非球形颗粒在移动床中流动特性的离散单元法直接数值模拟

Discrete Element Modeling of Non-spherical Particle Flowing in the Moving Bed

采用多元颗粒模型对玉米形颗粒在移动床内的流动进行了离散单元法(discrete elementme thod,DEM)直接数值模拟。玉米形颗粒由4个叠加在一起的球元构成。讨论了玉米形颗粒的碰撞机制及运动过程中的受力情况,主要是碰撞力和重力。通过实验验证了模型的正确性。研究了移动床内的颗粒流动特性,分析了摩擦系数对壁面所受应力、颗粒空隙率及速度分布的影响。结果表明,摩擦系数越大,卸料所需时间越长,且在2种摩擦系数μ=0.24、0.44下,壁面都会产生过压力现象。空隙率随着摩擦系数的增大而增大;摩擦系数越小,水平方向上的速度分布越均匀,颗粒的流动越接近整体流。

Discrete element model was developed to simulate the corn-shaped particles flowing in the moving bed. The corn-shaped particle was described by four overlapping sphere. Contact force and gravity force were considered when establishing the models. In addition, flowing characteristic of particles in the moving bed was studied. The effect of friction coefficient on the wall normal force, voidage and velocity distribution was analyzed. The results show that the discharge rate decrease with the friction coefficient increasing and the ＂over-pressure＂ phenomenon occurs at two different friction coefficients μ = 0.24, 0.44. The voidage also increases as the friction coefficient increases. Increasing the friction coefficient, the voidage also increases. And the velocity distribution is more uniformity and close to the mass flow with the friction coefficient deceasing.