Flow separation control using unsteady pulsed suction through endwall bleeding holes in a highly loaded compressor cascade

Unsteady pulsed suction (UPS) as a novel unsteady flow control (UFC) technique is applied in a certain highly loaded compressor cascade for the control of flow separations. Some related aerodynamic parameters such as excitation frequency and time-averaged suction flow rate are studied in detail. UPS and steady constant suction (SCS) are investigated to analysis comparatively the control effects of flow separations with the same time-averaged suction flow rate. The results show that UPS can provide appreciable improvement of cascade performance in a wide range of excitation frequencies. There are different optimum frequencies under different time-averaged suction flow rates, but the optimum frequencies are both an integer multiple of the natural frequency of vortex shedding. Based on the optimum frequency, the total pressure loss coefficients under the time-averaged suction flow rates ms=0.4% and ms=0.53% are reduced by 9.4% and 14.2%, respectively. The time-averaged suction flow rate plays a more crucial role than the excitation frequency. Simultaneously, UPS can provide a better flow control effect than SCS with the same time-averaged suction flow rate in the control of flow separation. The time-averaged suction flow rate range that can obtain positive effects for UPS is wider than that for SCS. Additionally, the potentials of UPS at off-design points are also validated.