Research On Flow Characteristics Of Steam Ejector Based On Enhanced Mixing Theory

Compared with other fluid machinery,the ejector system has the advantages of no moving parts and simple structure,and has been widely used in the industrial field.However,in the design and processing of ejectors,long-term experience or semi-empirical formulas obtained from production practice and basic aerodynamic theory cannot be used to accurately design and judge the performance of ejectors and solve the problem of low ejector coefficients.First,based on the one-dimensional model of the ejector proposed by B.J.Huang and Fan Shi Kong,etc.,I establish a one-dimensional calculation model and design a C language calculation program to calculate and analyze the influence of working parameters and geometric structure on the flow parameters and ejection performance of the key nodes of the ejector.The one-dimensional model has the optimization characteristic of the natural balance between the ejection coefficient and the outlet pressure,which is of great significance for optimizing the ejector structure and improving the ejection coefficient.Then,based on the research of the one-dimensional model,the SST k-ω turbulence model and the Aungier-Redlich-Kwong real gas equation,a three-dimensional numerical calculation model of the ejector was established.The effects of shock wave,choking,Prandtl Meyer flow and double boundary layer formation on the ejector performance were studied by numerical simulation under different working parameters and geometric structures.According to the flow characteristics,the geometric structure is comprehensively optimized to improve the ejection coefficient of the conventional ejector.At the same time,using the three-dimensional simulation results,partial correction coefficients of the one-dimensional calculation model are fitted and corrected to improve the accuracy of the one-dimensional calculation model.Finally,based on the simulation research of conventional ejector,adopting the passive mixing technology in the enhanced mixing theory,design the three-petal ejector to control the mixing intensity between the working steam and the ejected steam.The nozzle designed for the three-petal ejector can control the internal shear strength by changing the tip radius Rce;the external shear strength by changing the convex corner radius Rro;and the overall mixing intensity can be controlled by changing the difference between the tip and the convex corner radius.The impact of shock wave,choking,deflected flow and double shear flow in the three-petal ejector on the ejector performance and mixing intensity is studied,and the ejection coefficient is further improved.