGAD design. Subsequently a set of optimal parameters is selected to further the analysis of the PGAD mechanism. The case study results show that the PGAD can make the bending moment at the wing root due to gust reduced by 16%. In addition, the BFF speed of the flying-wing aircraft is increased by 4.2%. The investigation reveals that the PGAD mode and its interaction with the wing bending mode and short period oscillation of the aircraft can have beneficial aeroelastic effect on both gust alleviation and flutter suppression. © 2017 Elsevier Masson SAS
Zhang J.,The First Aircraft Institute |
Zhang D.,The First Aircraft Institute
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2016
There are significant differences between high altitude long endurance (HALE) solar-powered unmanned aerial vehicles (UAVs) and conventional propulsion aircrafts. The configuration method for HALE solar-powered UAV has its own peculiarity, and some critical technical details must be paid attention to during schematic design. The mechanism of the general design method based on weight balance and energy balance for the HALE solar-powered UAV is analyzed. Some important factors are summed up including the power needed for level flight, the styles of configuration of HALE solar-powered UAV, the optimization of flight profile, operating environment influence, etc. The conclusions may be referred to in the configuration design and scheme optimization of solar-powered UAV. © 2016, Press of Chinese Journal of Aeronautics. All right reserved.
Xiao H.,Xi'an University of Science and Technology |
Gao C.,Xi'an University of Science and Technology |
Dang Y.-Q.,The First Aircraft Institute
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2011
The waverider configuration is an important configuration of hypersonic cruise vehicle. Hypersonic flow around a multi-objective optimization designed waverider is experimentally studied by pressure measurement, force measurement and Schlieren observation at M=6 and 7 and angle of attack ranging from -4° to 8°. The results show that the aerodynamic characteristics of all the components of the waverider are good. The forebody precompression quality meets the design requirements well, the forebody shock is exactly caught by the lip of the inlet and the flow is quickly expanded at the aft body.
Yang C.-F.,The First Aircraft Institute |
Zhang J.-Z.,Nanjing University of Aeronautics and Astronautics
Experimental Thermal and Fluid Science | Year: 2012
Experimental study was conducted to investigate the enhanced cooling performance caused by ridge-shaped tabs located along the upstream edge of the film cooling holes. Three covering ratios of ridge-shaped tab on film hole and four blowing ratios were considered in the present. The results show that the presence of ridge-shaped tabs in the nearby region of the primary film cooling holes mitigates the primary vortices due to mainstream-coolant jet interaction in the downstream region. The lower penetration of coolant jet provides an increment in the film cooling effectiveness and also enhance heat transfer coefficient over the baseline case. The ridge-shaped tabs provide enhancements in cooling effectiveness, but this is at the expense of larger pressure drop, especially for ridge-shaped tabs with bigger covering ratio. © 2011 Elsevier Inc.
Ji H.,The First Aircraft Institute |
Zhang C.,Northwestern Polytechnical University |
Qiao S.,Northwestern Polytechnical University
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2015
6061-O and 6061-T4 aluminum alloy sheets with 0.04 inch (1.02 mm) nominal thickness are widely used in the aviation industry. After argon arc welding, the sheets were subjected to a solution heat treatment followed by a quenching and tempering treatment (T62 treatment), afterwards fabricated to specimens. The fatigue tests were carried out at 60 Hz, stress ratio of 0.1 both in atmosphere and water at room temperature, and loading direction was perpendicular to welding bead. The fracture morphologies were examined by scanning electron microscopy (SEM). The results show that the fatigue life in water is considerably decreased, and fatigue striation is not so clear compared with that in atmosphere, which might be attributed to the fact that the oxygen content on the fracture surface tested in water after dry treatment is much higher than that in atmosphere. Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.
