上向流水轮机中自由液面流动的数值模拟

为了更加准确地研究上向流水轮机内部流动情况,评价其水力性能,指导水力设计,建立了上向流水轮机（包括蜗壳和转轮）的全流道几何模型．利用非结构化网格划分技术进行流道的网格划分,在转轮叶片、蜗壳导叶等壁面进行网格加密,网格尺度的选择保证满足湍流计算对壁面y+的要求．基于RNG k-ε湍流模型进行水轮机内部流场的求解,利用流体体积法进行自由液面捕捉,得到上向流水轮机在考虑自由液面时的内部流动模拟结果．基于数值计算结果进行了水轮机内部流动的损失分析,研究发现：在水轮机固定导叶和转轮进口之间的流道存在较大的损失,占总损失的73％;内部流动细节显示该区域的台阶结构是损失的直接诱因,同时造成了转轮进口流态恶化；可通过改进上向流水轮机过渡段的设计消除台阶，以改善上向流水轮机能量性能.

Numerical simulation of free surface flow in updraft free exit flow hydropower turbine

To study the turbine′s internal flow more accurately and improve its hydraulic performance, a geometrical model of the whole flow passage, including casing and runner, was established. An unstructured grid was applied to segment the runner, encrypt the grids on the inner surfaces of the runner blades and the casing guide vane. The sizes of grid clusters were made to meet the y+ for turbulence simulation. Based on RNG k-ε turbulence model, the internal flow was simulated. Taking the effect of free surface flow into consideration, by applying volume of fluid method, a simulated internal flow in an updraft free exit flow turbine was obtained. On the basis of the computation of simulation results, the internal flow loss was analysed. It was found that the largest loss was between the stay vanes and the runner inlet, which amounted to 73% of the total loss. The flow details show that the step structure of the area was the direct cause of the loss and exacerbated the runner′s inflow condition. Accordingly, where and how to improve the turbine′s energy performance was inferred.