Ejector Recirculation and Entrainment

Confined-jet flow structures were investigated in the context of an ejector ramjet application. An ejector apparatus was constructed with variable mixing chamber diameters and downstream flow restrictions in the form of an orifice plate. The performance of the ejector was characterized by its entrainment and compression ratios for 30 unique geometric combinations. A mixing chamber diameter that was incrementally larger than the orifice plate diameter maximized the entrainment ratio performance of the ejector. Measurements of the wall static pressure, collected by wall pressure taps, were used to determine the relationship between the ejector performance and the confined-jet flow structures within. Experimental wall static-pressure measurements were supplemented by Reynolds-averaged Navier–Stokes [Formula: see text] shear-stress transport computational fluid dynamics simulations of 18 ejector geometric combinations. The initial static-pressure gradient, axial length of the confined-jet flow, location of the recirculation core, and recirculation eddy separation and reattachment points were investigated for a correlation to the maximum entrainment performance of the ejector. The recirculation eddy size and fully developed location of the confined-jet flow showed little evidence of correlation to the ejector performance.