Experimental Studies on Mixing in Supersonic Ejector

A supersonic ejector uses a primary flow expanded from high pressure to supersonic speeds to entrain a secondary flow and pump it to higher pressures. Figure1 shows the schematic of the flow through an ejector that has complex interactions between shock, shear layers, boundary layers within a varying area duct. The understanding of mixing between a supersonic stream and its coflow within a duct is crucial in design of a supersonic ejector. The length of the duct required for complete mixing of the streams followed by shock trains is specified by rule of thumb methods. Hence most of the literature deals with designing ejector for various applications and there is scarcity of experimental data on mixing phenomena in ejector, an essential requirement for optimal design considerations[3]. This motivated setting up a 2D supersonic ejector facility at the Laboratory for Hypersonic and Shock Wave Research, IISc, Bangalore, for experimentation on flow mechanics and mixing studies within the ejector. Static pressure measurements along the wall and shadowgraphs obtained at different operating conditions and their interpretations towards the objectives are described in this paper.