Study On Thermal Electrochemical Characteristics And Performance Optimization Of Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell(PEMFC)is a clean and efficient energy conversion device,which can convert the chemical energy in hydrogen and oxygen gas into electrical energy directly.It has the advantages of high power density,low working temperature,rapid start-up and no pollution.It is the most promising power conversion equipment in the 21 st century.However,the output performance,cost and service life of PEMFC have always been the main limitations to commercialization.Thus,overcoming the limitations has become the focus of researchers.In recent years,numerical simulation method has become one of the important means in the study because of its flexible controllabil ity and convenient micro mechanism analysis.In this work,based on numerical simulation method the output performance of proton exchange membrane fuel cell was studied carefully.Firstly,the influence of operating conditions,such as the working temperat ure,gas pressure and gas relative humidity,on the performance of fuel cell were studied.Then,aiming at the traditional "groove ridge" runner design,two runner schemes superior to the traditional design are proposed.The main work of this paper is as follows:In the first part,this paper establishes a one-dimensional two-phase PEMFC electrochemical thermal multi physical field coupling model,focuses on the influence of different gas working pressure,gas relative humidity and cell working temperature on the performance of the cell,and expounds the influence mechanism of micro material distribution on the macro performance curve,so as to clarify the relationship between operating conditions and cell performance,and provide ideas for the design of fuel cell flow field.In the second part,aiming at the defects of the traditional " channel-rib" channel design,that is,the uneven distribution of reaction gas in the catalytic layer caused by the solid rib ridge,this paper proposes to replace the solid ri b ridge with the porous rib ridge,and analyzes the effects of different height and porosity of the porous rib ridge on the cell performance and mass transfer under the rib.The results show that the channel scheme with porous rib ridge can effectively imp rove the mass transfer capacity under the rib ridge,and make the fuel cell performance of the porous rib ridge scheme higher than that of the traditional " channel-rib" channel scheme.In addition,under the working voltage of 0.4V,when the height and por osity of the pore rib ridge are 1mm and 0.8 respectively,the output performance of the fuel cell reaches the best,and the current density is 19.54% higher than that of the traditional "channel-rib" channel.In the third part,to further improve the output performance and mass transfer capacity of the fuel cell blockage with the same volume and height were added on the basis of the channel scheme with porous rib ridge.The effects of different combinations of different boss shapes on the output performance and mass transfer performance of PEMFC are analyzed.The results show that the cell performance of the channel scheme with bosses is the best among the designs mentioned in above.The performance of the fuel cell with boss channel scheme composed of diver sion upwind boss + obstruction boss + diversion leeward boss is the highest,Under the working voltage of 0.4V,the output performance of the cell with bosses is 4.30%higher than that of the channel scheme,and 24.40% higher than that of the traditional solid rib scheme.