The effect of aspiration configuration on aerodynamic performance in compound lean compressor cascades of gas turbines

Highlights: • Typical aspiration configurations in compound lean stators are evaluated. • Computational results on secondary flow and loss control are analyzed. • Mechanisms of blade leaning are elaborated to reveal the values of aspiration. • Response surface method is adopted to optimize the composite application. • Each composite application has the advantage of loss or hub-stall control. - Abstract: Advantages and disadvantages of typical aspiration configurations applied in compound lean compressor cascades are discussed in this paper. The blade leaning mechanism is elaborated first, and then a thorough study on the synergistic effect of aspiration and blade leaning on the flow field structure and the aerodynamic performance, especially the boundary layer development in blade passages, which is conducted by CFD. The calculations show that the spanwise pressure gradient in positive lean cascades is adopted to reduce the corner loss. Meanwhile, with increasing incidence, the reversal flow is accumulated near the midspan due to the redistribution of the boundary layer, which contributes to the broadening of the operation range. With the introduction of suction surface aspiration, the loss of the cascade is effectively reduced which results from the suppression of the boundary layer development on the blade suction surface. However, due to the limited controlling capacity towards the corner separation, the boundary layer thickness in the corners is almost unaffected, which leads to the restricted improvement of the operation range. Endwall aspiration is more powerful in removing the corner separation to significantly delay the occurrence of hub-stall. Nonetheless, the increased aspirated flow loss counteracts the loss reduction near the endwalls.