增殖剂球床载气体流动特性

Pore flow analysis of sweep gas in tritium breeder pebble bed

增殖剂球床是聚变堆或混合堆产氚包层可选结构之一,准确把握增殖剂球床中载带气体的流动特性有助于提高对球床载氚过程的认识并优化包层设计。采用离散元程序PFC3D模拟增殖剂小球的填充行为,在球床内不同位置随机截取不同尺寸的控制体,利用布尔运算中的"差集"得到孔隙范围,建立孔隙分布的三维几何模型,进一步划分网格并用计算流体力学(CFD)方法求解,得出控制体上单位长度的压降以及单元体内的速度分布特征,计算结果发现载带气体速度分布与γ分布很类似,且只要选取恰当的控制体,通过计算流体力学方法可以较好地分析整个球床孔隙内流体的流动,有利于进一步研究载氚及相关过程。

Solid breeding blanket is an important type of breeding blanket for fusion reactor or fusion-fission hybrid reactor.It is helpful for the study of tritium sweeping and the optimization of solid breeding blanket structure when one has a good knowledge of the sweep gas pore flow in the pebble bed.In this paper,the packing and porosity distribution in the tritium breeder pebble bed are obtained with the discrete element code PFC3 D,and three different sizes of control cells are obtained at randomly distributed positions.With the Boolean operation,the ball volume is subtracted from the cell to get the three-dimensional calculating domain of pore flow.And then this domain is meshed and a computational fluid dynamics（CFD）solver is used to solve the flow equations and get the velocity distribution and pressure drop per length.The results indicate that the velocity magnitude distribution obeys the Gamma distribution.CFD solver is proven to be a reliable tool for sweep gas pore flow when the control cell is properly chosen.This study is helpful for further research of tritium releasing and sweeping.