二维导流管喷动床离散颗粒动力学模拟

Kinetic simulation of two-dimensional spouted bed with draft plates by discrete element method

采用离散单元法(DEM)-计算流体力学(CFD)双向耦合数值方法对二维导流管喷动床进行了模拟,颗粒的运动通过DEM模型描述,而气体的运动用Navier-Stokes方程进行求解,气体和固体颗粒之间的相互作用通过曳力形式传递。文中将DEM和边界元方法(BEM)结合起来解决颗粒在具有复杂边界设备内的运动。通过采用BEM+DEM-CFD相结合的方法进行模拟计算,得到了喷动床的最小喷动速度,研究了不同表观气速下床内的流型,得到了二维导流管喷动床的床层压降与表观气速的关系,统计分析了喷射区、环隙区内颗粒的运动速度和相应的空隙率,全面地描述了二维导流管喷动床内的气固流动特征。

A discrete element method （DEM）-computational fluid dynamics （CFD） two-way coupling method was employed to simulate the hydrodynamic in two-dimensional spouted beds with draft plates. The motion of particles was modeled by DEM and the gas flow was modeled by Navier-Stokes equations. The interactions between gas and particles were considered by a two-way coupling method. The motion of particles in the spouted bed with complex geometry was solved by combining DEM and boundary element method （BEM）. The minimal spouted velocity was obtained by the BEM ＋ DEM-CFD simulation and the variation of the flow pattern of the bed with different superficial gas velocity was studied. The relationship between the pressure drop of the spouted bed and the superficial gas velocity was achieved from the simulations. The radial profile of averaged vertical velocities of particles and the profile of averaged void fraction in the spout and the annulus were statistically analyzed. The flow characteristics of the gassolid system in the two-dimensional spouted bed were clearly described by the simulation results.