固液两相流下离心泵内特性和颗粒分布的数值模拟研究

Distributions of Solid/Liquid Two-Phase Flow Fields in Centrifugal Pump:A Simulation Study

基于计算流体动力学(CFD)和数值模拟的方法,研究固液两相流下的离心泵内特性变化规律、颗粒分布和速度,从而进一步探索离心泵的磨损规律。计算结果表明,颗粒的浓度和密度对离心泵内特性存在一定的影响,总压和湍动能系数k(液相)随着θ角度增大呈现出周期性波动的现象,并且总压和湍动能系数k(液相)在不同的工作条件下的波动的规律比较相似。在不同的颗粒浓度下,蜗壳中固相颗粒浓度沿着蜗壳半径方向向外逐渐增大,其中隔舌出口附近的蜗壳内边缘处的浓度最高,且在隔舌出口附近颗粒分布较为不均匀。此外,颗粒密度对颗粒在离心泵内分布的影响较为明显。相比于大密度颗粒工况,当颗粒密度较小时,离心泵流道内颗粒分布较为均匀。颗粒速度大小和浓度的分布在叶片的工作面和背面有着明显的不同,在叶片工作面上,颗粒在叶轮进口附近易集中,在叶片背面上,颗粒在叶轮进口附近和叶片末端易集中,从而推断在叶片工作面入口上边缘处和在叶片背面的末端磨损更有可能被磨损。

The fields of solid/liquid two-phase flow,in centrifugal pump,were empirically approximated,mathematically formulated with standard κ-ε and Euler multiphase flow models,theoretically analyzed and numerically simulated with CFD software.The influence of the volume fraction and density of particles,κ and pressure on the erosion of impeller blades was investigated.The simulated results show that the volume fraction and density have a major impact.For instance,as the density increases,the uniform radial density distribution significantly changes into a gradient one,peaking at the inner edge of volute near the tongue-exit and resulting in serious erosion there.The increasing radial distributions of particles’ velocity/density on the front-face are slightly higher than those on the back-face of blade.Serious erosions occur most likely at the inner-edges of front-face and outer-edges of back-face of blades,where the higher particle velocity and density produce stronger collision impact.