Turbulence Decay Inside the Channels of an Automotive Catalytic Converter Monolith

摘要

This paper reports a multi-scale study of the turbulence decay inside of a monolith. It is a well-known fact that the turbulence at the automotive catalytic converters affects the conversion of chemical species, the composition of the exhaust gas, and the performance of the engine significantly. Basically, the flow is highly turbulent before the monolith; nevertheless, it is usually assumed to be fully laminar inside of it. The present work uses numerical simulations at two different scales: a Reynolds-averaged version of the Naiver-Stokes (RANS) model is used to model gas flow inside the whole converter and LES model is applied to study the decay of turbulence inside a single channel. The inflow boundary conditions for LES are taken from the large-scale simulations carried out using RANS. Results of RANS were validated against published experimental data. CFD software ANSYS-Fluent 17.2 was used for RANS and LES simulations. The results for the channels with the highest and the lowest Reynolds number shows that the turbulence intensity decays quickly, but, can remain high for a significant distance, depending on its position and the duty of the converter, the turbulence intensity can remain high through its entire length.