Numerical study on the effect of microporous layer crack changes on water management in gas diffusion layer of proton exchange membrane fuel cell

The existence of the microporous layer (MPL) enhances the transport of reactive gas and liquid water in the gas diffusion layer (GDL), which is a crucial part of the proton exchange membrane fuel cell (PEMFC). However, it is still unclear how the shape and size of MPL surface cracks affect the transmission of liquid water in GDL. Therefore, a three-dimensional volume of fluid (VOF) model is developed to study the relationship between MPL crack and GDL liquid water transport. First, the random direction method is used to reconstruct the carbon fiber layer of GDL, which is in good agreement with the experimental data. Secondly, the morphological changes of MPL are analyzed, and two kinds of cracks with different topological shapes are proposed. The parameters of crack area, width and depth of the numerical model are designed according to the MPL porosity. Finally, the relationship between MPL crack variation and liquid water saturation/variation in GDL is investigated by numerical modeling. The results show that the shape, area, width and depth of MPL crack affect the water fraction in GDL. The impact of crack on the transfer path of liquid water in GDL is mainly in the early stage of water inflow. With the increase of water inflow, this impact is mainly related to the structure of GDL.