Numerical Simulation And Study On Impact Factor Of Light-off Characteristic Of Three-Way Catalytic Converter

Relative to Euroâ…¡, Euroâ…¢emission regulations add the test of emission in 40s after cold-start. In order to meet the more strict emission regulations, the key question is how to make the three-way catalytic converter to light-off and increase the conversion efficiency. So it is necessary to do a numerical simulation on light-off characteristic and conversion efficiency of three-way catalytic converter in cold-start stage.Based on the consideration of the heat transfer and mass transfer phenomenon in TWC, the one-dimension single-channel and three-dimension multi-channel model of the monolith are established. Based on the analysis of gas-solid multiphase catalytic reaction, the chemical reaction model is established. When the reaction is controlled by the chemical dynamic, the reaction rate is introduced by consideration of the adsorption and desorption effects. When the reaction is controlled by mass transfer, the diffusion coefficient is established which can present the flow rate increases in small Reynolds domain; for the internal diffusion, the internal diffusion coefficient is derived, and then the internal diffusion is coupled with chemical reaction to represent the phenomenon that the diffusion and the chemical reaction occur cocurrently.According to its configuration, the monolith is considered to be a porous media. Based on the monolith model and the use of software FLUENT, the research on the light-off characteristic and conversion efficiency of three-way catalytic converter is processed. In the beginning of cold-start, the monolith is heated only by the gas; after light-off, the monolith is heated by the heat released by the chemical reaction. So in order to meet the more strict emission regulations, it is necessary to quicken the rise of temperature and shorten the light-off time of the monolith.At last, the impact of the monolith length, cell density, wall thickness and noble metal dosage on the light-off characteristic and conversion efficiency of three-way catalytic converter are analyzed and could provide a guide for the optimization of three-way catalytic converter.