颗粒间碰撞对气固两相流中细长颗粒流化取向分布的影响

Effects of Inter-particle Collisions on the Orientation Distribution of Slender Particles in Gas-solid Flows

细长颗粒循环流化在工业生产中具有广泛的应用背景,如生物质秸杆在循环流化床中的燃烧,烟丝在循环流化床中的干燥、加湿等。细长颗粒在流化床内流化运动过程中,不可避免地存在颗粒之间的碰撞。文中根据直接模拟蒙特卡罗方法、刚体动力学原理及动量守恒定律,建立起气固两相流中细长颗粒间相互碰撞的三维数学模型。通过对比实验结果发现,考虑颗粒间碰撞的模拟结果比不考虑颗粒间碰撞的模型的模拟结果更加接近实验结果。研究发现,细长颗粒的取向分布随径向位置变化很大,颗粒间碰撞对细长颗粒的取向分布随高度及长径比的变化规律没有明显影响。

Circulating fluidizations of slender particles are applied widely in industry processes, such as the combustion of biomass stalks and the drying or wetting of cut-tobaccos. There inevitably exist inter-particle collisions in the process of cylindrical particles＇ fluidizing. Three-dimensional mathematical models of inter-particle collision of slender particles in gas-solid flows were successfully established with the direct simulation Of Monte-Carlo（DSMC） method, the kinetic of rigid and momentum conservation law. Comparison of simulated results of the established models with the experimental results shows that the simulated results of the models involving in inter-particle collision are much closer to the experimental results than those of the models not involving in inter-particle collision. It is found that the orientation distribution of slender particles is evidently affected by the radial positions, and the change laws of the orientation distribution of cylindrical particles with the axial positions and slenderness ratios are not visibly affected by the inter-particle collision.