Study On Current Density Distribution Of PEMFC

The performance of a PEMFC (Proton Exchange Membrane Fuel Cell) depends on many interactive parameters. Measuring local current density in PEMFC is an important approach for detailed studies. In this paper, using completely segmented regions of PEMFC to different clamping pressure, oxidant, operation temperature, flow rate of air, gas humidity, investigate into the properties of segmented cells under shoulder and channel in the PEMFC. The main research contents and results are as follows:(1) The clamping pressure had different effect on segmented cells of the PEMFC. Using oxygen as oxidant, the properties of segmented cells under shoulder was better than segmented cells under channel. Within a certain range, increasing the clamping pressure reduces the resistance of segmented cells under shoulder that enhances the performances of segmented cells under shoulder. In contrast, increasing the clamping pressure beyond it, the current density of segmented cells under shoulder become was lower. In addition, clamping pressure had a negligible effect on the current density of segmented cells under channel.(2) The oxidant had different effect on segmented cells of the PEMFC. Using air as oxidant, the properties of segmented cells under shoulder were better than segmented cells under channel at low current density. However, the properties of segmented cells under channel were better than segmented cells under shoulder at high current density, being more apparently with current density increased. In addition, there was a point, where the property of segmented cell under channel was the same as the property of segmented cell under shoulder, and it gradually shift to lower current density along the flow filed from upstream to downstream. Using oxygen as oxidant, the properties of segmented cells under shoulder were better than segmented cells under channel, whatever the current density was low or high.(3) The operation temperature had different effect on segmented cells of the PEMFC. the properties of segmented cells were better with the operation temperature increased from 55℃to 65℃. The properties of segmented cells under shoulder become better and better along the flow filed, probable because of gradually accumulation of water under shoulder along the flow filed, while the properties of segmented cells under channel become lower and lower along the flow filed, probable because of gradually decreasing of oxygen concentration under channel along the flow filed. The properties of segmented cells decreased in outlet when the operation temperature was 70℃, probable because it was too high especially in outlet.(4) The flow rate of air had different effect on segmented cells of the PEMFC. Using air as oxidant, the properties of segmented cells under shoulder were lower than the properties of segmented cells under channel, especially at high current density. The properties of segmented cells improved with the flow rate of air increasing, especially of segmented cells under shoulder. The properties of segmented cells under channel gradually decreased along the flow filed from upstream to downstream, while the properties of segmented cells under shoulder were lower but more evenly.(5) The gas humidity had different effect on segmented cells of the PEMFC. With the reactant RH increased from 60% to 100%, the performance of PEMFC was gradually improved. Using air as oxidant, the properties of segmented cells under channel had a more significant improvement than the properties of segmented cells under shoulder with the reactant RH increased, because the properties of segmented cells under channel was mainly affected by the degree of wetting in membrane, while the properties of segmented cells under shoulder was mainly affected by the oxygen concentration.