双层搅拌体系中固液两相流的数值模拟研究

发布时间：2018-03-08 15:01

本文选题：液固两相流　切入点：固体悬浮　出处：《华东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：固液非均相反应广泛存在于化工生产过程中,这类反应体系中固相在搅拌釜内的分散状态对反应过程起关键作用。本文以计算流体力学(CFD)技术为研究手段,应用多重参考系法以及欧拉多相流模型,对双层搅拌釜内固液两相流进行数值模拟,分别考察了搅拌釜的结构参数、内构件挡板以及研究体系的物性参数对颗粒悬浮性能的影响。论文主要得到以下结论：双层下压式斜桨中,上下层桨叶间的协同作用可以有效促进主体循环流动,提高釜内整体湍动程度,改善颗粒悬浮状况；安放角θ=45°、层间距S=0.5T时可以适宜的功率获得较强的轴向流动和湍流脉动,有利于实现固相在釜内的均布分布；流线型的碟形底结构可以很好地顺应流体的运动方向,有效减小釜底的死区面积。内构件挡板的安装可以有效消除流体的切向运动,促进釜内形成整体轴向循环流动,同时发现釜内增设四块挡板,且挡板的离壁距离为3.4mm时,颗粒的悬浮性能最优。颗粒的直径、密度以及体积浓度的增大均会降低固相在釜内的悬浮均匀性,并且这种现象在粘度相对较低的流体中更加严重。此外还发现,较之单层搅拌体系,双层体系对固相粒径和密度的变化更为敏感,但对固相体积浓度的变化适应性更高。
[Abstract]:Solid-liquid heterogeneous reactions are widely used in chemical production. The dispersion state of solid phase in agitator plays a key role in the reaction process. In this paper, computational fluid dynamics (CFD) technique is used as a research tool. By using multiple reference system method and Euler multiphase flow model, the solid and liquid two-phase flow in a double-layer agitator is numerically simulated, and the structural parameters of the agitator are investigated respectively. The main conclusions of the paper are as follows: the synergy between the upper and lower layer blades can effectively promote the main circulating flow in the double-layer down-pressure inclined propeller, and the influence of the physical parameters of the inner member baffle and the system on the suspension performance of the particles is studied. Increasing the whole turbulence degree in the kettle and improving the particle suspension condition, the proper power can be obtained when the angle 胃 is 45 掳and the interval between layers is 0.5 T, which is advantageous to realize the uniform distribution of the solid phase in the kettle. The streamline disc bottom structure can conform to the direction of the fluid movement and reduce the dead zone area of the bottom of the kettle effectively. The installation of the inner member baffle can effectively eliminate the tangential movement of the fluid and promote the formation of the integral axial circulation flow in the kettle. At the same time, it is found that the suspension performance of the particles is optimal when four baffles are added in the kettle and the distance from the wall of the baffle is 3.4 mm. The increase of the diameter, density and volume concentration of the particles will reduce the suspension uniformity of the solid phase in the kettle. Moreover, the phenomenon is more serious in the fluid with relatively low viscosity. In addition, it is found that the two-layer system is more sensitive to the change of particle size and density than the single-layer mixing system, but more adaptable to the change of solid volume concentration.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ027

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