Y型微通道中空泡动力学特性研究

发布时间：2018-03-25 15:44

本文选题：空泡　切入点：对称Y型微通道　出处：《大连海事大学》2017年硕士论文

【摘要】：近年来,微流控技术发展迅速,气液两相流动的应用引起人们极大的关注。空泡技术在生物医学、化学工程和国防军事等领域发挥着巨大的作用。因此探索空泡动力学特性对于实现对空泡的有效利用和主动控制具有重要的意义。本文主要针对微通道入口方式和微通道壁面润湿性对空泡动力学特性的影响进行了系统性研究,主要内容如下:1.基于Y型汇流方式采用120° Y型微通道,气液两相入口对称。借助高速摄像技术对Y型微通道分叉处空泡的产生过程进行研究,重点分析流速、气液流速比以及通道尺寸对空泡动力学特性的影响。研究结果表明:空泡产生方式主要包括挤压、滴流和过渡,并且分别对应三种流型为段塞流、液滴流和弹状流。空泡大小随着流速、气液流速比以及通道宽度的增大而增大。空泡生成周期随流速的增大及气液流速比的减小而缩短。2.采用非对称Y型微通道进行试验,微通道入口角度分别为30°、45°、60°和75°。分别以蒸馏水和含0.1%SDS水溶液作为连续相,由Y型微通道水平分支口进入;空气作为分散相,由Y型微通道另一分支口进入,重点分析流速、气液流速比以及表面张力对空泡动力学特性的影响。研究结果表明:随着微通道入口角度的改变主要出现五种流型:平行流、射流、段塞流、弹状流和液滴流。空泡大小随微通道入口角度的增大而减小。表面张力减小,有助于生成更小体积的空泡,且空泡生成周期缩短。3.将激光加工和自组装技术制备的疏水/超疏水表面通过胶粘法粘接在微通道中作为微通道壁面,然后借助高速摄像系统对空泡在具有不同润湿性的壁面处的运动过程进行拍摄。研究流速、壁面疏水性和通道尺寸对空泡动态接触角的影响。试验结果表明:壁面疏水性越强,空泡动态接触角比值越大。随着流速的增大,空泡在壁面处的动态接触角和两侧壁面处的动态接触角比值均减小。通道尺寸越小,空泡受限制作用增强,空泡动态接触角比值接近1,且随着通道尺寸增大,动态接触角比值的增大幅度先升高后下降。
[Abstract]:In recent years, microfluidic technology has developed rapidly, and the application of gas-liquid two-phase flow has attracted great attention. Chemical engineering, national defense and military play an important role, so it is very important to explore the dynamic characteristics of cavitation in order to realize the effective utilization and active control of cavitation. And the effect of wettability on the dynamics of cavitation was studied systematically. The main contents are as follows: 1. Based on the Y-shaped confluence mode, a 120 掳Y microchannel is adopted, and the gas-liquid two-phase entrance is symmetrical. By means of high-speed camera technique, the cavitation process at the Y-shaped microchannel bifurcation is studied, with the emphasis on the analysis of the velocity of flow. The effects of gas-liquid flow velocity ratio and channel size on the dynamic characteristics of cavitation are studied. The results show that the cavitation generation modes mainly include extrusion, trickle flow and transition, and the three flow patterns are slug flow, respectively. Droplet flow and slug flow. The cavitation size increases with the increase of flow velocity, gas-liquid flow velocity ratio and channel width. The cavitation formation period is shortened with the increase of flow velocity and the decrease of gas-liquid flow velocity ratio. The inlet angles of microchannel are 30 掳~ 45 掳~ 60 掳and 75 掳respectively. Distilled water and aqueous solution containing 0.1%SDS are taken as continuous phase and entered by horizontal branch of Y-type microchannel respectively, and air as dispersion phase enters by another branch of Y-type microchannel. The effect of velocity ratio of gas-liquid flow and surface tension on the dynamic characteristics of cavitation is studied. The results show that there are five main flow patterns: parallel flow, jet flow and slug flow with the change of inlet angle of microchannel. Slug flow and droplet flow. The size of the cavitation decreases with the increase of the inlet angle of the microchannel, and the surface tension decreases, helping to generate a smaller volume of cavitation. The formation period of cavitation was shortened. 3. The hydrophobic / superhydrophobic surface prepared by laser processing and self-assembly was bonded to the wall of microchannel by adhesive method. The effects of flow rate, wall hydrophobicity and channel size on the dynamic contact angle of cavitation are studied. The experimental results show that the hydrophobicity of the wall is stronger. The larger the ratio of dynamic contact angle of cavitation is, the smaller the ratio of dynamic contact angle of cavitation at the wall and the ratio of the dynamic contact angle on both sides of the wall decreases with the increase of the velocity of flow. The smaller the channel size, the more the cavitation is restricted. The dynamic contact angle ratio of cavitation is close to 1, and the increasing amplitude of the dynamic contact angle ratio increases first and then decreases with the increase of channel size.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O35

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