电场作用下复杂液滴的聚并动力学机理研究

In the complex droplets, the interfacial tension dynamic distribution and the rheological characteristics of the bulk phase are significantly changed by surfactant and polymer, which are the primary causes that hinder the efficient separation for the chemical flooding produced liquid in the electric field. The classical electrohydrodynamic theory focused on the pure droplets is hard to reveal the dynamic mechanism of electrostatic coalescence of complex droplets under the condition of interfacial tension dynamic distribution and viscoelasticity in bulk phase, which becomes the key scientific problem that restricts the development of electrostatic coalescence technology. By combining numerical simulation with droplet experiments adopting high speed microscope photography, this subject is going to investigate the dynamic behaviors of complex droplet during the electrocoalescence process, such as interface movement, liquid film instability and fusion of complex droplet. The mechanism of surfactant transportation on the bulk phase and the interface in the electric field, as well as the mechanism of the bulk viscoelastic effects on the internal and external circulations of droplets in the electric field are explored at the micro-nano scale. Based on this, the correlation mechanism of bulk phase flow and interface motion under the condition of dynamic interfacial tension, bulk viscoelasticity and electrohydrodynamic coupling is revealed. A coupling model of electrohydrodynamics-interface dynamics-rheology is established to elucidate the electrostatic coalescence mechanism of complex droplets. Finally, the scientific methods to improve the electrostatic coalescence efficiency of complex droplets will be proposed. The multiphysics multiphase interfacial behaviors studied in the research belong to the category of micro-nano scale. The research results are of great scientific significance to the improvement of theoretical systems of electro-coalescence, which also provide theoretical instruction for enhancing the demulsification efficiency of chemical flooding produced liquid and designing of the new and efficient electrostatic coalescer.

复杂液滴中表面活性剂与聚合物等显著改变了界面张力分布规律与体相流变特性，是阻碍化学驱采出液高效静电破乳的根本原因。基于纯净液滴的电水动力学理论，难以揭示界面张力动态分布和体相粘弹性条件下复杂液滴静电聚并的动力学机理，成为制约静电聚结技术发展的关键科学问题。本项目针对复杂液滴静电聚并过程中界面运动、失稳及融合等动力学问题，采用高速显微实验和数值模拟相结合的方法，在微纳尺度上研究电场激励下表面活性剂在体相与界面上的运移机理以及体相粘弹性对液滴内外环流的影响机制。在此基础上揭示动态界面张力、体相粘弹性和电水动力耦合条件下液滴体相流动与界面运动的关联机制，建立电水动力学-界面动力学-流变学耦合模型，得到提高复杂液滴高效静电聚并的科学方法。本研究属于多物理场多相界面的微纳尺度研究范畴，研究成果对完善多相分离理论体系具有重要科学意义，为提高化学驱采出液的破乳效率和研发高效电脱水设备提供理论依据。

根据任务书的研究内容，采用高速显微实验和数值模拟相结合的方法，在微纳尺度上研究电场激励下表面活性剂在体相与界面上的运移机理以及体相粘弹性对液滴内外环流的影响机制。在此基础上揭示动态界面张力、体相粘弹性和电水动力耦合条件下液滴体相流动与界面运动的关联机制。主要研究成果如下：.（1）探究了不同液滴粒径、聚合物浓度、表面活性剂浓度下液桥的演变规律，对比了液桥扩张中惯性力和粘滞力的作用，确定了液桥的扩张模式，揭示了表面活性剂分子运移对液桥演变的影响机理。.（2）基于纯净界面运动模型与界面流变学本构方程相耦合，实现了对粘弹性界面运动过程的理论描述，从界面动力学角度揭示了界面粘弹性对界面瞬态响应过程的影响机制。.（3）发现了高强电场强度下液滴不聚并的现象，揭示了液滴接触后的离子迁移和动态界面张力导致液滴不聚并的机理。.（4）探究了等径异性液滴电聚并过程中的界面演变和体相射流特征，基于对称液桥扩张规律，对非对称液桥的扩张规律进行了定量描述。提出了界面能量转化机理，定量描述了射流演变规律和涡流尺寸，提出了液滴混合程度相图。.（5）揭示了非等径液滴电聚并过程中的界面演变和体相射流特征，基于界面能量转化机理解释了液滴粒径比、界面张力差、连续相粘度对射流演变的影响机理。发现了区别于体相混合的界面混合方式，获得了液滴混合模式相图。.（6）阐明了电场参数、界面性质和粘度比对聚并特征的影响规律，阐释了静电聚并过程中的电场、流场分布特征及其演化规律。.（7）分别研究了交流电场、脉冲直流电场和双极性方波电场下双液滴不聚并行为，阐明了不同时变电场下频率对双液滴聚并临界电场强度的影响和双液滴不聚并行为的机理。.研究成果完善了静电聚并理论体系，为新型静电聚结设备的研发提供了有力的理论指导。.项目研究期间，参加国内外学术会议5次，做会议报告4次；发表SCI论文17篇（一区4篇，二区11篇，三区2篇）；申请国家发明专利4项，已授权4项。