Finite element and analytical stress analysis of a solid oxide fuel cell

Abstract

An analytical and finite element model of a single, anode supported solid oxide fuel cell has been developed in order to predict the stress in ceramic components subjected to an idealised operating duty cycle representing cooling from sintering, warming to a uniform temperature of 800°C where anode chemical reduction takes place, operation at low, medium and high power and finally cooling to room temperature.An Abaqus™ finite element model used the temperature distribution predicted by a computational fluid dynamics model at low, medium and high power to solve for the stress distribution throughout the duty cycle. The finite element model included the effects of thermal expansion, residual stress from manufacture, material properties changes due to chemical reduction of the anode and visco-plastic creep. The level of stress relaxation predicted by the finite element model is significant at SOFC operating temperatures and timescales of several thousand hours.An analytical model of the stress distribution in thin multilayer plates where the layers have different coefficients of thermal expansion was developed to cross check the finite element model. In the analytical model the multilayer plate is either free to bend or constrained to remain flat. The maximum principal stresses predicted by the analytical and finite element models were found to agree to within 4%.