Effect of circumferential non-uniform tip clearance on the flow in a transonic compressor

In order to clarify the influence of circumferential non-uniform tip clearance (CNTC) on the flow, this paper studies the tip clearance structures with different minimum clearance sizes and distribution forms while ensuring the consistency of the average tip clearance size. The results indicate that CNTC can directly affect the tip flow structure, and the effective structure can significantly expand the stall margin (SM). The flow structure analysis shows that CNTC mainly influences the tip leakage flow rate (TLF) and tip leakage angle (TLA). The smaller the minimum clearance size is, the smaller the TLF. The distribution of CNTC primarily affects the TLA, and a larger tip clearance size on the suction surface will result in a better flow trend. When the minimum tip clearance size is 0.5 τ and the suction surface tip clearance size is 1.5 τ, the CNTC structure achieves a SM improvement of 5.72% and a peak efficiency improvement of 0.22%. The partial CNTC results show that the modifications of each region are independent, and the direct superimposition can approximately obtain the distribution trend of the overall modification. It is more effective for the front modification, while the effect of the rear modification is weak. It is worth noting that an enlargement of the clearance on the suction surface will cause the internal flow within the clearance to be directly influenced by the shock wave, which will directly affect the modification effect.