Characteristics Of Shock-train At Complicated Geometrical And Incoming Flow Conditions

Shock tarins as an important phenomenon in the isolator of scramjet has prominent influences on the design of the isolator. Whereas, the results obtained by the current theory of shock train which is based on the simple geometrical and incoming flow conditions deviate from the practical operating conditions of the isolator. As a result, the numerical and experimental study of the shock trains in the isolator is performed at the complicated geometrical and incoming flow conditions. Firstly, the 2D and 3D numerical simulations of the internal flow field in curved isolator are conducted. The influences of different curvatures, cross-sections and area distribution on the shock trains are obtained. Then, a simulation method for the incident shock and the corner expansion waves is advanced and validated with the Achen experimental results. By the method the effects of the incident waves on the shock trains are obtained. Finally, an experimental model of a straight isolator with a forebody inlet is manufactured and tested in the NHW wind-tunnel.The results indicate that the geometrical conditions like curvatures, area distributions and cross-sections substantially affected the flow patterns, the total/static pressure distributions and the limit back pressures of the isolator. At the higher Mach number, the proper curvature can decrease the asymmetry flow pattern of the duct while the divergence can reduce the limit pressure. Compared with the straight rectangle duct, the secondary flow of the curved duct is stronger and occupies a larger region. With the interference of the incident shock and the reflected shocks, the asymmetry of the shock train is improved, and the supersonic core flow region of the shock train deflects to the top surface and the bottom surface of the isolator alternatively with its upstream propagation. With the rise of incident point and angle of the cowl induced shock, the pressure gain across the shock train is substantially decreased and the pressure distributions deviate from the Waltrup empirical formula continuously.The validation and experimental results show that the simulation method with incident shock waves is feasible, and the conclusions of flow characteristics in the isolator are creditable.