Effect of combined boundary layer suction on the separation control in a highly loaded transonic compressor cascade

Abstract

A numerical investigation is conducted to explore the potential of combined slot suction in controlling the shock wave and flow separation in a transonic compressor cascade. The three slots in the combined scheme are arranged in different directions on the suction surface and endwall. The locations are determined by the shock wave and separation point in the baseline cascade. Based on these locations, two combined schemes and three single schemes are provided to explore the control mechanism. For each suction scheme, five bleed mass ratios are examined at the same inlet Mach number. The results suggested that the cascade throughflow loss could be decreased by three single schemes. However, the cascade performance is improved slightly or even deteriorated when the losses generated by the suction are considered. The key reasons are the local effects of single scheme and the opposite trend between corner stall and the suction surface separation. Both corner stall and the suction surface separation are eliminated by the combined scheme with two slots, and the maximum reduction in throughflow losses is 75%. The new corner separation evolved from the horseshoe vortex limited the performance of combined scheme. When the bleed mass ratio excided 5%, the combined scheme with three slots is better than the two slots scheme in loss control. The reason is the improved endwall boundary layer and the eliminated new corner separation. By inducing the horseshoe vortex into the slot, the interaction of the two endwall slots eliminates the new corner separation.