搅拌槽内流场数值模拟和表面曝气的研究
文献类型：学位论文
| 作者 | 孙海燕 |
| 学位类别 | 博士 |
| 答辩日期 | 2003 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 中国科学院过程工程研究所 |
| 导师 | 毛在砂 |
| 关键词 | 搅拌槽 各向异性湍流模型 电导探针法 表面曝气 反应器 数值模拟 |
| 其他题名 | Numerical Simulation of Fluid Flow in Stirred Tanks and Investigation of Surface Aeration |
| 学位专业 | 化学工艺 |
| 中文摘要 | 搅拌槽是广泛应用于化工、溶剂萃取、环境工程和生物化工等领域的一种反应器.反应器内的三维流动很复杂,而在反应器的放大和设计中,研究者多采用一些与整体值有关的经验、半经验关联式,缺少对局部特性的定量研究.在理论研究方面,给出了一些简化的模型,但所需参数和边界条件多依赖实验数据.针对这种情况,该文从计算和实验两个方面对搅拌槽反应器内的局部流动和分散特性进行了研究.为了使数值模拟有更广的适用性,该文首次将各向异性显式代数应力模型(ASM)用于单相Rushton桨搅拌槽内流场的数值模拟.给出了合适的封闭分散相雷诺应力的方法,并首次提出适用于搅拌槽内的局部旋流修正,以改进两流体模型.该文着重对模型中相间作用力的表达进行研究,考察不同的曳力表达式对计算结果的影响,确定了合理又简单的曳力表达式.通过对曳力和虚拟质量力的大小进行比较,认为在相间作用力模型中应包括其它研究者在气液搅拌槽研究中没有考虑过的虚拟质量力,最终建立了包含虚拟质量力的Rushton桨搅拌槽的三维气液两流体模型,模拟所得气含率分布与实验数据变化趋势一致,气体速度分布趋势更加合理. |
| 英文摘要 | Stirred tank reactors are widely used in chemical -industry, solvent extraction, environmental protection engineering and fermentation processes. Up till recently, empirical correlations have been used as tools for design, scale-up and operation of stirred tanks. In view of the complex turbulent three-dimensional flow in stirred tanks, these empirical relations are clearly inadequate. To fully understand the processes occurring in stirred tanks, mathematical modeling and experimental research of local hydrodynamic behavior are desired. This dissertation is devoted to the above tasks. In accordance to the anisotropic feature of turbulent flow, an anisotropic k-s turbulence model and an anisotropic algebraic stress model are adopted to predict the turbulent flow field and turbulent characteristics generated by a Rushton disc turbine with the improved inner-outer iterative procedure. The predicted turbulent flow is compared with experimental data and the simulation by the standard k-e turbulence model. The anisotropic turbulence models are found to give better prediction than the standard k-s turbulence model. The predicted turbulent flow field is in accordance to experimental data and the trend of turbulence intensity can be effectively reflected in the simulation, especially at near impeller tip locations. The distribution of turbulent shear rate in the stirred tanks is simulated with the established numerical procedure. Accurate interfacial models are needed in the simulation of the two-phase flow in a gas-liquid stirred tank based on the two-fluid model. Different drag coefficient equations are tested in predicting the mean velocity of gas and liquid and the gas fraction in order to choose a simple and reasonable drag force equation. The drag force and the virtual mass force in the bulk region and the impeller stream region are examined and analyzed. It is suggested that the virtual mass force is not negligible and should be included in the model. The drag force and virtual mass force are adopted to predict the distribution of gas holdup and velocity components of gas and liquid. The results demonstrate that the model including the virtual mass force gives better prediction of the gas holdup and has little effect on the prediction of the velocity of liquid. The gas holdup in surface aerating operation is measured with a conductance probe, and the systematic experimental data at different operating conditions are obtained. The experiment operaions are simulated numerically with a tentative rate equation of gas uptake as a function of the local hydrodynamics. The gas holdup prediction are found to fit rather well with experimental results near the surface, but the prediction is lower than the experimental data at the other region due to the imperfection of the present model. |
| 语种 | 中文 |
| 公开日期 | 2013-09-16 |
| 页码 | 164 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1378]  |
| 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 | 孙海燕. 搅拌槽内流场数值模拟和表面曝气的研究[D]. 中国科学院过程工程研究所. 中国科学院过程工程研究所. 2003. |
入库方式： OAI收割
来源：过程工程研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。