Aerodynamic Analysis And Optimization Design Of Centrifugal Impeller With High Rotating Velocity

The aerodynamic performance of impeller decides the efficiency of centrifugalcompressor as a key work-part to change mechanical energy to pressure energy. Theaerodynamic design of impeller is tied to development of impeller machinery andbecome the research focus of aerodynamic field. To improving the centrifugalcompressor to higher pressure ratio and efficiency, the aerodynamic analysis anddesign of unshroud impeller is becoming hot point due to its high running intensityand circumference velocity.The present dissertation contains two parts. Firstly, the multi-objectiveoptimization design was carried out on a centrifugal impeller for a typical compressorusing inverse design methodology to improve the aerodynamic performance includingefficiency, total pressure ratio and stable working region. The other part is the flowcharacteristics in Eckardt impeller with three tip clearances is investigated using thenumerical simulation method. The effect of tip clearance on the aerodynamicperformance and flow field of the impeller is analyzed.The inverse optimization design of centrifugal impeller is based on the analysisof original impeller. The flow field of the original impeller and the aerodynamicperformance are investigated using the numerical simulation，and then the impeller isoptimized in following ways:1) keeping the original meridian type, the threedimensional geometry of blade was design and compared by controlling thedistribution of blade loading;2) With optimal blade loading, the blade exit width wasoptimized to weaken the flow separation at blade exit of impeller suction side;3) Withoptimal blade loading, the effect of inlet width of impeller was investigated in order toenlarge the working range and remove the separation. The aerodynamic performanceof the final optimization impellers were numerically analyzed and the optimalgeometry and aerodynamic parameters are obtained.The influence of tip clearance on flow field and the aerodynamic performance ofthe unshroud centrifugal impeller were investigated using the numerical simulationmethod. The results indicated the tip clearance made the aerodynamic performance ofthe impeller decreased, but their relationship is not linear. The clearance leakagedepends on the distribution of blade loading. The main flow effected by leakage flow mainly lie on midstream and downstream. Although the leakage vortexes wouldgenerate under different working conditions, the structure of vortexes showed largedifference. The flow loss generated by leakage flow itself is almost neglected, and theclearance vortexes mixed with downstream main flow is the major factor leading toflow loss.The results provide guidance for the design and optimization of the complexthree-dimensional centrifugal impeller.