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摘要：本文采用国际普遍学习和采用的 CFD 方法，通过使用 ANSYS 数值模拟 螺带斜叶组合桨搅拌槽流场中的流体运动情况。具体的，模拟选取外螺带和斜 叶桨为组合构型，基础溶液为密度 1350 kg/m³，黏度为 4 Pa•s 糖浆溶液，固定 外螺带转速，考察了转速比及旋转方向的影响，得到各种数值条件下螺带斜叶 组合桨流场中的混合时间、剪切速率分布、流场速度分布、体积平均剪切率和 最大剪切率。分析模拟计算结果，发现转速对流体流场速度分布、剪切速率以 及混合时间有较大影响，斜叶桨的存在确实有助于提高搅拌槽内的轴向循环流 动，内部斜叶桨转速越大，组合桨搅拌槽中流体速度越大，混合时间越短。异 向具有较高的径向流及剪切速率。本次数值计算更进一步的了解了该类型组合 桨搅拌槽对流场特性，剪切速率。这一系列结果可为后继生产对于此种构型的 选择、改良生产工艺、优化搅拌器提供参考。66302
毕业论文关键词：同轴异速组合桨；流场特性；剪切速率；混合时间；计算流体力学
Numerical simulation of mixing characteristics in helical ribbon-diameter combined impeller stirred tanks
Abstract：In this paper, the CFD method is used in this paper to simulate the fluid motion in the flow field of the agitator tank with the oblique lobes. The simulation select the outer helical ribbon and the oblique paddle as the combined configurations. The basic solution is syrup solution with a density of 1350 kg / m³, a viscosity of 4 Pa
• s. The influence of the speed ratio and the rotation direction with a fixed outer ribbon speed is investigated. The mixing time, the shear rate distribution, the velocity distribution of the flow field, the volume average shear rate and the maximum shear rate in the pitch field of the coniferous blade are obtained under various numerical conditions. The results show that the speed has a great influence on the velocity distribution of the fluid flow rate, the shear rate and the mixing time. The existence of the oblique paddle does help to improve the axial circulation flow in the stirred tank. The greater the fluid velocity in the mixing tank, the shorter the mixing time. The opposite direction has a high radial flow and shear rate. This numerical calculation further understood the flow field characteristics and shear rate of this type of mixing column. This series of results can provide a reference for subsequent production for
the choice of such configurations, improved production processes, and optimized agitators.
Key Words： Coaxial impellers; Flow characteristics; Shear strain rate; Mixing time; Computational fluid dynamics
目录
1 前言 6
1.1 本课题所用技术及其原理概况 6
1.1.1 搅拌槽计算流体力学现状 6
1.1.2 组合型搅拌槽的研究现状 7
1.2 本课题的研究目的和意义 9
1.2.1 研究目的 9
1.2.2 研究意义 9
1.3 数值模拟方法 9
1.3.1 控制方程 9
1.4 旋转桨叶模拟处理方法 11
1.5 数值方法 11
1.6 计算软件 11
2 实验方案 13
2.1 构建反应器模型