CONTROL OF SEPARATIONS IN A HIGHLY-LOADED AXIAL COMPRESSOR CASCADE BY TAILORED BOUNDARY LAYER SUCTION

In order to study the effectiveness and mechanisms of boundary layer suction (BLS) in controlling both the boundary layer separation on the whole span of suction surface (SS) and the three-dimensional (3D) separation in the corner, a 3D linear compressor cascade was investigated by tailored BLS. First, experimental investigations at a range of incidences from-10 degrees to 10 were undertaken on both the original cascade and the aspirated cascade (SS1) in a high-subsonic cascade wind tunnel. The results show that the profile loss coefficient of the aspirated cascade is reduced remarkably as the suction flow ratio increases at the incidences from -5 degrees to 8 degrees. Based on the experimental investigations, numerical simulations were employed to study the flow fields of the original and aspirated cascade in detail. It was found that part blade span suction on the aspirated cascade can effectively remove the separation at the suction span where suction slot exists, resulting that the flow fields of other spans deteriorated. Due to the interaction of separations both on the SS and the end-wall, the 3D separation in the corner are more complicated, so another three tailored BLS schemes were designed totally in order to fully remove both the boundary layer separation on SS and the 3D separation. It was found that the span-wise distribution of static pressure was changed after suction and it could influence the transport of the low-energy fluid between the end-wall and the mid-span. The separation over the whole span of SS and the 3D separation in the corner were fully eliminated by combined suction scheme (CS). Finally, the incidence characteristics of the 3D linear cascade under the control of CS scheme were investigated numerically together with the suction flow rate matching problem of the different suction slots.