Investigation On Tip Leakage Flow Of High-loading Compressor Cascade With Boundary Layer Suction

High-pressure ratio and high-efficiency of compressor are always required in modern high-performance aircraft design. High-loaded compressor cascade is the most effective method to increase the engines thrust-weight ratio. However, adverse pressure gradient increases with the growing of cascade loading in compressor result in separation of boundary layer. It becomes one of the most important factor to restrict the improvement of profile loading. Tip leakage flow is another factor to restrict the performance of compressor and reduces its efficiency. Tip leakage flow produces large tip leakage loss, and the unsteady pressure caused by vortex is closely related to compressor stability. Secondary flow has more drastic influence in high-loaded compressor cascade than general cascade, as well as the tip leakage flow. Therefore, to study and control leakage flow is significant to the application of high-loaded cascade.High-loaded cascade at low speed is studied to investigate the mechanism of boundary layer suction controlling tip leakage flow. Firstly, the CFD that was verified by an experiment was conducted to study the effect of boundary aspiration on corner in high-loaded compressor cascade without tip clearance. Flow mixing caused by vortex, such as concentrated shed vortex, passage vortex and corner vortex, is the major reason of entropy generation in passage. Boundary layer suction improve the momentum of incoming flow and delay the separation of it, which inhibits the generation of concentrated shed vortex and reduces loss caused by vortex and the scale of corner separation. By contrast, corner separation can be avoided with the suction on end-wall. However, the boundary layer movement lead to the generation of separation bubble in middle-span, which has been the source of loss in flow field. In addition, boundary layer suction on suction side show much more flexible than end-wall with variable incidence angle, and loss decrease gradually with the increase of mass-flow.Secondly, the tip clearance is introduced and the mechanism of aspiration controlling leakage flow is simulated as well. Tip leakage vortex breakdown caused by strong adverse pressure gradient and large curvature results in the low-energy fluid spreads out remarkably, which has a large blockage effect on incoming flow. Boundary layer suction on shroud along the flow direction has achieved desired effect as a result of tip leakage vortex has axial vorticity, and the slot located in suction side is superior to pressure side. Turbulent kinetic energy dissipation generated by tip leakage flow reduce on account of the inhibition of tip leakage vortex generation and development, so the blocking effect lower brought by vortex. In consideration of previous result, new approach that combination of slot on profile and shroud drop both the tip leakage loss and corner separation. Morphological of concentrated shed vortex and tip leakage vortex change apparently while passage vortex shows discrepancy in location and size in consequence of aspiration. Therefore, the vortex in passage redistribute perfect the flow property. The integrated aspiration behave excellently variation with gap size, and tip leakage loss reduce with the mass-flow addition.