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In recent years, several methods to regenerate PM (Particulate Material) from DPF (Diesel Particulate Filter) have been developed to meet getting more stringent emission regulations. A favorable technology is NO2 -assisted regeneration method due to the capability of continuous regeneration of PM under much lower temperature than that of thermal regeneration. The minimization of maximum DPF wall temperature and the fast Light-off during regeneration are the targets for the high durability of the DPF system and the high efficiency of regeneration. In this study, one-channel numerical modeling has been adopted in order to predict a thermal behavior of the monolith during regeneration and a conversion rate of NO2 from NO with a combined exhaust system of DOC (Diesel Oxidation Catalyst) and DPF. The simulation results are compared with experimental data to verify the accuracy of the present model for the integrated DOC and DPF modeling.

We used a one-dimensional monolithic catalyst model to predict the transient thermal and conversion characteristics of a dual monolithic catalytic converter with a Palladium only (Pd-only) catalyst and a Palladium/Rhodium (Pd/Rh) catalyst. Prior to the numerical investigation of the dual-catalyst converter, we modified the pre-exponential factor and activation energy of each reaction for both catalysts to achieve acceptable agreement with experimental data under typical operating conditions of automobile applications. We validated the conversion behavior of the lumped parameter model for each catalyst against different engine operating conditions. Two higher cell density substrates, Pd-only catalyst (600cpsi/3.9mil) and Pd/Rh catalyst (600cpsi/4mil), for faster light-off and improved warm-up performance are used in this study and the two monoliths has been connected without the space between monoliths.

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia(NH3) in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis can not be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea.

Mathematical modeling of three-way catalytic converter (3WCC) operation is used increasingly in the optimization of automobile converter systems. But almost all of previous computational models were based on "adiabatic one- channel" approach with the reaction kinetics computations, which is useful and efficient in predicting real-world performance of the catalyst. However, as long as flow maldistribution is not accounted for in the models, simulation results will not be reliable. In this work, two-dimensional performance prediction of catalyst coupled with turbulent reacting flow simulation has been performed and the results were compared with experimental data and one-channel simulation in the literature. The computational results from this study show the better prediction accuracy in terms of CO, HC and NO conversion efficiencies compared to those of 1-D adiabatic model. Varying cell density and hot spot moving pattern within the monolith during warm-up period are also considered.

HC and CO emissions during the cold start contribute the majority of the total emissions in the legislated driving cycles. Therefore, in order to minimize the cold-start emissions, the fast light-off techniques have been developed and presented in the literature. One of the most encouraging strategies for reducing start-up emissions is to place the warm-up catalyst, in addition to the main under-body catalyst, near the engine exhaust manifold. This study numerically considers three-dimensional, unsteady compressible reacting flow in the warm-up and main catalysts to examine the impact of a warm-up catalyst on thermal response of the main catalyst and tail pipe emission. The effects of flow distribution and loading condition on the temperature distribution and emission performance have also been investigated.

This work attempts a systematic investigation of the effects of flow maldistribution on the light-off behavior of a monolithic catalytic converter. To achieve this goal, a combined chemical reaction model and three-dimensional computational fluid dynamic modeling technique has been developed. The computational results reveal that the influence of area ratio was significant during high flow transient conditions. The cross-sectional area ratio with the smaller value increases the thermal gradient due to flow maldistribution in the monolith, which degrades performance of catalytic converter. Due to locally concentrated high velocities, large portions of the monolith remain cold and CO,HC are unconverted during warm up period. Therefore, flow maldistribution can cause a significant retardation of the light-off and can eventually worsen the conversion efficiency.