Back-Pressure Effect on Shock-Train Location in a Scramjet Engine Isolator

The isolator of the scramjet decelerates the incoming high Mach flow to a lower Mach number and stabilizes the flow before it enters the combustor. Because of the unsteady combustion phenomenon and inconsistent completeness of the combustion, pressures within the combustor can vary drastically. These pressure variations can propagate forward and affect the flow field in the isolator - worst case unstarting the inlet. In this research, the shock train location VS. the back-pressure is examined experimentally. The back-pressure is artificially created by symmetric (top and bottom) ramps that can close the flow area. Raising/lowering ramps result in higher/lower back-pressure. Higher back-pressure moves the shock train forward, with too high a back-pressure causing un-start. This experiment is conducted for a variation in Reynolds number, ramp angle, and two incoming Mach #s, and will result in a relationship between back-pressure and shock train location for various airflow conditions.