微流燃料电池空气阴极物质传输孔隙尺度模拟

采用格子Boltzmann方法研究了微流燃料电池空气阴极多孔扩散层内多组分物质传输特性。随机重构了扩散层,获得渗透率及有效扩散系数。建立了耦合边界电化学反应的二维模型,研究了过电位、孔隙率对氧气、水蒸气浓度分布及局部反应速率的影响。结果表明,常用的Bruggeman经验关联式会高估氧气有效扩散系数;扩散层孔隙结构对物质传输有重要影响,孔隙率减小使得传质阻力增大,导致局部氧气浓度降低,局部反应速率降低,而水蒸气浓度增大,当孔隙率从0.83降至0.7,催化界面平均氧气浓度从8.472降至8.466 mol·m^-3。

Pore-scale Modelling of the Mass Transport in the Air-breathing Cathode of Microfluidic Fuel Cells

Pore-scale modelling is performed to investigate the mass transport in a fibrous gas diffusion layer(GDL)of membraneless microfluidic fuel cells using Lattice Boltzmann method.The fibrous GDL is reconstructed by the stochastic method.The permeability and effective diffusivity of the reconstructed GDL are predicted and compared with empirical correlations.In addition,a 2 D GDL model coupled with boundary electrochemical reaction is developed to investigate the effects of overpotential and porosity on the concentration distribution of oxygen and water vapor,and local reaction rate.The modelling results suggest that the conventional Bruggeman correlation overestimates the oxygen effective diffusivity.Besides,the GDL porous structure can greatly affect the mass transport.The mass transfer resistance increases at decreased porosity,leading to the decreased local oxygen concentration and reaction rate,but the water vapor will accumulate to improve its local concentration.As the porosity decreases from 0.83 to 0.7,the average oxygen concentration at the catalytic interface decreases from 8.472 to 8.466 mol-m^-3.