Numerical and experimental study of separation control by boundary layer aspiration in a highly-loaded axial compressor cascade

Both experiments and computations are performed and analyzed to investigate the effectiveness and mechanisms of different slotted aspiration schemes in controlling the separated flows in a highly-loaded axial compressor cascade. It is found that the boundary layer aspiration on the blade suction surface can improve the incidence characteristics of the airfoil within most of the incidence range except of the extremely high incidence and the profile loss coefficient is reduced remarkably as the aspirated massflow increases. The combined aspiration is the most effective scheme to control both the separated flow on the blade suction surface and the three-dimentional hub corner separation, and an improper design of aspiration would lead to a deterioration of the flow field. Different aspiration schemes have different effectiveness in controlling the flow separation, which leads to various influences on the blade loading and the diffusion abilities. The cascade incidence characteristics of different aspiration schemes show that the part-span aspiration scheme (SS1) located on the blade suction surface can only improve the overall flow field in very high incidences, while the other schemes can reduce the overall loss coefficient within almost the whole incidence range, especially for the combined aspiration scheme. There always exists a closed separation in the cascade when the boundary layer separation is not removed completely on the blade suction surface and in the hub corner. In addition, the type of critical point is affected by the spanwise static pressure gradient, which has significant effects on the cascade performance.