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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。
In this paper, the discrete element method (DEM) model is used to simulate the gas-solid flow in a two-dimensional L-shaped directional cap fluidized bed. The Eulerian and Lagrange methods are used to process the gas field and discrete particle fields, respectively. The gas phase flow is obtained by solving the local average Navier-Stokes equations. The particle motion is obtained by solving Newton’s second law, taking into account the collision between the particles. The simulation results show that the particles have a clockwise circulation in the L-shaped directional cap air fluidized bed, so the lateral mixing characteristics of the bed material are better. Through the visualization experiment, it is observed that the bubble leaves the hood and has a horizontal offset during the upward movement, so the particles in the tail vortex of the bubble also follow the lateral displacement of the bubble. This is the main factor affecting the intragranular circulation in L-shaped directional hoods.