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Real-Time On-Board Indirect Light-Off Temperature Estimation as a Detection Technique of Diesel Oxidation Catalyst Effectiveness Level
Technical Paper
2013-01-1517
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
The latest US emission regulations require dramatic reductions
in Nitrogen Oxide (NOx) emissions from vehicular diesel engines.
Selective Catalytic Reduction (SCR) is the current technology that
achieves NOx reductions of up to 90%. It is typically mounted
downstream of the existing after-treatment system, i.e., after the
Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter
(DPF). Accurate prediction of input NO₂:NO ratio is useful for
control of SCR urea injection to reduce NOx output and NH₃ slippage
downstream of the SCR catalyst. Most oxidation of NO to NO₂ occurs
in the DOC since its main function is to oxidize emission
constituents. The DOC thus determines the NO₂:NO ratio as feedgas
to the SCR catalyst. The prediction of NO₂:NO ratio varies as the
catalyst in the DOC ages or deteriorates due to poisoning. Thus,
the DOC prediction model has to take into account the correlation
of DOC conversion effectiveness and the aging of the catalyst.
This research project is aimed at detecting the aging level in
the DOC in real time under actual operating conditions by
estimating the light-off temperature for hydrocarbon conversion.
The thermal energy balance used to compute indirect light-off
temperature includes a substrate heat rate storage term. This
energy balance equation is then applied to an instrumented DOC for
light-off temperature detection. Evaluation of the equation terms
shows that heat loss analysis to surroundings is negligible while
uncertainty in the post-fueling quantity to the exhaust stream was
found to have a significant impact on the estimated light-off
temperature. Ultimately, the light-off temperature can be
determined with only 1 thermocouple inside the DOC rather than the
original 12 thermocouples. A comparison analysis for fresh and aged
DOC's shows that clear light-off temperature shifts were
detected after the catalyst was thermally aged and the indirect
estimation could roughly predict the aged DOC conversion. This is
shown in detail in later sections of this paper. However, the
technology is still preliminary and further work on data
repeatability and consistency needs to be done before the
technology can be adopted for real-world application.
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Citation
Sutjiono, R., Tayal, P., Zhou, K., and Meckl, P., "Real-Time On-Board Indirect Light-Off Temperature Estimation as a Detection Technique of Diesel Oxidation Catalyst Effectiveness Level," SAE Technical Paper 2013-01-1517, 2013, https://doi.org/10.4271/2013-01-1517.Also In
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