Investigation of Performance Improvement for Axial Flow Compressor with Slots Casing Treatment with Inlet Distortion

In order to investigate the mechanism of performance improvement for axial flow compressor with slots casing treatment under inlet distortion, the isolated rotor of test rig for subsonic single stage axial flow compressor was chosen to investigate the mechanism of performance improvement for axial flow compressor with axial skewed slots casing treatment at 53.4% design rotating speed under inlet distortion with the help of 10 passages unsteady numerical simulation method, while taking the method of setting barriers along circumferential in the middle of inlet radial extension to produce distortion. Compared to inlet uniform with solid wall, the stall margin improvement and peak efficiency improvement of inlet distortion with solid wall were -5.88% and -1.44%, while the stall margin improvement and peak efficiency improvement of inlet distortion with casing treatment became 24.37% and -1.09%. As for inlet uniform with solid wall, the stall type of compressor was typical sudden stall, which resulted from the blockage caused by tip clearance leakage flow. Inlet distortion triggered flow separation at the suction surface of blade tip, and the flow separation distributed non-axisymmetrical along circumferential, the low velocity zone inside the blade tip passage was largely caused by the tip clearance leakage flow after inlet distortion, but compared to inlet uniform, the flow separation of the suction surface at the blade tip occurred in advance, and it exacerbated the negative effects of the tip clearance leakage flow in turn, i. e. the main cause of the compressor stall did not change in essence after inlet distortion. The injecting and pumping process from the upstream and downstream of casing treatment played a role in encouraging and pumping the flow of low velocity zone in the upstream and middle of blade tip passage, which restraining the leading edge spilled flow of blade tip and recirculation near the pressure surface of blade tip passage resulted by tip clearance leakage flow effectively, and improving the flow ability of blade tip passage.