ABSTRACT

Hydrocarbon fuels such as CH₄ can be converted into H₂ and CO by direct internal reforming (DIR) processes within the anode of solid oxide fuel cells (SOFCs). DIR-SOFCs can reduce system complexity and capital cost due to the elimination of external reformers. However, the strong endothermic reforming reactions at the cell entrance may result in large thermal stress, leading to premature failure. In this study, a numerical simulation study was carried out to analyze the effect of operating conditions and cell structures on temperature, composition and thermal stress distributions in DIR-SOFCs. A two-dimensional axisymmetric model was developed by considering the coupling effects of the chemical/electrochemical reactions; transport processes of mass, charge, or heat; and thermal mechanical stress. The failure probability of the cell was estimated by stress distributions. Simulation results show that the increase of the steam-to-carbon ratio and operating voltage leads to higher thermal stresses and higher failure probability. The introduction of a metal supportive layer may release the thermal stress problem at severe DIR-SOFC operation conditions, which leads to a flatter temperature distribution and smaller failure probability compared to anode-supported SOFCs.

摘要

_{CH 4}等碳氢化合物燃料可转化为 H ₂通过在固体氧化物燃料电池 (SOFC) 阳极内的直接内部重整 (DIR) 过程产生 CO。由于消除了外部重整器，DIR-SOFC 可以降低系统复杂性和资本成本。然而，电池入口处的强烈吸热重整反应可能会导致较大的热应力，从而导致过早失效。在这项研究中，进行了数值模拟研究，以分析操作条件和电池结构对 DIR-SOFC 中温度、成分和热应力分布的影响。考虑化学/电化学反应的耦合效应，建立了二维轴对称模型；质量、电荷或热量的传输过程；和热机械应力。通过应力分布估计电池的失效概率。仿真结果表明，提高汽碳比和工作电压会导致更高的热应力和更高的故障概率。金属支撑层的引入可能会在恶劣的 DIR-SOFC 操作条件下释放热应力问题，与阳极支撑的 SOFC 相比，这会导致更平坦的温度分布和更小的故障概率。