Modeling and Simulations of Polymer Electrolyte Membrane Fuel Cells With Poroelastic Approach for Coupled Liquid Water Transport and Deformation in the Membrane

Performance degradation and durability of polymer electrolyte membrane (PEM) fuel cells depend strongly on transport and deformation characteristics of their components especially the polymer membrane. Physical properties of membranes, such as ionic conductivity and Young's modulus, depend on the water content that varies significantly with operating conditions and during transients. Recent studies indicate that cyclic transients may induce hygrothermal fatigue that leads to the ultimate failure of the membrane shortening its lifetime and, thus, hindering the reliable use of PEM fuel cells for automotive applications. In this work, we present two-dimensional simulations and analysis of coupled deformation and transport in PEM fuel cells to improve the understanding of membrane deformation under steady-state and transient conditions. A two-dimensional cross section of anode and cathode gas diffusion layers, and the membrane sandwiched between them is modeled using Maxwell-Stefan equations for species transport in gas diffusion layers, Biot's poroelasticity, Darcy's law for deformation and water transport in the membrane, and Ohm's law for ionic currents in the membrane and electric currents in the gas diffusion layers. Steady-state deformation and transport of water in the membrane, transient responses to step changes in load, and relative humidity of the anode and cathode are obtained from simulation experiments, which are conducted by means of a commercial finite-element package, COMSOL MULTIPHYSICS.