Application of Chevron Nozzle to a Supersonic Ejector–diffuser System

Abstract

The supersonic ejector-diffuser system was widely used in many industrial applications. Recently, it is also being used as one of the most important components of the solar seawater desalination facility. That is because this system has many advantages over other fluid machinery like no moving parts and no direct mechanical energy input. The system makes use of high-speed primary stream to entrain the secondary stream through pure shear action for the purposes of transport or compression of fluid. However, the optimization of the ejector-diffuser system and its optimal operation condition are hardly known due to the complicated turbulent mixing, compressibility effects and even flow unsteadiness which are generated inside the ejector-diffuser system. Much effort has devoted to the performance improvement of the system since it bears relatively very low efficiency. The optimization of the ejector-diffuser system and its performance improvement are of practical importance in industrial field. In the present study, a Chevron nozzle was applied to activate the shear actions between the primary and secondary streams, by means of longitudinal vortices generated from the Chevron. A CFD method has been applied to simulate the ejector-diffuser flow field. The present CFD results were validated with existing experimental data. The operation characteristics of the ejector system were compared between Chevron nozzle and conventional convergent nozzle for the primary stream. The ejector-diffuser system performance is discussed in terms of the entrainment ratio, ejector efficiency, pressure recovery as well as total pressure loss.