Analysis and Optimization of Metallic Based Substrates for After-Treatment System by Means of Full-Scale CFD Simulations and Experiments

The tightening trend of regulations on the levels of admitted pollutant emissions has given a great spur to the research work in the field of combustion and after-treatment devices. Despite the improvements that can be applied to the development of the combustion process, pollutant emissions cannot be reduced to zero; for this reason, the aftertreatment system will become a key component in the path to achieving near-zero emission levels.

This study focuses on the numerical analysis and optimization of different metallic substrates, specifically developed for three-way catalyst (TWC) and Diesel oxidation catalyst (DOC) applications, to improve their thermal efficiency by reducing radial thermal losses through the outer mantle. The optimization process relies on computational fluid dynamics (CFD) simulations supported by experimental measurements to validate the numerical models carried out under uncoated conditions, where chemical reactions do not occur. Full-scale three-dimensional, multi-region models precisely describe the flow and temperature distributions allowing the evaluation of heat fluxes with the surrounding environment.

A test cycle was designed to replicate the typical warm-up of a catalyst followed by a drop in the gas temperature and then a drop in the mass flow, replicating the engine switch-off condition.

Different canning solutions and insulation strategies were considered at both numerical and experimental levels, and the results were compared. This allowed the validation of the numerical approach and identification of the best solution in terms of heat loss reduction and response time to heat up.