ABSTRACT The pebble-bed type reactor is one of the mainstreams for high-temperature gas-cooled reactor (HTGR), whose core is a packed bed composed of numerous spherical pebbles. In this work, discrete element model (DEM) is used to simulate the pebble flows in a thin pebble bed, and the packing peaks, top angles, trajectory and velocity deviations, retention time, and ratios are analyzed in detail. The effects of the pebble-pebble friction coefficient and pebble-wall friction coefficient, including their difference on the pebble flows are studied based on the trajectory analysis. The friction may bring higher packing peak, sharper top angle, larger diffusions of trajectory and velocity, as well as larger retention time, and ratio. However, if the pebble-pebble friction and pebble-wall friction are different, the effect of them on the pebble flow is quite different. The details and mechanisms are appropriately analyzed to explain the influence of pebble-pebble and pebble-wall friction on pebble flows. The results are helpful for better understanding of the pebble flow behavior under varied frictions.

中文翻译：

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基于轨迹的薄卵石层充填扩散摩擦分析

摘要 球床式反应堆是高温气冷堆（HTGR）的主流技术之一，其核心是由无数球状卵石组成的填充床。在这项工作中，离散元模型（DEM）被用来模拟薄卵石床中的卵石流动，并详细分析了填充峰、顶角、轨迹和速度偏差、保留时间和比率。基于轨迹分析研究了卵石-卵石摩擦系数和卵石-壁摩擦系数的影响，包括它们对卵石流动的影响。摩擦可能带来更高的堆积峰，更尖的顶角，更大的轨迹和速度扩散，以及更大的保留时间和比率。但是，如果卵石-卵石摩擦力和卵石-壁摩擦力不同，则 它们对卵石流的影响大不相同。适当地分析细节和机制以解释卵石-卵石和卵石-壁摩擦对卵石流动的影响。结果有助于更好地理解不同摩擦下的卵石流动行为。