水泵水轮机不同导叶开口的驼峰特性

Unstable head-flow characteristics of pump-turbine under different guide vane openings in pump mode

为研究水泵水轮机在不同导叶开口下的驼峰特性,对某一电站水泵水轮机模型水泵工况进行试验,得到不同导叶开口下的驼峰特性曲线,结果表明随着活动导叶开口减小,在低负荷区水泵工况扬程越高,扬程趋势越陡,同时驼峰现象更明显,但是驼峰区域变小.在试验研究的基础上,对该模型进行三维实体建模,并进行网格划分,采用SST k-ω模型、标准k-ω模型、RNG k-ε模型和标准k-ε模型分别对19 mm活动导叶开口下各个工况点进行数值模拟,最终确定SST k-ω湍流模型能够较好地符合试验结果.分别选取13,19,25 mm活动导叶开口进行数值模拟,得到水泵工况的扬程、力矩和效率与流量的关系曲线,与试验结果对比,其变化趋势一致.针对19 mm活动导叶开口低负荷工况点、驼峰区工况点、最优工况点和超负荷工况点进行流动特性对比分析,表明驼峰特性与转轮流道内和固定导叶部分流道内的流动分离及旋涡有关.

In order to obtain the unstable head-flow characteristics of pump-turbines under different guide vane openings,firstly,experiments are carried out on the pump-turbine model for a pump storage power plant in pump mode. It is shown that the head gets higher value and its slope becomes stepper at a low flow rate; the unstable head-flow effect exhibits more obviously with decreasing guide vane ope-ning,but the flow rate range for the effect is shrunk. Further,a 3D geometrical model of the pump-turbine model is generated and a set of mesh for its fluid domain is created. The steady turbulent flows in the pump-turbine model are simulated by using the SST k- ω,standard k- ω,RNG k- ε and standard k- ε turbulence models at various flow rates under 19 mm guide vane opening,showing the SST k- ω turbulence model can result in more accurate performance curves than the others against the experimental measurements. Consequently,the flows in the pump-turbine model are simulated bymeans of that turbulence model at 13 mm,19 mm and 25 mm guide vane openings and the head,torque and efficiency curves are obtained and compared with the experimental observations,and good agreement is demonstrated between them. Finally,the internal flow patterns in the unstable region,at part-load,best efficiency and over-load points are analysed at 19 mm guide vane opening. It is identified that the unstable head-flow effect is related to flow separation and vortex occurrence in the runner and a few stay vane passages.