轴流泵装置虹吸式出水流道内流机理数值分析

为研究轴流泵对虹吸式出水流道内部流动特性的影响机理,采用CFD(Computational fluid dynamic)方法对虹吸式轴流泵装置进行全流道的数值计算,在考虑了轴流泵与虹吸式出水流道内流相互影响的条件下定性地分析了虹吸式出水流道的流场特征,定量地研究了导叶体出口剩余环量和流量对虹吸式出水流道水力损失的影响,给出了相应的数学关系模型,并将泵装置性能预测结果与模型试验结果进行了对比。结果表明:受导叶体出口剩余环量和流量的双重作用虹吸式出水流道内部流态差异较大,虹吸式出水流道的水力损失主要集中于驼峰断面前的过流通道。各工况时虹吸式出水流道驼峰断面的速度加权平均角的均值为52.34°,不同工况时速度加权平均角变化范围仅在0.1°~2.3°之间。随流量系数的增大,驼峰断面的轴向速度分布均匀度逐渐增大,导叶体出口剩余环量则先减小后增大,在高效工况范围内导叶体出口剩余环量存在最小值。导叶体出口剩余环量通过影响虹吸式出水流道内部流态而对出水流道水力损失产生影响,虹吸式出水流道的水力损失与流量未呈二次方关系。

Numerical Investigation of Internal Flow Mechanisms of Siphon Outlet Passage in Pumping System

In order to analyze the flow influence mechanism of axial-flow pump on the siphon outlet passage, the three-dimensional internal flow of an axial-flow pumping system with siphon outlet passage was simulated based on CFD method under different running conditions. The relationship between guide vane outlet velocity circulation and flow rate had obvious influence on hydraulic loss and internal flow field of siphon outlet passage. The flow field characteristics of siphon outlet passage were analyzed qualitatively, and the mathematical relationship between them was analyzed quantitatively. The research results indicated that there was great difference between internal flow field of siphon outlet passage under different running conditions, and the hydraulic loss of siphon outlet passage was mainly concentrated on flow passage before hump section. The average value of velocity-weighted average swirl angle was 52.34°, and it had small fluctuation in the flow coefficient range of 0.35~0.70 for hump section. With the increase of flow coefficient, the axial velocity distribution uniformity of hump section increased gradually, while the guide vane outlet velocity circulation decreased firstly and then increased, and the minimum velocity circulation was in the high efficiency area. Guide vane outlet velocity circulation made the relationship of hydraulic loss of siphon outlet passage and flow rate more complicated, and there was no quadratic regression relationship between hydraulic loss and flow rate. These study results were available reference for design optimization of siphon outlet passage.