摘要
通过实验和离散元模型考察了移动床中颗粒的运动,在微观尺度分析了粒径分布和移动床出口大小对颗粒运动、床层结构等的影响.结果发现:颗粒的粒径分布对颗粒垂直速度分布有很大影响,不同粒径的混合有利于颗粒的流动;对于同一粒径分布G2/5与DO呈线性关系,移动床出口直径对系统的出料速率有很大影响;对不同粒径混合系统,移动床的空隙率和颗粒配位数分布曲线均只有一个峰,而对等粒径系统的分布曲线均有两个峰;在移动床出口上方都存在拱形的应力链,出口两侧颗粒运动的死区内颗粒间的应力很大,中心流动区域应力较小,在移动床的上部颗粒间的应力最小;移动床出口处颗粒与移动床底部壁面的应力很大,随着床层深度的增加,颗粒与移动床侧壁面的应力增加,但当床层深度达到一定值后颗粒与移动床侧壁面的应力不变;颗粒与底部壁面的应力要大于与侧壁面的应力.
A microscopic study of the particles flow in a moving bed was performed by means of discrete element method and experiment. The dependence of flow behaviors on the particles diameter distribution and orifice size was analyzed to establish the spatial and statistical distributions of microdynamic variables related to flow and force structures. The results showed that the distribution of particle diameter has great effects on particle vertical velocities, and that the mixing of different particle diameter is favorable for particles flow. Linear equations can be used to describe the relationship between discharge rate and orifice size by G2/5 vs Do for the same distribution of particles diameter. There is one peak value in porosity and coordination number distribution curves for the mixing of different diameter, with two peak values for uniform diameter distribution. The force structures of particles in the hopper are spatially non-uniform. There are arched stress chains above the orifice. Large stresses can exist in the dead zones around the orifice, while small stresses exist in the flow zone of the bed center and smallest stresses in the upper part of the bed.
出处
《浙江大学学报（工学版）》
EI
CAS
CSCD
北大核心
2006年第5期864-868,892,共6页
Journal of Zhejiang University：Engineering Science
