The Study On Characteristics Of Multiphase Momentum Exchange Enhanced Ejector

As a static supercharging equipment,ejector has some problems,such as low ejection performance,long axial dimension and poor anti-fluctuation ability.The fundamental reason is that the ejector momentum exchange efficiency is low and the equipment structure is fixed.In view of the existing shortcomings,the corresponding structural modification can improve the performance of ejector equipment,shorten the axial size and broaden the scope of use.In this paper,the design program of ejector under air/steam conditions was compiled,and the structure scheme under variable conditions and the idea of momentum enhancement optimization were studied.It was found that the adjustable mechanism of the axial distance and radial area of the driving nozzle can realize the adjustment of the ejector operating conditions.By adding momentum enhancement elements at the tail of the driving nozzle,the ejection performance of the equipment can be improved and the axial size of the equipment could be shortened by changing the traditional two-dimensional momentum exchange into threedimensional momentum exchange.In this paper,experimental research and numerical analysis were used to accomplish the following tasks:(1)Based on Sokolov's ejector design idea,the ejector design program under air/steam condition was compiled,and the key structural parameters of ejector were designed.The deviation between the ejection rate of air condition design and experimental results is 9.46 %,and that of steam condition is 45.30 %.On this basis,the prototype of the new ejector was trialproduced,and the design and processing of the momentum enhancement element,the axial position adjustment element of the driving nozzle and the radial area adjustable element of the driving nozzle were completed.erformance test platform was built to meet the experimental requirements of air/steam conditions.(2)The feasibility of the variable working condition structural scheme is verified by experiments and numerical results.It is found that there is a high performance range in the axial distance of the driving nozzle,which is 6 mm to 12 mm in the air condition and 7 mm to 19 mm in the steam condition.It is found that the actual optimal axial distance of the driving nozzle is slightly smaller than the theoretical value.The experimental and numerical simulation results show that the radial area adjusting mechanism of the driving nozzle can stabilize the performance of the ejector and resist pressure fluctuation.Compared with the adjusting cone structure,it keeps the normal driving fluid manifold and has less flow loss.Visual flow field analysis(PDPA,high-speed photography)was used to analyze the effect of flash on the jet core.It was found that with the increase of flash,the driving fluid beam could become wider and the optimum axial distance would changed.(3)The idea of momentum enhancement optimization was studied by experimental research and numerical analysis.It was found that the momentum enhancement element can significantly improve the ejection performance in the critical zone of ejector under air and steam conditions.The more the number of spoiler teeth,the stronger the optimization effect,but momentum enhancement element would cause a certain degree of reduction of the supercharging performance,and enhance the momentum exchange efficiency can also shorten the core length of the jet.