中文摘要：

采用颗粒离散元方法（PDEM），对模块式球床反应堆内球形燃料元件循环流动的流动特性进行数值模拟，分析了反应堆堆芯内速度场、球体混合情况和球体摩擦系数、壁面摩擦系数对流动特性的影响。计算结果表明，在圆柱结构区域内，颗粒以稳定质量流形式向下移动，颗粒径向偏移很小无混合现象发生；在倒锥形区域，颗粒受器壁结构的影响而向中心会聚流动，颗粒径向偏移增大；颗粒摩擦系数和壁面摩擦系数对颗粒流动的轨迹和滞留时间均有影响，降低摩擦系数有利于均衡燃料球和石墨球的停留时间。

英文摘要：

Motions of fuel and graphite pebbles in a two-dimensional pebble bed modular reactor （PBMR） have been numerically simulated by means of particle discrete element method （PDEM）. Velocity profiles, mixing and effect of frictional coefficient of pebbles and wall on flow behavior of particles was investigated. Results indicated that both fuel pebbles and graphite pebbles move down without radial movement, and uniform motion was formed in the column regime. While particles will be accelerated, some particles will attach to the walls at the taped part of reactor due to the reduction of sectional-area. The different residence time of fuel and graphite pebbles was found. The residence time of graphite pebbles is shorter than that of fuel pebbles. With the decrease of friction coefficient of pebbles and walls, the residence time of sphere particles were increased.