Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode

Abstract—In this paper we model and experimentally verify the evolution of liquid water and nitrogen fronts along the length of the anode channel in a Proton Exchange Membrane Fuel Cell operating with a dead-ended anode that is fed by dry hydrogen. The accumulation of inert nitrogen and liquid water in the anode causes a voltage drop, which is recoverable by purging the anode. Experiments were designed to clarify the effect of N2 blanketing, water plugging of the channels, and flooding of the GDL. The observation of each phenomenon is facilitated by simultaneous gas chromatography measurements on samples extracted from the anode channel to measure the nitrogen content, and neutron imaging to measure the liquid water distribution. A model of the accumulation is presented which describes the dynamic evolution of a N2 blanketing front in the anode channel leading to the development of a hydrogen starved region. Prediction of the voltage drop between purge cycles during non-water plugging channel conditions is shown. The model is capable of describing both the two sloped behavior of the voltage decay, and the time at which the steeper slope begins by capturing the effect of H2 concentration loss, and the area of the H2 starved region along the anode channel.