Study On Water Management Of Proton Exchange Membrane Fuel Cell

Proton Exchange Membrane Fuel cell can convert chemical energy into electric energy,which has the advantages such as high energy density,fast start-up speed and zero pollution and so forth.It is considered to be a potential power source for future vehicles.Therefore,the research on both the dynamic characteristics of PEMFC and its influencing factors are current research hotpots.Water plays an important role on affecting the performance of proton exchange membrane fuel cells,the efficiency of PEMFC greatly depends on the characteristic of water distributed on the proton exchange membrane,and the cell performance can be improved via proper water management.The traditional lumped parameter PEMFC model can only describe single characteristic of water concentration,in order to develop a PEMFC dynamic model which can reasonably and accurately study the internal water distribution characteristic in the PEMFC and is simple enough to be used in control system design at the same time,a controllable segmented PEMFC dynamic model is established by composing multiple distributed lumped models in series according to serpentine flow field in two-dimensional space based on the segmented method in this paper.The main research contents and innovations are listed as following:(1)Establish a segmented PEMFC dynamic model with predictable water distribution.Through linearizing the output voltage of sub model,a mathematical differential equation model that can be used in control system is realized.Under different humidified conditions,the deviations on polarization curve,current density and membrane water content distribution between the model before and after linearizing the output voltage of sub model are within the acceptable range,which proves the rationality and accuracy of the controllable segmented PEMFC dynamic model demonstrated by the mathematical differential equation.(2)Based on the Comsol Multiphysics software,a three-dimensional PEMFC cathode model with five channel serpentine flow field is established,and the results on mass distribution of the physical simulation model and the controllable segmented PEMFC dynamic model are compared.It is further proved that the controllable model can accurately predict the distribution of parameters such as membrane water content,surface impedance and oxygen molarity with comparative accuracy.(3)Finally,according to the structure and parameters of single PEMFC in an 800 W PEMFC stack,a controllable segmented PEMFC dynamic model and a three-dimensional PEMFC cathode model of are established respectively corresponding to the flow channel size.The experimental results show that the errors on polarization curve in ohmic polarization zone of the controllable model and the three-dimensional model compared to experimental results are within 5% and 3% respectively.This study established a controllable segmented PEMFC dynamic model which was distributed in two-dimensional spatially and could predict water distribution in a fuel cell based on the mathematical differential equations and a three-dimensional PEMFC cathode model based on Comsol Multiphysics.Finally,the rationality and accuracy of the two models are verified by simulation and experiment,the controllable dynamic model based on mathematical differential equation can be used in the further optimization design of control system.