MODELING THE EFFECTS OF GAS CHANNEL FLOODING ON THE VOLTAGE-CURRENT CHARACTERISTICS OF PEM FUEL CELL

摘要

It has been reported recently that water flooding in the gas channel (GC) has significant effects on the voltage-current characteristics of a proton exchange membrane (PEM) fuel cell. However, the theoretical treatment of these effects on the fuel cell performance is still preliminary. A one-dimensional fuel cell model including the effects of two-phase flow in the GC is proposed to investigate the influences of inlet conditions on the water distribution in fuel cell and its performance by means of coupling the GC and membrane electrode assembly (MEA) modeling domains. The model predicts that the GC conditions, which are closely correlated to the inlet conditions, significantly affect the liquid water saturation level in the MEA. An increase in the inlet air pressure or humidification level leads to more severe water flooding, while an increase in the inlet airflow rate helps mitigating the water flooding. The simulated voltage-current characteristics under various inlet conditions are verified against experimental data and simulation results of a published computational fluids dynamics (CFD) model. They indicate that the relative humidity and stoichiometry of inlet air are crucial to the fuel cell performance, particularly at high current densities, due to their influences on the liquid water distribution in the fuel cell. The correlations between the inlet conditions and the fuel cell performance are addressed in the proposed model through a more accurate treatment of two-phase water transport in the cathodic MEA and GC. These are important for appropriate water management in fuel cells.