Numerical Investigation of Secondary Flow Control by Boundary Layer Suction on the End-Wall in a Highly-Loaded Axial Compressor Cascade

In order to explore the effectiveness and mechanisms of the boundary layer suction at different stages of the formation of the three-dimensional corner separation within a linear axial cascade, three slotted suction schemes have been investigated numerically at an off-design operating condition. Unlike the slot designed along the suction surface in most previous researches, the slotted schemes are along the pitch-wise direction applied on the end-wall in current paper. The results show that it is the most effective choice to conduct boundary layer suction at the position ahead of the interaction point between the suction side leg of the horseshoe vortex and the suction surface. The loss coefficient is reduced remarkably in the hub corner and the onset location of the passage vortex can be delayed. The decreasing in loss and blockage in the hub corner leads to an increasing of that near mid-span. The flow patterns can be changed after the suction, i.e., the span-wise and stream-wise movement of the critical points (i.e. saddle point, regular node and spiral node or focus according to the topological rules.), which contributes to the variation of loss and blockage generation. The span-wise distribution of the radial gradient of static pressure coefficient is also an indication of the strength of the mixing process.