Wu X.,AVIC China Helicopter Research and Development Institute
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2015
Based on the technology features and configuration characteristics, the high-speed rotorcraft can be classified as the compound helicopter, the tilt-rotor/wing rotorcraft, and the rotor/wing-interchanging rotorcraft. After studying the technology development of three categories of the high-speed rotorcraft, the developing direction and trend are analyzed. Furthermore, combined with the current status of high-speed rotorcraft in China, recommendations and measures are proposed to improve the development level of high-speed rotorcraft in China. © 2015, Editorial Department of Journal of NUAA. All right reserved.
Cao L.,Beihang University |
Cao Y.,Beihang University |
Li C.,AVIC China Helicopter Research and Development Institute
Beijing Hangkong Hangtian Daxue Xuebao/Journal of Beijing University of Aeronautics and Astronautics | Year: 2014
A nonlinear dynamical model of the helicopter-slung-load coupling system was presented, based on single mass-point hypothesis. Under this hypothesis, the consideration of the slung-load brought in extra degrees of freedom and constraints, which made the equations of motion increased by 4 orders, and being a set of implicit differential algebraic equations. By distinguishing the generalized acceleration terms from the quadratic generalized speed terms in the inertia forces, the equations of motion can be turned into a set of explicit ordinary differential equations. For the helicopter model and the helicopter-slung-load model, trim states for zero-side-slipping forward flight were first computed, using direct numerical approach, and the results were compared with flight test data. Then, both of the two models were linearized under small-perturbed conditions, and modal decomposition was performed on these linearized models. Results show that 2 new dynamical modes would be introduced by the single-mass-point slung-load. Motions of the slung-load's 2 degrees of freedom would be coupled with the helicopter's altitude response, and modify the characteristics of helicopter's inherence modes, make some of them worse.
Shen Z.,Nanjing University of Aeronautics and Astronautics |
Zhao N.,Nanjing University of Aeronautics and Astronautics |
Hu O.,AVIC China Helicopter Research and Development Institute
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2014
This work presents a new Cartesian-based ghost cell method for two-dimensional high Reynolds number compressible viscous flows. Based on the six fundamental assumptions used in the law-of-the-wall, a wall function-ghost cell method (WF-GCM) is developed to treat turbulent wall boundary conditions. Reference points are employed to compute primitive variables and turbulent properties at ghost cells. Meanwhile, the turbulent variables at the near wall cells and boundary cells are modified by using the wall function model. The turbulent boundary conditions are incorporated into a Reynolds average Navier-Stokes (RANS) finite volume solver that includes the SST k-ω turbulence model. Finally, the transonic flow past a RAE2822 airfoil and supersonic flow past a circle cylinder are simulated with adaptive Cartesian grid. Good agreement with the experimental datas shows the accuracy and efficiency of the presented WF-GCM. ©, 2014, Editorial Board of ACTA AERODYNAMICA SINICA. All right reserved.
Xu L.,Beihang University |
Chen L.,Beihang University |
Li X.,Beihang University |
He T.,AVIC China Helicopter Research and Development Institute
Applied Optics | Year: 2014
In this paper, we propose a projective rectification method for infrared images obtained from the measurement of temperature distribution on an air-cooled condenser (ACC) surface by using projection profile features and cross-ratio invariability. In the research, the infrared (IR) images acquired by the four IR cameras utilized are distorted to different degrees. To rectify the distorted IR images, the sizes of the acquired images are first enlarged by means of bicubic interpolation. Then, uniformly distributed control points are extracted in the enlarged images by constructing quadrangles with detected vertical lines and detected or constructed horizontal lines. The corresponding control points in the anticipated undistorted IR images are extracted by using projection profile features and cross-ratio invariability. Finally, a thirdorder polynomial rectification model is established and the coefficients of the model are computed with the mapping relationship between the control points in the distorted and anticipated undistorted images. Experimental results obtained from an industrial ACC unit show that the proposed method performs much better than any previous method we have adopted. Furthermore, all rectified images are stitched together to obtain a complete image of the whole ACC surface with a much higher spatial resolution than that obtained by using a single camera, which is not only useful but also necessary for more accurate and comprehensive analysis of ACC performance and more reliable optimization of ACC operations. © 2014 Optical Society of America.
Peng Y.,AVIC China Helicopter Research and Development Institute |
Chen P.,AVIC China Helicopter Research and Development Institute |
Sun Q.,AVIC China Helicopter Research and Development Institute
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2011
A mathematical model of the canted tail rotor is developed based on the blade element theory. UH-60A helicopter is taken as an example to carry out the trim calculation. The validation of the model s made by comparison between calculation results and flight test data, which indicates that the model of canted tail rotor is reasonable, accurate, and proper for the application n engineering. The effect of different canted angle on the required power of helicopter n hover is calculated, which concludes that the optimum canted angle of UH-60A s between 20° and 25°. The trim characteristics of helicopter in ever flight with canted tail rotor and conventional tail rotor are calculated and analyzed. The longitudinal trim of helicopter is changed when the tail rotor tilted up. Finally, the advantages and disadvantages of canted tail rotor are discussed.