Effect of flame-holding cavities on supersonic-combustion performance

An experimental study was performed to evaluate the flame-holding and mixin g enhancement characteristics of supersonic reacting flow over acoustically open cavities. Several configurations of acoustically open cavities were p laced inside a supersonic-combustion duct just downstream of the fuel injec tion ports. The resulting changes in flame behavior and combustion characte ristics were assessed using schlieren visualization of the unconfined flow and wall pressure measurements of the confined flow along the duct. The res ults were then compared with the baseline case, which used no cavity. Altho ugh 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 str ategically placed inside the combustion duct led to a faster increase in th e axial pressure force. The data showed that the recovery temperature was h igher and the total pressure profile was more uniform at the exit plane, su ggesting enhanced volumetric beat release and faster mixing associated with the cavity- influenced flowfield.