According to the shock wave and expansion wave theory,a constant pressure gradient curved compression system is designed and proven by wind tunnel test.The influence about inflow condition and design parameters on the property of constant pressure gradient curved compression system is investigated by numerical analysis.The result shows the initial compression angle is the most important influence parameter for constant pressure gradient curved compression system.Predictor formulas for the profile lines of constant pressure gradient curved compression system and curved shock wave is given.The maximum relative error between shapes for curve shock wave of predictor formulas and experiment is 4.8 percent.

本文采用加速的方法,数值模拟了侧压式进气道自起动现象.研究结果表明低马赫数不起动的侧压式进气道通过加速可以实现自起动,此时的侧压式进气道流场总体性能与直接起动的进气道流场总体性能存在差异,使得直接起动的进气道有较高的总压恢复.

According to the shock wave and expansion wave theory,a model with constant pressure gradient curved compression system was designed at Ma = 5. 3. The curved compression model was tested in Ma = 3. 85 and Ma = 5. 3 wind tunnel at the condition of uniform inflow and simulated forebody boundary layer non-uniform inflow. The experimental results indicate that the pressure distribution of model surface are of constant pressure gradient feature in uniform inflows. The uniformity of outlet flowfield is worse at inflow Mach number Ma = 5. 3. The incoming flow non-uniformity has a dramatic effect on the pressure distribution of model surface and the uniformity of outlet flowfield.

An experimental study was performed at Mach 3.85 wind tunnel about back pressure and self-starting characteristics for sidewall-compression inlet with variable internal contraction ratio. The results show that, the internal contraction ratio has effects on back pressure characteristics of sidewall-compression inlet; the inlet with internal contraction ratio 1.19 can withstand a maximum back pressure of 23.42 times static pressure; the inlet with internal contraction ratio 1.24 can withstand a maximum back pressure of 26.44 times static pressure; The sidewall-compression inlet can realize self-starting by moving cowl backwards.

At the condition of Ma 5.3 wind tunnel incoming flow, designed a curved compression system with constant pressure gradient and modified with boundary layer thickness. Experimental study and numerical simulation of the curved compression system are presented. The curved compression system model has been tested in the NUAA 100×100mm M5.3/3.85 wind tunnel at the condition of uniform incoming flow. The static pressure along the centerline of the model and the total pressure at the exit section were measured and the schlieren photographs of the curved shock were taken. The results indicated that the experiments results coincide better with the results of numerical simulation. Along the curved compression system constant pressure gradient were obtained at Ma 5.3/3.85 and exit section flowfields were approximate uniform. Compared with the isentropic compression surface, the length of newly design curved compression system can be reduced about 35 percent and the pressure gradient along compression surface is lower, so the newly curved compression system can reduce the danger of boundary layer separation. These show that constant pressure gradient design method is feasible. © 2009 by the American Institute of Aeronautics and Astronautics, Inc.

The numerical method is based on the theory of oblique shock wave and expansion wave.Comparison the shape of curved shock and static pressure along curved compression surfaces between numerical method and Fluent calculation.With Fluent software,calculated the design point performance of 2-D inlets with constant pressure gradient non-convention compression surface,convention isentropic compression surface and 3-wedges compression surface,respectively.Results show:the shape of curved shock obtained by numerical method coincide better with the result of Fluent calculation;pressure increase evenly along the compression surface designed on constant pressure gradient,that is useful to reduce the damage of boundary layer separation;compared with the isentropic compression surface,the length of curved compression surface designed on constant pressure gradient can be reduced about 21.6%.

Compression surfaces are designed by using short lines with equal compression angle or increasing compression angle. Two dimensional supersonic flow fields are investigated when incoming flows pass through the compression surfaces. The results show that the compression surfaces can shape curved shock and pressure gradient along the surfaces is nearly constant, but the magnitude of constant pressure gradient depends on arrangement of short lines. It is shown that inlets with the noneonventional compression surfaces are more advantageous in keeping the stability of boundary layer than that one with conventional compression surfaces and their performance are similar at design point, but at off design point, the performance of inlets with non-conventional compression surfaces are better.

A combination of CFD simulation and experimental study was performed at Mach 3.85 with total pressure 0.7 MPa and total temperature 300 K.A three-dimensional sidewall-compression inlet with movable cowl is applied perform.Results show that self-starting Ric of the model inlet is between 1.24 and 1.28.For a model inlet which has started will keep starting condition until Ric reaches 1.33 by moving cowl forward.Delay phenomenon exists during the process of cowl backward and forward.The sidewall compression inlet model can realize self-starting by moving cowl backward.