Low stoichiometry operation of the anode side of a low-temperature proton exchange membrane fuel cell – A modeling study

A single-channel proton exchange membrane fuel cell model (anode side) based on computational fluid dynamics is used to investigate the possibility of operating a fuel cell at low stoichiometric flow ratios using completely dry inlet hydrogen. A case study of three different stoichiometric flow ratios (ξ = 1.01, ξ = 1.03, ξ = 1.05), three different operating temperatures (343.15 K, 347.15 K, 353.15 K), and three different operating pressures (1 atm, 1.2 atm and 1.5 atm) are presented. It is found that the predicted hydrogen concentration and relative humidity (RH) in the catalyst layer (CL) have opposite trends: the RH in CL decreases with increasing stoichiometric flow ratios, but it reaches 100% at the outlet. While hydrogen concentration in CL increases with increasing stoichiometric flow ratios and the largest difference is at the inlet, with a maximum of 3.6%. The results also suggest that PEM fuel cells may be operated in a stoichiometric flow ratio as low as ξ = 1.01 at the anode side. This cell operation would allow open-ended anode operation without a recirculation system, thus significantly reducing system complexity and cost. The CFD code is disclosed to provide a starting point for more complex model development.