A new approach for the modeling of turbulent flows in automotive catalytic converters

Abstract

This work presents a new approach to predict turbulent flows inside of a catalytic converter taking into account a decay and ignition of turbulence at the entrance and exit zone of the monolith, respectively. The core part of the converter is a monolith substrate, which is commonly represented as a homogeneous porous medium due to computational limitations. Such simplification eliminates any interaction with the solid when the flow is entering and leaving the substrate. This work extends the previously addressed decay of the turbulence entering the monolith, with the turbulence generation exiting it. This is achieved using an immersed boundary condition immediately after the porous medium, whose values are estimated using a local Reynolds, based on observations made in a discrete channel geometry. The results are compared with commonly used converter models, finding substantial differences in the effective viscosity and kinetic energy inside and after the monolith. The proposed model agrees with the one obtained in discrete geometry, and it also prevents unrealistic changes in the flow observed in existing models. The distinguishing feature of the proposed model is its simplicity in terms of implementation in any commercial or open-source CFD software. Model performance using models based on Reynolds-averaged Navier–Stokes equations (RANS) and Large eddy simulations (LES) of the whole automotive converter is illustrated.