Study on two-phase transport and performance characterization in orientational structure proton exchange membrane fuel cells at high water content

Abstract

With advances in catalyst technology, the power of commercial fuel cells has generally enhanced, imposing higher demands on water management. Clarifying the gas-liquid flow and performance characteristics under high water content is critical for improving the dynamic stability and lifetime of the fuel cell. In this study, the evolutions of gas-liquid flow and the performance of fuel cells at high water content are investigated using water injection. Differences in gas-liquid distribution and performance between the orientational and straight channels under high water content are discussed. Results show that the liquid water distribution of the orientational channels is more uniform compared to straight channels. The orientational plate has a blocking effect on the liquid droplets, and droplets first fill the channel and then flow downstream. Water mist dissipates faster in the orientational channels after switching to high voltages due to increased gas velocity induced by the orientational plate. In the cathode, the liquid water mainly forms film flow because of the low oxygen velocity, and the droplets in the orientational channels enable rapid movement driven by the upstream droplet pushing forces. Anode water injection improves membrane wettability and cell performance, suggesting anode water injection potential as a humidification method. The orientational channel demonstrates superior water retention, with the highest performance improvement observed during upstream water injection and achieving up to 95 % net power improvement. However, cathode water injection may degrade performance due to water flooding.