Impact of incidence angle on tip leakage flow control ,by endwall suction in a compressor cascade

In order to reduce the tip leakage loss and improve the tip passage blockage caused by the tip leakage vortex, numerical simulation was conducted to investigate the flow control effect of suction scheme with endwall slot in flow direction on the tip leakage flow in a diffuser cascade. The impact of incidence angle on flow control effect was analysed emphatically. Results showed that the leakage vortex intensity and the leakage loss were reduced by the endwall suction scheme by directly controlling the development of the tip leakage flow. The influence of endwall suction on the cascade flow field at the design and negative incidence angles was limited to the vicinity of the blade tip. However, at a large incidence angle, suction can advance the boundary layer separation in the low span region, and the position of the vortex shedding on the suction surface of blade raised to about 70% span. Therefore, the overall impact of the endwall suction scheme on the cascade at a large incidence angle was determined by both the reduction of leakage loss and the increase of separation loss. With the suction flow rate of 07%, the overall total pressure loss coefficient of aspirated cascade decreased by about 90%, 108% and 68%, respectively, at the incidence angles of -8°, 0°and +4°, and increased by about 57% at the incidence angles of +8°.