Design and Capturing of Shock Wave in Ejector by Numerical Simulations

Series of two convergent-divergent nozzles is called ejector; the first or primary nozzle accelerates high pressure primary fluid to low pressure and at supersonic speed. The low pressure developed at the end of primary nozzle entrains the fluid in the secondary nozzle. Eventually, these two fluid streams meet at constant area section resulting in a shock wave. Afterwards, diffuser increases the pressure to desired range. In this paper, numerical simulations are used for designing and shock capturing in ejector using R134a as a refrigerant. The flow analysis is done by Reynolds averaged Navier Stokes equation (RANS) using k-epsilon turbulence model. At first, simulations are done for each nozzle and later they are combined in case of ejector. In case of ejector, rapid fluctuations in pressure and magnitude of velocity showed that there are series of shock waves that result in increase in pressure in ejector. The pressure and Mach number contours explained the physics behind the suction and entrainment of secondary fluid in ejector.