Abstract:

In order to improve the transport characteristics of liquid water inside a proton exchange membrane fuel cell (PEMFC), the surface structure characteristics of the gas diffusion layer (GDL) were obtained by white light interferometry and the seated drop method, and the influence of the surface structure of the diffusion layer inside the baffle-type flow channel on the flow characteristics of the droplets was investigated by the volume-of-fluid (VOF) method. The results show that, regardless of whether the surface structure of GDL is considered or not, the hydrophobicity of the surface is significantly enhanced with the increase of polytetrafluoroethylene (PTFE) content in GDL, which leads to the shortening of the outflow time of droplets in the baffle-type runner, the reduction of the spreading area of the droplets, and the corresponding reduction of the pressure drop in the runner. And compared with the smooth GDL surface, the irregular structure and pore characteristics of the actual rough GDL surface significantly enhance the droplet adhesion, resulting in a longer flow time of the droplets on the rough surface, the spreading area increasing, and the pressure drop in the flow channel increasing. When the PTFE mass percentage content is 40%, the droplet flow time on the actual rough GDL surface is shortened by 28.57%, the pressure drop in the flow channel is reduced by 16.32%, and the spreading area of the droplets showes a tendency to decrease.

Key words: proton exchange membrane fuel cells (PEMFC), surface structure of gas diffusion layer, baffle flow channel, droplet flow characteristics