Numerical simulation and thermal stress analysis of direct internal reforming SOFCs

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.