Hydrogen And Oxygen Mixed Gas Catalytic Combustion For EA Safety Effect Based On FLIR Image

Proton Exchange Membrane Fuel Cell(PEMFC) as a zero pollution high energy-efficient electric source has a wide range of application in the future. While in actual fuel system researching, we find that when starting up or shutting down the fuel cell system,hydrogen-oxygen interface will exist. Meanwhile membrane electrode assembly (MEA) local defects and system failure may make hydrogen,oxygen mixed gas directly contact with MEA. In these cases besides electrochemical problem,the simple catalytic combustion occurs too.These may affect MEA security issues and electrical performance,especially for the cell using hydrogen and oxygen as its fuels.Based on infrared imaging technology, by simulating the starting and shutting process of fuel cell stack, MEA local defects, system failure as a result of hydrogen and oxygen mixed gas directly contact with MEA. The paper explores the impact of catalytic combustion under certain conditions on MEA temperature changes and fuel cell performance.The results were as follows:(1)Catalytic combustion occurred at hydrogen-oxygen interface of PEM fuel cell during startup and shutdown.(2)Catalytic combustion occurred on the hydrogen-oxygen interface with the edge of the diffusion and expansion of the reaction gas, which led to an increase in MEA temperature. Temperature increased by the amount of incorporation of the reactive gas. Under the same conditions, temperature raise at shutdown compared with startup the former one was higher than the latter one.(3)As the hydrogen flow increased from20ml/min to120ml/min, catalytic combustion front expansion accelerated, only little change in temperature MEA at about8.5℃.fuel temperature increased from room temperature to60℃, MEA temperature increased.Hydrogen humidity increased from100%to40%, MEA temperature increased.Local typical defects of MEA including membrane pinholes, cracks and off the diffusion layer, some failure occurs in the system may make a relatively large amount of hydrogen and air mix.MEA and the catalytic combustion experimental study were carried out.The results were as follows:(l)Partial loss of diffusion layer made catalyst layer direct contact with air and hydrogen. Temperature raised about8-10℃helping to catalytic combustion, but the effect was not very obvious.(2)When MEA had a pinhole, hydrogen leaked directly to the other side, to create a continuous catalytic combustion, temperature raise to about70℃, by the MEA V-I performance test and C-V test, the high catalytic combustion temperature changed active area and microstructure of the catalyst layer, it will not only affect the performance, but also affect its safety.(3)The reaction of the hydrogen mixed with air or oxygen when direct contact with MEA, were very easy to produce high temperature, specially reaction with air, the temperature accumulated to395℃extremely easy to produced high temperature, to achieve carbon ignition point, direct reaction with oxygen produce fire burning, changing the active area and microstructure of the catalyst layer, not only seriously affecting fuel cell safety, but also affect fuel cell performance.Under normal conditions, catalytic combustion reaction on hydrogen-oxygen interface will make MEA temperature rise, it will not immediately affect its safety and performance. However, defects of MEA and the system failure, in some cases, will not only seriously affect the safety of the fuel cell, but also affect the fuel cell performance.