Characteristics and mixing-controlled mechanism of rotating detonation wave under high Mach number flight conditions

This study performs three-dimensional numerical simulations with detailed chemical kinetics to examine rotating detonation wave (RDW) under Mach number 6 flight conditions, employing dual fuel injection at upstream and downstream locations within the isolator. Theoretical and numerical analyses reveal that upstream oblique shock waves (OSWs) generated by RDWs, which are deflected downstream, have limited upstream propagation under Mach number 6 flight conditions and tend to induce trailing RDWs near the primary RDWs. We propose a parameter-extraction method focusing on combustible gases near the RDW to establish local mixing quality as important controlling factors for RDW propagation structure. The results reveal that inadequate upstream mixing causes RDWs to degenerate into upstream OSWs, where the theoretical Chapman‒Jouguet velocity of the combustible gas is lower than its synthetic velocity. Fuel distribution, controlled by the ratio of upstream to downstream injection orifices, considerably modulates mixing quality. An increased upstream fuel injection proportion directly intensifies RDWs through improved mixing efficiency. Overmixed conditions lead to upstream propagation of RDW, perturbing inlet stability, whereas undermixed conditions cause RDW destabilization or extinction. Within an appropriate range, better-mixed conditions generate stronger RDW intensity, with a broader high-heat-release zone and accelerated propagation velocity. Furthermore, mixing quality exerts indirect control on RDWs: intensified interactions between counterclockwise-rotating waves and the RDWs under poorer-mixed conditions elevate local temperatures and pressures axially upstream of the RDWs. These results advance understanding of RDW stabilization mechanisms under high Mach number conditions, offering critical insights for extending the operational envelope of rotating detonation ramjet engines.