PEMFC气体扩散层气液两相跨尺度界面输运孔尺度机理研究

Water management plays a crucial role in maintaining the performance and durability of PEMFCs. Gas Diffusion Layer (GDL) is a key component in PEMFC in terms of improving the water management. Due to the special multi-layered structure and extreme variations in microstructure and characteristic scale between different components, the complex gas-liquid cross-scale interfacial dynamic behavior has a critical impact on the water management of PEMFCs. In this project, to reveal the underlying transport mechanism of interfacial liquid water transport, the two-phase cross-scale interfacial transport process in GDL and its influencing factors will be investigated by a pore-scale modeling which combine the two phase lattice Boltzmann method and the pore network model. Based on the reconstructed microstructure of the components and morphology of the interfaces between MPL and GDL/CL, a local interfacial regional pore-scale modeling based on two-phase lattice Boltzmann method will be established to reveal the fundamental water transport mechanism across the interfaces. According to the revealed underlying transport mechanism, a two-phase multilayered topologically equivalent pore network (TEPN) for the full-scale GDL will be established to investigate the structural parameters and the interfacial effect on two-phase transport behavior and to study the impacts of two-phase cross-scale interfacial transport on electrode flooding. Along with the accomplishing of this project, it is expected to provide theoretical basis and technical support for improving water management, design and optimization for interface morphology and microstructure of electrode.

水管理是影响PEMFC性能和寿命的关键技术。气体扩散层在水管理中扮演着重要角色，不同分区间界面两侧特征尺度及微结构的巨大差异使得界面区域气液两相输运表现为跨尺度界面输运，并对水管理产生重要影响。项目拟从介观孔尺度出发，发展结合LBM与孔隙网络模型各自方法优势的气液两相跨尺度界面输运模型。在对GDL微结构及界面形貌特征进行准确描述的基础上，构建GDL局部界面区域（CL|MPL、MPL|CPL）气液两相传输的LBM孔尺度模型，揭示气液两相跨尺度界面传输的物理机理。然后，基于LBM模型揭示的物理机制，构建GDL全厚度尺寸上考虑了跨尺度界面传输机制的气液两相拓扑等价孔网络模型，揭示GDL结构参数以及界面效应（界面两侧特征尺度及微结构的巨大差异）对两相传输的影响规律，探寻界面传输对GDL全局内两相输运的影响。项目成果将为优化界面形貌，改善两相界面输运，提高水管理和电池性能提供重要的理论指导。

质子交换膜燃料电池水管理对燃料电池的性能和寿命有重要的影响，气体扩散层是氧气和液态水传输的重要场所，其内部的跨尺度界面传输对水管理性能产生十分重要的影响。本项目以孔隙模型为工具，探索了气体扩撒层内微观结构信息对传输特性的影响机制。建立气体扩散层的规则孔隙网络模型研究了梯度化微孔层内的传输特性，从孔隙尺寸角度揭示了孔隙率梯度化的作用机制，并对孔隙率梯度化微孔层的相关参数进行了系统的研究。另外，建立混合润湿气体扩散层的规则孔隙网络系统研究了亲水程度、润湿性分布以及孔尺寸分布对液态水和氧气传输性能的影响。除此，气体扩散层内的局部大孔设计对性能的影响也被探究，考虑了微孔层的裂缝以及基质层的沟槽。采用随机算法重建了气体扩撒层的微观结构，并利用最大球算法提取了拓扑空间等价孔隙网络模型,探索了纤维结构参数对两相传输性能的影响。研究结果为设计具有高级水管理能力的气体扩散层提供了理论指导。