Nature of tip clearance flow in subsonic unshroud impeller of centrifugal compressor

The tip clearance seriously affects the aerodynamic performance of unshroud centrifugal impeller.The flow field in impeller with three tip clearances was investigated using the numerical simulation method,and then the effect of tip clearance on the aerodynamic performance of impeller,blade loading,flow angle across the tip clearance and the motion of leakage vortex was analyzed in detail.The results indicate different tip clearances have little effect on the blade loading profile,but a value reduction of static pressure from the middle to the trailing age of blade.The flow loss on tip clearance is hardly generated by leakage flow itself.The main flow is disturbed by leakage flow in the second half of the flow channel rather than in the first half.There exist amounts of vortexes near the shroud which cause significant entropy increase which leads to energy loss.The results are hoped to help to develop the aerodynamic model of tip clearance in unshroud centrifugal impeller.