Study on the Influence of GDL Porosity Distribution Variation on PEMFC Performance Under Assembly Pressure

The porosity of the gas diffusion layer (GDL) significantly impacts the performance of proton exchange membrane fuel cells (PEMFCs). Assembly pressure in PEMFCs leads to GDL deformation and alterations in porosity distribution. This study integrated a three-dimensional (3D) GDL deformation model with a 3D two-phase PEMFC model, employing a four-term Fourier series model to optimize the fitting of the GDL porosity distribution curve. The approach quantitatively assessed the impact of GDL porosity distribution under assembly pressure on PEMFC performance. Results reveal an arched porosity distribution in GDL, peaking in the middle of low channels adjacent to ribs. High porosity enhances oxygen and heat conduction but excessive porosity may cause uneven current density distribution, hindering GDL drainage. Furthermore, the analysis compares performances at various GDL compression ratios and thicknesses, showing an initial rise then fall in current density with increasing pressure. This represents a trade-off between the adverse impact of GDL compression on mass transfer losses and the favorable impact of reduced ohmic losses. At the optimal pressure, the current density is 3% higher than neighboring values at the same potential, and within the optimal GDL thickness range, the current density error remains below 1%.