Experimental Investigation on Dual-Purpose Cavity in Supersonic Reacting Flows

Experimental studies are in progress to investigate the possible use of cavities for performance gain in supersonic reacting flowfield. While high-speed flow over an open cavity may or may not result in highamplitude resonance depending on the cavity dimensions, both situations are of interest because a recirculating cavity flow would provide stable flameholding while an unstable cavity could be used to enhance the rate of turbulent mixing. Several wall cavities with various sizes and aspect ratios were evaluated for flow stability characteristics with a Mach 2 air stream, and were placed inside a combustor where exothermic reaction occurred between high-temperature fuel-rich products from a gas generator and Mach 2 air flow. The preliminary results obtained from a series of open flow testing are presented in this paper. Both stable and unstable cavities were tested with reacting flow, which was created by injecting the fuel-rich products at 45 degrees into the Mach 2 air stream. Flame length and luminosity were substantially modified by the use of such cavities. Currently, ducted supersonic combustion tests are underway.