Role of tip leakage flow on flow instability and its control with circumferential groove casing treatment

In order to provide a state-of-the-art understanding of the flow field in axial-flow compressor in the perspective of enhancing its stability by using passive means,the detailed tip flow structure and inception of rotating stall were measured in a subsonic compressor rotor with high response pressure transducers.The inception of spike-type rotating stall that correlated with the tip leakage vortex was detected in this compressor.The physical processes occurring when approaching stall and the role of complex tip flow mechanisms on flow instability in current subsonic compressors were assessed by using time-accurate single blade passage computations.Based on these observations,circumferential groove casing treatment was introduced to control the tip leakage flow;and the physical mechanism responsible for stall margin improvement attributed to circumferential groove casing treatment was explored.