泵腔径向间隙对多级离心泵泵腔内部流场的影响

为研究泵腔径向间隙对泵腔内部流场的影响,更好地优化多级泵水力性能,选取某悬臂式多级离心泵为研究对象,应用计算流体力学(CFD)与试验相结合的方法对泵腔内部流场进行研究.k-ε湍流模型下的数值计算结果与多级泵外特性试验值吻合较好,说明应用数值计算对泵腔内部流场进行分析是可靠的.设计3种泵腔间隙方案,对比分析了泵腔内部切向速度分布及压力脉动情况.结果表明:随着测速点位置半径的减小,前泵腔切向速度逐渐增大,且液体旋转速度会超出叶轮旋转速度,而后泵腔中切向速度总体呈现逐渐减小的趋势;泵腔间隙区域及叶轮出口处压力脉动主要集中在0~1 680 Hz范围内,压力脉动主频均出现在1倍导叶叶频处,主频脉动幅值由首级向末级逐级递减;泵腔间隙区域压力脉动也受到叶轮叶片数的影响,次主频出现在1倍叶轮叶频处,且在其他叶频倍频处均发生压力脉动现象.

Influences of radial clearance between impeller and diffuser on flow field in side chambers of multistage centrifugal pump

To understand the influence of radial clearance between impeller and diffuser on flow field in two side chambers and optimize hydraulic performance even better, a cantilevered multistage centri-fugal pump was selected as a study model. The flow field in the pump side chambers were analyzed based on combination of computational fluid dynamics(CFD)method and experimental measurement. The numerically predicted performance with the standard k-ε turbulence model showed good agreement with the experimental data, demonstrating CFD method can replace experimental approach in analysis of the flow field in the pump. Three radial clearances designed and the fluid tangential velocity distribution as well as pressure fluctuation in the two side chambers were compared. The results showed that the dimensionless tangential velocity in the front side chamber increases with reducing radius observed, and the fluid rotational angular velocity can exceed the impeller rotational angular speed, but the dimensionless tangential velocity decreases with reducing radius in the rear side chamber essentially. The pressure fluctuations in the radial gap and impeller exit are mainly with a frequency in the range of 0-1 680 Hz, but also the dominant pressure fluctuations occur at diffuser blade passing frequency. The amplitude of pressure fluctuations with the dominant frequency decreases progressively from the first stage to the last stage. The pressure fluctuation in the radial gap is also affected by the number of impeller blades. The secondary dominant pressure fluctuations appear at impeller blade passing frequency, and the pressure fluctuations also exist at the other multiplications of impeller blade passing frequency.