Emission Control Science and Technology

, Volume 3, Issue 4, pp 275–288 | Cite as

Nitric Oxide Reduction of Heavy-Duty Diesel Off-Gas by NH3-SCR in Front of the Turbocharger

  • T. Rammelt
  • B. Torkashvand
  • C. Hauck
  • J. Böhm
  • R. Gläser
  • O. DeutschmannEmail author


This paper investigates the impacts and effects of higher pressure on NH3-SCR of NOx corresponding to positioning the SCR catalyst in front of the exhaust gas turbine, which is an option in heavy-duty and off-road diesel engine applications (1, 2, 3, 4). The influence of applied pressure up to 500 kPa on the selective catalytic reduction (SCR) of nitrogen oxides by NH3 over commercial V2O5/WO3-TiO2-type catalysts (VWT) is studied experimentally and numerically. The model includes a detailed reaction mechanism for standard and fast SCR and a two-dimensional description of the flow field and diffusion in the honeycomb-structured catalyst. The pressure effect on catalytic conversion, residence time, and mass transfer are examined for varying temperature and two different channel sizes, i.e., 25 and 300 cpsi (channels per square inch) at constant mass flux from the engine. Pre-turbo positioning of the catalyst leads to a significant increase in NOx conversion due to higher pressure aside from the positive temperature effect. However, with increasing channel size, diffusional mass transport limits the reaction rate, and reduces the benefit of increased residence time due to the decrease in diffusion rates with increasing pressure. The achievable increase in conversion is transformed into a length reduction of the catalyst.


SCR Pre-turbo Diesel engine Aftertreatment 



We gratefully acknowledge the versatile technical and financial support of the Research Association for Combustion Engines e.V. (Forschungsvereinigung Verbrennungskraftmaschinen e.V. FVV) and the participating industrial partners from the automotive sector. We thank the Steinbeis GmbH für Technologietransfer (STZ 240 Reaktive Strömungen) for a cost-free academic license of DETCHEM™.


AV;Area velocity (m h−1)

V C Catalyst volume (m3)

S C Specific catalyst surface (m2 m−3)

rChannel radius (m)

ρdensity (kg m−3)

uAxial velocity (m s−1)

zAxial coordination (m)

ppressure (Pa)

henthalpy (J kg−1)

vRadial velocity (m s−1)

λThermal conductivity (J m−1 s−1 K−1)

Ttemperature (K)

j i Diffusion flux (mol m−2 s−1)

Y i Mass fraction of species i (–)

k i Reaction rate coefficient

C i Concentration of species i (mol)

θ i Surface coverage with species i (–)

E i Activation energy (kJ mol−1)

RUniversal gas constant (J mol−1 K−1)

τResidence time (s)

V R Volume flow (m3 s−1)

D ij Binary diffusion coefficient (m2 s−1)

N A Avogadro constant

\( {k}_B^3 \)Boltzmann constant

M ij Reduced mass (kg)

\( {\sigma}_{ij}^2 \)Reduced diameter (m)

\( {\Omega}_{ij}^{\left(l,s\right)\ast } \)Reduced collision integral

\( {T}_{ij}^{\ast } \)Reduced temperature(K)


i,jSpecies number


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Institute of Chemical TechnologyUniversität LeipzigLeipzigGermany
  2. 2.Institute of Chemical Technology and Polymer ChemistryKarlsruhe Institute of TechnologyKarlsruheGermany

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