喷动流化床中杆状颗粒混合特性的CFD-DEM模拟

CFD-DEM investigation on mixing of rod-like particles in spout-fluid bed

采用计算流体力学-离散单元法(CFD-DEM)模型对杆状颗粒在喷动流化床中的流动及混合行为进行数值模拟研究,其中杆状颗粒采用超椭球模型进行描述.通过模拟结果,考察流化气速、喷动气速和颗粒形状对流动与混合的影响.结果表明,杆状颗粒在喷动流化床中的流动具有典型喷动床的喷动特性;提高喷动气速与流化气速均有助于颗粒混合,且流化气速对流动与混合的影响大于喷动气速.颗粒形状主要通过颗粒互锁与颗粒长轴取向一致性这2个因素影响颗粒混合,提出较简单的方法用以量化颗粒长轴取向的一致性.在上述2个因素的作用下,当杆状颗粒长径比较小时,增加长径比会抑制颗粒混合;当长径比较大时,增加长径比会促进颗粒混合.

The flow of rod-like particles in a spout-fluid bed was simulated by computational fluid dynamics/discrete element method(CFD-DEM), with rod-like particles being modeled by super-ellipsoids. The impacts of fluidization gas velocity, spout gas velocity and particle shape on the flow and mixing of rod-like particles were analyzed. The simulation results showed that the flow behaviors of rod-like particles in a spout-fluid bed basically accorded with the typical spout characteristics. Increasing fluidization gas velocity and spout gas velocity both can improve particle mixing, and the fluidization gas velocity has more effect on the particle mixing than the spout gas velocity does. The impact of particle shape on the particle mixing is mainly realized through the factors of consistency of particle orientation that is quantified by the proposed method and interlock between rod-like particles, so that the mixing degree decreases firstly and then increases with the particle aspect ratio.