Abstract:

During the operation of automotive fuel cells, dynamic loads may drastic changes in local physical quantities of the fuel cell, which in turn leads to a sharp decline in fuel cell performance and service life. To prevent the occurrence of the issues above, a thorough analysis of the local dynamic characteristics of the fuel cell under dynamic operating conditions is necessary. This study considers the 7-layer structural features of the membrane electrode assembly, and the energy transport facilitated by gas component diffusion and gas-liquid two-phase macroscopic convection, while also taking into account the localized energy changes resulting from phase transitions between gas-liquid-membrane phases. Building upon these considerations, a two-phase, non-isothermal, three-dimensional dynamic physical model of the fuel cell has been established. This model reveals the internal features of the fuel cell under dynamic loads, particularly focusing on the heat and mass transport, as well as the dynamic response characteristics of electrochemical reactions, in the catalytic layer region beneath the channel and rib of the bipolar plate along the flow channel. Furthermore, it elucidates the mechanisms underlying the formation of dynamic behaviors. The research findings indicate the presence of significant spatial-temporal thermal-mass response non-uniformities within the membrane electrode during the step change in current load, resulting in a decrease of approximately 20 mV in fuel cell output voltage, triggering additional power losses and heat generation, thereby causing further increasing in local temperature.

Key words: proton exchange membrane fuel cell, dynamic modeling, transient response, heat transfer, three-dimensional model

摘要：

车用燃料电池运行过程中，动态负载可能引起电池局部物理量剧烈变化，进而导致电池性能和使用寿命急剧下降。为了防止上述问题的发生，需要深入分析动态工况下电池局部动态特征。本研究考虑膜电极7层结构特征、气体组分扩散以及气液两相宏观对流带来的能量输运，同时考虑水在气-液-膜三相之间相变引起的局部能量变化，建立了燃料电池两相、非等温、三维动态物理模型，揭示动态载荷下燃料电池内部特征，特别是在流道方向和极板沟脊下催化层区域的热质输运以及电化学反应动态响应特征，并阐明了动态行为形成机理。研究结果显示，在电流负载阶跃过程中膜电极内部存在显著的热质时空响应不均现象，导致变载过程中电池输出电压下冲约20 mV，引发额外功率损失和产热，从而造成局部温度进一步上升。

关键词: 质子交换膜燃料电池, 动态建模, 瞬态响应, 传热, 三维模型