基于孔隙尺度的燃料电池气体扩散层结冰研究

针对燃料电池用气体扩散层内液态水在孔隙尺度下的动态结冰过程,首次引入了一种介观模拟尺度方法——格子Boltzmann方法.首先,构造燃料电池用真实气体扩散层三维微孔隙结构;其次,通过一维半无限大空间凝固热传导、二维直角区域凝固和二维介质方腔凝固三组数值试验严格考察该凝固模型中液态水、固体冰和碳纤维不同热物理参数选取的精确性,证明引入的格子Boltzmann方法在研究燃料电池气体扩散层中结冰现象的有效性;最后,针对孔隙率分别为0.5、0.6、0.7、0.8和0.9的二维气体扩散层在孔隙尺度下的结冰过程进行模拟研究.模拟结果表明,对应孔隙率分别为0.5、0.6、0.7、0.8和0.9时,气体扩散层孔中液态水完全结冰量纲一时间F_0分别为2.67、3.11、3.68、4.31和4.84,有自然对流情况下的结冰时间F_0比无自然对流时分别减少0、0、0.001、0.001和0.007.

Pore-scale Investigation of Water Freezing in Gas Diffusion Layer for Proton Exchange Membrane Fuel Cell

In terms of freezing process of liquid water inside gas diffusion layer for proton exchange membrane fuel cell(PEMFC) under pore-scale prospective, a mesoscopic simulation tool is proposed here to be involved in PEMFC-lattice Boltzmann method(LBM). First, true gas diffusion layer structure for PEMFC was built in pore-scale level. Then, accuracy of thermophysical parameters in the model was validated through one-dimensional half-space solidification, two-dimensional solidification in semi-infinite corner and two-dimensional solidification in cavity with porous numerical experiments, proving the effectiveness of application of lattice Boltzmann method on freezing mechanism in gas diffusion layer for PEMFC. Finally, the freezing process of gas diffusion layer with porosity ranging from 0.5 to 0.9 in pore-scale was investigated. The simulation results show that for two-dimensional gas diffusion layer with 0.5, 0.6, 0.7, 0.8 and 0.9 porosity, the dimensionless freezing time F0 is 2.67, 3.11, 3.68, 4.31 and 4.84, respectively and the dimensionless freezing time for cases with natural convection is 0, 0, 0.001, 0.001 and 0.007 less than that without natural convection, respectively.