Feasibility of employing the restarting process to evaluate the self-starting ability for hypersonic inlets

Abstract

Accurate evaluation of hypersonic inlet self-starting performance is very crucial for the stable and efficient operation of scramjet engines. However, few ground hypersonic wind tunnels could provide a continuously and slowly accelerating free stream conditions to directly validate the self-starting ability of hypersonic inlets so far. Some experimental restarting approaches have been explored to evaluate the self-starting performance of hypersonic inlets. To clarify the feasibility of such approaches, the self-starting process and the restarting process caused by withdrawing plug at the exit of a two-dimensional hypersonic inlet were studied using unsteady numerical simulation in this paper. The results show that, even though the freestream Mach number (5.54) of the restarting process is lower than the self-starting Mach number (5.715), the hypersonic inlet can finally rebuild the started flow field owing to the significantly higher moving speed downstream across the inlet internal contraction section caused by the big buzz. Hence, the additional unsteady effect should be suppressed as far as possible during the initial pre-blockage process in the restarting experiment applied to evaluate the self-starting performance of hypersonic inlets.