不等粒径流化床的软球模拟

Soft-sphere simulation with unequal particle diamete rs in gas-solid fluidized beds

基于颗粒轨道模型,提出了粒径分别服从均匀分布与正态分布的软球方法,其中流体运动用Navier-Stokes方程描述,颗粒运动服从牛顿第二定理.模拟了不等粒径流化床中的气泡和节涌现象,并分别研究了表观气速、颗粒刚度系数、粒径分布不同时,固相颗粒的速度分布规律.其研究结果表明:分布板结构和表观气速对气泡行为有一定影响,随表观气速的增加,气泡形成、上升、破裂的速度加快;并且刚度系数越大,颗粒轴向速度随时间衰减越快;宽粒径分布的颗粒轴向速度大于窄粒径分布的颗粒轴向速度.

Based on the particle-motion discrete model, a soft-sphere method used for the simulation of fluidization was established in which particle diameters were unequal. The particles motion obeyed the Newton＇s second law, and fluid motion was described by the Navier-Stokes equation. The abovementioned model was used for simulating bubbling and slugging behavior in the fluidized beds. Then the distribution of solids velocities was studied at different gas superficial velocities, stiffness and distributions of particle diameters. Simulation results indicated that the structure of distributor and gas superficial velocity showed some influence on the bubbling phenomena, and the formation, rise and break of bubbles were accelerated with increasing gas superficial velocity. The bigger the stiffness, the quicker the decay of axial solids velocities with increasing time. At the same time, axial solids velocities of wide distribution of particle diameters were bigger than that of narrow distribution.