Unstart/restart hysteresis characteristics analysis of an over-under TBCC inlet caused by backpressure and splitter

For a better understanding of the flow instability in TBCC inlet, the unstart/restart characteristics have been investigated. Firstly, the flow field of TBCC inlet at different transition stages are analyzed. As the splitter rotates from upside to downside (transition from low-speed inlet to high-speed inlet) with a fixed backpressure, the shock train moves downstream. The maximum backpressure that the inlet can tolerate also rises. Secondly, according to the unstart boundary (namely maximum backpressure) and restart boundary, it can be found that if the inlet is propelled to transit from started state to unstarted state, inlet restart cannot be achieved along the same control route. Unstart/restart hysteresis loops in each transition phase are discussed according to the simulation results. Besides the hysteresis behavior under backpressure, the same phenomenon is also observed during the inlet transition process. Finally, the distinctiveness of the hysteresis caused by inlet mode transition is also discussed.