Study On Flow Control And Mechanism Of Low Specific Speed Centrifugal Compressor Volute

The low specific speed centrifugal compressor for electric supercharger has a good application prospect in improving the low-speed performance of internal combustion engines and the power density of fuel cells.This paper takes a low specific speed centrifugal compressor as the research object,and uses numerical simulation to study the effects of volute asymmetry and unsteady flow characteristics on the flow field distribution of the compressor.This paper proposes change the diameter of the centrifugal compressor's volute channel to realize the flow control of the flow field.The study found that the narrowing effect of the volute seriously damages the performance of the compressor,and the performance of the compressor is most obvious under non-design conditions decreases.In addition,induced by the asymmetric geometry of the volute,the average static pressure fluctuations in the compressor impeller outlet,diffuser outlet,and volute passage become larger as the flow rate increases.The nearer the centrifugal compressor is to the choke condition,the stronger the asymmetric distribution of the flow field.By exploring the influence of the unsteady of the centrifugal compressor on the compressor performance and flow field distribution,it is found that Unsteady calculation of compressor pressure ratio and efficiency are higher than steady calculation.The average static pressure fluctuation in the circumferential direction of the volute channel is increased,the asymmetric distribution of the compressor flow field is more intense.Based on the influence of volute asymmetric and unsteady flow characteristics on the distribution of compressor's flow field,this paper proposes a method of change the diameter of the volute channel to control the flow in the flow field of the centrifugal compressor.The results show that as the diameter of the volute passage increases,the performance and stable working range of the centrifugal compressor increase,but the performance improvement of the centrifugal compressor is decreasing.Considering the comprehensive cost and performance improvement,the 1.2 times original centrifugal compressor volute channel diameter centrifugal compressor is selected as the optimal design.Compared with the original centrifugal compressor,its performance and stable working range have been improved.After optimization,the pressure ratio of the centrifugal compressor at the design conditions increased by 0.8627%,and the efficiency increased by 3.2525%.Compared with the original compressor,the stable working range of the centrifugal compressor is widened,and the asymmetric characteristics of the flow field distribution are weakened,which realizes the flow control of the internal flow field of the compressor.