Visualization study of improving anode water management by variable pressure hydrogen supply in proton exchange membrane fuel cell

Abstract

To alleviate the prolonged closure of anodic outlet, which causes water to gradually accumulate in the porous layers that hinder hydrogen transfer in dead-ended anode mode. This study proposes an anode variable-pressure hydrogen supply strategy. The hydrogen supply pressure is suddenly reduced for a period before triggering purging, creating a pressure difference between the membrane assembly electrode and flow channels to induce water discharging into the flow channels, then directly purging out of the cell. Optical visualization is utilized to observe and analyze the effect of this strategy on water distribution and quantified through voltage, power, purging pressure change, and water coverage rate. Experiments indicate that the sudden pressure change in the variable pressure hydrogen supply mode effectively promotes water discharge from the porous layers, provides higher water coverage within the entire flow field, and promotes the fusion of neighboring droplets to form larger ones for better water management. Compared to normal mode, the proposed strategy achieves 3.4% performance improvement at 0.32A/cm2. Furthermore, a higher abrupt pressure difference favors porous layers drainage, but the optimal low-pressure duration requires a trade-off between drainage facilitating hydrogen transport and recovery of the membrane water content.