Fresh and Aged SCRT Systems Retrofitted on a MY 1998 Class-8 Tractor: Investigation on In-use Emissions 2011-24-0175
In order to comply with stringent 2010 US-Environmental
Protection Agency (EPA) on-road, Heavy-Duty Diesel (HDD) emissions
regulations, the Selective Catalytic Reduction (SCR) aftertreatment
system has been judged by a multitude of engine manufacturers as
the primary technology for mitigating emissions of oxides of
nitrogen (NOx). As virtually stand-alone aftertreatment
systems, SCR technology further represents a very flexible and
efficient solution for retrofitting legacy diesel engines as the
most straightforward means of cost-effective compliance attainment.
However, the addition of a reducing agent injection system as well
as the inherent operation limitations of the SCR system due to
required catalyst bed temperatures introduce new, unique problems,
most notably that of ammonia (NH₃) slip. Even the most refined
systems, while performing flawlessly during standardized
certification tests, may encounter excursions during real-world
operation, thereby leading to possible formation of secondary
emissions and emit unacceptable high NOx.
The following study, funded by the South Coast Air Quality
Measurement District (AQMD) and supported by Johnson Matthey, was
initiated to provide a better understanding of the performance and
especially durability of retrofit exhaust aftertreatment systems
comprising of Diesel Particulate Filter (DPF) and SCR devices.
Specifically, two SCRT® systems retrofitted to a Class-8 Heavy-Duty
Diesel (HDD) truck, whereof one was new and another been in on-road
operation for the duration of 15 months, were evaluated on a
chassis dynamometer with regard to overall system performance,
secondary emissions formation and NOx conversion
efficiency deteriorations due to catalyst aging. SCR conversion
efficiencies ranged between 67% to 71% and Particulate Matter (PM)
filtration efficiencies above 90%, depending on vehicle test cycle.
No statistical evidence for a reduction in SCR® efficiency over the
course of a 15 months on-road operation period could be found at
the 5% significance level.
Citation: Littera, D., Besch, M., Cozzolini, A., Carder, D. et al., "Fresh and Aged SCRT Systems Retrofitted on a MY 1998 Class-8 Tractor: Investigation on In-use Emissions," SAE Technical Paper 2011-24-0175, 2011, https://doi.org/10.4271/2011-24-0175. Download Citation
Daniele Littera, Marc Besch, Alessandro Cozzolini, Daniel Carder, Arvind Thiruvengadam, Adam Sayres, Hemanth Kappanna, Mridul Gautam, Adewale Oshinuga
West Virginia University, South Coast Air Quality Mgmt District
10th International Conference on Engines & Vehicles