Flow mechanism and aspiration strategies in an ultra-highly loaded supersonic compressor cascade

In order to improve the performance and eliminate flow separations, boundary layer suction/aspiration, was carried out in an ultra-highly loaded (UHL) supersonic compressor cascade with a super-high diffusion (D) factor of 0.81. Firstly, the numerical simulation method is validated using existing experimental data. Secondly, three different suction schemes of blade suction surface are designed and investigated numerically under two-dimensional (2D) conditions. Thirdly, six different endwall suction schemes are designed and calculated, and an optimal endwall suction scheme is obtained. At last, suction surface coupled with endwall suction is integrated in the UHL supersonic compressor cascade so as to eliminate both trailing edge separation and corner separation. Under 2D conditions, the UHL supersonic compressor cascade experiences a strong normal shock wave with pre-Mach number of 1.6, and significant flow separation exists inside the blade passage under shock wave/boundary layer interaction. Due to the flow separation near the suction surface, the normal shock wave becomes an oblique shock wave at the shock wave foot. By arranging suction slot at 30% to 70% axial chord on suction surface, trailing edge separations can be effectively eliminated. Under three-dimensional (3D) conditions, an optimal endwall suction slot is distributed from the shock foot to the trailing edge near the suction surface. With the optimal endwall suction scheme, corner separation is effectively removed. However, after endwall suction, flow separation near mid-span is increased considerably. With appropriate suction mass flow, the separation along spanwise direction can be eliminated and the flow field inside the cascade becomes a 2D pattern. By adopting the coupled suction surface and endwall suction, both corner separation and trailing edge separation are eliminated effectively, and the diffusion ability of the supersonic compressor cascade is also improved significantly. The suction effect of suction slot on suction surface is similar to that of 2D conditions.