Annular Supersonic Ejector Design and Optimization

Abstract

An ejector is a device that entrains a secondary flow into a high speed stream that is generated by expansion of high pressure motive gas [1]. These ejectors can be broadly classified into central ejectors and annular ejectors. A large majority of applications involve central ejectors where the motive gas flow is injected along the centre of the flow passage of the secondary flow. Dutton and Carroll [2] proposed an optimization procedure for such ejectors without taking the mixed supersonic flow region into account and generated the design curves considering the constant Total temperature, Molecular weight and Specific heat ratios. However in some applications involving high temperature gases such as in ramjet/scramjet and gas turbine test facilities, an annular supersonic ejector is more appropriate where annular injection of the motive gas at the periphery of the flow passage is desired to avoid the exposure of the motive gas flow nozzle to the high temperature combustion product gases. A design and optimization procedure for an annular supersonic ejector based on the earlier approach [2] with the mixed supersonic flow region and incorporating variable Total temperature, Molecular weight and Specific heat ratios in the model has been developed based on simplified one dimensional constant area mixing model and verified using CFD software Fluent.