摘要
结合离散单元法模拟,引入Ashton混合指数动态跟踪流化床内物料混合进程。颗粒速度分布和气固流动特性分析显示,内部颗粒循环尺度是影响床内混合方式的重要因素。气泡以轴向上升运动为主,加之颗粒自重作用,床内颗粒循环贯穿整个床层高度,颗粒能够实现快速整体混合,轴向具有明显的对流混合特征;另一方面,气泡径向运动彼此约束,内部颗粒循环径向呈现区域化分布,不同区域间的颗粒横向运动受到抑制,以扩散混合为主;相同条件下,轴向混合速度是径向混合速度的3.5倍。模拟所得混合时间尺度与颗粒速度在量值上与相关文献试验结果具有良好的一致性。
In the simulations of fluidized beds with discrete element method （DEM）, Ashton mixing index was introduced to evaluate the dynamic mixing process of the particle system. Analysis of the particle velocity distribution and the gas-solid hydrodynamics indicate that the scale of inner particle circulation is crucial in determining the mixing pattern within the beds. Due to bubbles＇ pronounced ascending movement and the inherent direction of gravitation, particle circulating stream penetrates through the whole bed axially, which induces a faster convective blending mode along the bed height. On the other hand, bubbles＇ lateral motion is restrained by their neighbors, and particle circulations are localized. Therefore, particles＇ horizontal activities are reduced, then the diffusive mixing is the prominent mode in the lateral direction. Under the same condition, the axial mixing rate is 3.5 times of the lateral. The magnitudes of the mixing time scale and the particle velocities agree well with the reported experiment results.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2006年第21期119-124,共6页
Proceedings of the CSEE
关键词
热能动力工程
流化床
离散单元法
混合指数
轴向混合
径向混合
thermal power engineering
fluidized bed
discrete element method
mixing index
axial mixing
lateral mixing
