Supersonic combustion experiments with a cavity-based fuel injector

Recent results from combustion experiments in a direct-connect supersonic c ombustor are presented. Successful ignition and sustained combustion of gas eous ethylene have been achieved using an injector/flameholder concept with low-angle, flush-wall fuel injection upstream of a wall cavity. Two interc hangeable facility nozzles (Mach 1.8 and 2.2) were used to obtain combustor inlet flow properties that simulate flight conditions between Mach 4 and 6 at a dynamic pressure of 47.9 kPa. Mainstream combustion was achieved at e quivalence ratios between 0.25 and 0.75 using only a spark plug and no othe r external ignition aids. Delta-force levels between 667 and 1779 N were me asured, with corresponding combustor pressure ratios between 3.1 and 4.0. V ideo records of the flame zone show an intensely active combustion zone wit h rapid flame spreading. One-dimensional performance analysis of the test d ata indicates a combustion efficiency around 80% with an average combustor skin friction coefficient of 0.0028.