Abstract
This paper presents a computational investigation of the effect of engine exhaust gas modulations on the performance of an automotive catalytic converter during cold starts. The objective is to assess if the modulations can result in faster catalyst light-off conditions and thus reduce cold-start emissions. The study employs a single-channel based, one-dimensional, non-adiabatic model. The modulations are generated by forcing the variations in exhaust gases air-fuel ratio and gas compositions. The results show that the imposed modulations cause a significant departure in the catalyst behavior from its steady behavior, and modulations have both favorable and harmful effects on pollutant conversion during the cold-starts. The operating conditions and the modulating parameters have substantial influence on catalyst behavior.
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Abbreviations
- C j g :
-
gas phase concentration of species j, mol/m3
- C j s :
-
surface concentration of species j, mol/m3
- c pg :
-
specific heat of gas, J/(kg·K)
- c ps :
-
specific heat of substrate, J/(kg·K)
- D h :
-
hydraulic diameter, m
- D j :
-
diffusion coefficient of species j, m2/s
- G a :
-
geometric surface area, m2/m3
- DH k :
-
heat of reaction of species k, J/mol
- h g :
-
heat transfer coefficient between flow and substrate, J/(m2·s·K)
- h ∞ :
-
heat transfer coefficient between substrate and atmosphere, J/(m2·s·K)
- km j :
-
mass transfer coefficient for species j, m/s
- L :
-
catalyst length, m
- Nu :
-
Nusselt number, dimensionless
- Pr :
-
Prandtl number, dimensionless
- R k :
-
reaction rate of k th reaction, mol/(m2·s)
- Re :
-
Reynolds number, dimensionless
- Sc :
-
Schmidt number, dimensionless
- S ext :
-
external surface to volume area ratio, m2/m3
- t :
-
time, s
- T ∞ :
-
ambient temperature, K
- T g :
-
gas temperature, K
- T s :
-
substrate temperature, K
- ν g :
-
gas flow velocity, m/s
- X inlet :
-
species concentration at the catalyst inlet, mol/m3
- X outlet :
-
species concentration at the catalyst outlet, mol/m3
- z :
-
coordinate along catalyst axis, m
- ɛ:
-
void volume fraction, dimensionless
- λ g :
-
thermal conductivity of gas, J/m·s·K
- λ s :
-
thermal conductivity of substrate, J/(m·s·K)
- ρ g :
-
gas density, kg/m3
- ρ s :
-
substrate density, kg/m3
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Shamim, T. Effect of engine exhaust gas modulation on the cold start emissions. Int.J Automot. Technol. 12, 475–487 (2011). https://doi.org/10.1007/s12239-011-0056-2
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DOI: https://doi.org/10.1007/s12239-011-0056-2