Oscillating Flows in a Model Pulse Detonation Engine Inlet

A supersonic inlet with backpressure excitation to simulate the flowfield experienced by the inlet of a pulse detonation engine was tested at Mach 2.5. The excitation was varied from 15 to 50 Hz, and increasing the blockage at the exit plane varied the amplitude. Flow visualization using schlieren and PSP was used to obtain lower wall surface-pressure distribution. The pressure oscillations were confined to the downstream of the throat, and no adverse effects were observed on the flowfield upstream of the throat, that is, the inlet remained started for all conditions. The effect of increasing the excitation frequency was a decrease in the amplitude of the pressure perturbations. The effect of increasing the excitation amplitude was an increase in the upstream distance over which the perturbation was sensed. Schlieren photographs and flow visualization using PSP indicated the shock motion within the last g of the inlet and showed that the 2D wall pressure variation was restricted to a small region in front of the periodic blockage. (CSA)