50 MWe光热电站填充床储罐的高温蠕变与机械性能研究

High Temperature Creep and Mechanical Properties of the Packed-bed Thermal Storage Tank in 50 MWe Solar Power Plant

针对光热电站填充床储罐在高温蠕变与交变应力作用下存在断裂失效致熔盐泄漏的现象,在综合考虑罐体真实结构与应力荷载的基础上,发展了可用于分析大型商用填充床储热器蠕变与机械性能的热-力耦合数值方法,并模拟获得了不同储-放热时刻下典型347H材质储罐蠕变损伤时间与机械应力的动态变化规律。结果显示:储-放热过程中,罐体壁面的温度变化速率明显低于填充床区域,壁板1-4(4.2<H<12.5 m)在储热6 h结束时刻与壁板5-6(H<4.2 m)在储热结束8 h后均会产生高温蠕变损伤现象;热盐顶部流入、冷盐底部流入的运行方式使得罐体各壁板的蠕变时间不尽相同,单次循环下,最顶端壁板的蠕变时间为18.5 h,约为最底端壁板的7.4倍;壁面应力受温度梯度影响显著,储热时较高的温度梯度易导致较大的峰值应力;大部分壁板(2.1 m<H<12.5 m)均处于低应力水平状态(<30 MPa),但大角焊缝位置极易产生由应力集中导致的塑性损伤现象。

In order to analyze the packed-bed tank failure and molten salt leakage problems induced by the high temperature creep and alternative stress in the solar power station,a coupled thermal-mechanical method for analyzing the creep and mechanical performances of the commercial tank with 347H material was developed by taking into account the real structure and stress loads,and the corresponding dynamic characteristics in different charging-discharging time were further numerically studied.The results show that the temperature change rate of the tank wall is obviously lower than that of the packed-bed region,and the creep phenomenon occurs at first on the wallboards 1-4(4.2<H<12.5 m)at the end of charging(t=6 h),then on the wallboards 5-6(0<H<4.2 m)when they experience another 8 h after charging.The operation strategies of hot and cold molten salts flowing respectively into the tank from the upper and bottom locations lead to the creep time of wallboards differing significantly.In single cycle,the creep time of the top wallboard is 18.5 h,which is 7.4 times that of the bottom wallboard.Meanwhile,the wall temperature gradient has important influence on the stress performance,and higher temperature difference leads to larger peak stress.Besides,although the stress of most wallboards(2.1 m<H<12.5 m)is lower than 30 MPa,the plastic damage phenomenon could be easily induced by the stress concentration of the fillet weld region in the bottom wallboard.