Effect of flame-holding cavities on supersonic-combustion performance

An experimental study was performed to evaluate the flame-holding and mixing enhancement characteristics of supersonic reacting flow over acoustically open cavities. Several configurations of acoustically open cavities were placed inside a supersonic-combustion duct just downstream of the fuel injection ports. The resulting changes in flame behavior and combustion characteristics were assessed using schlieren visualization of the unconfined flow and wall pressure measurements of the confined flow along the duct. The results were then compared with the baseline case, which used no cavity. Although the cavities improved the combustion performance from the baseline, the amount of enhancement was dependent on the particular shape of the cavity as well as the flow conditions. Certain cavity configurations that were strategically placed inside the combustion duct led to a faster increase in the axial pressure force. The data showed that the recovery temperature was higher and the total pressure profile was more uniform at the exit plane, suggesting enhanced volumetric beat release and faster mixing associated with the cavity- influenced flowfield.