It is important to elucidate the transient characteristics of polymer electrolyte membrane fuel cell (PEMFC), because it may be operated at a wide range of loads, and may have frequent starts and stops. In these unsteady conditions, the water management problem such as the flooding in cell and the drying of proton exchange membrane (PEM) tends to occur and degrades the performance of PEMFC. Based on these issues, a two dimensional, two-phase and transient numerical simulator for unit-PEMFC has been developed to study the transient characteristics of PEMFC. As for the gas/ liquid two-phase flow formulation in GDL. multiphase mixture model have been employed. In this study, we derived four time constants, which characterize the transient response of PEMFC. In addition, we numerically simulated the transient response of PEMFC to step-wise change of load current from 0.5 to 1.0 A/cm2 and succeeded to explain the transient response of cell voltage ( Vcell) by the four time constants. The results show that, just after the change of current, Vcell decreases by IR resistance in a moment, and then decreases in 10-1 s time-scale by the re-distribution of oxygen gas and by the charge of electric double layer capacitor. Then Vcell increases slightly in 101 s time-scale by wetting of PEM. Finally, V cell decreases again in 102 s time-scale by the development of liquid saturation in GDL.
|Number of pages
|Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
|Published - Mar 2007
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanical Engineering