Study On Cold Start Performance Of Proton Exchange Membrane Fuel Cell At Low Temperature

Proton exchange membrane fuel cells has the characteristics of high efficiency,cleanliness,and sustainability at normal temperature environment.Therefore,from as small as electronic product to as large as aerospace equipment all are appeared in fuel cells.However,when a device using a proton exchange membrane fuel cell as a power source operates in a low temperature(<0?)environment,the battery will have a series of problems such as difficulty in starting,output degradation and life reduction.These problems will hinder the market application of proton exchange membrane fuel cells.Therefore,low temperature cold start has become a frontier in fuel cell research.Based on the serpentine flow field with good output performance under normal temperature conditions,this thesis studies the effects of changing fuel cell operating parameters on the cold start-up performance of the battery at different ambient temperatures by combining model analysis,numerical simulation and experiment.The main work of this paper is as follows:(1)By analyzing the shape of water inside the flow channel of PEMFC under normal temperature environment,the flow diffusion of water and the effect of liquid phase transformation on the mass transfer in the battery under low temperature environment,it can be concluded: when the internal temperature of the battery is lower than the freezing point,the water remaining in the catalytic layer and the gas diffusion layer is condensed,resulting in a decrease in the activation area of the catalytic layer and a decrease in battery starting performance.(2)Establish a three-dimensional,multi-phase PEMFC cold start mathematical model.Numerical simulation of current density distribution,pressure drop distribution,hydrothermal distribution and polarization curve of fuel cells in low temperature environment using fluid simulation software.By analyzing the influence of ambient temperature,battery starting voltage and fuel gas stoichiometry on the cold start performance of the battery: The lower the ambient temperature,the greater the temperature gradient on the catalytic layer and the higher the water content near the inlet of the proton exchange membrane.When the battery is started at a constant voltage of 0.5V,the current density distribution on the proton exchange membrane is more uniform.When the anode side fuel gas stoichiometric ratio is increased at different ambient temperatures,the battery output current density increases when the battery is stable,and the battery has a good cold start performance.However,as the temperature decreases,the stoichiometric ratio of the fuel gas increases and the output performance of the battery decreases.(3)Select suitable materials and component assembly proton exchange membrane fuel cells according to PEMFC working conditions.Establish PEMFC low temperature start test platform and perform cold start performance test according to experimental requirements.Experiments verify the change of output current density,voltage and polarization curve of the battery under different ambient temperatures,and analyzed the output characteristics of the battery after the battery cycle cold start.The lower the ambient temperature,the lower the starting temperature of the battery with a constant voltage of 0.5V and the stoichiometric ratio of the fuel gas to 3.5,which is beneficial to the cold start of the battery.Verify the accuracy of numerical simulation results through experiments and provide strategies for low-temperature startup of fuel cells.