【作者】 张宏伟；

【导师】 王燕民；

【作者基本信息】 华南理工大学 ， 材料学， 2013， 硕士

【摘要】 介质搅拌磨是一种高效节能的超细粉碎和分散设备，是目前制备微米，亚微米和纳米颗粒的主要工业制备设备之一，在物料的超细粉碎和分散工程中占有重要的地位。但是，对其基础理论研究相对较少，至今尚未形成完整的介质搅拌磨的设计的依据和基本理论。本论文第一章综述了超细粉体的范畴、特性及制备，介绍了介质搅拌磨的基本结构、粉碎机理及其性能和工艺参数，简述了国内外对介质搅拌磨的研究现状，对比了目前所用的数值模拟方法与传统实验方法各自的特点。另外，还给出了本论文的研究内容和意义。本论文第二章简要地介绍了本实验所用的CFD方法理论基础和相关的计算模型。本论文第三、四章利用现有的计算流体动力学(CFD)FLUENT软件对叶轮式和棒销式两种现代介质搅拌磨磨腔内的三维单相流层流及湍流流场进行了仿真数值模拟，并分析和讨论了不同参数(搅拌器转速、流场粘度、搅拌器几何结构及尺寸)对磨腔内流场特性(平均速度、切向速度、速度梯度、涡量、粘性耗散率、湍动能、湍流强度和能谱)的影响。数值模拟结果表明，在磨腔内相邻搅拌器之间区域的流体能量在轴向上发生分散并重新分配,从而产生随机分布的涡量；磨腔中能量集中分布在搅拌器周围及靠近腔内壁区域内，可为有效研磨区；在一定范围内增大搅拌器转速，可使流体速度及速度梯度有所增大，由于流体之间剪切力作用与流体速度梯度大小成正比，从而,改善有效研磨所需的能量利用效果。但是转速过大，流场湍动能在传输过程中耗散较多；粘度越小的湍流场，湍流强度越大，以致可施加能量利用效率越高；介质搅拌磨的结构及尺寸是影响流场特性的关键因素。在相同条件下，尺寸合适的棒销式介质搅拌磨流场分布特性优于叶轮式介质搅拌磨。还发现,轴径比与搅拌器间距尺寸的合理选取对流场运动特性的影响至关重要。本论文第五章对叶轮式介质搅拌磨磨腔内的单相流(水)湍流场的流体速度进行了实测。实测所得流体速度变化情况及运动轨迹与模拟结果近似，两者的平均速度值相差较小。此项有关单相流流场仿真数值模拟分析和实验验证的研究结果已应用于实际应用的介质搅拌磨的参数优化设计和机型放大结合，并取得了良好效果，这表明所用模拟方法可行。最后,给出了本论文研究工作所获得的主要结论和今后工作展望。更多还原

【Abstract】 Stirred-media mill as a ultra-fine grinding/dispersion equipment can produce micron-,submicron-and nono-sized particles for various materials in industrial productions. However,a few work on the corresponding basic studies have carried out, and a complete theoroticalsystem for the optimum design and basic theories of the mills has been not established so far.In Chapter1, the classification, properties, application, development andpreparation of ultrafine-powder were introduced. Also, the basic structure, mechanism,processing parameters of the stirred media mill were described, and recent developmentson the related research work were summarized. The experimental and numericalsimulation methods were represented. In addition, the objectives and contents of thisthesis were also given.In Chapter2, the basic theory and algorithm of computational fluid dynamic (CFD)for the simulation of fluid fields were described in details. The CFD methods for thesimulatiton of fluid field in stirred media mill, especially for the CFD (FVM), were alsointroduced.In Chapters3and4, the flow behavior (i.e., velocity magnitude, velocity gradients,shear stress, turbulence intensity and turbulent transmission) of laminar or turbulentfields in impeller-and pin-stirred media mills under different conditions was analyzed bythe CFD (FVM). The simulated results indicate that the fluid energy dispersion andrelocation occur in the axial direction in the region between adjacent agitators in thegrinding chamber, resulting in a randomly distributed vorticity. The grinding energy inthe chamber is concentrated in the areas around the agitator and close to the inner wall inwhich the effective grinding zone can be forecasted. Due to the shear forces between thefluids, the fluid velocity and its gradient increase when the agitator shaft speed increasesin a certain range, resulting in the improvement of the energy utilization efficiency in themill. When the shaft speed is too large, the turbulent kinetic energy dissipation of theflow field during transmission increases more rapidly. The smaller the flow viscosity is, the greater the turbulence intensity and the higher energy utilization efficiency will be.The design and size of the agitator is a key factor affecting the characteristics of fluidflow field. Under the same condition, the energy utilization efficiency of stick pin-stirredmill with the appropriate size is superior rather than that of impeller-stirred mill. Therational ratio of shaft diameter to the stirrer pitch is essential to the characteristics offluid flow movement in the grinding chamber.In Chaper5, the turbulent water veloctiy in the grinding chamber was measured bya pitot tube. The results obtained show that the measured fluid velocity and fluidpathlines in the chamber is similar to the simulated results, and the difference betweenthe measured (or experimental) and simulated average velocity values is slight. It isconfirmed that the simulation method used in this thesis can be used for the optimumdesign of stirred media mills.The final chapter of this thesis gave the main conclusions obtained and some futurepromising outlooks.更多还原