Knowledge Management System Of Guangzhou Institute of Energy Conversion, CAS
| T型微通道中液液相微反应器微流控装置的研究 | |
| Alternative Title | Study of droplet formation as liquid-liquid microreactors in a microfluidic T-junction device |
| 刘志鹏 | |
| Thesis Advisor | 徐进良 |
| 2008-05-31 | |
| Degree Grantor | 中国科学院广州能源研究所 |
| Place of Conferral | 广州能源研究所 |
| Degree Name | 硕士 |
| Keyword | 液滴 破裂 排列 界面不稳定性 微通道 微反应器 |
| Abstract | 液液（气液）相微反应器技术是一种发展很快、应用很广的化工、生物技术，在生命科学以及诸多相关领域已经得到非常广泛的应用，成为研究热点之一。本研究工作是在对目前微反应器微流控研究现状综合分析的基础上提出两种T型微通道结构的液液相微反应器微流体控制装置，并对其形成原因进行实验分析。 在基于T型微通道的微反应器微流控装置的实验研究中，以水为分散相、硅油为连续相，对宽度800μm、深度为30μm的T型垂直交错结构微通道中油包水型液液相微反应器的形成进行了实验研究。通过改变分散相和连续相流量配比，生成了大小可控的纳升级液滴。对两相流量和液滴直径的关系以及流速、压力在液滴形成过程中的变化趋势进行了分析，得到粘性剪切力和界面张力是液滴形成的主要因素。通过数据分析了液滴形成中几何关系随时间的变化规律，由此建立液滴频率和直径的半经验公式。研究了液滴流向120μm微通道时，在台阶突扩处的破裂问题，提出Oh数是决定液滴破裂的关键性参数。如果不发生液滴破裂，在台阶突扩处液滴出现三种排列方式：交错双排Z字型，珍珠项链型和单排型液滴排列。并发现流量较大时，两相在主通道内形成层流，并在微通道的台阶突扩处生成新的两种类型液滴。 在基于T型垂直微通道的不稳定性的实验研究中，以辛烷为分散相，水为连续相，对宽度为200μm、深度为40μm的T型交错微通道内水包油型液液相微反应器的形成进行了实验研究。通过改变分散相和连续相流量比例，在T型节点的下游发现两种液滴形成方式：射流状液滴和滴状液滴。比较了两种液滴形成过程中界面张力、粘性剪切力和惯性力的关系，分析了形成两种液滴的界面不稳定性，得到界面不稳定是微尺度下液滴形成的主要原因，而较大的粘性剪切力可以提前激发界面失稳。最后，分析了由表面活性剂的浓度引起的Marangoni效应对液滴形成的影响。 |
| Other Abstract | Technology of liquid-liquid microreactors is a rapid developing and widely used by chemical and biological engineering, which is widely applied onto life science and other related fields. In the present work, two kinds of new microfluidic T-junction device have been put forward on the basis of the synthetical analysis of the previously reported microreactor microfluidics, in which a series of experiments and analysis of microreactor formation have been performed. For the microreactor microfluidics based on the T-junction device, droplet formation in a 30μm high, 800μm wide microfluidic T-junction device, which is used as liquid-liquid microreactors, were investigated experimentally using water as the dispersed phase and silicone oil as the continuous phase. The production of micron size droplets with a perfectly controllable diameter is affected by flow dynamics of both the dispersed and the continuous phase. Experimental results, including the relation between diameter and flow rates, and the change of the velocity and pressure at drop break-up process, had been analyzed in detail. As the conclusion, the break-up is dominated by shear-stress force and surface tension force. We reported the periodic process of droplet generation in a microfluidic device, which was found that the ratio of the length to the width of the ellipse, biscuit droplet keeps linearly increasing versus time during a full cycle, and develop a scaling law for the droplet frequencies and sizes. Depending on the Oh number, the droplet may or may not breakup into smaller ones when it enters the downstream 120μm deep microchannel. For the non-breaking up cases, three self-assembled, ordered droplet patterns, reverse droplet, pearl necklace, single droplet, appear. For large relative flow rate, droplet breakup occurs in branched microchannel network by two different mechanisms with the two liquids flow in parallel along the shallow channel segment. For the microreactor instabilities based on the T-junction device, droplet formation in a 40μm high, 200μm wide microfluidic T-junction device were investigated experimentally using n-Octane as the dispersed phase and water as the continuous phase. Depending on flow dynamics of both the dispersed and the continuous phase, two different droplet formation mechanisms are distinguished: jetting and dripping. Experimental results, included the relation among surface tension force, shear-stress force and inertial stress force, and instabilities of interface in two mechanisms of droplet formation had been analyzed in detail. Experimental observations support the break-up is dominated by interfacial instabilities, and larger shear-stress force could trigger this instability in advance. Consequently, Marangoni effect which is caused by the change of the surfactant concentration on the droplet properties had be analyzed. |
| Pages | 64 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.giec.ac.cn/handle/344007/5802 |
| Collection | 中国科学院广州能源研究所 |
| Recommended Citation GB/T 7714 | 刘志鹏. T型微通道中液液相微反应器微流控装置的研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2008. |
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