Jiang J.,Northwestern Polytechnical University |
Zhang Y.,The First Aircraft Institute |
Sun Q.,Northwestern Polytechnical University
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2010
To simulate the progressive fracture of the bolted structure, a Global/Local analysis strategy is used. In both Global and Local coordinates, the nonlinear finite element analysis with EWK fracture subroutine is carried out. The result shows that the dangerous zone is located near the edge of the bolt hole. Failure element begins to appear when the applied load is up to 42% of the maximal load, then the crack spreads stablely along the circle of the bolt hole edge till the applied load reaches 48% of the maximal load. The crack spreads instantly afterward, thus leading to the collapse of the whole structure. The Global/Local analysis strategy can improve the efficiency of the entire analysis process.
Xin L.,Northwestern Polytechnical University |
Bai J.,Northwestern Polytechnical University |
Dong J.,The First Aircraft Institute |
Liu Y.,Northwestern Polytechnical University
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2015
Based on the N-S equations of multi-block structural grid and the method of structure flexibility coefficient matrix, an approach to CFD/CSD non-linear coupling problem based on radial basis functions (RBF) interpolation technology is established, RBF&Delaunay mesh motion method is adopted, which is used to compute the non-linear aeroelasticity of flexible aircraft with high aspect radio. This method is validated using DLR F6 configuration simulation. According to this method, static aeroelasficities of a civil aircraft under no jet/jet condition are investigated, showing that the engine jet can make wing plus twist, which is weaken wing sweepback effect, then the leading and trailing edge bending deformation increase and most of the favorable current profile twist angles decrease. Studies show that under the powered condition, the pressure distribution of rigid wing is changed, its lift confficient is reduced. The static aeroelastic deformation is a coupling effect, where the engine jet region is mainly influenced by jet while the outer wing is mainly by elastic deformation. The result of numerical simulation demonstrates that considering the aeroelasticity effect for no jet condition, the lift coefficient decreases by about 16% and the lift drag radio decreases by 8.4%. Whereas for powered case, the lift coefficient decreases by 18%, the lift drag radio decreases by 36%. Therefore, it is necessary to analyze static aeroelasticity of high aspect radio civil aircraft under powered condition. ©, 2015, Editorial Office of Acta Aerodynamica Sinica. All right reserved.
Wang C.,Northwestern Polytechnical University |
Song B.,Northwestern Polytechnical University |
Huang P.,Northwestern Polytechnical University |
Tang C.,the First Aircraft Institute
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2016
This work proposes a hierarchical nonlinear control scheme for quadrotor to track 3D trajectory subject to payload variation and fast time-varying wind gust disturbance. In terms of dynamics model, the 6 DOF dynamics model with parametric and nonparametric uncertainties is built up. Wind gust and propeller momentum drag model are implemented to quantify the wind impact (force and moment disturbances) on quadrotor. In terms of control design, adaptive robust controller is developed for dynamic subsystem to deal with moment disturbance and estimate the system parameters. Global sliding mode controller is implemented for kinematic subsystem to generate adequate desired attitude angles for tracking the planned 3D trajectory. Simulations and experiments under various conditions are carried out for verification, and the results indicate the effectiveness, adaptiveness and robustness of the control strategy. © 2016 Springer Science+Business Media Dordrecht
Yin Z.,Northwestern Polytechnical University |
Li Y.,The First Aircraft Institute |
Tan S.,The First Aircraft Institute
Jixie Qiangdu/Journal of Mechanical Strength | Year: 2010
Under the abnormal landing, the aircraft structure must guarantee the safety of passengers according to China Civil Aviation Regulations 23(CCAR 23). For the first time, the crashworthiness model of some civil aircraft fuselage structure is carried out. The influence of crash velocity has been taken into account. Under different crash velocity, the acceleration of floor, impact force, and energy absorption capability have been analyzed. Numerical results show that horizontal velocity influences the impact force, energy absorption, and acceleration of the floor. And some horizontal velocity is beneficial for crashworthiness of the aircraft structure. And these provide a reference for reliability design and evaluation of this aircraft.