Liquid water within the cathode Gas Diffusion Layer (GDL) and Gas Channel (GC) of Proton Exchange Membrane Fuel Cells (PEMFCs) is strongly coupled to gas transport properties, thereby affecting the electrochemical conversion rates. In this study, the GDL and GC regions are utilized as the simulation domain, which differs from previous studies that only focused on any one of them. A Volume of Fluid (VOF) method is adopted to numerically investigate the two-phase flow (gas and liquid) behavior, e.g., water transport pattern evolution, water coverage ratio as well as local and total water saturation. To obtain GDL geometries, an in-house geometry-based method is developed for GDL reconstruction. Furthermore, to study the effect of GDL carbon fiber diameter, the same procedure is used to reconstruct three GDL structures by varying the carbon fiber diameter but keeping the porosity and geometric dimensions constant. The wall wettability is introduced with static contact angles at carbon fiber surfaces and channel walls. The results show that the GDL fiber microstructure has a significant impact on the two-phase flow patterns in the cathode field. Different stages of two-phase flow pattern evolution in both cathode domains are observed. The liquid water in the GDL experiences water invasion, spreading, and rising, followed by the droplet breakthrough in the GDL/GC interface. In the GC, the water droplets randomly experience accumulation, combination, attachment, and detachment. Due to the difference in surface wettability, the water coverage of the GDL/GC interface is smaller than that of the channel side and top walls. It is also found that the water saturation inside the GDL stabilizes after the water breakthrough, while local water saturation at the interface keeps irregular oscillations. Last but not the least, a water saturation balance requirement between the GDL and GC is observed. In terms of varying fiber diameter, a larger fiber diameter would result in less water saturation in the GDL but more water in the GC, in addition to faster water movement throughout the total domain.

质子交换膜燃料电池 (PEMFC) 的阴极气体扩散层 (GDL) 和气体通道 (GC) 内的液态水与气体传输特性密切相关，从而影响电化学转化率。在这项研究中，GDL 和 GC 区域被用作模拟域，这不同于以前的研究只关注其中任何一个。采用流体体积 (VOF) 方法对两相流（气体和液体）行为进行数值研究，例如水传输模式演变、水覆盖率以及局部和总水饱和度。为了获得 GDL 几何形状，开发了一种内部基于几何形状的方法用于 GDL 重建。此外，为了研究 GDL 碳纤维直径的影响，通过改变碳纤维直径但保持孔隙率和几何尺寸不变，使用相同的程序重建三个 GDL 结构。壁润湿性通过碳纤维表面和通道壁处的静态接触角引入。结果表明，GDL 纤维微观结构对阴极场中的两相流模式具有显着影响。观察到两个阴极域中两相流模式演化的不同阶段。GDL中的液态水经历水侵、扩散和上升，随后在GDL/GC界面发生液滴突破。在气相色谱中，水滴随机经历积累、结合、附着和脱离。由于表面润湿性的不同，GDL/GC界面的水覆盖小于通道侧壁和顶壁。还发现GDL内部水饱和度在见水后趋于稳定，而界面局部水饱和度保持不规则振荡。最后但并非最不重要的是，观察到 GDL 和 GC 之间的水饱和度平衡要求。就不同的纤维直径而言，较大的纤维直径会导致 GDL 中的水饱和度较低，但 GC 中的水较多，此外整个区域的水运动速度更快。观察到 GDL 和 GC 之间的水饱和度平衡要求。就不同的纤维直径而言，较大的纤维直径会导致 GDL 中的水饱和度较低，但 GC 中的水较多，此外整个区域的水运动速度更快。观察到 GDL 和 GC 之间的水饱和度平衡要求。就不同的纤维直径而言，较大的纤维直径会导致 GDL 中的水饱和度较低，但 GC 中的水较多，此外整个区域的水运动速度更快。