基于CFD的离心泵关死点流动性能分析

Flow Performance Analysis of Shutoff Condition in Centrifugal Pump Based on CFD Simulation

流体动力学数值计算(CFD)被广泛用于研究离心泵内部的流场和外特性预测,在设计工况下计算准确性较高,近年在流体机械领域的研究中占有重要位置。然而针对关死点工况离心泵流场的CFD模拟,现有研究都是采用极小流量作为边界条件,难以得到水泵关死点的真实流动性能。本文采用完全零流量的边界条件,以常用的IS125型管道离心水泵为例,借助于瞬态CFD流场计算技术,进行关死点及其附近工况的非定常流场数值模拟和性能预测,并得到实测结果的验证。研究结果发现,在非设计工况尤其是关死点和小流量工况下,叶轮每个通道内具有不同的流场分布和过流能力,导致水泵性能参数出现较大的脉动现象。在关死点工况下,蜗壳隔舌所承受的流动冲击最为严重,靠近蜗壳上游的叶轮通道是排水状态,而靠近蜗壳下游的叶轮通道则是吸水状态。本文提出的关死点和小流量工况下离心泵流场计算方法能较为有效的预测该工况下泵的扬程和轴功率,得到的叶轮流道过流能力大小的结论,具有一定的学术和工程价值。

CFD simulations on flow field of centrifugal pumps are widely used to investigate the inner flow and predict pump performance due to its convenience and accuracy, which have already been an effective tool in fluids machinery field. However, CFD research of the shutoff is currently performed by means of the minor-flow assumption, which is different from real operating conditions and difficult to well predict pump performances at shutoff conditions. In this paper, the zero-flow boundary condition is applied to numerical simulation of unsteady flow for the IS125 centrifugal pump with the unsteady CFD techniques. The pump performances are predicted and verified by the pump performance test. The numerical result shows that there are different distributions of flow field and flow rates in the impeller channels, leading to serious fluctuations of pump performance. At the shutoff, the volute tongue suffers from the most serious flow impact among various operating conditions. It is also found that the channels of the impeller close to the upstream of volute are water-discharging, but the channels of the impeller near the downstream of volute are water-inhaling. This method enables effective investigation of the flow field and characteristics at shutoff conditions. The obtained impeller channel flow ability may have academic and engineering values.