To determine the key factors influencing the efficiency and stability of a subsonic axial flow compressor stage at off-design speed

experimental and numerical investigations were conducted to analyze the evolution of its secondary flow near the end-wall over a full stable operating range. The results show that a hub corner stall and a tip leakage flow dominate the endwall region of the rotor at a large mass flow condition. However

the full-span blade stall due to the over-diffusion inhibite the hub corner stall at peak efficiency and near stall flow conditions. The flow separation in the corner region of the casing of the stator blade is three-dimensional

but don't evolve into a hub corner stall even at the near stall flow condition. The leakage flow of the stator near hub could decrease and energize the cross-flow due to the overturning of the fluid near the casing

thus inhibiting or mitigating the hub corner stall. However

the control effect is influenced by different flow conditions of the compressor. At the near stall condition

a decrease in the stage efficiency mainly comes from the fact that the leakage flow has not enough capability for suppressing the hub corner stall

while the compressor stage stability is limited by the flow blockage arising from the secondary flow near the rotor tip.