Study of the clearance leakage flow characteristics of a transonic axial-flow compressor

Clearance leakage flow exercises a major influence on the formation of rotating stall of an axial flow compressor. The authors have conducted a single-passage and multi-passage non-steady numerical simulation by utilizing the transonic axial-flow compressor of NASA rotor 37. The single-passage non-steady calculation results reveal that at an operating condition approximating to compressor stalling speed, there exists a clearance leakage-flow self non-steady behavior at the blade tip. In addition, the non-steady simulation results under two different back-pressure conditions have been compared. When the back pressure at the outlet is comparatively high, the unsteady behavior of the clearance leakage flow is extremely unstable. When the back pressure at the outlet is relatively low, the above-mentioned unsteady behavior is stable. The multi-passage non-steady numerical simulation results indicate that at an operating condition approximating to the stalling speed, when the outlet back pressure is comparatively high, the clearance leakage flow will oscillate unsteadily, triggering the inception of a spike type rotating stall and resulting in a concrete embodiment of overflow from the blade tip leakage at the leading edge. However, when the outlet back pressure is relatively low, the unsteady behavior of the clearance leakage flow has all along been relatively stable.