Experimental Investigation of Shock Train Dynamics Under Various Fuel Injection Schemes in a Mach 2.5 Cavity Combustor

This study experimentally investigates the scram-to-ram mode transition in a rectangular Mach 2.5 supersonic combustor featuring a cavity flame holder, for two different fuel injection locations positioned at distances of H and 2H upstream of the cavity leading edge. The mode transition and associated flow and flame dynamics are visualized by time-resolved simultaneous(20kHz) CH* chemiluminescence and Schlieren imaging. Previously, the scram-to- ram transition was defined solely by the pressure rise near the fuel injection point. Now, along with this, the transition is characterized in this work by the presence of a pre-combustion shock train, jet penetration fluctuations, upstream ignition, and flame propagation. Experimental observations indicate that changing the fuel injector location does not significantly affect the average heat release distribution within the combustor. However, it has a substantial impact on the dynamics of the mode transition.