Numerical analysis of the impact of non-uniform gas diffusion layer deformation on the performance of proton exchange membrane fuel cells

Abstract

Proton exchange membrane fuel cells (PEMFCs) typically require assembly under specific conditions to ensure good air-tightness, mass transfer, and electrical conductivity. However, the stress and strain produced on cell components due to assembly pressure can affect the performance and lifespan of the cells. To thoroughly investigate the effects of assembly mechanics on the transport processes and output performance of the cells, this study employed the finite element method (FEM) through the ANSYS static structural module to analyze the deformation of the gas diffusion layer (GDL) and its material property changes under pressures ranging from 0.0 to 2.5 MPa. The adjustment of material properties following non-uniform deformation of the GDL was implemented using UDFs (User-Defined Functions) in FLUENT. A three-dimensional two-phase flow computational fluid dynamics (CFD) model of the PEMFC was established, and the transport processes and output performance of a single PEMFC under different assembly pressures were simulated based on the variable material properties UDFs. The results indicate that the optimal assembly pressure for the PEMFC lies between 1.0 and 2.0 MPa. At low voltages of 0.3 to 0.4 V, the cell exhibits better performance under assembly pressures of 1.0 to 1.5 MPa; at voltages of 0.5 to 0.7 V, better performance is achieved under pressures of 1.0 to 2.0 MPa. Finally, the impacts of different operating temperatures, gas relative humidity levels, and gas stoichiometric ratios on the cell performance for an optimal pressure of 1.5 MPa were analyzed. The results show that the cell performs best at a temperature of 353.15 K, with an anode relative humidity of 80% and a cathode relative humidity of 100%, and with an anode stoichiometric ratio of 2 and a cathode stoichiometric ratio of 3. These findings provide a theoretical basis for the assembly and high-performance operation of fuel cells.