Aerodynamic Mechanism And Validation Of A Fluidically Variable Hypersonic Inlet

Using the methods of theoretical analysis, numerical simulation and wind tunnel test, this paper deals with the aerodynamic mechanism, design and analysis method, parametric analysis that related with a fluidic shock control technique and a fluidically variable hypersonic inlet based on this control technique.A theoretical analysis and design method is firstly developed for the fluidic shock control technique. The required shock displacements of the fluidically variable inlet are computed at different Mach numbers and the related equation is deduced. The relation of the injection mass flow rate, mass flow distribution, injection angle with the momentum thickness of the boundary layer is also established, Then, a theoretical prediction method of the required secondary flow rate for a given shock control requirement is developed in an iterative manner. The theoretical analysis shows that when the desired displacement of the first ramp shock remains the same, the required secondary mass flow rate decreases substantially with the increase of injection angle due to the interference of the tangential momentum of the secondary flow, which is consistent with the results obtained by two-dimensional computations. As compared with the CFD results, the theoretical prediction error for the secondary flow rate is between 6.35% and 16.47%.Parametric researches on the fluidic shock control method are performed by means of numerical simulation to obtain the influence of the injection distribution, injection pressure ratio and injection angle. Wind tunnel tests are also conducted to validate the concept to control the shock waves by secondary flow injection. The results show that, to achieve the same displacement for the external shock wave, more secondary flow will be consumed for the inlet with injection slots angle against the main flow, which validates the result obtained by the theoretical analysis.Three kinds of fluidically variable inlets using the fluidic shock control method are proposed, and the detailed arrangements of the main and secondary flow paths are also given. The flow mechanism, aerodynamic performance, and feasibility are studied by integrated simulations with full flow path. The results show that, the shock-on-lip condition can be maintained from Mach 5 to 6 with a maximum cost of about 2.2% secondary flow ratio. At low flight Mach number conditions, the mass flow ratio of the inlet can be enhanced by more than 20% and the total pressure recovery ratio is also increased at different degrees. In addition, these three kinds of variable inlet have their own specialties. The independently controlling scheme can control each external shock freely. For the scheme that the secondary flow cycling between the internal and external parts, the first shock can be deflected outwards monotonically and the second shock is weakened. For the scheme that the secondary flow cycling in the external path, the mass flow rate of secondary flow is out of the influence of the pressure fluctuation caused by the throttling process of the inlet.The shock-on-lip Mach number, switch Mach number and the shock system arrangement of the fluidic variable hypersonic inlets are investigated by numerical computations. The results show that, the mass flow ratio increases substantially with the decrease of the shock-on-lip Mach number of the fluidic variable inlet, whereas the required displacement of the external shocks increases and the consumption of the secondary flow also rises. In addition, the design method for the optimal shock system configuration of fluidically variable hypersonic inlet is different from that of conventional fixedgeometry inlet.Finally, three test models with the control devices installed inside are designed and tested to validate the feasibility of the three fluidically variable hypersonic inlets. According to the test results, these experimental models are all able to achieve a shock-on-lip condition at Mach number of 5.74 by the injected secondary flow and the external and internal flow structure is established normally. Experiments are also conducted to obtain the influence of the angle of attack and the downstream throttling for the fluidically variable inlet. The results show that the inlet can operate normally in a certain range of angle of attack and the forebody shocks are not interfered during the throttling process.