The study on the unsteady characteristics of tip leakage flow in circumferential skewed axial fan under off-design conditions

In this paper, the unsteady characteristics of tip leakage flow in axial fans with circumferential skewed blades were investigated at offdesign conditions using wall pressure test. The static pressure fluctuations near blade tip were captured at offdesign conditions by using pressure sensors mounted on casing wall. From the measured results, instantaneous characteristics of tip leakage flow in circumferential skewed fans were analyzed. Based on the measurement results, as the flow rate decreases, the broadband frequency components of tip leakage flow tend to increase in the low frequency domain. The forwardskewed blade is found to be effective in controlling tip leakage flow to expand from blade leading edge to tail edge. the TLF component of the BSK rotor propagates more fast than that of FSK rotor. The instability of tip leakage flow under offdesign conditions is controlled by circumferential skewed blades.