Experimental Study On Performance Of An Open-cathode PEMFC Under Thermal Radiation

Proton exchange membrane fuel cell（PEMFC）,as an environment-friendly and efficient power generation device,has attracted much attention.The open-cathode PEMFC is easily affected by environmental conditions because of its unique structural design,whose oxidant and coolant required for stack reaction are supplied by the axial fans.Previous studies on the environmental adaptability of open-cathode PEMFC mostly focused on the effects of ambient temperature and relative humidity on the stack output performance.But the variation range of temperature and relative humidity was narrow.Furthermore,for the abnormal high-temperature environment,such as thermal radiation,the study on the stack performance has hardly been touched.Therefore,this paper carried out the experiments to focus the performance variation law and the optimization mode of anode inlet parameters of an open-cathode PEMFC stack with 10 single-cells under thermal radiation environment.Based on the performance parameters and test requirements of the experimental stack,a set of PEMFC measurement and control platform was established.The system scheme design,hardware equipment selection and host computer interface development of a 500W PEMFC measurement and control platform were finished.The platform had the functions of reaction gas supply and regulation,N₂ purging,stack water and thermal management,remote measurement and control,real-time data acquisition and storage and so on.Meanwhile,an interactive and friendly host computer interface was developed,which had the functions of system login,control and monitoring,real-time parameter curve display and alarm.It laid a foundation for the subsequent stack test of environmental adaptability and optimization of operating parameters.The variation laws of the open-cathode PEMFC stack characteristic parameters under thermal radiation environment were clarified.The effects of different thermal radiation intensities,fan voltages and load currents on stack output power,ambient air temperature and relative humidity,stack temperature and single cell voltage were analyzed.It was found that the thermal radiation was beneficial to improve the overall temperature of the stack to a certain extent.But the stack performance cannot be improved with the increase of its temperature.On the contrary,under the thermal radiation environment,the stack output power was degraded,and however the stack was able to run continuously.With the increase of radiation intensity,the stack performance was degraded more significantly,and higher load current and lower fan voltage led to excessive high internal temperature of the stack,and thus the output power was further reduced.In addition,the variation of characteristic parameters of the stack for high thermal radiation environment was also analyzed.The result demonstrated that when the load current was too high,and even if the fan voltage was set to the maximum value,the temperature of No.1 single cell soon exceeded limit operating temperature after the stack was exposed to the thermal radiation.Meanwhile,its voltage degraded to 0 m V quickly,and finally the stack stopped running.Based on output performance and temperature evolutions of stack under different thermal radiation environments,the effect of anode inlet parameters on the stack performance optimization under high radiation environment was further studied.The effects of different hydrogen supply modes on mitigating the stack performance degradation were analyzed,and the effects of hydrogen inlet flow rate,hydrogen pressure and relative humidity on the stack output power,mean temperature and single-cell voltage were discussed.The results showed that the increase in the hydrogen flow rate could reduce the rise of stack temperature,but it also led to serious dehydration of some single cells,so the degradation amplitude of output power was increased.The stack power degradation was relieved at low load current,and the duration of stack operation was prolonged at high load current before and after thermal radiation with the increase of hydrogen inlet pressure.In addition,hydrogen humidification significantly alleviated the stack output power degradation caused by high thermal radiation environment.Hydrogen humidification could effectively improve the water content of proton exchange membrane inside the stack,and therefore the voltage degradation of all single cells was alleviated and the stack adaptability to the thermal radiation environment was improved.