小流量下周向弯曲叶片叶顶泄漏流特性的实验研究

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

对带有周向前弯和周向后弯叶片的低压轴流风机,采用壁面动态压力测量技术试验研究了小流量工况下叶顶泄漏流的频谱特性。在机匣壁面布置动态压力传感器捕捉由泄漏流诱发的壁面压力信号,基于测量结果详细阐述了小流量工况下周向弯曲叶片叶顶泄漏流诱发的流动不稳定性。结果表明:随流量的降低,泄漏涡引起的频率分量逐步凸显,并向更低频段转移,具有明显的宽频特性;周向弯曲叶片控制了泄漏流动从前缘至尾缘的传播速度,前弯叶轮的泄漏流动传播速度最慢,后弯叶轮次之;周向弯曲叶片对叶顶泄漏流诱发的不稳定流动具有控制作用。

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 fluctua- tions 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 com- ponents 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 compo- nent 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.