Optimization of Metallic Substrate by 1D simulations to fulfill High Power Cold Start Conditions

The future of the internal combustion engine is strictly related to his capability to have Life Cycle Emission comparable to the pure Battery Electric Vehicles. To achieve this goal, it will be necessary not only to have carbon free fuels but also to increase the hybridization of the powertrain in order to have lower fuel consumption. On the other hand, it will be necessary to reduce to almost zero any further emissions of pollutants. For this reason, highly sophisticated exhaust aftertreatment must be developed. One particular use case is the so-called High-Power Cold Start. This can occur for the Plug-In Hybrid Electric Vehicles when the transition from pure electric drive to ICE assisted drive happens during high load request, for example an acceleration on the freeway ramp. This use case has been evaluated by CARB and in many other works. Nevertheless, in this particular paper, the Authors would like to investigate which Metallic Substrate Technology fits better during a HPCS. This condition is quite different compared to a normal cold start: the exhaust gas flow and the quantity of available energy are much higher: the catalyst must be able to heat up quickly (like in a conventional cold start) but the needed volume above the light off temperature must be much bigger in order to convert a higher quantity of pollutants. A 1D tool will be used to quickly identify and choose the best substrate technology to tailor specific requirements of back pressure and light-off time under the assumption ideal gas distribution at the inlet and with simplified chemistry. Then, the test cycle will be simulated with a 1D code accounting for detailed chemistry in the catalyst and investigating the effects of the washcoat loading and PGM composition. Additionally, the impact of water condensation/evaporation and hydrocarbon adsorption on the overall abatement efficiency of the catalyst will be evaluated by means of specific submodels. Measured data of raw engine emissions and gas temperature will be used as boundary condition to model the driving cycle and the numerical results will be compared with measured cumulated tailpipe emissions to validate the numerical model. Based on the validation, strategies for improving the efficiency will be considered acting on the geometry of the catalyst and keeping the same measured emissions of the experimental campaign as boundary conditions.