Droplet Dynamics in a Proton Exchange Membrane Fuel Cell with Ejector-Based Recirculation

Effective water management plays a significant role in improving the performance and lifetime of proton exchange membrane fuel cells (PEMFCs). The ejector can take full advantage of the huge pressure potential between the high-pressure fuel tank and the PEMFCs to realize fuel gas recovery, and it is usually adopted for the auxiliary drainage of hydrogen/oxygen stacks. In this study, the dynamic behavior of liquid water droplets in the cathode flow channel of a PEMFC operating in ejector-based recirculation mode was numerically investigated. The effects of the operating current density of the fuel cell as well as the pore size of the water inlet boundary on the droplet behavior were studied, and the number of contact surfaces between the droplet and the flow channel were investigated. The results show that the speed of water removal from the flow channel with ejector-based recirculation can be increased by 37.5% when the fuel cell operates at 1.0 A cm(-2). Moreover, the hydrophobic side and top surfaces are more suitable for water slug removal when the PEMFC operates at a high current density, owing to the shorter drainage period. We herein provide recommendations for effectively enhancing the water management of a PEMFC with ejector-based gas recirculation.