混流式水轮机叶片疲劳裂纹分析及其改进方案

Fatigue cracks analysis and improvement scheme of the Francis turbine runner blades

近年来,国内外一系列大型混流式水轮发电机组频繁发生转轮叶片的疲劳裂纹问题,对电站机组的安全稳定运行构成了严重威胁。本文以混流式水轮机为研究对象,通过全流道CFD计算及基于顺序流固耦合的转轮结构应力场计算,分析该转轮产生疲劳裂纹的原因。随后提出在叶片出水边和上冠连接处加装应力释放三角块的方案,以降低叶片最大有效应力值、改善叶片应力分布。计算结果表明该方案可以明显降低叶片最大有效应力、改善叶片应力分布。计算结果也可为其它水轮机转轮的疲劳裂纹及其应力特性分析提供参考。

Fatigue and cracks often occur to large hydraulic turbines, which seriously affect the safety and stability of the operation of hydraulic power station. Computational fluid dynamics （CFD） simulations of the Francis turbine including the spiral case, stay vane, guide vane, runner vane and draft tube were used to analyze the stress characteristics based on the sequential fluid-structure interaction （FSI） method. The fatigue and cracks in the Francis turbine runner blades were analyzed. A triangular block for stress releasing was added at the junction of the trailing edge and crown of the runner blade to reduce the stress concentration and improve stress distribution. The analysis results show that the triangular block is effective in reducing the stress concentration and improve stress distribution of the Francis turbine runner blades