PEMFC启停工况下的阳极氢空混合区域分析

Analysis of hydrogen-air mixing region in PEMFC anode under startstop condition

质子交换膜燃料电池在启停工况下,一般认为,阳极流道中形成氢空界面,产生阴极高电位,导致阴极材料发生电化学腐蚀。实际上,氢气与空气接触时会发生对流与扩散,阳极流道中将形成氢空混合区域。通过推导氢空混合区域的运动学模型与电解质电势分布数学模型,进行氢空混合区域范围、时间及电解质电势数值计算。结果表明,氢空混合区域导致的阴极高电位持续时间远超氢空界面存在时间;对应的电解质电势为-0.304~-0.260 V;氢空混合区域的分布范围与持续时间受入口气体流速及流道当量直径影响;当量直径每增加0.1 mm,混合区域最大值将增加4 mm,整体阴极高电位的持续时间将延长1.25%。以上结果为阳极流场的设计和启停工况下的控制策略提供了理论依据。

Under the start-stop conditions of proton exchange membrane fuel cells,it is generally acknowledged that the hydrogen-air front forms in the anode flow channel,resulting in high cathode potential,which leads to the electrochemical corrosion of cathode materials.In fact,when hydrogen contacts with air,the convection and diffusion occur,and a hydrogen-air mixing region forms in the anode channel.The range,time and electrolyte potential of the hydrogen-air mixing region were calculated by deriving the kinematics model of the hydrogen-air mixing region and the mathematical model of the electrolyte potential distribution.The results show that the duration time of the cathode high potential caused by the hydrogen-air mixing region is longer than the existence time of the hydrogen-air front,and the corresponding electrolyte potential is-0.304--0.260 V.The distribution range and duration time of the hydrogen-air mixing region are affected by the inlet gas flow rate and the equivalent diameter of the flow channel.For each 0.1 mm increase of the equivalent diameter,the maximum value of the mixing area increases by 4 mm,and the duration time of the overall cathode high potential extends by 1.25%.The above results provide the theoretical basis for the design of the anode flow channel and the control strategy under start-stop conditions.