| Liquid-ring pump is to realize the suction and discharge of gas through the movement of the gas-liquid interface in the pump.As an important part of the flow passage in the liquid-ring pump,the casing has a great influence on the shape of the gas-liquid interface.Reasonable design of the casing profile can improve the hydraulic performance of the liquid-ring pump in a certain range.This study proposes to use the method of combining numerical simulation and experiment to optimize the casing profile of the suction section and exhaust section of the liquid-ring pump under the working conditions of vacuum pump and compressor,use the direct free surface deformation method to parametrically control the entire casing profile,and construct the response surface agent model of the relationship between the casing profile parameters of the liquid-ring pump and the hydraulic performance of the vacuum pump condition and the compressor working condition according to the Box-Behnken experimental design principle.The NSGA-Ⅱ algorithm is used to optimize the performance of liquid-ring vacuum pump and liquid-ring compressor,and finally the internal and external characteristics of the optimization model and the initial model are compared and analyzed,which provides a reference for the optimal design of the casing profile of the liquid-ring pump.The main research contents and conclusions of this paper are listed follows:(1)The external characteristics and internal flow field structure of the liquid-ring pump are studied by combining numerical simulation and experimental testing,and the results show that the numerical simulation has high calculation accuracy,which can effectively replace the experiment for the optimization analysis of the casing profile of the liquid-ring pump.The Box-Behnken experimental design was selected to sample the casing profile parameters of the liquid-ring pump,and the casing profile of the liquid-ring pump was parameterized by the direct freeform deformation method,and the response surface agent model of the relationship between the casing profile parameters and the vacuum pump working conditions and compressor hydraulic performance of the liquid-ring pump was constructed respectively.(2)According to the response surface model,the influence of the casing profile on its performance under the working conditions of the vacuum pump is analyzed,and the results show that the casing profile at the beginning of the suction port for the liquid-ring vacuum pump has the greatest influence on its efficiency,and the casing profile at the end of the suction port has the greatest influence on its imported vacuum and shaft power;The influence of the casing profile of the suction section on the performance for the liquid-ring vacuum pump is significantly greater than that of the exhaust section casing profile,and the influence of the exhaust section casing profile on the pump performance is mainly concentrated in the compression area;The larger radial size of the casing profile helps to increase the inlet vacuum of the vacuum pump.The greater diffusion degree of the suction area runner area and the shrinkage rate of the exhaust area runner area,the liquid-ring vacuum pumps also have greater shaft power and lower hydraulic efficiency.(3)Analyze the influence of the casing profile on its performance under compressor working conditions,the results show that the casing profile at the beginning of the suction port for the liquid-ring compressor has the greatest influence on its efficiency,and the casing profile at the end of the suction port has the greatest influence on its inlet suction volume and shaft power;The impact of the casing profile of the suction section on the performance for the liquid-ring compressor is also greater than that of the exhaust section casing profile,and the influence of the casing profile on the shaft power for the liquid-ring compressor is consistent with the liquid-ring vacuum pump;The larger the radial size of the casing profile and the diffusion of the runner area of the suction segment,the greater the inlet suction volume of the compressor.(4)The response surface agent model is combined with the NSGA-Ⅱ multiobjective optimization method to optimize the vacuum pump condition of the liquid-ring pump and the casing profile of the compressor condition respectively.The results show that the overall performance of both optimized models is higher than that of the original model.For the liquid-ring vacuum pump,the maximum inlet vacuum of the optimized model is increased by 4.5% compared with the initial model,and the maximum efficiency of the optimization model is 1.3% higher than that of the initial model;For the liquid-ring compressor,the maximum inlet suction of the optimized model is 6.4% higher than that of the initial model,and the maximum efficiency of the optimization model is 1.2% higher than that of the initial model.(5)Analyze the influence of the casing profile for the liquid-ring pump on the internal flow structure under vacuum pump conditions and compressor conditions,the results show that the change of the casing profile will cause the corresponding change in the shape of the gas-liquid interface in the liquid-ring pump,the larger radial size of the casing,the larger the small cavity volume formed between the gas-liquid interface and the hub,and vice versa,the smaller the smaller;The sawtooth shape of gas-liquid interface in the pump is more obvious when the diffusivity of suction area and the shrinkage of exhaust area are larger.The smaller radial size of the casing profile in the compression area of the exhaust section,the greater the pressure energy of the gas in the pump,which helps to reduce the return of the exhaust outlet,thereby improving the hydraulic efficiency of the pump. |
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