轴流泵非稳定工况下叶轮进口流场试验研究

Experiment research on inlet flow field for axial-flow pump at unsteady operating condition

在小流量工况下,由于轴流泵不稳定工况区(马鞍区)的存在,使其稳定运行的范围大大缩小.详细测量了轴流泵能量性能参数,获得了'双马鞍'形的扬程-流量曲线,采用PIV技术对0.73Qd,0.55Qd0,.43Qd及0.33Qd流量工况下的叶轮进口轴面流场进行了二维流速测量.结果表明:小流量工况下,在叶轮进口靠近壁面处存在明显回流,回流区域随流量的减小而增大,同时叶轮进口轴面内湍流强度也随着流量减小而增大;相同工况下,轴向流速的湍流强度低于径向流速的湍流强度,靠近叶轮外壳处的湍流强度大于靠近轮毂处的湍流强度;通过流道壁面上的丝线示踪,显示了随着流量的减小,叶轮进口外壁处的流体由轴向流动向周向流动的演化过程.研究结果表明小流量工况下,轴流泵叶轮进口流场不稳定导致水泵效率偏低,为进一步提高水泵性能提供了参考.

The operating region of axial-flow pumps is greatly reduced due to the existence of unstable operating range at low flow-rate condition.The energy performance of an axial-flow pump was measured in detail,and head-flow curve with bi-saddle was obtained.Particle image velocimetry（PIV） techno-logy was used to measure the two-dimensional flow fields at the inlet axial plane under the flow rate of 0.73Qd,0.55Qd,0.43Qd and 0.33Qd.The experiment results show that backflow exists at the impeller inlet close to the wall,and the backflow zone increases with the decreasing of flow rate.With the decreasing of the flow rate,the turbulence intensity obviously increases,the turbulence intensity of axial velocity is higher than one of radius velocity and the turbulence intensity near the case wall is much higher close to the hub.The flow at the inlet wall evolutes from axial direction to circumferential direction can be seen clearly by the silk lines.The experimental results indicate that the lower performance of axial-flow pump at the low flow rate condition is due to the unstable flow at the inlet impeller.This provides a reference for further improvement of axial-flow pumps performance at low flow rate condition.