Tip leakage flow and loss mechanism analysis of a low specific speed centrifugal impeller

The rear stage centrifugal compressor in aeroengine multistage compressors exhibits low specific speed characteristics， with intensified impacts caused by secondary flow， particularly those induced by tip clearance leakage flow， yet the underlying loss mechanisms remain to be fully elucidated. This study focuses on a low specific speed centrifugal compressor stage with abundant experimental data， employing validated three dimensional numerical simulations and entropy production analysis to quantitatively assess high loss sources within the centrifugal impeller. The formation and development of tip clearance leakage flow in main blades and splitter at both peak efficiency and near stall conditions are investigated， along with their mechanistic impacts on flow losses and aerodynamic blockage. Results reveal that in low specific speed impellers， secondary flow losses dominated by tip clearance leakage account for over 50% of total losses， significantly degrading efficiency and pressure rise capability above 60% span of the impeller. The flow characteristics and mechanisms differ between the two sides of splitter passages： the interaction between main blade and splitter tip leakage flows， redistribution of splitter streamwise loading， and increased relative tip clearance collectively lead to progressive flow deterioration in the suction side passage and migration of low loss regions in the pressure side passage. These effects induce severe flow blockage within the passage， particularly accentuated near the trailing edge region.