| With the widespread use of centrifugal compressors in the national defense industry、civil and energy power fields,centrifugal compressor gradually develops towards large flow coefficient and high pressure ratio.Its performance has attracted more and more attention.The demand of high pressure ratio of the centrifugal compressor makes the load increased.The high load of the centrifugal compressor causes the relative Mach number of the impeller to be higher,which makes it easy to generate shock wave at the suction side of the blade.The loss caused by the shock wave and the interference between the shock wave and the boundary layer can greatly reduce the efficiency of the centrifugal compressor and adversely affect the efficient operation of the compressor.Therefore,weaken the shock intensity,reduce the influence range of shock wave is the key factor of designing the high efficiency,wide operating range of high pressure ratio centrifugal impeller.In this paper,the semi-open centrifugal impeller(Krain)with a designed pressure ratio of 4.7 is taken as the object of study.NUMECA software is used to simulate the centrifugal impeller.Through the comparison between the experimental and the numerical simulation results,it is found that the numerical simulation can accurately predict the gas flow and the angular eddy in the flow channel,which verifies the numerical simulation accuracy.Through the analysis of the internal flow field,there is a strong shock wave at the inlet of the impeller.Secondly,carring out the basic simulation design of Krain impeller.The influence of different axial length,different leading edge sweep angle and different leading edge shape on the internal flow field and overall performance of high pressure centrifugal impeller is studied,especially the impact on the entrance shock.The results show that when the ratio of axial length L to impeller diameter D2(L/D2)is larger than 0.3,and the blade is swept by 7.5 ° can improve the overall performance of the impeller and increase the impeller choke margin.The elliptical leading edge of the blade can effectively control the shock intensity,and with the increase of the aspect ratio,the intensity of the shock wave becomes weaker and weaker,when the aspect ratio increases to 3,the performance improvement is less obvious.Finally,the redesign and strength checking of Krain centrifugal impeller are carried out.Through comparison with the original Krain impeller flow field,it is found that the shock intensity and the influence range of shock wave are effectively controlled.At the design condition,the impeller efficiency is increased by 0.3%,and the vaneless diffuser efficiency is increased by 1%. |
