Abstract:

A visual experimental device was built to study the distributive mixing process in a horizontal self-cleaning single-shaft kneader. Meanwhile, the finite element method (FEM) with the mesh superposition technique (MST) was adopted to obtain the velocity distribution, shear rate distribution and mixing index distribution in the single-shaft kneader with a highly viscous Newtonian fluid. Then the particle tracking technique was used to analyze the whole and local distributive mixing process in the kneader. The statistical analysis was performed based on the particles’ trajectories to calculate the length of stretch and mixing efficiency. The effect of kneader configuration on the flow filed and mixing process was also investigated. Results show that the experimental data agree well with the FEM simulation results. There exists the periodical intermeshing interaction between the static kneading bars on the kneader wall and the dynamic kneading bars on the rotating shaft, which improves the self-cleaning performance, shear rate, whole and local distributive mixing process, disperse mixing ability and mixing efficiency. The length of stretch exponentially increases with time and the time averaged mixing efficiency remains positive during the mixing process.

Key words: single-shaft kneader, numerical simulation, CFD, hydrodynamics, mixing

摘要：

选取卧式单轴捏合反应器为研究对象，搭建了一个可视化实验装置来研究其分布混合过程，并且通过三维有限元数值模拟方法和网格重叠技术获取了高黏牛顿流体在反应器中的流速分布、剪切速率分布与混合指数分布，进一步采用粒子示踪技术分析了全局与局部分布混合过程，对示踪粒子的运动轨迹进行统计分析得到了拉伸率与混合效率，并且考察了搅拌结构对流动与混合过程的影响。结果表明，实验与数值模拟结果吻合较好。捏合反应器中几乎不存在流动死区，搅拌轴上的动态捏合杆与搅拌槽壁面上的静态捏合杆之间存在周期性的捏合作用，可以强化自清洁性能、剪切作用、整体与局部分布混合过程、分散混合性能以及混合效率。拉伸率随着混合时间以指数形式增加，时均混合效率大于零。

关键词: 单轴捏合反应器, 数值模拟, 计算流体力学, 流体动力学, 混合