Experimental Study of Cavity-Strut Combustion in Supersonic Flow

An experimental investigation of cavity-based flameholders with strut injectors in a supersonic flow is reported. In this ongoing research program, emphasis is placed on understanding cavity-based flameholders and providing alternative methods for improving overall combustor performance in scramjet engines. Three different struts with fuel injectors are mounted near the cavity leading edge to study flame propagation and ignition of fuel in the core flow region. Planar laser-induced fluorescence of the OH radical is used to identify the flame zone around the cavity and strut-wake regions over a range of conditions. Shadowgraphy is employed to capture the flow features around the strut and cavity. In-stream probing is conducted to characterize the flow features associated with the different strut configurations. Stagnation-temperature profiles are obtained for all struts operating under the same condition in the combusting-flow study. Two cavity fueling schemes are used to compare flameholder performance. Direct cavity air injection is found to improve combustion significantly. For each strut, upstream and downstream fueling schemes are compared over a range of conditions. Overall, successful combustion is observed in the strut-wake region using upstream strut-fueling schemes for the three struts employed in this study.