H/D值对肘形进水流道水力特性影响的数值模拟

Numerical Simulation for Influences of Ratio of H/D upon Hydraulic Characteristics of Elbow Inlet Conduits

水泵叶轮中心线到进水流道底板的距离H与水泵叶轮直径D之比值(H/D),是进水流道的一个重要的设计参数,直接影响到泵站工程土建投资和水泵装置性能。本文采用有限体积法和非结构化网格,数值模拟了大型泵站肘形进水流道内部流场,并以水泵进口水流条件为目标函数,分析了不同H/D值对其水力特性的影响。计算结果表明,H/D值对肘形进水流道出口水流轴向流速分布均匀度影响较小,但随着H/D值的减小,流道的水力损失迅速增加,出口水流偏流角迅速增大,对水泵的进水条件产生不利影响,是制约H/D值进一步减小的重要因素。

The ratio of H/D, i.e. the vertical distance H from the pump propeller central line to the bottom of the elbow inlet conduit to the diameter D of the pump propeller, is an important design parameter, and it will directly affect the construction cost of pump station and the performance of pump units. Taking the flow conditions of pump as the objective functions, the definite volume method and unstructured grid are adopted in this paper to numerically simulate the influences of the ratio of H/D upon the hydraulic characteristics of elbow inlet conduits. The computational results show that although the distribution factor of the axial velocities in the outlet cross-section of the elbow conduit is less affected with the decrease of the ratio H/D, the head loss of the conduits and the swirl angle of the flow leaving the outlet cross-section tend to increase rapidly, which will adversely affect the flow conditions of pump, becoming the vital restriction factor to further reduce the ratio.