双吸泵正反转内部流场数值模拟及性能预测

为了研究双吸离心泵在正转和反转时不同的流动特性,基于CFX软件采用标准k-ε模型对双吸离心泵内部流场进行了数值模拟和性能预测.计算了双吸泵在正转和反转时各自最佳工况点的水力性能,并对比了双吸泵最佳工况点在正转和反转时流场特性的差异.最后将性能预测的计算值与试验值进行对比分析,表明该计算方法能够较准确地预测泵的性能.在双吸泵反转用作液力透平时,发现泵在反转工况下的高效区向大流量偏移,效率在大小流量区的变化差别很大,流量太小将使得泵的转矩方向发生改变,导致流体不再对叶轮做功,并且泵反转的最大损失发生在蜗壳到叶轮的过渡区,即叶片的出口处.通过内部流场的分析,得到了详细的压力和速度矢量分布规律,对进一步研究泵反转作液力透平进行水力设计提供了一定依据.

Numerical simulation of internal flow field and performance prediction of reversible double suction pump

To study the different behavior of a double suction centrifugal pump when it is running as a pump and a turbine, the standard k-ε two-equation turbulence model and CFX software are used to simulate the internal flow filed in pump and turbine modes and their performances are predicted. The hydraulic performances at best efficiency points are calculated respectively in pump and turbine modes, and a comparison of the flow field is made as well. The predicted performance curves in the pump mode are compared with the experimental values, showing the numerical simulation can predict the performance curves accurately. When the pump running as a turbine, the best efficiency point is moved to a larger flow rate and the efficiency varied greatly across the whole range of flow rate. A too small flow leads the torque acted on the impeller by the fluid to the reversed direction and stops doing work on the impeller. Moreover the largest energy loss occurs in the vaneless region between the impeller and volute, namely the outlet of the impeller. Through an analysis of the internal flow field in pump mode, the detailed distributions of pressure and velocity vector are obtained, and these results can provide a useful base on the hydraulic design of a pump as turbine.