Synergistic effects of bionic water-droplet flow field and surface wettability on liquid-water transport mechanisms

Flow-field structure optimization is one of the important ways to enhance reactant gas transport, improve water management, and increase the output performance of proton exchange membrane fuel cells (PEMFCs). This work suggests a serpentine bionic water-droplet flow field based on the traditional serpentine flow field. Initially, the output performance of the serpentine flow field and the serpentine bionic water-droplet flow field were numerically simulated. The findings demonstrate that the net power density of the serpentine bionic water-droplet flow field is 8.2% higher than that of the serpentine flow field when the maximum height is 0.65 mm and the period number is 8. Second, a gas–liquid two-phase flow model was established based on the VOF method to further investigate the effects of different GDL surface wettability and wettability-gradient combinations on liquid-water transport behavior and distribution characteristics in each channel. The results indicate that, under conventional wettability conditions, the average liquid-water volume fraction in the serpentine bionic water-droplet flow field is lower than that in the serpentine flow field. In particular, when the GDL surface contact angle is 120°, the liquid-water volume fraction is reduced by 28%, effectively alleviating flooding. The spatial configuration of the contact-angle gradient has a significant effect on liquid-water coverage, among which the forward transverse wettability gradient is more suitable for the serpentine bionic water-droplet flow field, reducing the water coverage by 13.8%. Meanwhile, the average liquid-water volume fraction is reduced by 26% compared with that of the serpentine flow field under the forward transverse wettability gradient.