X型叶片水轮机转轮流场的数值模拟

Numerical simulation of 3D flow in Francis turbine runner with X-type blades

X型叶片在最近几年被广泛用于高水头大容量混流式水轮机,其数值模拟对计算机的配置提出了更高的要求。模型的建立和网格的粗细直接影响着水轮机数值模拟的结果和对硬件资源的需求。本文从这两方面着手,解决硬件资源一定条件下的大规模流场计算问题。采用全流道和单流道两种几何模型、三种网格精度对X型叶片混流式水轮机转轮进行数值模拟,对能量特性进行了预估,并分析了转轮内部的流动细节。分析结果表明:单流道计算所得能量特性结果优于全流道计算结果,与实验结果一致,这是由网格的粗细引起的;X型叶片表面压力和速度变化均匀,转轮内流动顺畅,表现出良好的水力性能,与实际情况相符;用单流道模型来代替全流道模型对转轮流场进行数值模拟,可以提高计算精度,节省计算时间,降低计算成本。

Numerical simulation of large Francis turbine with X-type blades requires high-configuration computers. The results of numerical simulation and the demand of hardware resources are directly affected by the model and grids. The problem of large-scale flow computation is studied under limited hardware resource from the above two aspects. Two geometric models and three mesh scales are employed to simulate 3D turbulent flow in the Francis turbine runner with X-type blades. The hydraulic performance is predicted, and the flow details in the runner are analyzed. The results show that the performance features obtained by using single runner passage model are not only in good agreement with the experimental results, but also better than those obtained by using full runner model. The results also show that the pressure and velocity distributions on the surfaces of X-type blades are uniform, and the runner with X-type blades has＇good hydraulic performance. Numerical simulation with employing single runner model instead of full runner model can improve computing accuracy, save computing time, and reduce computing cost.