To clearly clarify how it affects the detailed tip clearance flow and flow mechanism by varying the upstream boundary layer thickness and tip clearance size, numerical studies were performed on a subsonic rotor, which is used for low-speed model testing of one rear stage embedded in a modern high-pressure compressor. Firstly, available experimental data were adopted to validate the numerical method. Second, comparisons were made for tip leakage vortex structure, the interface of leakage flow/mainflow, endwall loss, isentropic efficiency and pressure-rise between different operating conditions. Then, effects of different clearance sizes and inlet boundary layer thicknesses were investigated. At last, the self-induced unsteadiness at one near-stall operating condition was studied for different cases. Results show that increasing the tip clearance size has a deleterious effect on rotor efficiency and pressure-rise performance over the whole operating range, while thickening the inflow boundary layer is almost the same except that its pressure-rise performance will be increased at mass flow rate larger than design operating condition. Self-induced unsteadiness occurs at near-stall operating conditions, and its appearance depends largely on tip clearance size, while upstream boundary layer thickness has little effect.

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