Experiments in Supersonic Gaseous Ejector Using 2D-PIV Technique

Supersonic gaseous ejector is practically a supersonic confined jet, where the primary supersonic jet flows through the confined passage and thereby entrains the secondary flow from the ambient. In this paper, the flow field of the supersonic gaseous ejector is investigated prominently using 2D-PIV measurement technique to study the mixing progression between the primary and the secondary flow at different operating conditions. A rectangular supersonic gaseous ejector (air-air) of low area ratio (AR = 3.7) is used in this study. Two separate supersonic primary flow nozzles of design, Mach number (M_PD) 2.0 and 2.5, are considered in this experimentation. Differences between the supersonic free jet and the supersonic ejector or confined jet on the aspects of flow mixing are brought out clearly regarding flow kinematics. Centerline velocity decay, vorticity field, and wall static pressure distribution are used in parallel to explain the mixing progression in the ejector. Influence of the nozzle operating conditions on the gaseous mixing process is found to be prominent. Even a moderately underexpanded primary jet in a low AR supersonic ejector is observed to mix faster due to larger vorticity generation and early interaction of the mixing layer with the confined passage.