卧轴双转轮混流式水轮机的优化设计

采用CFD计算分析了国外某电站的卧轴双转轮混流式水轮机组效率较低、空化性能较差的原因：主要是流道复杂,水流不畅,导致水力损失较大.由于不允许对流道进行调整,因而只能对转轮部分进行优化研究.转轮优化从3个方面进行：采用不同的叶片翼型、调整转轮上冠线的曲度和左右转轮叶片位置.基于N-S方程和Spalart-Allmaras湍流模型,采用SIMPLIC算法,对优化后水轮机的全流道进行了三维定常湍流计算,获得了各过流部件的流动细节,预估了水轮机的性能.计算结果表明：采用Ⅲ型叶片转轮、B形上冠线,并且当左右2个转轮叶片位置不同这一方案时,水轮机过流量增大到28.55 m3/s,左转轮效率达92.24%,右转轮效率达91.78%.同时分析了计算转轮上的绝对压力值,得到了分别采用Ⅰ,Ⅱ,Ⅲ型叶片转轮的空化情况,结果表明：Ⅲ型叶片转轮的空化性能最好.

Optimization design of horizontal Francis turbine with two runners

The fluid dynamics through a horizontal Francis turbine with two runners in a power station aboard was analyzed by using a CFD code, suggesting the turbine was subject to a low efficiency and poor cavitation performance because of significant hydraulic loss caused from complex flow passage geometry and unsmooth flow. Since the update of stationary flow passages was unallowable, just the turbine runners can be optimized. It appears that there are three ways to optimize the runners, i.e. change the blade shape, adjust the runner crown profile and alter the relative location of two runners. Based on the N - S equations, Spalart - Alhnaras turbulence model and SIMPLIC algorithm, the three dimensional, steady turbulence flow in the optimized turbine was simulated, the details of flow were obtained and the hydraulic performance was predicted. The results showed that the flow rate was increased to 28.55 m3/s, the left and right runner efficiency were reached to 92.24% and 91.78% ; when the runner of type m and crown profile of type B and the two runners blades having a stagger pattern were adopted. Meanwhile, the cavitation performance of the runners of type I , II and III was analyzed, showing the runner of type m has the best cavitation behavior.