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由于水力机组内部流动的复杂性,在不同工况下的裂纹控制问题,国内外尚无完善的预测方法和评估标准。目前国内大型水电站,超过6 m直径混流式转轮不可避免出现裂纹,转轮裂纹萌生的位置主要集中在叶片与上冠和下环的焊缝处及其热影响区,这些裂纹的萌生,严重影响机组运行的安全性和可靠性。通过对转轮裂纹产生的原因进行分析,认为焊接残余拉应力起到了加速裂纹形成和扩张的作用,还大大降低了转轮的抗疲劳强度。
Due to the complexity of the internal flow of hydraulic units and the crack control problems under different conditions, there is no perfect prediction method and evaluation standard at home and abroad. At present, large-scale hydropower station in China, cracks of more than 6 m diameter Francis runner inevitably occur. Runner crack initiation occurs mainly in the welds between the blade and the upper and lower rings and in the heat-affected zone. The occurrence of these cracks is serious Affect the safety and reliability of the unit operation. By analyzing the causes of the runner cracks, it is considered that the welding residual tensile stress plays an important role in accelerating crack formation and expansion, and greatly reducing the anti-fatigue strength of the runner.