Interaction mechanism between incoming vortex and tip leakage vortex breakdown of a compressor cascade

Abstract

Tip leakage vortex breakdown (TVB) is an important flow character that affects the performance of axial compressors. In this study, the interaction mechanism between incoming vortex (IV) and TVB is investigated to improve the performance of compressor cascade. First, the pitchwise location effect, swirling direction effect, and intensity effect are investigated under steady condition; then, an unsteady investigation is conducted based on the steady results. Under steady condition, TVB can be completely removed by the incoming vortex near the suction surface with different swirling directions, and the normalized circulation at the edge of incoming vortex is 0.7. The loss coefficient caused by TVB is also reduced; however, a new loss is induced by IV. The flow mechanism is that the interaction between the incoming vortex and tip leakage vortex (TLV) can increase the chordwise momentum at the vortex core and the stability of the TLV. For TLV and IV, the two vortices have a tendency to combine downstream of the compressor cascade if they have the same swirling directions. However, when the swirling directions are different, TLV and IV propagate separately, and the intensity and stability of TLV are much higher. The loss of TLV is higher for the anticlockwise IV scheme because the intensity of the TLV is greater due to the interaction between TLV and IV. By utilizing the incoming vortex under unsteady condition, the TVB can also be reduced. The unsteadiness of the compressor cascade with the incoming vortex is significantly reduced by reducing the TVB.