基于CFD-DEM的柱形颗粒固定床反应器流场特性数值模拟

A Coupled CFD-DEM Numerical Simulation of Flow Field Characteristics in a Randomly Packed Fixed Bed with Columnar-Shaped Particle

采用计算流体动力学-离散单元耦合法(CFD-DEM),研究了柱形颗粒随机堆积固定床床层的流场流动特性。建立更接近柱形催化剂实体形状的颗粒模型,采用颗粒随机堆积法建立了固定床床层,通过对床层内部的流动特性数值模拟,得到床层内部空隙分布云图及压力场和速度场的分布规律。改变管径和粒径的比值(N,简称直径比),建立N为3,5,10和20的反应器固定床床层,分析了直径比对流场特性的影响。结果表明,当N为5时,床层堆积较为密实均匀,压降较大,速率变化幅度较小,故此管径比下固定床反应器内柱状催化剂床层有较好的流场特性。

The flow field characteristics of fixed bed with randomly packed columnar-shaped particles were simulated by using computational fluid dynamics-discrete element method （CFD-DEM） coupling. By establishing a particle model closer to the solid shape of the columnar-shaped catalyst and numerically simulating the flow characteristics of the randomly packed fixed-bed, the distribution of the internal void and the distribution of pressure field and velocity field in the bed were obtained. By changing the ratio of the tube diameter and the particle diameter （N referred to as diameter ratio）, the fixed bed reactors with N=3, 5, 10, 20 were established and the effects of N on the flow field characteristics were analyzed. The results showed that when N was 5, the packed bed was dense and uniform, and the pressure drop was large and the velocity fluctuation was small. Therefore, a better flow field characteristic of the columnar catalyst bed in the fixed bed reactor was obtained with this diameter ratio.