Influence Mechanism Of Ejector Key Structure And Performance Analysis Of New Ejector

Ejector refrigeration system is a kind of energy-saving refrigeration technology using low-grade as dynamics,however,all of those systems have the disadvantage of low performance parameter.Ejector is the core component of ejector refrigeration system,and its performance is one of the key factors affecting system performance parameters.The complex process of internal supersonic mixingmixing involves many problems of fluid mechanics,such as shock wave,turbulence and"constant capacity"caused by congestion.a clear understanding of its internal flow field changes is central to improved its performance.In order to solve the performance deterioration of ejector in the subcritical working state,it is put forward a new structure of enthalpy adding ejector.This paper discussed how to improve its performance focused on the internal flow field distribution and shock characteristics of the ejector.It is study the structural characteristics of enthalpy adding ejector in order to solve the performance deterioration of ejector in the subcritical area.The main research contents and conclusions are as follows:Based on the Computational fluid mechanics software FLUENT as the research platform,it is established a reasonable numerical calculation model of ejector,studied the mesh independence and compared five commonly used turbulence models,which have RNG k-?、Standard k-?、Realizable k-?、Standard k-ωand SST k-ωturbulence models.The results show that the CFD results of the RNG k-?turbulence model are closest to the experimental results and the error is minimal.To simulate the flow field of a fixed structure ejector,it is studied the influence of the working parameters on the flow field distribution along ejector axis and shock intensity.The results are as follows:it is proved that there are optimal primary fluid pressure P_p~*and critical back pressure P_c~*;the pressure of primary flow,secondary flow and back pressure have a significant effect on the intensity and position of the shock wave;the ejection performance can be effectively improved when the shock intensity near the nozzle outlet is small.According to the key size design of ejector,it is discussed the characteristics of internal flow field and Mach wave caused by different size ejector.The results are as follows:there is an optimal nozzle diameter ratio where entrainment ratio and critical back pressure reach maximum at the same time.With the increase of nozzle diameter ratio,the compression shock nearly nozzle outlet increases first and then decreases.Different nozzle diameter ratio corresponds to different optimal nozzle distance,and the larger the nozzle diameter ratio,the smaller the optimum nozzle distance.Keep the inlet and outlet conditions of the ejector constant.with the increase of the mixing chamber diameter ratio,there is an optimal diameter ratio,which makesentrainment ratio maximum;with the increase of the mixing chamber diameter ratio,the critical back pressure decreases gradually.In order to improve the performance deterioration of the ejector in subcritical mode,the structure of enthalpy adding ejector is proposed by analyzing the fluild distribution characteristics.It is studied that the working characteristics curve of enthalpy adding ejector by numerical simulation.The results are as follows:Compared with the traditional ejector,introducted of high-grade adding flow in tdiffuser chamber,it is proved that the enthalpy adding ejector can keep the maximum entrainment ratio constant,and effectively expand the back pressure range in the double critical mode(P_b~*>P_e~*),and improved the working performance under subcritical working condition;Critical back pressure of enthalpy adding ejector equipped with cone-shaped pipe is greater than that of cone-expand-shaped pipe.As the throat increases,critical back pressure gradually increases.As the adding flow pressure increases,critical pressure increases gradually.There is 52 figure,16 tables and 104 references.