Numerical investigation of interaction between casing treatment and tip leakage flow in a transonic compressor rotor

Tip leakage flow has a strong effect on the transonic compressor performance and stability. Based on improved understanding of compressor rotor tip clearance flow, a new type of casing treatment was designed for a transonic axial-flow compressor rotor and numerical simulation of three-dimensional unsteady flow in the compressor rotor was carried out to verify the designed casing treatment. The numerical results (smooth wall case) agreed well with our experimental test data for estimation of the global performance, and this new type of casing treatment was found to increase the compressor stall margin by up to 52% without loss in efficiency at design point. The interaction mechanism between the casing treatment and tip leakage flow was analyzed in detail. It is found that the casing treatment could delay the tip leakage vortex breakdown and bleed the blockage zone caused by the tip leakage vortex breakdown into treatment slots, and therefore extend the stall margin of transonic compressor effectively.