A smoothed particle hydrodynamics model of reactive transport in the porous cathode of a solid oxide fuel cell

This dissertation presents the development of a computational model to investigate chromium poisoning in a solid oxide fuel cell (SOFC) cathode. Chromium poisoning occurs when volatile chromium species are formed at the air channel walls and migrate into the cathode where they react with the cathode surface and reduce the electrochemical activity of the fuel cell. The principal goal of this research is to investigate the transport and reaction mechanisms of chromium species in the cathode through pore scale computational modeling.;The smoothed particle hydrodynamics (SPH) method is used to solve the governing equations of the pore scale reactive transport problem. SPH is a Lagrangian particle based modeling method which uses the particles as interpolation points to directly discretize the governing equations of the system. SPH's Lagrangian framework allows for easy implementation of complex chemistry and physics at the interfaces and is able to easily model complex geometries such as the porous cathode microstructure.;The pore scale reactive transport model is used to investigate chromium poisoning through parametric studies of the reaction and transport properties of the cathode. Studies of the effects of reaction rate, diffusion rate, current density and chromium vaporization are presented to better understand the driving forces of chromium poisoning. These studies suggest the chromium reaction rates in the cathode varying through the thickness of the cathode and that the chromium reactions may be caused by more than one reaction mechanism.;The dissertation is organized as a compilation of three journal articles which discuss the details of the model which was developed, and its application to the problem of chromium poisoning in the cathode. An additional chapter on surface diffusion is also included and presents preliminary work on the development of a pore scale surface diffusion model.;Past SOFC modeling has focused on cell and stack level models which are unable to resolve the detailed physics occurring within the SOFC electrodes. Cell level models typically use Darcy scale models of the electrodes, which homogenize the microstructure and depend on effective properties to describe the transport and surface reactions in the electrodes. In the model presented here, the reactive transport of species in the cathode is modeled at the pore scale using a discrete representation of the SOFC cathode. This allows for the local conditions within the cathode to be resolved and does not require the use of effective parameters.