Experimental investigation on the effects of inlet circumferential distortion and optimized casing treatment in a transonic compressor

Abstract Casing treatment has been widely adopted to enhance the operating range of compressors by extending the stall margin. In this article, a high-precision experimental investigation is conducted in a transonic compressor with inlet circumferential distortion. Unsteady pressure is measured in the casing wall using a cluster of time-resolved transducers with axial and circumferential spatial resolution. The experimental data show that the optimized casing treatment improves the stall margin with minimal efficiency penalty for all measured inflow conditions. A comprehensive unsteady static pressure analysis indicates that the instability mode can be altered by inlet distortion. Shock structures and unsteadiness are affected by the inlet distortion, particularly in the exit of distorted region. Results of flow field structure analysis show that casing treatment can significantly modify the shock wave detachment, which is the primary stability enhancement mechanism of casing treatment. Furthermore, the implementation of casing treatment significantly enhances the disturbance tolerance of the compressor while effectively suppressing characteristic frequency bands induced by the unsteady fluctuation of tip leakage flow.