The discharge behavior of particles is important in many industrial applications, such as in the core of a pebble bed reactor, which uses a hopper bed filled with many large particles. In this work, a mixture composed of two particle types, freely discharged from a pebble bed, is simulated using the discrete-element method. One is a spherical pebble of diameter equal to that of the fuel pebble of the reactor. The other is a composite particle comprising three spherical pebbles bonded together. The included angle α of the three pebbles characterized the particle conformation, which may affect the discharge behavior of the mixture. The effects of volume fraction of the multi-sphere χ (equivalent to the number fraction) on the discharge are also analyzed. Flow patterns, number flow rate, discharge velocity, and mean force of the mixture are computed to help in revealing discharge features. The results show that increasing either α or χ reduces the discharge flow rate. Fittings and correlations give a quantitative evaluation of the independent effects of α and χ. The analysis of velocity and force explains the mechanism relevant to the main influencing factors α and χ. The results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core, especially adverse failure conditions.

颗粒的排放行为在许多工业应用中都很重要，例如在卵石床反应器的核心中，该反应器使用装有许多大颗粒的料斗床。在这项工作中，使用离散元素方法模拟了从卵石床自由排放的由两种颗粒类型组成的混合物。一种是直径等于反应堆燃料小卵石的球形小卵石。另一个是包含三个粘结在一起的球形小卵石的复合颗粒。三个小卵石的夹角α表征了颗粒的构象，这可能会影响混合物的排放行为。多球体体积分数χ的影响还分析了放电上的（相当于数量分数）。计算混合物的流型，数流率，排放速度和平均力，以帮助揭示排放特征。结果表明，增加α或χ会降低排出流量。拟合和相关性对α和χ的独立作用进行了定量评估。速度和力的分析解释了与主要影响因素α和χ有关的机理。结果有助于更好地理解二元混合物的排放特征，并有助于定量评估反应堆堆芯的排放行为，尤其是不利的故障条件。