下推斜叶桨无挡板搅拌槽内液固两相流的数值模拟与实验研究
文献类型：学位论文
| 作者 | 单贤根 |
| 学位类别 | 硕士 |
| 答辩日期 | 2007-06-02 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 禹耕之 |
| 关键词 | 无挡板搅拌槽 液固两相 多流体模型 相含率 数值模拟 下推斜叶桨 |
| 其他题名 | Numerical Simulation and Experimental Study of the Liquid-Solid Two Phase Flow in Unbaffled Stirred Tank with Pitched Blade Turbine |
| 学位专业 | 化学工程 |
| 中文摘要 | 搅拌槽是过程工业中一类常见的混合设备，广泛应用于化工、冶金、石化、环境工程和生物化工等领域。在搅拌槽内，混合介质随旋转的搅拌桨运动，与搅拌槽内的固体壁面相互作用，形成复杂的拟周期性三维湍流流动，对于液固两相体系，固相的引入使流动状况变得更为复杂。目前，液固两相体系流动特性的研究主要采用实验和数值模拟两种方法，由于斜叶桨搅拌槽具有复杂的几何结构，针对搅拌槽内液固两相体系流体动力学特性及固相分布的研究尚待深入。本文以三叶下推斜叶桨无挡板搅拌槽内液—固两相体系为研究对象，从实验和数值模拟两方面对其流动和分散特性进行了研究。 在数值模拟方面，首先针对数值模拟中斜叶桨固体边界条件处理复杂的难题，提出一种利用数学矢量距离的方法对斜叶桨叶进行数学表征，在数值模拟的计算过程中实现桨叶固体边界的自动识别，从而方便有效地在圆柱坐标体系下用结构化网格来处理具有复杂几何形状桨叶的搅拌槽。在此基础上，采用基于Eulerian-Eulerian观点的“两流体”模型来建立描述搅拌槽内液—固两相流的数学模型，并且采用k-ε-AP两相湍流模型对体系湍流特性进行描述，并对Reynolds时均控制方程中的脉动关联项进行分析从而得到一套适合于本模拟体系的脉动关联项，最终对搅拌槽内液—固两相流的流体动力学特性进行了三维全流场数值模拟。将计算结果与实验数据进行比较发现，本文计算出的固体颗粒在搅拌槽内的分布情况与实验数据吻合较好。 在实验研究方面，采用PC-6A粉体浓度测量仪对70o三叶下推斜叶桨无挡板搅拌槽内液—固两相分散体系的局部浓度分布进行测量，液相采用自来水，固相采用粒度为80 um的二氧化硅固体颗粒。考察了在一定的固体颗粒相含率条件下，搅拌转速、搅拌桨离底高度等操作条件对分散相局部浓度分布的影响。结果显示，在较高的搅拌转速下，固体颗粒容易被输运到搅拌槽上方，悬浮效果比较好；在不同搅拌桨离底高度范围内，较低的离底高度能实现较好的固体颗粒悬浮。 |
| 英文摘要 | Stirred tank is commonly used in many industrial processes, like chemistry, hydrometallurgy, petrochemistry, environmental engineering, bio-engineering and so on. The flow in the stirred tank is often three-dimensional, recirculating and turbulent as the interaction of rotating impeller with stationary circle of the tank. It becomes much more complicated when another phase is introduced. Traditionally, the design and scale-up of stirred tank resorts to a stagewise procedure involved with costly pilot plant tests. Nowadays, Computational Fluid Dynamics (CFD) has been used in research to gain better understanding of the hydrodynamics of single phase and two-phase flow in stirred tank. The major objective of this dissertation is to investigate the hydrodynamic characteristics of liquid-solid two-phase system in an unbaffled stirred tank generated with PBTD (Pitched Blade Turbine Downwards), which was scarcely addressed so far. In numerical simulation part, the vector distance was proposed to deal with the complex boundary of the PBTD, which makes it possible to resolve the whole tank in cylindrical coordinator effectively. Then, the three-dimensional flow of solid-liquid suspension in a stirred tank with PBTD is formulated by the ‘two-fluid’ approach and the two-phase k-ε-AP turbulence model with the full incorporation of the second-order turbulent fluctuation correlation appearing in the Reynolds time averaged governing equations and numerically simulated using full flow field procedure. Contrast the results from numerical simulation and experiment, a good agreement was reached of solid particle distribution in the stirred tank. In experimental research part, a 3-blade, 70o PBTD axial impeller was used in an unbaffled contoured bottom cylindrical stirred tank with diameter of 300 mm for good axial flow, suspension and distribution of solid particles. The local solids concentration was measured using PC-6A Fiber Optic Reflection Probe. The liquid phase is water, and the solid phase is dioxide silicon with diameter of 80 um. The influences of operation conditions including different impeller agitating speed and impeller off-bottom clearance on solids concentration distribution were studied. The results indicate that, the higher the impeller speed, the easier the solid particle can be transferred to the zone above, then a better suspension can be achieved. In the scope of measurement, the lower of the off-bottom clearance leads to better suspension and less solid concentration below the impeller. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 122 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1161]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 单贤根. 下推斜叶桨无挡板搅拌槽内液固两相流的数值模拟与实验研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2007. |
入库方式： OAI收割
来源：过程工程研究所
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