Optimization of Ejector Geometric Parameters Using CFD

Abstract : Compression of a low pressure vapor without any rotating parts or direct external power sources is possible through a supersonic ejector. A high pressure vapor leads the compression of the low pressure vapor by pure fluid mechanics. Entrainment ratio is a major characteristic of the ejector performance and is highly dependent on its geometry. Based on pre-specified operating conditions, the flow behavior inside the ejector is studied by using computational fluid dynamics "CFD" "ANSYS FLUENT 15.0" software. The aim of this paper is to design ejector geometry and assess and quantify the impact on performance of geometry of ejectors. First a 1-D mathematical model is carried out to predict the ejector geometry, meaning the diameters of each zone. Second, the 1-D model results are converted into 2D figures and studied in CFD. Major challenge is to reveal the mixing process at different parts of the supersonic turbulent flow and to study the effect of the geometry on the effective ejector area. Results show the effect of the geometry on the entrainment ratio, in particular the length of ejector throat.