Lattice Boltzmann simulation of liquid water transport inside and at interface of gas diffusion and micro-porous layers of PEM fuel cells

In this study, an optimized stochastic model is developed to reconstruct the realistic 3D microstructure of gas diffusion layer (GDL) and micro porous layer (MPL). With considering GDL and MPL microstructure simultaneously, a 3D lattice Boltzmann (LB) model is developed to study the role of MPL macro crack in liquid water transport and redistribution at GDL/MPL interface. The proposed model is validated with visualization experiment in literature, and then the effects of different Poly Tetra Fluoroethylene (PTFE) distributions and pressure differences are investigated. The results show that PTFE distribution under vacuum-drying is almost uniform inside GDL, and the continuous switching of wettability between carbon fiber and PTFE can accelerate the liquid water permeation. PTFE under air-drying will accumulate at one side of GDL and reduce the porosity in this region, and thus the larger pressure difference or longer time is needed for liquid water break-through. As the pressure difference increases, the retaining amount of liquid water inside the narrow pore is increased. Inserting of MPL only latches the liquid water in GDL region close to macro crack, which helps reduce the water flooding and improve the gas transport to active sites. (C) 2019 Elsevier Ltd. All rights reserved.