Research on inner flow and energy characteristics of air ejector for liquid-ring vacuum pump

Abstract

To analyze the complex flow characteristics, and reveal the mechanisms of energy transfer and hydraulic loss of the liquid-ring pump ejector. The numerical simulation and experiment were applied to analyze the complex shock wave structure, vortex evolution characteristics in the ejector and its influence on hydraulic performance, which provides a novelty reference for the optimization design of the ejector. Furthermore, novelty is expressed in the performance analysis of the ejector based on the performance of its matching liquid-ring pump. The results show that the λ-shock wave and Mach disk are formed inside the nozzle under the action of supersonic jet, and the triple point is formed as the incident shock wave, the reflected shock wave and the Mach disk intersect. The shock wave, as it propagates, changes from Mach reflection to regular reflection, and meanwhile, the position of triple point moves from the initial Mach disk to the new Mach disk. With the interaction of shock wave and jet boundary layer, the shock train is formed in the core region of the jet. The pressure, density and Mach number are oscillatory distributed in the shock wave region. There is a relatively large velocity gradient between the high speed primary flow and the low speed secondary flow near the outlet of nozzle, which induces the formation of opposite rotating vortices in the shear layer of the cylinder. With the evolution of the vortex, the high speed jet transfers energy through the cylindrical shear layer and is accompanied by the large hydraulic loss. The total entropy production of the ejector increases with the increase of primary flow pressure. The entropy production rate has a strong correlation with the vorticity magnitude.