【作者】 李岩；

【导师】 高殿荣；

【作者基本信息】 燕山大学 ， 流体机械及工程， 2007， 硕士

【摘要】 层流搅拌槽在化学工业、生物工程、制药工程、材料加工等领域有着广泛的应用。当所处理的介质对剪切力敏感时,搅拌的速度很低,流动的雷诺数很小,从而使混合效率降低。在层流搅拌槽内诱发混沌混合可以有效地提高混合效率,缩短混合时间,在工程应用中有着广阔的前景。本文主要对层流搅拌槽内混沌混合的形成机理、混合特性、影响因素以及在工程实际上的应用作了理论分析、数值模拟以及可视化实验的研究。论文主要的研究内容如下:(1)对混沌混合增强混合效率的原理进行介绍,提出一种非周期、非对称三维混沌混合的构想,运用叶轮运动的非周期性以及叶轮结构及其在搅拌槽中布置的非对称性,来增加对搅拌槽中层流流体的搅动,诱发三维混沌混合现象,提高混合效率。(2)使用CFD仿真软件对搅拌槽内的三维层流混和进行仿真和模拟。模拟了以下四种不同情况下的三维层流流场:同心六叶片叶轮,转轴相对于叶片偏心的六叶片叶轮,转轴叶片都相对于桶偏心的六叶片叶轮,同心三叶片叶轮,并对所产生的三维流场进行了后处理和特性分析,解释了由于几何形状的非对称性诱发层流搅拌槽内三维混沌混合的机理。(3)通过对三种不同方案下,即叶轮匀速转动、叶轮速度按照时间周期性变化转动、叶轮按照时间周期性正反转转动的实验结果的分析、比较,定性的验证了层流搅拌槽内运用叶轮运动的非周期性来增加对搅拌槽中层流流体的搅动,诱发三维混沌混合现象,破坏搅拌槽中不利于充分混合的隔离层的生成,从而提高混合效率这一理论的正确性。更多还原

【Abstract】 Laminar stirred tanks are widely used in chemical engineering, biomedical engineering, pharmaceutical engineering, and material process. When the media in stirred tank are shear stress-sensitive, either the rotate speed or the Reynoles number is quite low, mixing is often inefficient. Generating a chaotic mixing in laminar stirred tank can effectively improve the mixing efficiency, shorten the mixing time, and have wild future in engineering application.In the paper, the studies of theory analysis, numerical simulation and experiment were done to reveal the form mechanism, mixing characteristic, influence factor and application in engineering of chaotic mixing in laminar stirred tank. The main content of the paper is as follows:(1)Introduce the theory of how chaotic mixing improve the mixing efficiency, bring forward an idea of aperiodic and dissymmetrical three-dimensional chaotic mixing, use the non-periodicity of impeller rotation and the dissymmetrical of impeller configuration and disposal in stirred tank to enhance the agitation of laminar fluid in stirred tanks, generate a three-dimensional chaotic mixing, improve the mixing efficiency.(2)Use CFD software to simulate the three-dimensional laminar mixing in stirred tank. Simulate the three-dimensional laminar flow field of four different conditions: the impeller with 6 bladed is concentric with the vessel, the impeller with 6 bladed is eccentric to the rotating axis and the vessel, the impeller with 6 bladed and the rotating axis are eccentric to the impeller, the impeller with 3 bladed is concentric with the vessel. Post-process and characteristic analyze the three-dimensional flow field, and explain the mechanism of dissymmetrical geometry figure generate three-dimensional chaotic mixing in laminar stirred tank.(3)According to analyze and compare the experiment results of three different cases: steady RPM, co-reverse periodic RPM, time-periodic fluctuation of RPM, qualitative validate the theory of using the non-periodicity of impeller rotation to enhance the agitation of laminar fluid in stirred tanks, generate a three-dimensional chaotic mixing, destroy isolated mixing regions which is bad to whole mixing in stirred tank, improve the mixing efficiency.更多还原