Pulsed suction towards unsteady active flow control in an axial compressor cascade including clearance leakage effects

Abstract

Tip leakage flow (TLF) induced by the gap between the stationary and rotating components brings complex flow structures, and this leads to a considerable loss in the compressor. Boundary layer suction is considered an efficient method to compensate the disadvantages brought by the TLF. In this study, the effect of hole-type pulsed suction (PS) on the TLF in a compressor cascade is investigated through a series of wind-tunnel experiment. PS is a more advanced technology over the constant suction (CS), and it considers improving of the compressor flow field from both spatial and frequency domain. The results indicate that the optimal aerodynamic performance is obtained when using PS at 25 % cx with a mass flow rate of 0.66 % and an excitation frequency of 100 Hz. First, flow control mechanisms are analyzed in terms of flow structures based on oil visualization and dynamic pressure results. The PS technique can induce significant periodic features and increase local intermittently momentum exchange. A connection between the local intensity of the excitation frequency and loss reduction at the cascade outlet is observed. Subsequently, the influence of the PS hole axial position is investigated, and the PS is found to contribute further control to the vortex structures than the CS. Finally, the effectiveness of the PS technique at different tip clearance sizes and inlet incidences is assessed to confirm its superiority over the CS technique in controlling TLF.