A streamlining method for ejector nozzle profile optimization based on polynomial function

Abstract

In this study, ejector performance was optimized by streamlining the primary nozzle profile using polynomial functions. Thirteen streamline nozzle profiles with different initial and exit expansion half-angles which determined by quadratic and cubic functions were established, and their performance are discussed. The results indicate that the nozzle profiles designed by cubic function have the best performance than quadratic function. To improve the effective working range, the ejector should have an initial expansion half-angle that is as small as possible and an exit expansion half-angle that is as large as possible. To enhance the entrainment ratio, the ejector should have a constant exit expansion half-angle and a minimum initial expansion half-angle of 1°. An excessive initial expansion half-angle caused a sealed Mach number contour inside the nozzle, which wasted energy to reduce the velocity and increase the static pressure, decreasing the working efficiency of the primary flow. In addition, the entrainment ratio significantly decreased with a large exit expansion half-angle (greater than 17°).