| Proton Exchange Membrane Fuel Cell(PEMFC)can break through the limitations of the Carnot cycle and directly convert chemical energy into electrical energy as a new type of energy conversion device.PEMFC has been regarded as the future mobile power source,and has attracted the attention of many scholars,due to its high efficiency,zero pollution and other advantages.However,there is still a lot of work to be done before the large-scale application of PEMFC,such as further improving its output performance.Aiming at the problem of low fuel cell output performance,this paper studies the influence of operating temperature,working pressure,humidity,and proton exchange membrane(PEM)thickness on fuel cell output performance.And the steady-state single-channel fuel cell model is established to reveal the distribution characteristics of various physical quantities inside the fuel cell under different operating conditions,and to explore the influence of different operating conditions on the current density and water content distribution on the PEM.The main contents are as follows:First,the types and working principles of PEMFC are described,the net output voltage is analyzed,and the research progress on battery output performance is summarized in recent years.And based on fuel cell dynamics,thermodynamics and flow field analysis theories,a three-dimensional steady-state calculation model of a single flow channel is established,in which the physical parameters and boundary conditions are set.Then numerical calculations are performed in COMSOL to simulate the secondary current distribution,the transfer of concentrated materials,the flow of porous media,and the heat transfer process of solids.The polarization curve of PEMFC under different operating conditions is calculated,and the distribution cloud diagram of hydrogen,oxygen,water content and current density in the steady state of battery operation is obtained.Finally,the simulated results are compared and analyzed,that is,under the same conditions and geometric parameters,the polarization curve is calculated under the condition that one of the four variables of the fuel cell’s operating temperature,pressure,humidity and proton exchange membrane thickness is changed in sequence.And the distribution cloud diagram of the water content and current density on the proton exchange membrane during its operation is made a comparison.The results show:(1)When the relative humidity of the battery is 100%,the operating pressure is 2atm,and the operating temperature range is 333K～353K,as the operating temperature rises,the maximum power of the fuel cell increases and the battery’s reaction rate speeds up.The increase of the water content of the proton exchange membrane accelerates the conductivity of the membrane,thereby reducing the internal resistance of the battery and the activation overvoltage,ohmic overvoltage and concentration overvoltage of the fuel cell.Finally,the output voltage of PEMFC is increased.(2)When the operating temperature of the battery is 353 K,the relative humidity is 100%,and the operating pressure is 1atm～2atm,increased pressure will grow in number of the water content of the PEM and accelerate the battery reaction rate and improve the output performance of the battery.When the operating temperature of the battery is 353 K and the operating pressure is 2atm,the higher the air intake and humidity of the battery,the higher the water content of the PEM,the wider the distribution range of current density,and the better the output performance of the battery.(3)The thickness of the PEM has a great influence on the performance of the fuel cell,mainly the distribution of its water content and current density.The thinner the inner membrane is in a certain range,the lower the internal resistance value,the smaller the ohmic loss voltage,and the higher the output voltage and output power of the fuel cell. |
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