Mechanism of stall margin improvement associated with the blowing circumferential grooved casing treatment

Tangent blowing in the circumferential grooves has the effect of achieving broader stall margin in the previous experiments. Three-dimentional numerical simulation has been performed for a subsonic axial-flow compressor rotor both with the blowing circumferential grooved casing treatment and archetypal casing treatment. The calculated overall performance lines showed good agreement with the experiments. The mechanism was that the blowing circumferential grooved casing treatment can achieve broader safety margin and improve the efficiency compared with archetypal casing treatment. This conclusion was obtained by detailed analyzing the flow-field at the blade tip of two kinds of casing treatment.