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许多大型水轮机投产后短期内都出现了不同程度的裂纹问题,研究表明动应力值较大是引起转轮叶片产生疲劳裂纹的主要原因之一。该文对万家寨二号机组转轮进行了流固耦合计算,发现较大应力区与实际裂纹出现的部位基本一致。接着进行了动载荷作用下转轮的瞬态动力分析,采用Newmark算法得出了导叶开度变化时转轮的应力分布,当动载荷变化频率较大时,算出动应力大致在15～20MPa左右,与经验值比较接近。这些结果印证了动应力值过大是叶片产生裂纹的主要原因,从而为水轮机在设计阶段就进行优化提供了可能。
Many large-scale hydraulic turbines come into short-term problems with different degrees of cracking. Studies have shown that the larger dynamic stress is one of the main causes of fatigue cracks in the runner blades. This article has carried on the fluid-structure coupling calculation to the runner of Wanjiazhai No.2 unit and found that the locations of the larger stress zone and the actual crack appear basically the same. Then the transient dynamic analysis of the runner under dynamic load was carried out. The Newmark algorithm was used to get the stress distribution of the runner with the change of the guide vane opening. When the dynamic load changed frequently, the dynamic stress was calculated to be about 15 ~ 20MPa Around, and the experience value is relatively close. These results confirm that the main reason for the cracked blade is that the dynamic stress is too large, which makes it possible to optimize the turbine during the design stage.