Ramp Injector Scale Effects on Supersonic Combustion

The combustion field downstream of a 10deg compression ramp injector has been studied experimentally using wall static pressure measurement, OH planar laser-induced fluorescence, and 2kHz intensified video filtered at 320nm for OH emission. Nominal test section entrance conditions were Mach 2, 131kPa static pressure, and 756K stagnation temperature. The experiment was equipped with a variable-length inlet duct that facilitated varying the boundary-layer development length for nearly constant injector shock structure conditions. By varying the boundary-layer thickness from 40% of the ramp height to 150% of the ramp height, changes in the combustion flowfield downstream of the injector could be diagnosed. It was found that flame shape changed, the persistence of the vortex cores was reduced, and combustion efficiency rose as the incident boundary layer grew. Unsteadiness within the flameholding region also varied greatly over the range of conditions studied, and largest unsteadiness was observed at intermediate boundary-layer heights.