非均匀带电微孔介质内电渗流的多物理输运机理研究

The surface charge of microporous media comes from the automatic physical and chemical interactions between solid surfaces and the electrolyte and ions near the surfaces, and its value depends on the local solid-liquid properties, including temperature, ionic concentration, and pH etc. When the liquid properties are position dependent, the inhomogeneity and dynamic variation of surface charge will influence electro-osmotic flow and ion transport significantly. This project is to investigate the electro-osmosis in inhomogeneously charged microporous media, which couples fluid flow, mechanical, thermal and chemical processes. We will consider the polarization between surface charge and electrical double layers and build up a theoretical model to accurately predict the inhomogeneous distribution and dynamic variation of surface charge. Combining with large-scale high-efficiency pore-scale modeling, we will systematically analyze the effects of fluid properties, pore structure geometries and pore size on the transport characteristics of electroosmosis in inhomogeneously charged microporous media. Compared with the experimental data, the modeling results are used to reveal the physical mechanism of electro-osmotic flow and ion transport in inhomogeneously charged microporous media. The theoretical achievements will provide supports of optimization and designs for three typical applications in energy and environments, including CO2 sequestration, unconventional oil and gas exploitation, and nuclear waste burial and protection.

微孔介质壁面电荷来自于壁面与壁面附近电解质溶液及离子的自发性物理化学相互作用，其大小依赖于当地的固-液特性，包括温度、离子浓度、pH等，当溶液特性随位置发生变化时，壁面电荷的非均匀及动态变化分布将对电渗及离子输运产生重要影响。本项目针对非均匀带电微孔介质内电渗流这一耦合了流-力-热-电-化学反应的复杂输运过程，考虑微孔介质壁面电荷与双电层的极化作用，拟建立理论模型准确预测非均匀分布及动态变化的壁面电荷；结合大规模高效的孔隙尺度模拟，系统分析流体特性、通道结构几何特性以及尺度效应对非均匀带电微孔介质内电渗流输运特性的影响规律；对比实验测试结果，揭示非均匀带电微孔介质内电渗流与离子输运的物理机制。研究成果将为二氧化碳埋存、非常规油气开采以及核废料埋藏保护等能源环境典型案例提供优化设计和理论支持。

微孔介质壁面电荷分布的非均匀性及动态变化对分析电渗流动及离子输运规律及机理至关重要。本项目针对非均匀带电微孔介质内电渗流这一耦合了力-热-质-电-化学反应的复杂输运过程展开系统研究，经过四年刻苦攻关，取得了三方面重要进展：（1）提出了表征流体流动-离子输运-电场分布-电荷排布相互耦合或解耦的定量化准则数（M），结合孔隙尺度高效模拟，系统的揭示了非均匀带电微孔介质内非线性电渗流规律与离子输运的物理机制；（2）考虑壁面电荷与双电层的电-化作用，建立了“电四层”理论模型准确预测非均匀分布及动态变化的壁面电荷；（3）与实验结合，针对非常规油气开采及核废料埋藏保护两个典型案例提供理论分析和技术支持。本项目相关成果发表在相关领域顶级期刊（JCIS、JFM、AC、JGR、EST及JPSE等）论文共21篇，其中SCI收录21篇；培养毕业博士硕士研究生6人，博士后出站1人；项目负责人入选 “万人计划-科技创新领军人才”，并获得国际多孔介质学会的“InterPore P&G Award for Porous Media Research”奖励。