3D lattice Boltzmann modeling of droplet motion in PEM fuel cell channel with realistic GDL microstructure and fluid properties
A 3D multi-component multi-phase lattice Boltzmann model is developed to study the droplet motion in the flow channel of proton exchange membrane fuel cell. The model is capable of reaching realistic density and viscosity ratio, tunable surface tension with low spurious velocity and is also validated by various benchmark tests in both static and dynamic states. For the first time, the effect of realistic microstructure of gas diffusion layer (GDL) on droplet dynamic behavior is comprehensively studied in terms of comparison with smooth channel, contact angle and droplet size with the motion processes clearly illustrated. The simulation results show the GDL microstructure can amplify the material wettability, affect the motion direction and impede the droplet motion. More hydrophobic GDL can effectively accelerate the transport. However, it is observed the droplet may reach the sidewall due to the presence of GDL and the motion is therefore severely impeded regardless of the GDL contact angle or droplet size, which is hard to avoid but deadly for the water management. For this problem, a novel water management strategy is proposed and the results show the hydrophilic side & top wall can effectively remove the liquid water from the GDL surface, decrease pressure drop and prevent reactant maldistribution.