特低扬程大流量贯流泵站水泵选型

Pump selection of ultra-low head and large flow tubular pumping station

针对特低扬程大流量水泵的选型问题,以某设计净扬程仅0.32 m的贯流泵站为例,进行水泵性能预测.利用现有水力模型的泵段特性曲线及装置特性曲线进行相似换算,并对计算结果进行比较.通过进一步的数学推演,提出了采用水泵泵段特性参数推算泵装置效率指标的方法,并结合数值模拟及装置模型试验进行验证.结果表明,对于运行净扬程1 m以下竖井贯流泵装置,可利用现有南水北调的低扬程水力模型降低nD值进行选型计算.由于水泵流道水头损失占比较高,其最优工况效率与具有3 m左右扬程水泵相比低了约6%,故采用扬程差距较大的模型装置特性参数换算的偏差较大,采用模型泵泵段特性参数换算更准确.采用泵段效率和泵装置效率换算公式,对泵段曲线工况点及对应流道损失进行换算,可较为准确地预测装置效率曲线高效区扬程范围,可为特低扬程泵站设计提供参考.

To study the selection of ultra-low head and large flow pump,a tubular pumping station with a design net head of only 0.32 m was taken as an example to predict the pump performance.By using the existing pump model,the similar conversion of pump section characteristic curve and device cha-racteristic curve were compared for this pumping station.After further mathematical deduction,a me-thod of using the characteristic parameters of model pump section to calculate the efficiency of the pump device was proposed,and the results were verified by numerical simulation and model test.The results show that the existing low head pump model in the South-to-North Water Diversion Project can be used to convert for the shaft tubular pump device with operating head below 1 m by reducing diameter and rotational speed.Due to the high proportion of pump channel head loss,the optimal working efficiency of the pump is about 6%lower than that of the pump with about 3 m operating head.The cha-racteristic parameters deviation converted from model device with larger head difference is larger,and the characteristic parameters converted from model pump section is more accurate.The conversion formulas of pump section efficiency and pump device efficiency were used to convert the operating point of pump section curve and the corresponding flow channel loss,which can accurately predict the head range of high efficiency zone in device efficiency curve.The calculation method can be a reference for the design of ultra-low head pumping station in the future.