水动冷却塔直驱混流式水轮机转轮数值模拟优化

针对比转数仅有54的水动冷却塔直驱混流式水轮机,选取影响水轮机转轮效率的6个重要水力参数β1,β2,b0/D1,Φ/D1,Z,a/D1,每个因素取2个水平,设计L8（2^7）正交表,生成8个设计方案.通过CFD软件分别对8个方案的水轮机进行全流道数值模拟,采用理论分析和CFD技术分析转轮水力损失特性,对比其结果、优化转轮参数,再将优化后方案进行数值模拟和外特性试验,对比得到的结果,表明使用正交化方法结合CFD技术可在较少的试验方案下有效地改进水轮机叶轮水力性能,达到水轮机优化设计的目的.在设计流量点Q为5 000 t/h处,优化后的模型转轮输出功率为156.57 kW,水轮机效率达到86.51%;数值模拟效率比试验效率低0.11%,实测结果的基本趋势与数值模拟结果相一致.

Numerical simulation and hydrodynamics optimization of direct-drive Francis turbine runner in cooling towers

For a Francis turbine with a specific speed of just ns = 54 used in cooling towers, six design parameters of runner such as β1,β2,b0/D1,Φ/D1, Z and a/D1 which may have effects on the turbine performance are selected, then eight design cases are generated by using orthogonal experimental design array L8（27） in which there are two levels for each factor. The steady 3D turbulent incompressible fluid flow is simulated for each design by means of a CFD package, consequently the hydraulic loss characteristics of the runners are analyzed, and the design parameters are optimized. The performance of the op- timized runner is predicted and measured. The predicted output power and efficiency of the turbine with the optimized runner are 156.57 kW and 86.51% respectively at the design point （ Q =5 000 t/h）, showing just 0.11% lower than the measurement of efficiency. This suggests that orthogonal design array combined with CFD technique can help reduce the number of design cases and improve the hydraulic performance of turbine runner effectively so as to realize its hydrodynamics optimization.