Optimization of Geometric Shape and Axial Noble Metal Distribution in a Dual Monolithic Catalytic Converter for Emissions Reduction of Gasoline Engine

In practical applications, monolithic catalytic converters are operated at non-isothermal conditions. In this case, the active metal distribution along the length of the converter may influence its performance. Indeed, better conversions can be achieved by controlling the distribution of the same quantity of active material. In this study, a one-dimensional catalyst model has been adopted to predict the transient thermal and conversion characteristics of a dual monolithic catalytic converter with Platinum/Rhodium (Pt/Rh) catalysts. The optimal design of a longitudinal noble metal distribution of a fixed amount of catalyst is investigated to obtain the best performance of a dual monolithic catalytic converter by using a micro genetic algorithm with consideration of heat transfer, mass transfer, and chemical reaction in the monolith during FTP-75 cycle. The optimal axial distribution of the catalyst is determined by solving the multi-objective optimization problems which are to minimize both the CO cumulative emissions during FTP-75 cycle, and the difference between the integral value of a catalyst distribution function over the monolith volume and total catalytic surface area over total monolith volume. The parametric investigations for three cell densities of the front monolith are carried out by varying the volume ratio between front and rear monoliths with fixed volume and cell density of the rear monolith