Dynamic Incompressible Navier-Stokes Model of Catalytic Converter in 1-D Including Fundamental Oxidation Reaction Rate Expressions

Abstract

Classical one-dimensional (1D) models of automotive catalysts are effective in designing catalyst systems that meet current emission standards. These models use various assumptions in order to simplify the mathematical formulation. Although these postulations have been effective in the past, they might not work with new versions of catalytic converters and the architectures being proposed. In particular, classical models neglect viscosity, conductivity and diffusion in the bulk gas phase. However, in low flow rate regenerative catalysts, these terms might become important. In order to account for these phenomena, an updated model is proposed for the dynamically incompressible flow in the converter. At the same time, derivation and utilization of these terms is studied for proper inclusion in the model. Furthermore, it is evident from the history of catalyst modeling that precise reaction rate expressions are needed for accurate predictions. In order to determine the correct reaction rate expression, this work includes the history of the fundamental reactions of automotive catalysts including carbon monoxide (CO), hydrogen (H2) and nitric oxide (NO) oxidation on a widely used material formulation (platinum catalyst on alumina washcoat). A detailed report of these reactions is incorporated for the reader in order to understand the reaction mechanism along with the creation of a reaction rate expression. Using this review, the CO oxidation reaction is modeled in order to validate the changes proposed in the updated flow model. Moreover, the importance of using the model for determining the characteristics of the catalyst in low flow conditions is presented. This work ends by describing the success and failures of the revised model as compared to the classical model.