Abstract:

The flow channel structure of a proton-exchange membrane fuel cell (PEMFC) has an important influence on the reaction gas flow, heat exchange, and electrochemical reactions. Common flow channels are concentrated in serpentine, interdigital, point-shaped, wavy, parallel, and related improved channels. However, their gas uniformity, water management, and output performance require improvement. Inspired by the Koch snowflake in the field of mathematical geometry, a new channel structure is proposed, i.e., taking the center of the circle as the center to radiate around. Based on six main channels, different levels of branch channels are added in turn to form 30 channel outlets. A three-dimensional steady-state unidirectional isothermal fuel-cell model was developed. Under an operating temperature of 60 ℃ and inlet relative humidity of 100%, a fuel cell testing platform was built for the experiments and simulated using ANSYS Fluent 2020. The model simulation results were consistent with the experimental results, thereby verifying the effectiveness of the model. The simulation results of the new channel and the traditional serpentine channel were compared, and the current density of the membrane electrode, oxygen mass distribution in the channel, water mass distribution at the interface between the channel and gas diffusion layer, membrane water content, and channel pressure were analyzed. The results showed that, compared with the serpentine channel, the new channel has a lower inlet and outlet pressure difference and slower flow rate but has advantages such as a more uniform distribution of reaction gas, better water management effect, and higher membrane current density and output power. The peak current density increased by 9.60%, and the peak power density increased by 12.70%, which is expected to provide new ideas for the innovation of fuel cell flow channel structure.

Key words: proton exchange membrane fuel cell, koch snowflake, new flow channel, numerical simulation