CFD Study of Ejector Efficiencies

This paper presents a method to evaluate ejector efficiency in function of local flow parameters. The paper is divided into two parts. In the first part, a Computational Fluid-Dynamics (CFD) approach for convergent nozzle ejectors is presented and computational results are validated using experimental velocity and temperature profiles at different sections. The validation process includes the evaluation of seven Reynolds-Averaged Navier–Stokes (RANS) turbulence models: the Spalart-Allmaras and the k–omega SST models show better performance in terms of convergence capability and flow and thermal field prediction. In the second part, local flow phenomena and their influence on ejector component efficiencies are investigated. The validated CFD approach is used to determine the efficiencies of the ejector primary nozzle, suction chamber, and mixing zone. Efficiency maps, regressing equation linking efficiencies, and local flow quantities are proposed and discussed. Finally, global ejector performance is mapped and considerations are outlined.