Mechanism of improvement on axial-flow compressor stability with assembled casing treatment

Influences of the stability of subsonic axial-flow compressor were investigated by full-annulus unsteady numerical method with axial skewed slot casing treatment(CT), self recirculation casing treatment and assembled casing treatment respectively. Assembled casing treatment was composed of axial skewed slot and self recirculation casing treatment. The numerical results show that the ability of assembled casing treatment to improve the rotor steady operating range is the best, followed by self recirculation casing treatment. Compressor could gain 12.86%, 16.47% and 22.72% stall margin improvements with three kinds of casing treatment. The fundamental flow mechanism was obtained by detailed analysis of the flow-filed in rotor passage. The analytic results indicate that the bad effect made by flow separation is weakened with assembled casing treatment, and high velocity flow discharged from injecting part can restrain the tip clearance leakage flow spillage from adjacent tip passage at leading edge. The leakage flow is also sucked into axial skewed, preventing the occurrence of leading edge spilling flow.