Research On The Ejector Model With The Introduction Of Real Gas And Analysis Of Mixing Characteristics

Ejector is a type of device which can improve the pressure of ejector fluid without directly consuming mechanical energy through energy conversion between two fluids with different pressures and temperatures,and has been extensively used in refrigeration,chemical industry and aerospace fields.Based on the two-dimensional thermodynamic model of ejector,this paper explores the mixing mechanism of two fluids and the structural characteristics of the mixing chamber through theoretical analysis and numerical calculation.The main research contents and conclusions are expressed as follows:Firstly,considering the complexity of fluid flow and mixing process in the ejector,this paper introduced the physical properties of CO₂ actual gas,based on the critical circle theory,combined with one-dimensional gas dynamic function and hydrodynamic equation,to build a two-dimensional thermodynamic model of the ejector and obtain the theoretical formulas of velocity,mass flow rate,critical circle radius and ejection coefficient of the fluid in the critical section of the ejector.The relative errors were 6.1%,7.4%,8.3%,9.6%and 9.2%,respectively,comparing the calculated values of ejection coefficient with the experimental values in the literature,which verified that the model had certain credibility and the errors were more stable.Secondly,based on the above thermodynamic model,through numerical calculation,the influence of the inlet pressure of the two fluids on the critical circle position,the mass flow rate and velocity of the ejector fluid is studied,and then the relationship between the inlet pressure and the ejection coefficient is obtained.The results show that the critical circle position is more affected by the ejector fluid pressure than the working fluid pressure.When the pressure of ejector fluid is lower than 5MPa,the mass flow rate of ejector fluid increases linearly with the increase of ejector fluid pressure,and when it exceeds 5MPa,the mass flow rate of ejector fluid increases slowly.The velocity of ejector fluid is negatively correlated with ejector pressure,positively correlated with working fluid pressure,and more influenced by ejector fluid pressure.When the critical circle radius increases or decreases due to the change of working fluid pressure,the ejection coefficient decreases or increases as a whole.When the pressure of working fluid and ejector fluid increases unilaterally,the ejection coefficient tends to increase.Finally,combined with the thermodynamic model,the concept of excess length is introduced for the optimization design of the mixing chamber structure,the structural characteristics of the mixing chamber are analyzed with Computational Fluid Dynamics（CFD）,and the relationship between the mixing chamber structure and the velocity field and pressure field of the mixed fluid is obtained,that is,the velocity The field is the main factor that determines the radial size of the mixing chamber,and the pressure field is the main factor that determines the axial size.