An advanced numerical model for energy conversion and crack growth predictions in Solid Oxide Fuel Cell units

A dynamic mathematical model capable of predicting the energy conversion and crack propagation in Solid Oxide Fuel Cell (SOFC) unit is developed. Finite Element Method (FEM) and eXtended Finite Element Method (XFEM) are used to solve the multiphysics phenomenon taking place in the SOFC during service. A pre-existing crack is assumed lying within one of the cell's porous electrodes and far from the cell's electrochemically active sites (electrodes/electrolyte interfaces), and thus it is assumed to not affect the electrochemical reactions. The pre-existing crack propagates instantaneously once the crack-tip equivalent stress intensity factor (SIF) overcomes the porous electrode material toughness. Due to their small opening, cracks are assumed to affect only the heat conduction within the solid phase of the porous electrodes. The coupled fluid flow, fluid's energy transfer in the porous electrodes, and mass transport are solved using advanced FEM based schemes, where transition between SOFC interfaces (mainly porous electrodes/flow channels) does not require any special treatment. The heat transfer in the solid phase of the porous electrodes and the thermo-mechanical problem are solved using the XFEM. The predicted energy conversion is validated using experiments from the literature as well as our previously published experiments [J. Power Sources 272 (2014) 233-238]. The developed FEM/XFEM numerical tool is used to investigate the effect of temperature gradients on the propagation path of a pre-existing crack within an anode-supported SOFC. The crack propagation path is found to depend on the position of the pre-existing crack relative the SOFC interfaces as well as its initial orientation.