质子交换膜燃料电池冷启动的数值模拟

冷启动是质子交换膜燃料电池（PEMFC）商业化所面临的挑战之一，在PEMFC冷启动实验中，通过中子成像技术已经观测到电池内部存在过冷水，因此本文模型重点考虑过冷水对电池冷启动性能的影响。通过引入结冰概率函数对过冷水结冰过程的随机性进行描述，从而建立了PEMFC冷启动的三维、瞬态和多相流动数学模型。基于该模型，研究电池阴极催化层中离子聚合物的体积分数和质子交换膜的厚度对电池冷启动性能的影响。研究结果表明，增加阴极催化层中离子聚合物的体积分数，可有效促进阴极催化层中的反应生成水向质子交换膜中进行扩散，从而充分利用膜内的储水空间；减少质子交换膜的厚度，能促进质子交换膜中的离聚物水向阳极催化层扩散，在大电流密度工况下可有效缓解阳极的“膜干”现象。

Numerical simulation of cold start processes in proton exchange membrane fuel cell

Cold start is quite important for the commercialization of proton exchange membrane fuel cell (PEMFC). In PEMFC cold start experiment, super-cooled water inside the cell has been observed by neutron imaging technology. Here, we have proposed a model to address the effects of super-cooled water on the PEMFC cold start performance. By introducing the icing probability function to describe the randomness of freezing process, we established a three-dimensional, transient and multi-phase mathematical model. The PEMFC cold start performance was investigated with various ionomer volume fraction in cathode catalyst layer (CL) and membrane thickness. The results showed that increasing the ionomer volume fraction in cathode CL could effectively promote the diffusion of product water from the cathode CL into the membrane, and thus water storage space inside the membrane could be utilized more efficiently. Moreover, reducing the membrane thickness helps to enhance the diffusion of ionomer water from the membrane into the anode CL, thereby alleviating the anode dehydration phenomenon at high current density.