Research On Transient Performance Of PEM Fuel Cell

The transient behavior of PEMFC (polymer electrolyte membrane fuel cell) is studied in this paper. Experimental and numerical simulation methods are combined to describe the inner mass transfer of PEMFC with corresponding experimental results. The steady state of PEMFC is studied. The O₂ diffusion velocity is main symbol of cathode catalyst layer and GDL's (gas diffusion layer) mass transfer capability. Liquid water is firstly appeared under the channel ridge, and do not influence the gas mass transfer and battery's output. The liquid water may accumulate under the channel groove, and influence the gas mass transfer and battery's output by the change of voltage and relative humidity. When the saturation of GDL (gas diffusion layer) under channel groove is very large, ,the output of the PEMFC will badly drops. The transient perforrn of PFMFC is studied and the numerical model used in this study is considered to be capable of describing the PEMFC's transient behavior. The response time of PEMFC can be divided into two parts: the response time of mass transfer and the response time of liquid water balance. The response time of mass transfer is between one or two seconds, while the response time of liquid water balance is between several minutes or hours. In this study, the influence of cathode relative humidity and temperature to PEMFC is considered salience. The PEMFC's response characteristic can be improve by changing operation condition. At 60℃or 70% to 90% relative humidity, the water content in polymer electrolyte membrane is higher. The influnceof liquid water on mass transfer is not salience, and the PEMFC's output current density is 1.4 times of steady state's. The water content of polymer electrolyte membrane and the PEMFC's output current density are lower by the rise of temperature and the decline of relative humidity, At 90℃or 10% relative humidity, the current density in transient state is 0.5 to 0.8 time of steady state's.