Experimental parametric studies on the performance and mixing characteristics of a low area ratio rectangular supersonic gaseous ejector by varying the secondary flow rate

A low area ratio rectangular supersonic gaseous ejector is subjected to parametric evaluation to calculate the performance parameters like stagnation pressure ratio, compression ratio, entrainment ratio and the mixing parameter known as non-mixed length for a wide range of operating conditions by varying the secondary flow rate. The operating conditions are achieved by varying the design Mach number of the primary flow nozzle, the total pressure of the primary flow and the secondary flow rate. Air is used as the working fluid in both the primary and secondary flow. The ejector is operated in the mixed regime. Mach number ratio is used as the non-dimensionalization parameter, and fully-expanded jet height is used as the scaling variable to collapse the huge set of obtained data for parametric studies. With variation in the secondary flow rate, staging is observed in the compression ratio, entrainment ratio, and also in the non mixed length. Variation in the entrainment ratio and non-mixed length are observed to be linear, and it scales well with the fully-expanded jet height when there is a deficit in the secondary flow. Also, when there is no secondary flow, the non-mixed length is observed to be 80% lower in comparison with the case, where the secondary flow is uncontrolled. Schlieren visualization and wall static pressure measurements supplement the findings. (C) 2018 Elsevier Ltd. All rights reserved