板式固体氧化物燃料电池的热应力分析

Analysis on Thermal Stress of a Planar Solid Oxide Fuel Cell

为了深入掌握固体氧化物燃料电池(SOFC)的结构性能,进而提高其可靠性,在对SOFC的内部流动和电化学特性进行数值模拟,对顺流和逆流两种流动情况下板式SOFC内温度分布、电势特征和电流密度特征进行分析的基础上,将数值计算得到的温度场作为载荷施加到SOFC的热应力模型中,建立了数值模拟SOFC的有限元热应力模型,对SOFC关键结构中的三合一电极板中的热应力分布特征进行了分析研究.研究结果表明:相对于顺流形式,逆流形式燃料入口附近的温度梯度要大得多;材料间热膨胀系数的不匹配导致了热应力的产生;热应力的大小与温度分布和温度梯度密切相关.由于过大的热应力可能会导致SOFC结构开裂甚至破坏,该研究工作为SOFC单电池和电池堆的设计优化提供了重要的理论依据.

A thermal stress finite element model for a planar solid oxide fuel ceil （SOP＇C;） was established to study the structural performance of SOFC and improve its reliability. Numerical simulations for both co-flow and counter-flow planar SOFCs were performed by coupling the SOFC electrochemical model with the Naive-Stokes equations. The distribution characteristics of temperature, electric potential and current density were analyzed based on the simulation results. The distribution characteristics of thermal stress in the SOFC positive electrode-electrolyte- negative electrode were investigated using the developed SOFC thermal stress finite-element model. The simulation results indicate that the temperature gradient near the fuel entrance for the counter-flow pattern is much greater than that for the co-flow pattern. The thermal stress is mainly attributed to the mismatches of coefficients of thermal expansion between different materials and is closely related to the temperature gradient and distribution. The thermal stress may lead to cracks and destroy the SOFC structure. This research provides theoretical basis for design and optimization of the SOFC cell and stack.