Multiphysics Numerical Simulation And Cold Start Preheating Analysis Of Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell(PEMFC)with the characteristics of high power generation efficiency,large specific power,low working temperature and no pollution has gradually been a focus field worldwide.Research on PEMFC has always related to its performance,life expectancy and costs currently.The gas-liquid two-phase flow inside the fuel cell serves an important factor that affects the performance of the fuel cell.The mathematical model of multiphase,multi-dimensional and multi-physics of PEMFC single channel is developed to study the flow of the fluid in the fuel cell,the diffusion of the species in the microstructure of the porous electrode,the electrochemical reaction and the transmission mechanism of water phase change.The effect of operating parameters on the performance of fuel cell was analyzed and changing the geometry of flow field plate could optimize the fuel cell.Secondly,the existing forms of water in the PEMFC under different environments were explored.The removal of residual liquid water was discussed after the shutdown of the proton exchange membrane fuel cell at low temperature.Finally,theoretical analysis and numerical simulation is provided to assist cold start of the PEMFC in low temperature environment.The specific research results are as follows:(1)The numerical simulation of three-dimensional PEMFC is provided to analyze the effect of the humidity of reaction gas,operating pressure,operating temperature and other parameters on the performance of the fuel cell.The results of numerical simulation show that:Increasing the anode gas relative humidity can decrease the proton transfer resistance;When the operating temperature is lower than the critical temperature,increasing the operating temperature increases the catalyst activity and decreases the liquid water saturation in the cathode side Increasing the operating pressure can improve the rate of diffusion of reactant gases.Meanwhile,it can reduce the phase change of the water vapor.(2)The internal residual water needs to be purged after shutdown in low temperature for PEMFC to prevent residual liquid water phase change ice doing harm to the fuel cell structure or the next start failed.The fuel cell is purged by dry nitrogen for that the water content in PEMFC is between 3 and 5.It is the prerequisite for the successful start in the next time.(3)The use of liquid water and nitrogen circulation assisted pre-heating cold start can significantly decrease preheating time of fuel cell in order to avoid that the starting failure can do damage to the components of fuel cell when the PEMFC is started in low temperature.The preheating time of the fuel cell is 8.55 seconds whose cathode and anode adopts a countercurrent mode when the temperature of the fuel cell and the preheating fluid is at-30? and 30?,respectively.