An investigation of geometrical factors of multi-stage steam ejectors for air suction

Abstract

Given the structural limitations of ejectors, in order to enhance the flexibility of them to suit various industries, several ejectors may be connected to each other serially. Moreover, steam ejectors are employed in different applications to draw air. In this study, through the agency of computational fluid dynamics, the geometric parameters of multi-stage steam ejectors for air suction were examined, the result of which was validated against experimental data. In this regard, considering an ejector with two stages, attempts were made to investigate the effects of geometric parameters including the diameters of the nozzle, the mixing chamber, the throat, and nozzle exit position (NXP) for either ejector. Accordingly, having evaluated the effects of the mentioned parameters, the most suitable values were selected to satisfy not only the proper functioning of each stage but the entrainment and compression ratio as well. The compression ratios obtained for the first and the second stages are 4.25 and 2.875, respectively which gives rise to a compression ratio of 12.219 for the multi-stage ejector. Eventually, for the final geometry of the ejectors, the Mach number, as well as pressure contour, were demonstrated and analyzed.