基于CFD的高速离心泵进口段流动数值模拟分析

Numerical Simulation and Analysis of the Flow at the Inlet of a High Speed Centrifugal Pump Based on the Software CFD

基于CFD的理论基础应用RNG k-ε湍流模型,对某一高速离心泵进行内流场数值模拟,研究回流现象。通过不同工况下的分析计算,发现诱导轮前进口段的回流漩涡范围随着流量的增加呈现逐渐减小的趋势;利用一个无量纲数来分析回流涡旋的变化范围,高速离心泵在小流量0.6Q_d工况下,进口段的回流漩涡为2.26;在大流量1.4Q_d的工况下回流漩涡的大小为0.45,结果表明:随着流量增加涡流变小,图像和数值能更全面地展示漩涡的结构和大小;模拟分析回流漩涡对诱导轮的压力和速度的影响,由于回流漩涡的水力损失,减少了诱导轮进口前缘处的压力,使诱导轮前缘处产生了一小部分低压区,增大了诱导轮发生空蚀的几率。通过对高速泵进口段不良流动的分析,为高速离心泵的设计与优化提供理论参考。

Based on the CFD fundamentals and by using the RNG k- ε turbulent flow model,a numerical simulation of the flow field inside a high speed centrifugal pump was performed with its returning flow phenomenon being disclosed.Through an analysis and calculation under various operating conditions,it has been found that the range of the returning flow vortexes at the inlet of the inducer wheel assumes a law of gradual descending tendency with an increase of the flow rate. A non-dimensional number was used to analyze any change in the range of the returning flow vortexes. Under the operating condition of the high speed centrifugal pump having a small flow rate 0. 6Q_d,the magnitude of the returning flow vortexes at the inlet was 2. 26. Under the operating condition of the high speed centrifugal pump having a large flow rate 1. 4Q_d,the magnitude of the returning flow vortexes at the inlet was 0. 45. It has been found that with an increase of the flow rate,the magnitude of the returning flow vortexes will decrease and the image and numerical values can show the structure and magnitude of the vortexes in a comprehensive way. The influence of the returning flow vortexes on the pressure and speed on the inducer wheel was also simulated and analyzed. Due to the hydraulic losses arisen from the returning flow vortexes,the pressure at the leading edge of the inlet of the inducer wheel went down and a small part of the low pressure zone emerged at the leading edge of the inlet of the inducer wheel,thus enhancing the possibility of cavitation on the inducer wheel. On the basis of an analysis of the unfavorable flow at the inlet of a high speed pump,the foregoing can offer theoretical reference for design and optimization of high speed centrifugal pumps.