混流式转轮叶片数对鱼类撞击死亡率的影响

Effect of Blade Numbers of Francis Runners on Fish Strike Mortality

鱼类在通过水轮机流道时会受到其内部高速旋转的转轮叶片撞击而出现伤亡。为了优化某电站混流式转轮的鱼类通过生存率,综合计算流体动力学分析方法与鱼类-叶片撞击的数学模型,研究了不同优化转轮方案下的鱼类撞击死亡率及机组能量性能,获得了混流式水轮机过流量及转轮叶片数对鱼类死亡率的影响规律。研究结果表明,在额定水头下,鱼类通过转轮的撞击死亡率与转轮的流量以及叶片数呈正相关关系;对于原始转轮,当流量增加到额定流量时,鱼类通过转轮的撞击死亡率达到了16.85%;而叶片数为13和11的两个优化转轮则使额定流量下的鱼类撞击死亡率比原始转轮分别降低了2.93和5.3个百分点。最后,通过分析两个优化转轮的鱼类生态性能与能量性能,选择采用13叶片的优化转轮作为最终方案。

The fish in the dam reservoir will die from the strike of rotating runner blade with high speed when passing the turbine flow passage. In order to improve the survival rate of the fish,a method for evaluating the strike mortality of fish in Francis turbine runner was presented. This method contained three steps. Firstly,the CFD method was adopted to obtain the velocity field inside the Francis turbine runner. Secondly,based on the blade-strike model and the absolute velocity distribution on the inlet of runner,the probability of fish struck the runner blade was calculated. Finally,according to the fitting model of radial basis function（RBF） neural network,the lethality rate of fish owing to blade strike was obtained,and then the strike mortality of fish passed through the runner could be calculated. Based on this method,the strike mortality of fish of the initial and the optimized runner at different operation points were calculated. The influence of the turbine discharge and blade numbers on the mortality rate of fish was researched. From the result,it can be concluded that the mortality rate of fish passed through the runner was positively correlated with the discharge and the number of runner blades under the rated head.For the initial runner,the strike mortality rate of fish reached 16. 85% at rated point. Compared with the initial runner,the strike mortality rate of fish at rated point was reduced by 2. 93 and 5. 3 percentage points,which meant these two optimized runner had better ecological performance of fish than the initial runner. According to the comparison of ecological performance and hydraulic efficiency,the optimized runner with 13 blades was chosen as the final scheme. The research methods and contents can provide valuable reference for the fish friendly optimization of Francis turbine.