CFD study on inlet unstart prediction of dual-mode scramjet

Abstract

Dual-mode scramjet has become a viewpoint in the research fields of propulsion systems of aeronautics and astronautics. The key operating process of the dual-mode scramjet is from a started situation to an unstarted situation. The operating process composes of three phases. The first phase is when the pseudo shock wave is in the combustor. The second phase is when the pseudo shock wave is in the isolator. The last phase is when inlet unstart happens. In this study, two-dimensional numerical model has been made to replicate the process before inlet unstart. The location of pseudo shock wave has been determined in according to the location of the plug. As the throat area of the plug is decreasing, pseudo shock wave goes upstream. The prediction of inlet unstart has been focused in terms of the throat area ratio. The transition point of throat area ratio just before inlet unstart has been indicated. The transition points of throat area ratio in steady simulation and unsteady simulation are different. This is because the transition information needs time to spread from the plug to upstream location. The difference could be used for predicting the inlet unstart.