Experimental and numerical study on the two-phase flow inside a cracked gas diffusion layer of PEMFC

Abstract

The presence of cracks in the gas diffusion layer (GDL) can have a significant impact on the flow of two phases within Proton Exchange Membrane Fuel Cells (PEMFCs). This study focuses on investigating the transport process of two-phases flow in a GDL sample using both experimental and numerical methods. The porous structure of a hydrophobic carbon paper, serving as the macro-porous substrate (MPS) of the GDL, is examined using synchrotron radiation X-ray phase contrast Computed Tomography (CT). A 3-D model with various crack geometries is then created, and a Lattice Boltzmann Method (LBM) simulation is employed to analyze the flow behavior within the GDL model. The findings reveal that the water intrusion mode in the MPS primarily depends on its hydrophobic nature, but the width and depth of the cracks also significantly influence both the rate and path of water intrusion. Increasing the crack width from 7 μm to 28 μm results in a 30% increment in water intrusion rate, while the intrusion path remains unchanged. However, when the crack width reaches 42 μm, the crack itself becomes the primary path for water intrusion, doubling the intrusion rate. Furthermore, an increase in crack depth leads to a higher invasion rate of the liquid phase, consequently increasing the liquid storage volume within the GDL. This research provides a novel approach for analyzing cracked GDLs and demonstrates the potential to optimize the water management process of PEMFCs through GDL microstructure design.