基于动态边界的双吸离心泵叶片渐进磨损及泵性能预测

Progressive Erosion and Pump Performance Prediction of Double Suction Centrifugal Pump Vane Based on Dynamic Boundary

过流边界形态随磨损时间的变化对客观真实地反映双吸离心泵磨损特性及磨损形貌至关重要。采用欧拉-拉格朗日方法,配合磨损壁面几何重构的动态边界法,对黄河平均含沙量及粒径下甘肃省景泰川泵站双吸离心泵进行固液两相流计算,结合实验数据,预测了该泵叶片渐进磨损特性,分析了叶片磨损机理及壁面几何形貌变化对泵性能影响。结果表明:以冲击角函数最大值对应冲击角α_0为阈值,小于α_0磨损形貌呈类圆形凹坑,大于α_0磨损形貌呈沟槽状,冲击角在50°~75°范围且冲击速度高的叶片区域磨损率大,叶片磨损程度严重;根据该泵水力性能损失率变化特性,将预测期划分为3个阶段,磨损率在初期增长率最大,但在数量级上远小于中、后期,使前1000 h磨损阶段扬程损失率、效率损失率、叶片质量损失率均小于其他阶段;上述3个参数的增长均呈初期慢、中期快、后期减缓的趋势,最大增长率均在磨损中期,参数变化曲线斜率分别为1.51×10^(-3)、1.97×10^(-3)、4.12×10^(-3),在1000~6000 h磨损时长范围内,磨损导致双吸离心泵性能下降最快。

The change of overflow boundary morphology with erosion time is important to objectively and realistically reflect the erosion characteristics of double suction centrifugal pumps and erosion morphology.The Euler-Lagrange method and the dynamic boundary method of geometric reconstruction of the erosion wall were used to calculate the solid-liquid two-phase flow of the double suction centrifugal pump of Jingtaichuan Pumping Station in Gansu Province under the average sand content and the value of grain size of the Yellow River.The progressive erosion characteristics of the pump vanes were predicted,and the effects of the vane erosion mechanism and the change of wall geometry on the pump performance were analyzed combining the experimental data.The results showed that taking the maximum value of the impact angle function corresponded to the impact angleα0 as a threshold to distinguish erosion patterns.If impact angle was less than the threshold,the erosion pattern was liking a rounded crater,if it was bigger than the threshold,the erosion pattern was liking a groove.The erosion rate was high in areas where the impact angle was in the range 50°~75°and the impact velocity was high,which both led to high level of blade erosion.The prediction period was divided into three phases based on the characteristics of the rate of change of the hydraulic performance loss.The erosion rate had the largest growth rate in the early stages,but the values were orders of magnitude smaller than those in the middle and late stages,so that the head loss rate,efficiency loss rate and mass loss rate of blade in the first 1000 hours of erosion was less than in other stages.All these parameters showed a trend of slow growth in the early stage,fast growth in the middle stage and slow growth in later stage,and maximum growth rate in the middle stage,values of 1.51×10^(-3),1.97×10^(-3),and 4.12×10^(-3) respectively.Erosion caused the fastest performance degradation of double suction centrifugal pump in the 1000 hours to 6000 hours erosion length range.