Research progress on cavity configuration optimization for supersonic combustors

In air-breathing hypersonic vehicles, scramjet propulsion systems face core challenges such as fast and adequate fuel-supersonic airflow mixing, effective combustion, and robust flame stabilization. As one of the most widely used flame stabilization devices in scramjet combustors, the cavity shows a profound influence on the fuel mixing and combustion process, as well as the combustor performance. This paper systematically reviews research progress on the effects of cavity configurations on flow characteristics and combustor performance in supersonic combustors. First, a concise overview of the supersonic cavity is introduced, including the basic configurations, the typical flow structures, and physical effects of the supersonic cavity. Second, the influence of fundamental cavity configuration parameters, including cavity length, depth, length-to-depth ratio, rear-wall inclination angle, and front-wall inclination angle, on flow and combustion characteristics such as cavity recirculation zone structures, fuel residence time and flame stability is summarized and analyzed. Third, the optimization of two-dimensional cavity configurations is system-atically elaborated on the basis of three physical mechanisms: extension of recirculation zones/vortical structures; reconstruction of shock/expansion wave systems; and modulation of shear layer dynamics. Furthermore, three-dimensional cavity optimization is discussed, with a focus on the streamwise vortex enhancement and lateral mass exchange. Finally, recommendations are proposed for the configuration optimization and design of cavity flameholders, taking into account the current research status and technical bottlenecks.