混流式水轮机转轮简化模型焊接过程的数值模拟

在确定混流式水轮机转轮简化模型、解决分段焊焊接热源加载的问题及解决各独立实体间接触边界节点不重合的热传导问题的基础上,对转轮模型焊接过程的温度场与应力场进行了数值模拟。得到了焊接过程中各起弧点的热循环曲线、纵向应力的演变规律与焊后应力场的分布情况。结果表明:焊后应力的峰值出现在叶片与上冠或叶片与下环接触面附近的叶片上。这个结果可以较好地解释水轮机转轮叶片疲劳裂纹的产生和扩展的失效行为。

SIMULATION ON WELDING PROCESS OF FRANCIS TURBINE RUNNER'S SIMPLIFIED MODEL

Runner's temperature field and stress field during the period of welding are simulated on the basis of attaining simplified model of Francis turbine runner, realizing the thermal source loading of multi-pass welding and solving the problem of conduction between independent entities. Thermal cycle curves of different striking places, evolvement process of longitudinal stress and residual stress field after welding are obtained. The simulation result shows that maximal welding stress appears along the adjacent area between blades and bands or blades and crown. The result can explain why fatigued crack on the turbine runner's blade appears and extends.