薄壁吸收塔内部浆液晃动减震机制及应用

Shock Absorption Mechanism and Application of Slurry Sloshing in Thin-Walled Absorption Tower

发电厂中的吸收塔属于薄壁圆柱壳结构,同时由于顶部有质量较大的除尘设备,进烟口开洞削弱了底部刚度,在地震作用下容易发生屈曲破坏.为了提高结构的抗震性能,针对吸收塔结构特点,提出了利用内部浆液晃动的减震思路.采用可考虑流固耦合效应的数值模拟与振动台试验方法,研究了内部浆液高度对于结构自振特性的影响,分析了内部浆液晃动对于结构地震响应的减震机制和影响规律.浆液的存在对结构的自振特性影响显著,当内部无浆液时,结构第1阶振型主要以结构顶部晃动为主,当存在浆液时,结构第1阶振型主要以液体晃动为主,浆液高度越大,结构自振周期越大.地震作用下塔内浆液吸收部分地震波能量,继而转化成浆液的长周期竖向振动,在一定程度上起到减震作用.振动台试验表明,吸收塔内部浆液的晃动降低了结构的地震响应,浆液高度为8.5 m时相对于无浆液工况,加速度最大值降低42%,位移最大值降低56%.通过回归拟合,提出了地震响应衰减系数和浆液高度的函数关系,在浆液高度超过4.0 m以后,地震响应随液位的增大变化不明显,建议在满足工艺要求的前提下,吸收塔内部浆液高度取值范围为4.0~8.5 m.本文的研究成果为考虑内部浆液影响的薄壁圆柱壳结构地震响应分析和抗震性能评估提供了参考依据.

The absorber in power plants is a thin-walled cylindrical shell structure.The smoke inlet opening of the absorption tower weakens the rigidity of the bottom,thereby making it prone to buckling failure during an earthquake action owing to high-quality dust removal equipment at the top.Therefore,to improve the seismic performance of the structure,according to the structural characteristics of the absorption tower,the idea of using the internal slurry to minimize vibration is proposed.The damping mechanism and influence law of slurry on seismic response of the structure are analyzed.The presence of slurry has a considerable effect on the structure’s natural vibration characteristics.When there is no slurry inside,the first-order mode of vibration is dominated by the top sloshing of the structure,and when there is a slurry in the structure,the first-order mode of vibration is mainly liquid sloshing.Hence,the higher the slurry height,the larger the natural vibration period.Under the earthquake action,the slurry in the tower absorbs part of the seismic wave energy and then transforms into the long-period vertical vibration of the slurry,which plays the role of damping to a certain extent.The shaking table test reveals that the shaking of slurry in the absorber will minimize the seismic response of the structure.Compared with the case without slurry,when the slurry height is 8.5 m,the maximum acceleration and maximum displacement decrease by 42%and 56%,respectively.Therefore,the functional relationship between seismic response attenuation coefficient and slurry height is proposed using regression fitting.After the slurry height exceeds 4.0 m,the seismic response does not change significantly with the increase in the liquid level.It is suggested that the slurry height in the absorber should not be less than 4.0 m or more than 8.5 m on the premise of meeting the process requirements.The findings of this study can provide a reference for seismic response analysis and seismic performance evaluation of thin-walled cylindrical shell structures,considering the influence of internal slurry.