Experimental and simulation analysis of liquid capillary fingering process in the gas diffusion layer

In a proton exchange membrane fuel cell (PEMFC), water movement through the gas diffusion layer (GDL) is essential for water management. Using a combination of experiments and simulations, this paper investigates the capillary fingering process of liquid water within the GDL and analyzes the effects of flow field type, GDL compression ratio, and contact angle on the capillary fingering of liquid water within the GDL. The results reveal finger-stopping, splitting, and fusion during the injection of non-wetting liquid, which is not conducive to rapid water movement within the GDL. When water breaks through the top layer of the fibers, a finger path between the inlet and the gas channel is formed, and the liquid preferentially migrates along this path. Due to the existence of air cross-flow, the GDL water saturation for the serpentine/cross-finger flow field is 17.2%. The water preferentially produces directional flow in the through-plane direction as the compression ratio rises, and the GDL water saturation falls to 24.18%. The distribution of anisotropic contact angles determines the flow state of liquid water, making water removal from the GDL easier. The results and findings here are expected to lead to more reliable water management and related high-power technologies of PEMFCs.