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The selective catalytic reduction has seen widespread adoption as the best technology to reduce the NOx emissions from internal combustion engines, particularly for Diesels. This technology uses ammonia as a reducing agent, which is obtained injecting an ammonia carrier into the exhaust gas stream. The dosing of the ammonia carrier, usually AdBlue, is the major concern during the design and engine calibration phases, since the interaction between the injected liquid and the components of the exhaust system can lead to the undesired formation of solid deposits. To avoid this, the thermal and kinematic interaction between the spray and the components of the after treatment system (ATS) must be modeled accurately. In this work, the authors developed a Conjugate Heat Transfer (CHT) framework to model the kinetic and thermal interaction among the spray, the eventual liquid layer and the pipe walls.

In the field of automotive exhaust catalysts, foam-type substrates have been proposed as alternatives to the well-established honeycomb substrates. The ceramic foams developed and manufactured in our laboratory are capable of redistributing the flow of exhaust gases, enhancing turbulence, mass transfer and species mixing, without increasing flow resistance and pressure drop to prohibitive levels. Based on the characteristics of turbulent mass and heat transfer, ceramic foam based catalysts have the potential for achieving similar pollutant conversion performances as state of art honeycomb catalysts with substantially lower precious metal requirements. In this paper we demonstrate this potential with a small Diesel powered Heavy Duty truck with a ceramic foam Diesel Oxidation Catalyst (DOC). Given the substantial differences in geometrical properties between foams and honeycombs a direct comparison with equal coating thickness, amount and precious metal amount is not feasible.

The transient heat transfer behavior of an automotive catalytic converter has been simulated with OpenFOAM in 1D. The model takes into consideration the gas-solid convective heat transfer, axial wall conduction and heat capacity effects in the solid phase, but also the chemical reactions of CO oxidation, based on simplified Arrhenius and Langmuir-Hinshelwood approaches. The associated parameters are the results of data in literature tuned by experiments. Simplified cases of constant flow rates and gas temperatures in the catalyst inflow have been chosen for a comprehensive analysis of the heat and mass transfer phenomena. The impact of inlet flow temperatures and inlet flow rates on the heat up characteristics as well as in the CO emissions have been quantified. A dimensional analysis is proposed and dimensionless temperature difference and space-time coordinates are introduced.