Effects Of H-shaped Flow Channel Structure On The Microfluidic Fuel Cell Performance

Microfluidic fuel cell is an energy conversion device which is infinitely potential in this energy crisis era.It has got more and more attention because of its numbers of advantages,such as hot water without considering management,low cost,easy integration,etc.But the disadvantage of low power density and low fuel utilization limits its widespread application,and one of the important factors in cell power density and fuel efficiency is the structure of the flow channel.Traditional flow channel cross section is rectangular,but the inhibition of fuel diffusion and fuel crossover rectangular is not ideal for this type.Fuel diffusion and fuel crossover will form a mixed potential and a parasitic current thus reduce the cell performance.In this dissertation,a new H-shaped structure has been proposed in order to control the fuel diffusion and fuel crossover region.Numerical method has been taken to study the performance of traditional rectangular and H-shaped fuel cell,and the results were verified by experimental results.The main work and achievement are listed as follows.A single-phase and three-dimensional mathematical model about the fuel cell has been established under the steady state,and the flow channel inside the fuel cell,mass transfer,charge transfer,and reaction kinetics have been simulated.The research showed that the ridge of the H-shaped cross-section can restrain the fuel diffusion and fuel crossover,so the performance of the fuel cell was improved.With the increase of the fuel flow rate,the performance of the two types was increased.Compared to the rectangular one,the H-shaped one reached a bigger increasement of 15.2% on the power density and 13.4% on the fuel utilization under lower fuel flow rate.The rectangular one produced higher parasitic current than the H-shaped one under the same conditions.With the increase of fuel concentration,the performance of the two types was first increased and then decreased.Compared to the rectangular one,the H-shaped one reached a bigger increasement of 19.1% on the power density and 16.9% on the fuel utilization under high fuel concentration.With the increase of aspect ratio,the performance of the H-shaped fuel cell was first increased and then decreased,because a small aspect ratio can restrain the fuel crossover but also limit the transportation of the proton,in the contrary,a big aspect ratio cannot restrain the fuel crossover effectively but the limitation of the transportation of proton is weakened.Third,the cathode gas diffusion layer and anode permeation layer which are the key components of the fuel cell were made in the lab,and the fuel cell was assembled and texted.The results were in agreement with the simulation ones,which showed that the simulation model can predict the performance of the fuel cell.In the meanwhile,the concentration of the electrolyte solution has been proved to have an effect on the performance of the fuel cell in the high current density section,while not in the low current density section.At the end of this dissertation,an orthogonal experiment was design to find out the best combination strategy for the maximum power density and fuel utilization respectively.