静电场中液滴聚并过程的数值模拟及机理研究

发布时间：2018-10-18 09:29

【摘要】：近年来随着电流体动力学的不断发展,其在纳米技术、生物医药技术、微机械系统、萃取及微重力研究等方面得到了推广与应用。电动流体力学中存在复杂的流动与传热传质现象,其界面特性与内部流动的研究有助于揭示电场作用下分散相液滴与连续相之间的质量、动量与能量传递过程。本文采用漏电介质模型研究了分散相液滴在连续相液体内部的聚并过程,揭示了影响液滴聚并过程及效率的重要因素,为静电场作用下原油电脱水或破乳等应用提供了一定的基础研究数据。本文运用FLUENT的UDF模块将电场力以源项的方式添加到动力学方程中,并采用VOF(Volume of Fluid)方法对两相流体界面进行追踪,采用基于瞬态的压力隐式算子分算法(Pressure Implicit with Splitting of Operators,简称PISO),对电场与流场耦合作用下液滴的聚并过程进行了数值模拟。首先,本文数值研究了静电场作用下处于另一种不相溶液体的分散相液滴的变形与内部流动现象。研究了电场强度对分散相液滴变形率的影响、分析了液滴变形方向、内部流动方向与液体的物性参数之间的关系;研究了液滴的破碎模式及液滴破碎极限与韦伯数的关系,并分析探讨了电场作用下分散相液滴变形与内部流动的形成机理。其次,基于电场作用下单液滴的变形原理,采用数值计算方法研究了双液滴的聚并过程。详细探讨了电场强度、分散相液滴的表面间距、液滴粒径比和分散相液滴间的相对角度等操作参数对液滴聚并效果的影响。采用理论方法分析了两个液滴之间的作用力,分析探讨了影响液滴聚并的主要因素。最后,以液滴聚并过程中长短轴和液桥长度为特征参数,对液滴聚并过程进行了详细的分析和探讨。采用图像方法获得了电场作用下几组不同初始间距的分散相液滴长短轴、液桥形态(曲率与长度)等表述液滴聚并行为的特征量,分析探讨了操作参数对特性量的影响。
[Abstract]:In recent years, with the development of electrohydrodynamics, it has been widely used in nanotechnology, biomedical technology, micromechanical system, extraction and microgravity research. There are complex phenomena of flow and heat and mass transfer in electrokinetic fluid dynamics. The study of the interfacial characteristics and internal flow is helpful to reveal the mass momentum and energy transfer process between dispersed droplets and continuous phases under the action of electric field. In this paper, the coalescence process of dispersed droplets in the continuous phase liquid is studied by using the leakage medium model, and the important factors affecting the coalescence process and efficiency of liquid droplets are revealed. It provides some basic research data for the application of electric dehydration or demulsification of crude oil under electrostatic field. In this paper, the electric field force is added to the dynamic equation by the source term with the UDF module of FLUENT, and the interface of the two phase fluid is traced by the VOF (Volume of Fluid) method. The transient pressure implicit operator division algorithm (Pressure Implicit with Splitting of Operators,) is used to simulate the coalescence process of droplets under the coupling of electric field and flow field. Firstly, the deformation and internal flow of dispersed droplets in another insoluble liquid under the action of electrostatic field are numerically studied. The influence of electric field intensity on the deformation rate of dispersed droplet is studied, the relationship between the direction of droplet deformation, the direction of internal flow and the physical parameters of liquid is analyzed, and the breakup mode of droplet and the relation between the breakage limit of droplet and Weber number are studied. The formation mechanism of dispersed droplet deformation and internal flow under the action of electric field is analyzed. Secondly, based on the deformation principle of the ordered droplets under the action of electric field, the coalescence process of two droplets is studied by means of numerical calculation. The effects of electric field strength, surface spacing of dispersed droplets, droplet particle size ratio and relative angle between dispersed droplets on droplet aggregation were discussed in detail. The force between two droplets is analyzed by theoretical method, and the main factors affecting the coalescence of droplets are discussed. Finally, the long and short axis and the length of liquid bridge in the process of droplet coalescence are taken as the characteristic parameters, and the process of droplet coalescence is analyzed and discussed in detail. By using the image method, several groups of droplets with different initial spacing were obtained to describe the coalescence behavior of droplets, such as the long and short axis of dispersed droplets, the shape of liquid bridge (curvature and length), and the influence of operating parameters on the characteristics of droplets.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O361.4

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