Transport Processes In Proton Exchange Membrane Fuel Cell With Fractal Tree-like Flow Field

Proton Exchange Membrane Fuel Cell(PEMFC)has some advantages,such as high efficiency,eco-friendly virtue,fast startup and so on,so it develops a wide prospect application.Transport processes in PEMFC with fractal tree-like flow field can help us to expose the relationship between the cell performance and the cell structure parameters and the operation conditions.The papers focus on the transport processes in the fuel cell,which is used to simulate a 3-dimensional,gas-liquid two phase,isothermal model to investigate the fluid flow,multi-component transport and electrochemical reaction.Oxygen concentration,water concentration,water content in PEM,current density were described emphatically.Main content of this thesis are:(1)Fractal tree-like structure exists widly in the nature and has many excellent properties in mass transportation.The studies on the steady transmission characteristics of PEMFC with fractal tree-like flow field are from when the fuel cell at high current density and low current density,and compared with the traditional parallel channel which has the same porosity and activity area.The results show that the PEMFCwith fractal tree-like flow field has a better performance.(2)The start,work and stop of PEMFC needs the fast response time,especially the proces s of mass transfer at the start has an important influence on the performance.he study of the transient transfer response characteristics about the fractal tree-like microchannel PEMFC have shown that Hydrogen in the interface to have a balance need about 0.6s,and the cathode oxygen in the interface to have a balance need about 0.3s,while the current density to have a balance is also need about 0.3s.(3)The results of experimental study and computer numerical simulation are the sim ilar with fractal-tree like PEMFC.The polarization curve of polarization performance s imulation is consistent,the power density curve is consistent too.In the testing,curre nt density with the change of voltage and it with the change of the hydrogen stoichio metric ratio value relative is smaller than the result of the numerical simulation,the ti me to achieve the stable time of current density is longer than the simulation.