稠密固液循环流化床内流体湍流脉动对颗粒分散的影响

Effect of Liquid Turbulent Fluctuation on Particle Dispersion in Dense Liquid-Solid Circulating Fluidized Bed

通过计算流体动力学模拟研究了固液循环流化床内流体湍流对高浓度颗粒的扩散作用。根据湍流机制下高浓度颗粒在液体中的分散机理,建立了同时考虑颗粒碰撞、流体拖拽和流体湍流扩散输运的欧拉-欧拉双流体模型。利用该模型对稠密固液循环流化床提升管内颗粒的分散运动进行了数值模拟,预测出颗粒轴向速度和体积浓度的径向分布,与相应条件下的实验数据符合很好。表明考虑流体湍流扩散输运的理论模型更能精确预测高浓度颗粒在循环流化床提升管内的运动情况;也表明即使针对以颗粒碰撞为主的稠密固液湍流体系,尺度较大的流体湍流涡也会因促使颗粒扩散输运,影响颗粒空间分布。工作为稠密固液循环流化床内两相流体动力学分析奠定了基础。

The effect of fluid turbulence transporting to dense particles in the solid-liquid circulating fluidized bed（CFB） was investigated theoretically and numerically by Computational Fluid Dynamics（CFD） simulation.Based on the dispersion mechanisms of the dense particles dispersed in liquid phase,an Eulerian-Eulerian two-fluid model considering simultaneously the particle-particle collision,the fluid drag and the turbulent transport was established.Using the model to calculate the particle dispersing motion,the radial distribution of the solid holdup and the particle axial velocity in dense solid-liquid CFB were predicted,and the predicting results agree well with the experimental results published in literature.It shows that,even though in the dense solid-liquid turbulence system,the big-scale fluid turbulence vortexes can affect the particle distribution by impelling the diffusion transport of the particles,and the model established can accurately predict the particle motion in the dense solid-liquid CFB.This study lays a foundation for the hydrodynamic analysis of the dense solid-liquid two phase flow in CFB.