PIV Experimental and Numerical Investigation of Cold Flowfield of Scramjet Combustor with Inlet/Isolator

This paper focuses on the cold flowfield of scramjet combustor by PIV and CFD, including the detailed structures of the flowfield near the steps, cavity and the expansion wall. PIV data and the Schlieren image are acquired along the whole flowfield, which agree with each other in the flowfield structure, shock wave position and shape in the same inlet and backpressure conditions under the high back pressure; for the low back pressure, it is also true if the static pressure measured from the down wall near the exit of the combustor is modified. Furthermore, the experimental result is compared with unsteady CFD simulation. The flow structure inferred from the PIV data agrees well with that obtained from numerical simulation. The vortex of the cavity is also measured clearly in the PIV experiment. From the result it is shown that when the backpressure is increased, the shock wave and flowfield structure will oscillate, and even will change its position from the up to down, and so on, although the inlet and the outlet condition are kept the constant. It is presumed as the result of the oscillation phenomena in the upstream isolator flow. Under a certain high backpressure, the recirculating flow in the cavity will flow back even upstream of the cavity.