Numerical Simulation Of Cavitation Effect In Liquid-Liquid Ejector

The ejector has many advantages of simple structure,reliable operation,convenient processing and comprehensive utilization,so it is widely used in aerospace fields.For example,it can reduce the temperature of the engine’s tail nozzle and reduce its infrared signal.The ejector works mainly by ejecting the absorbed fluid through the working fluid.The two different fluids are mixed with each other in the mixing chamber and the throat of the ejector to finish the transfer and exchange of momentum and mass.In the process of fluid flowing,because of the decrease of the cross-sectional area at the outlet of the ejector nozzle,the flow rate of the fluid increases and the pressure drops,the cavitation phenomenon is easy to occur and cause the cavitation problem of the ejector,thus affecting the cavitation flow ratio of the ejector and reducing the efficiency of the ejector.So three-dimensional geometric model is established by Creo and the division of ejector structured grid will be finished by ICEM,based on the numerical simulation of the finite volume method and the Large Eddy Simulation method,considering the influence of ejector device cavitation cavitation factors and carries on the research,including inlet pressure of ejector device,suction fluid pressure,outlet pressure,diffusion area ratio,length of pipes,pipe length,nozzle distance,etc.Vapor phase volume fraction and flow ratio of ejector increase with the decrease of outlet pressure.The ejector cavitation will occur under low outlet pressure,and the flow ratio of the ejector will not change at this time,that is,the cavitation flow ratio of the ejector.The main area of cavitation is concentrated at the inlet of the throat and near the front wall of the ejector throat.With the increase of working fluid pressure from401 kPa to 441 kPa,the ejector is in cavitation state,and the scope of cavitation region is gradually expanded.The peak velocity on the ejector axis also increases with the increase of the working fluid pressure,but the flow ratio is opposite.With the increase of the pressure of the suction fluid,the cavitation effect of the ejector becomes more serious,and the flow rate of the suction fluid and the flow ratio of the ejector also increase.As the area ratio increases from 5.5 to 11,the cavitation flow ratio of the ejector increases continuously,and the efficiency also increases from 12.4% to30.3%.With the increase of throat tube length,diffusion tube length and nozzle distance,the cavitation flow ratio and efficiency are firstly increased and then decreased.Finally,on the basis of the above research,the shape structure of the ejector throat inlet was optimized,and the ejector cavitation was greatly improved,and the ejector efficiency was also significantly improved,reaching 36.15%.