Numerical investigation on flow choking induced by local heat release and large-scale flow separation in a supersonic combustor

Flow choking during the scramjet operation has attracted considerable research attention because it restricts the development of wide-speed-range scramjet. Further investigations on the flow choking mechanism under supersonic combustion are also necessary. In this study, a numerical simulation is conducted to investigate flow choking induced by local heat release and large-scale flow separation in a supersonic combustor. The compressible solver PeleC with block-structured adaptive mesh refinement and detailed hydrogen/air chemical reaction mechanism is employed as the calculation tool, and two numerical cases with low inflow Mach numbers (1.5 and 1.8) are performed. The results indicate that transverse fuel injection induces boundary layer instability and decreases the core flow Mach number and total pressure, thereby increasing the possibility of flow choking. The intense heat release-core flow-boundary layer interaction rapidly enhances the local heat release and boundary layer instability, further decreasing the core flow Mach number. Flow choking is triggered by the continuous contraction of the effective core flow area, during which the premixed combustion-dominated heat release plays a crucial role. The upstream propagation of flow choking leads to the dominance of diffusion combustion over premixed combustion in terms of heat release. The jet in the choked crossflow-induced flame structure is composed of wrinkled, corrugated, and broken flamelets. A novel flow choking mechanism induced by an acoustic converging channel is proposed and verified using a one-dimensional pressure-area theory.