直流蒸汽发生器蒸干点波动引起的热应力及疲劳分析

Analysis of Thermal Stress and Fatigue Induced by Dryout Oscillation in Once Through Steam Generator

为研究蒸干点波动对蒸汽发生器传热管造成的损伤,以Babcock&Wilcox公司设计的直流蒸汽发生器为原型,首先利用一、二次侧耦合传热的方法得到相关热工水力参数,通过对比不同波动频率下蒸干点径向温度分布确定波动频率的影响,利用有限元分析得到传热管应力分布,最后根据S-N曲线对传热管进行疲劳评估,并探讨相关因素的影响。研究结果表明,蒸干点波动频率较低时径向温度分布与稳态相似,接触二次侧的传热管外壁面更容易发生疲劳损坏,虽然交变应力小于限值,但在堆内环境下存在一定运行隐患,温度波动幅值增大会导致传热管寿命明显下降,采用弹性约束有利于缓解蒸干点波动引起的疲劳。本研究为直流蒸汽发生器传热管在蒸干点波动条件下的寿命预测及安全运行提供了参考。

In order to study the damage of the heat transfer tube caused by dryout oscillation,the once through steam generator designed by Babcock&Wilcox company is taken as a prototype.Firstly,the relevant thermal and hydraulic parameters are obtained by using the method of primary and secondary side coupled heat transfer.By comparing the radial temperature distribution of dryout point at different fluctuation frequencies,the influence of fluctuation frequency was determined,and the stress distribution of heat transfer tubes was obtained by finite element analysis.Finally,the fatigue of heat transfer tubes was evaluated according to S-N curve,and the influence of related factors was discussed.The results show that when the fluctuation frequency of the drying point is low,the radial temperature distribution is similar to the steady state.The outer wall in contact with the secondary side is more prone to fatigue damage,although the alternating stress is less than the limit value,there is a certain operating risk in the reactor environment.The increase of temperature fluctuation frequency will lead to the obvious decrease of the life of heat transfer tubes,and the use of elastic constraint is helpful to alleviate the fatigue caused by the oscillation of steam drying point.This study provides a reference for the life prediction and safe operation of the heat transfer tubes of once-through steam generator under the condition of fluctuating evaporating point.