L型定向风帽流化床中气-固流动的离散元素法模拟及可视化研究(英文)

DISCRETE PARTICLE SIMULATION AND VISUALIZED RESEARCH OF THE GAS-SOLID FLOW IN FLUIDIZED BEDS WITH L-TYPE WIND CAPS

该文采用离散元素法DEM模型对二维L型定向风帽流化床中的气-固流动特性进行模拟。欧拉方法与拉格朗日方法分别用来处理气相场与离散的颗粒场。气相流动通过求解局部平均Navier-Stokes方程获得,通过求解牛顿第二定律得到颗粒的运动,同时考虑颗粒之间的碰撞。模拟结果表明,在L型定向风帽流化床中,颗粒存在顺时针方向的循环流动,因此床料的横向混合特性较好。通过可视化试验观察到:气泡离开风帽后,在向上运动过程中有横向的偏移,因此气泡尾涡中的颗粒也跟随气泡做横向的偏移。这是影响L型定向风帽流化床中颗粒内循环的主要因素。

DEM (Discrete Element Method) is used to simulate the gas-solid flow of a two-dimension fluidized bed with L-type wind caps in this paper. Eulerian and Lagrangian methods are used to deal with gas-field and discrete particles respectively. The gas flow is determined by local average Navier-Stokes equation, the motion of individual particle is obtained by solving Newton抯 second law of motion, particles collisions are taken into account. The simulation result indicates that there is clockwise particles circulation in fluidized beds with L-type wind caps. Therefore the transverse mixing characteristic of bed material is good. Through visualized experiments, we observe there is transverse movement of bubbles after bubbles leave out L-type wind caps. So particles in trailing vortex of bubbles also move transversely, this is an important factor that results in particles circulation in fluidized beds with L-type wind caps.