Design Concept with Tip Leakage Vortex Control for Centrifugal Compressor Flow Stabilization

Centrifugal compressor applied to turbochargers is required to operate stably in wide range from choking to surging. In our past research, authors suggested a design policy called STB (flow Stabilization by inducing Tip leakage vortex Breakdown) concept, which indicates "Operating range can be enhanced with uniform blockage region generated by tip leakage vortex breakdown". In this study, authors tried to validate the STB concept by redesigning a given impeller into a wide range compressor. In this research, detailed analyses showed that non-uniform and unstable stall occurred at small flow rate in the conventional impeller. On the other hand, in the redesigned new impeller having high inducer loading, unsteady numerical calculation showed that the strengthened blade tip leakage flow generated a circumferential uniform blockage region, which could stabilize its internal flow. As a result of performance test of the new impeller, considering that the surging flow rate at the same shaft speed was reduced by 3% and the pressure ratio at the surging point had been improved from 2.8 to 2.9, the surging flow rate at the pressure ratio of 2.8 could be reduced by 8%. In this way, it was found that the tip leakage flow was dominant with the stall phenomenon of the centrifugal compressor, and it was also confirmed that the STB concept was one of the effective means for the operation range enhancement.