潜水贯流泵装置过流部件水力性能分析与优化

为研究潜水贯流泵装置过流部件的水力性能,该文采用CFD方法对潜水贯流泵装置进行数值计算,分析了不同过流部件形式对泵装置内水力性能的影响,并对计算结果进行试验验证。结果表明:潜水贯流泵装置灯泡体支撑片的数量会影响导叶与支撑片之间的水流流态,支撑片的数量应与导叶片数一致。潜水贯流泵装置宜采用椭球体的灯泡体尾部形式,能避免回流、脱流等不良流态的产生。采用流线形进线孔,并且将进线孔与支撑片结合在一起,能改善出水灯泡体的流态,提高装置效率。在闸门槽间的进水流道过渡形式宜采用渐缩方管式。优化后泵装置在最优工况点的效率提高2.5%,达到78.0%。在最高效率点,数值计算预测扬程和流量的不确定度均小于1%,试验与数值计算结果吻合较好。该研究可为潜水贯流泵装置在实际工程中推广应用提供参考。

Hydraulic performance analysis and optimization on flow passage components of diving tubular pumping system

Abstract: Diving tubular pump is a kind of low-head large-flow horizontal pump. This type is postpositive bulb pump and the motor is coaxial with pump, which is suitable for irrigation or storm drainage pumping station. For the advantages of excellent hydraulic performance, compact structure, good noise resistance and low operating cost, diving tubular pump is widely applied in low head pumping station. The internal structure of diving tubular pumping system is more complex than other pumping systems for the combination of motor and rotor. Bulb, support slices, cable hole, inlet passage and outlet passage constitute the flow passage components of diving tubular pumping system, which have influence on the internal flow pattern and hydraulic loss of diving tubular pumping system. For low head condition, small increase of hydraulic loss will result in large efficiency loss of pumping system. So the analysis on hydraulic performance of flow passage components of diving tubular pumping system needs to be carried out. In this paper, to acquire hydraulic performance of flow passage components, the inner flow field of diving tubular pumping system is calculated by CFD (computational fluid dynamics). The influence on hydraulic performance of pumping system with different flow passage components is analyzed and the experiment is performed to verify the result of numerical calculation. The head and efficiency difference between model test and CFD simulation are less than 1% in the best efficiency point condition, and the high efficiency range predicted by CFD coincides with the results of the experiment. In order to acquire the influence on hydraulic performance for different numbers of support slices, 3 kinds of slices'' numbers are simulated to show that the number of support slices affects the flow pattern between guide vane and support slice. The hydraulic loss of bulb part increases with the number of support slices. The hydraulic loss of pumping system is relatively lower while the support slices'' number is equal to guide vane''s, which is 5 in this pumping system. Also the shape of bulb tail of pumping system has influence on the flow pattern in outlet passage. Three kinds of bulb tail shapes are calculated, including cone, semi-ellipsoid and semi-sphere. Cone is bad shape for bulb tail, due to the bad flow pattern caused by blunt tail. Semi-sphere is better than cone for less hydraulic loss and better flow expansion in outlet passage. Compared to cone and semi-sphere, semi-ellipsoid is the best shape for bulb tail, which can prevent bad flow pattern like backflow and flow separation. Cable hole is a small pipe which locates at bulb, and its influence on flow pattern and hydraulic loss is ignored by manufactures for its small volume. This paper compares 2 different section shapes of cable hole, specific circle and streamline shape. The result shows that cable hole causes 16% hydraulic loss of bulb, and streamline shape acquires better pressure distribution on cable hole and slightly enhances the flow pattern behind cable hole. Besides, the combination of cable hole and support slice can improve the flow pattern in bulb part and improve efficiency of pumping system. The transition shape of inlet passage between 2 gate slots is also a key factor on hydraulic performance of diving tubular pumping system. Two transition shapes are calculated, including converging square pipe and converging square-circle pipe. Compared with converging square-circle pipe, converging square pipe decreases hydraulic loss of pumping system by 5% and acquires better flow pattern around gate slots. In addition, the other advantage of converging square pipe is the convenience for construction. In conclusion, the efficiency of optimized diving tubular pumping system increases by 2.5%, which reaches 78%. In best efficiency point, the uncertainty of hydraulic performance between simulation and test result less than 1%.