Active control method for restart performances of hypersonic inlets based on energy addition

Abstract The restart performance of the inlet is crucial to a hypersonic air-breathing propulsion vehicle. An active flow control method based on energy addition for the restart of hypersonic inlets is brought forward in this paper. Using Reynolds Averaged Navier–Stokes equations method, the effects of energy addition parameters on the restart performances of hypersonic inlets are investigated and the restart process is presented. This study verifies that the present method is feasible to improve the restarting capability of hypersonic inlets. The restart performances rely heavily on the energy addition parameters. Using energy addition properly, it usually yields a better inlet performance and more importantly enables the inlet restart again; otherwise, the large separation bubble still exists. Investigations on energy addition parameters further reveal that energy addition always increases the mass flow rate, and its center far from the cowl facilitates restarting the inlet and decreasing the stagnation pressure losses. It also appears advantageous to work with energy addition at a moderate power consumption and effective radius. Besides, the restart process indicates that the parabolic shock induced by heated region plays an important role on the restart performance. It alters the separation bubble, broadens the flow passage and enables more deflected air into the inlet. The adverse pressure gradients in the entrance are greatly changed as well. Finally, results also suggest that an appropriate effective time for energy addition is sufficient to restart the inlet. The variations of hysteresis loops show that energy addition prompts the separated bubble to disappear and the inlet to restart in advance. As a result, the restarting Mach number declines and the operation range of hypersonic inlets prominently enlarges.