Investigation of droplet dynamic in PEMFCs gas diffusion layer and gas channel with Micro-CT and lattice Boltzmann method

This study reconstructed the 3D structure of the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) using micro-CT technology and analyzed the droplet dynamics within the GDL and gas channel (GC) using the lattice Boltzmann method (LBM). A predictive model for droplet detachment at the GDL-GC interface was developed and its applicability under varying gas velocities and GDL wettability conditions was analyzed. Results indicate that, compared to single-scale GC spaces without GDL, significant differences exist in the droplet detachment trajectories and liquid bridge rupture points within the multi-scale GDL-GC spaces. Increased gas velocity and intrinsic contact angle within the GDL reduce the volume of detaching droplets and heighten detachment frequency. Optimal liquid water removal occurred at intrinsic contact angles between 120 degrees 140 degrees. Angles below this range impede droplet detachment in the GC, while angles above it result in water accumulation within the GDL. In the predictive model, the critical detachment force, generated by the liquid bridge connection, forms an angle with the gas flow, with its characteristic length defined by the minimum diameter at the bridge's necking.