A novel 1D approach for the simulation of unsteady reacting flows in diesel exhaust after-treatment systems

Abstract

A new one-dimensional approach, based on the solution of the governing equations for unsteady, reacting and compressible flows has been developed for the simulation of the hydrodynamics, the transient filtration/loading and the catalytic/NO2-assisted regeneration occurring in diesel particulate filters (DPF). The model is able to keep track of the chemical compounds, of the amount of soot transported by the flow, and it can estimate the increasing of back-pressure occurring in the exhaust system, due to the permeability variation of the porous wall and to the soot cake building up on the DPF porous surface. Further, a prediction of the oxidation of the deposited particulate induced by the Oxygen (collected in the exhaust gas), by the nitrogen dioxide (NO2), by the carbon oxide (CO) and by the hydrocarbons (HC) converted along the diesel oxidation catalysts (DOC) is given. A first validation of the code has been performed by the comparison with the results coming from computational fluid dynamics (CFD) and with experimental measurements published in literature. The proposed model has been included in an engine simulation code, in order to perform a simulation of a complete engine; results coming from an optimization work recently carried out on a 1.9 L JTD turbocharged diesel engine, equipped with a complex after-treatment system, are presented.