基于颗粒尺度DEM直接数值模拟的喷动流化床颗粒运动特性

采用离散元方法,对喷动流化床内的气固流动进行了三维直接数值模拟.气相场采用欧拉方法,固相场采用拉格朗日方法;对每一个颗粒考虑了碰撞力、携带力和重力;颗粒碰撞采用软球模型;气固耦合采用双向耦合.模拟中跟踪了每个颗粒的运动,获得了颗粒轴向速度、平均速度、颗粒浓度和颗粒平均碰撞频率随操作参数的变化规律.结果表明喷动气速度、流化气速度、颗粒平均速度、颗粒浓度和颗粒平均碰撞频率存在关联性:喷动气速度增加,颗粒在喷射区和环形密相区的平均速度增加,浓度减小,平均碰撞频率减小;流化气速度增加,颗粒速度、浓度和碰撞频率与喷动气速度增加具有相同的变化规律,但环形密相区的变化更为明显.

Particle-scale based DEM simulation of particle motion spout-fluid bed

Numerical simulations of particle motions in a spout-fluid bed were carried out three dimensionally by discrete element method(DEM).Eulerian method was employed to deal with the gas phase and Lagrangian method was employed to deal with the solid phase.Drag force,contract force and gravitational force acting on individual particle were considered when establishing the mathematic models.The collisions of particles were modeled by soft-sphere model.Gas-solid twoway coupling method was employed.Individual particle was traced in the simulation,and the variation regularities of the axial component of the particle velocity,mean particle velocity,particle concentration and mean particle collision frequency with the variation of operating parameters were studied.The results show that there are relations among spouting gas velocity,fluidizing gas velocity and the above particle motion information.The mean particle velocity increases, but concentration and mean collision frequency decrease in the annulus and the spout.The same variation regularity is obtained with the increasing fluidizing gas,but it is more obvious in the annulus than in the spout.