Inlet Design And Flowfield Analysis Of Integrated Airbreathing Hypersonic Vehicle

Hypersonic vehicle, with extensive military and commercial applications, is the hotspot of all the major counties in the world. The airframe/propulsion integration design and scramjet technology as the keys to achieve hypersonic flight are studied and focused by the researchers.Three kinds of hypersonic vehicle configurations are presented under Mach 7 and flight altitude H=30km design conditions. To meet the demand of an integrative design and the match of inlet/combustor with different cross-sections, a variable cross-section Busemann inlet designed by morphing streamline-traced methodology is introduced and applied. The aerodynamics characteristics of hypersonic vehicle configurations such as airframe external flowfield characteristics, lifting-drag ratio, drag characteristics and the performance of variable cross-section Busemann inlet were evaluated using the numerical simulation. It is found that the external flow and internal flow characteristics of all three configurations are basically the same as the design states. The forebody of Lifting-Body configuration has excellent waveride characteristics, and the lift-drag ratio of Lifting-Body is the highest at the design point. The whole Sim-Waverider vehicle “rides on” the shockwave, making the lift character the best. In the internal and external flow around the Sim-Waverider configuration, the body shock and internal compression shock of inlet are not disturbed by each other. Because there is nearly no strong shockwaves presented in the external flow of aircraft, the Blended-Scramjet-Body configuration has excellent drag characteristics. The variable cross-section Busemann inlet design method, which is used in this study for the design of different inlets, is suitable for the integrative configuration design of hypersonic vehicles. The inlets can not only satisfy the requirement for connection with different cross sections, but they also have a higher total pressure recovery and uniform exit flow.In order to study the structure and dynamics characteristics of oblique shock train inflow, a simple duct model are designed and investigated experimentally in a Mach 5 hypersonic wind tunnel. Back pressure of model is produced and varied by the close of two ramps at the end of model. Measurements made include high-speed schlieren imaging and simultaneous fast-response wall pressure along the length of model. Results show that the leading edge of shock train propagates upstream, and translates to be asymmetry with the increase of back pressure. The asymmetry state maintained throughout the last whole propagation process. Varying the rise speed of back pressure did not show any discernible effects with regard to propagated speed of the leading edge of oblique shock train. Not a steady motion state, there are two kinds of motion in the shock train propagation process: steadily forward and rapidly forward. The characters of shock train propagation are decided by the fluid structure, the pressure distribution of wall, the magnitude of back pressure, and the distance to the isolator exit, etc. Different wall pressure spectral characteristics of oblique shock train in duct are explored with different back pressure. But in the same case, all the pressure spectral characteristics of transducers in the shock train region are similar. In Case1, the dominant frequency is f1=512Hz; in Case2, the dominant frequency is f1=578Hz, the sub-resonance frequency is f2=260Hz that is close to the acoustic resonance frequency. Both the dominant frequencies got in the experiments are higher than the theoretical prediction of Piponniau model.