抽黄工程用离心泵固液两相流数值模拟

Numerical simulations of solid-liquid two-phase flows in centrifugal pumps of a Yellow River pumping project

基于Navier-Stokes方程和Eulerian-Lagrangian多相流模型,对一泵站离心泵固液两相流进行了双向流固耦合数值模拟,引入相关经验公式对离散固相动量方程进行修正,同时采用Alhert模型结合Mclaury磨损实验结果对过流部件的磨损计算方法进行了定义,并分析了各流量工况不同固相体积浓度下的流场特性和离心泵外特性变化规律。数值模拟计算结果表明:固相体积浓度对流场压力分布和流场流线有着显著的影响,伴随着固相体积浓度的增大叶轮叶片正背面平均压力均有着不同幅度的上升,而叶片前后压差却逐渐缩小,同时由于固相泥沙颗粒的存在对流场的紊动起到了抑制作用,一定程度上削弱了叶轮流道二次流动的强度,因此在个别工况下甚至出现了效率上升的情况;在小流量非设计工况下运行时,由于叶轮进口前水体发生预旋导致固相颗粒在离心力作用下与边壁发生撞击和切削,进而诱发了离心泵叶轮的口环磨损;固相体积浓度的递增将增大过流部件表面固相体积分数的分布,从而加剧过流部件的磨损程度。

By solving the Navier-Stokes equations and a Eularian-Lagrangian multiphase model, three- dimensional simulations of solid-liquid two-phases flows in centrifugal pumps were made by using two- way coupling of the two phases and modifying the momentum equations of discrete solid phase with empirical formulas. The Alhert erosion model combined with the Mclaury wear test results was adopted to calculate the erosion of flow components, and the flow features and variation in pump external characteristics were analyzed for working conditions of different flow rates and different volume concentrations of solid phase in the pump inflow. Calculations indicate that the volume concentration has strong influence on pressure distribution and streamlines. With the inflow volume concentration increasing, average pressure on both sides of the impeller blade is increased while pressure difference between blade inlet and outlet is gradually reduced. Existence of solid particles suppresses flow turbulences and consequently weakens the second flows in impeller passages, leading to even an increase in pumping efficiency in certain working conditions. Under small flow condition, a swirl is generated in the flow before its entering the impeller inlet, and solid particles under centrifugal force are impacting and cutting the solid surfaces, which causes wear erosion of impeller ring. An increase in the inflow volume concentration of solid phase will increase its volume fraction distributed over flow components and hence aggravate their wear erosion.