混流式水轮机转轮动载荷作用下的应力特性

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。

Stress of Francis turbine runners under fluctuant work conditions

Cracks occur in many large-sized turbines in short term after they are put into production. Research shows that high dynamic stress is one of the most important reasons of the cracks of the vanes. The fluid-structure interaction analysis was carried out on 2# turbine in Wanjiazhai in this paper. The range of bigger stress agreed with the distribution of the real cracks. Then the transient dynamic analysis of the turbine under fluctuant work conditions was performed, and the stress distribution under various openings of the guide vanes was calculated using the Newmark method. When the frequency of the fluctuant work conditions is high enough, the dynamic stress is about 15 to 20 MPa, which is close to the experienced data. These results confirm the statement that the reason of cracks is not the static stress but the high dynamic stress, so it is possible to optimize the turbine at designing stage.