Effects of tip injection in different locations on clearance leakage flow of turbine

In order to investigate the effects of the tip injection location on tip leakage flow of turbine, the detailed flow-field measurements at cascade outlet are taken with a five-hole probe for the turbine cascade with various tip-injection locations and tip clearance sizes under low speed conditions. The 3D flow fields near the tip region are compared by CFD simulation, and the effects of the tip injection location on the flow fields and losses are analyzed. The results show that the impacts of the blade tip injection on the tip leakage flow are gradually weaken with the increase of clearance size. The tip injection can effectively reduce the leakage flow kinetic energy near the tip region with a small gap. The loss caused by the leakage vortex is reduced and the loss due to the passage vortex increases at the same time. The injection near the suction side decreases the leakage vortex loss by 48.6% but the peak value of loss due to the passage vortex increases by 10.4%. The kinetic energy of leakage flow increases with the augment of the clearance size and tip injection has a negligible effect on the leakage flow. By reducing the leakage flow kinetic energy to weaken the interaction between leakage vortex and passage vortex, and control the large 3D flow separation to occur, it can effectively improve the performance of flow near the clearance.