微细多孔介质中耦合多相流和传质反应过程机理孔尺度研究

Coupled multiphase flow and reactive transport process in microscopic porous media is widely encountered and is a cutting-edge problem in many different fields such as energy, environment and chemical engineering. The microscopic structures of the porous media are complex, and the interactions between different processes as well as that between fluid and solid are very complex. Thus the transport phenomena as well as the coupled mechanisms of different processes are quite complicated, which involves many common basic scientific problems remaining to be further investigated. In this proposal, advanced pore-scale numerical methods and micro-fluidic visual experiments will be developed to study at the pore-scale the coupled multiphase fluid flow, mass transport and chemical reaction processes. Effects of capillary number, heterogeneous structures and surface wettability of porous media will be explored. Quantitative relationships between averaged concentration, bubble size, specific surface and dissolution rate will be analyzed. The pore-scale work aims to reveal the laws of multiphase distributions and evolutions, the mechanisms of interfacial mass transport and chemical reactions, the evolution laws of multicomponent concentrations, and the conversion laws of substance and energy under influence of multiple physicochemical processes. The work of this proposal is helpful to provide new efficient pore-scale study tools for transport processes in porous media. It also facilitates deep understanding of coupled multiphase flow, mass transport and chemical reactions in porous media. It will also theoretically support related engineering processes such as CO2 sequestration, fuel cell design, conventional/unconventional oil, etc.

微细多孔介质中耦合多相流和传质反应过程普遍存在于能源、环境、化工等诸多领域，是相关学科的前沿课题。多孔介质结构复杂、多物理化学场耦合且流固相互作用强烈，因此该问题的传输特性和耦合机制极为复杂，其中蕴含着若干认识尚不明晰的共性基础问题。本项目拟从孔尺度出发，发展先进孔尺度数值方法及微流控可视化实验手段，研究多孔介质中发生的两相流动、传热、传质及化学反应过程，研究毛细数、润湿特性、结构非均质性等因素对上述过程的影响，查明平均浓度、饱和度、比表面积、反应速率等间的量化关系，揭示相界面的分布和演化规律、相界面传质反应过程机制、组分浓度分布和变化规律、以及多个物理化学场作用下的物质/能量转化规律。本研究将为孔尺度研究多孔介质内传递过程提供新的有效手段，有助加深对多孔介质中耦合多相流传质反应过程机理的理解，为涉及这一基础科学问题的领域如CO2地质封存、燃料电池设计、常规非常规油气开采等提供理论支撑。

微细多孔介质中耦合多相流和传质反应过程普遍存在于能源、环境、化工等诸多领域，是相关学科的前沿课题。项目以CO2地质埋存和质子交换膜燃料电池为研究背景，研究多孔介质中耦合多相流-传质-反应过程这一基础科学问题。针对现有多孔介质多场耦合过程模型唯象、经验参数多等问题，基于介尺度格子Boltzmann方法（LBM），基于多孔介质实际结构，发展了考虑孔隙尺度多相流、传热、传质、反应及固体结构演变的孔隙尺度数值方法。研究了多孔介质中的CO2驱替盐水两相流动过程、CO2驱替油水两相的三相流动过程、CO2在盐水中的溶解过程，掌握了多组分浓度分布及变化规律，获得了平均浓度、反应速率、饱和度和相界面面积间的定量关系。研究了燃料电池膜电极（扩散层、微孔层和催化层）中输运过程。发展了新的孔尺度团聚块亚格子模型，孔尺度团聚块模型考虑了催化层复杂多成分微纳尺度结构，考虑了具有浓度跳跃、扩散系数差异大、局部非平衡溶解过程的跨相界面传质反应过程。该模型能够准确预测高电流下催化层内的传质阻力。基于新的孔尺度模型，研究了催化层孔隙率、电解液薄膜以及反应输运条件对电流密度的影响规律；提出了膜电极优化结构，协同调控了膜电极中多场输运过程，降低了贵重金属Pt载量。项目发表期刊论文19篇，其中SCI论文16篇。授权国家技术发明专利3项，软件著作权4项。项目负责人受邀请做国际会议邀请或主旨报告9次。项目培养硕士生两名。国际著名期刊《Progress in Energy and Combustion Science》（IF=29.4）邀请，撰写孔隙尺度复杂传递过程综述论文一篇。本研究研究成果为孔尺度研究多孔介质内传递过程提供新的有效手段，加深了对多孔介质中耦合多相流传质反应过程机理的理解，为涉及这一基础科学问题的领域如CO2地质封存、燃料电池设计等提供了理论支撑。