水泵水轮机“S”形区全流道数值模拟

为了解决水泵水轮机“S”形区所导致的水泵水轮机在水轮机工况并网困难问题,研究了水泵水轮机“S”特性工作区域的内部流动情况,选取国内某抽水蓄能电站模型水泵水轮机水力模型作为研究对象,进行几何建模,并借助计算流体动力学软件CFX进行全流道数值模拟.模拟采用了区别于传统RANS模型更为精细的分离涡模型进行计算,得到了水泵水轮机内部的流动状态以及外特性参数,并同模型试验值、理论分析结果进行对比验证.结果表明:分离涡模型的计算结果可以达到很好的精度,转轮流道内的流场与理论分析结果相吻合,外特性与试验值相吻合,仿真计算误差小于3％;随着流量不断减小,转轮进口流动分离现象逐渐增大,最终发展成旋涡对流道造成堵塞,堵塞还将引发转轮与双列叶栅之间的相互作用,导致整个流道流动不稳定性的产生.

Numerical analysis of flow in pump turbine operating in S shape region

In order to study the characteristics of internal flow in a pump turbine operating in the S shape region, the flow in the model pump turbine in a pumped storage power station in China was si mulated by using CFD code CFX. The detached eddy simulation model (DES) that is more precise than the traditional RANS model was applied in the simulation, consequently, the internal flow pattern and performance parameters of the pump turbine were obtained; and compared with the experimental data and the theoretical analysis results, respectively. It was shown that the results of DES model are quite good, causing the error between the estimated and experimental performance is less than 3%; further, the internal flow in the runner are in good agreement with theoretical analysis as well. As the flow rate decreases, the flow separation phenomenon near the runner inlet was strengthened gradually, and eventually a vortex was developed in the flow passages, causing a blockage to flow. Note that the vortex can induce rotor stator interactions among the runner and double circular cascade, which will results in instability of flow in the whole passage.