Transient Flow Uniformity Evolution in Realistic Exhaust Gas Aftertreatment Systems using 3D-CFD
Artikel i vetenskaplig tidskrift, 2022

To precisely control a vehicle powertrain to minimize emissions, accurate and detailed models are needed to capture the spatio-temporal variability of the variables of interest. The aim of this work is to analyze flow and temperature fields in a geometrically realistic — and thus complex — exhaust gas aftertreatment system under transient conditions. The spatio-temporal response of these fields to upstream step changes is predicted using three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) κ- ω simulations where the catalytic converter is described as a porous medium. A catalytic converter geometry with a 90∘-bend and a partially dead volume is used to demonstrate the effects of time-resolved flow maldistribution on the profiles of velocity and temperature. Two sets of transient simulations in terms of step changes in velocity and temperature are performed. Uniformity indices are used to characterize the distribution and variability of the different catalyst channels under transient conditions. The evolution of the uniformity indices as functions of time and axial distance into the catalyst are calculated at different cross-sectional planes. The results show that the evolution of the temperature uniformity is rate controlling, continuously modulating the otherwise much faster flow uniformity response via the fluid properties. The temperature uniformity time scale is determined by the balance of flow, thermal inertia, and the heat losses from the system. The interplay between pressure drop and heat losses governs the transition to the new steady state in uniformity. These types of transient simulations and analyses can contribute essential information when developing reduced-order engineering models to represent the spatio-temporal variability in exhaust aftertreatment systems, in particular during rapid events such as cold start.

Författare

Pratheeba Chanda Nagarajan

Chalmers, Mekanik och maritima vetenskaper, Förbränning och framdrivningssystem

Henrik Ström

Chalmers, Mekanik och maritima vetenskaper, Strömningslära

Jonas Sjöblom

Chalmers, Mekanik och maritima vetenskaper, Förbränning och framdrivningssystem

Emission Control Science and Technology

21993629 (ISSN) 21993637 (eISSN)

Vol. 8 3-4 154-170

Modellering av avgasefterbehandlingssystem för noll-utsläpp

Kompetenscentrum i förbränningsmotorteknik, 2019-06-03 -- 2024-01-31.

Ämneskategorier

Maskinteknik

Kemiteknik

Drivkrafter

Hållbar utveckling

Styrkeområden

Transport

Energi

DOI

10.1007/s40825-022-00217-6

Mer information

Senast uppdaterat

2024-02-09