Numerical study of inhomogeneous deformation of gas diffusion layers on proton exchange membrane fuel cells performance

Gas diffusion layers play a critical role in the operation of proton exchange membrane fuel cells. As the most compressible component in proton exchange membrane fuel cells, the non-uniform deformation mainly occurs on the interface between bipolar plates and gas diffusion layers caused by the special channel-rib geometry of the flow field, which results in a non-uniform variation of physical properties of gas diffusion layers, such as porosity, effective electrical conductivity, and gas diffusivity, consequently affects the cell performance. In this paper, a two-dimensional, across-the-channel, multi-physics and two-phase flow model based on the spherical agglomerate assumption is developed to investigate the complicated relationships between the non-uniform deformation and variation of physical properties of the gas diffusion layers, as well as the cell performance. A modified diffusion coefficient is introduced to describe the effect of the variation of species concentration on the effective diffusion coefficient based on the Bruggeman formula. Simulation results show that an optimal cell performance can be achieved by balancing the variation of porosity, effective electrical conductivity, and effective gas diffusion coefficient with respect to different degrees of deformation of gas diffusion layers.