Control of flow separations in compressor cascade by boundary layer suction holes in suction surface

Boundary layer suction is used in turbomachinery to control flow separation to enhance the loading capacity of a compressor. This paper focuses on both numerical calculation and experimental investigation with boundary layer suction holes made in the suction surface of a compressor cascade with a large camber angle. Experimental and numerical investigations are carried out with suction holes in different positions. In the experimental investigation, exit aerodynamic parameters are measured using a five-hole aerodynamic probe, and ink-trace flow visualization is adopted on cascade surface. Experimental and numerical results indicate that both side and middle suctions on the suction surface can efficiently remove low-energy fluid to increase the cascade load capacity while they effectively restrain the corner flow separation. The cascade aerodynamic performance is obviously improved by middle and side suctions, and it is also significantly altered by the position of suction changes. The middle suction holes have their best positions at about 60-66% chord length from the leading edge, and the side suction holes have their best positions a little downstream the corner separation line.