Unsteady Dynamics of Shock-Induced Combustion in High-Mach-Number Flows

Shock-induced combustion in a direct-connected combustor was experimentally and numerically investigated at Mach 10 flight conditions. This study aimed to reveal the establishment of shock-induced combustion and its transition to partially premixed-dominated combustion in practical combustor flows, highlighting the critical effects of fuel injection and shock wave/boundary-layer interaction on shock-induced combustion stability. The combustor consisted of a constant-area section, a diverging section, and two shock-generating wedges symmetrically mounted on the top and bottom walls of the combustor. Hydrogen fuel was injected through two symmetrical fuel injectors. Each fuel injector had three identical struts equally spaced along the spanwise direction. Oblique shock waves were generated through wedges at the end of the combustor diverging section. Wall pressure and hydroxyl radical (OH*) flame chemiluminescence imaging were used to characterize the transient phenomenon of flame stabilization and upstream propagation. Large-eddy simulations were conducted to analyze the unsteady flame propagating processes in association with experimental results. The nonuniformity of prewave parameters induced by strut injection, coupled with the exacerbation of boundary-layer separation caused by shock-induced combustion, led to combustion instability and engine performance deterioration.