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1.
Sci Total Environ ; 680: 132-139, 2019 Aug 25.
Article in English | MEDLINE | ID: mdl-31100665

ABSTRACT

Periodic regeneration is required to clean the diesel particulate filter (DPF) of heavy-duty diesel vehicle. In this study we analyze real-time particulate matter (PM) mass, particle number, and black carbon emissions during steady state driving active and passive diesel particulate filter (DPF) regenerations on a heavy-duty chassis dynamometer. Regeneration PM emissions were dominated by particles with count median diameter<100nm, with the majority <50nm. Results indicate that vehicle activity during DPF loading significantly affects regeneration particulate emissions. Average PM emission rates (gPM/h) from the 2010 MY vehicle were higher than the 2007 MY vehicle during all regeneration conditions in this study. Sequential forced-active regenerations resulted in reduced particulate mass emissions, but not in reduced particle number emissions, suggesting incomplete stored PM removal or effects of after-treatment fuel injection. Black carbon emission factors (EFBC) were 3.4 and 21 times larger during driving-active regeneration than during a 50 mph steady state cruise with a recently regenerated DPF for the 2007 and 2010 MY vehicle, respectively. Real-time PM emissions rates were lower during passive regeneration of the 2010 MY DPF, suggesting more modern passive regeneration technologies reduce total on-road particulate and ultrafine particulate emissions.

2.
Environ Sci Technol ; 52(10): 5868-5874, 2018 05 15.
Article in English | MEDLINE | ID: mdl-29671314

ABSTRACT

Recent tightening of particulate matter (PM) emission standards for heavy-duty engines has spurred the widespread adoption of diesel particulate filters (DPFs), which need to be regenerated periodically to remove trapped PM. The total impact of DPFs therefore depends not only on their filtering efficiency during normal operation, but also on the emissions during and the frequency of regeneration events. We performed active (parked and driving) and passive regenerations on two heavy-duty diesel vehicles (HDDVs), and report the chemical composition of emissions during these events, as well as the efficiency with which trapped PM is converted to gas-phase products. We also collected activity data from 85 HDDVs to determine how often regeneration occurs during real-world operation. PM emitted during regeneration ranged from 0.2 to 16.3 g, and the average time and distance between real-world active regenerations was 28.0 h and 599 miles. These results indicate that regeneration of real-world DPFs does not substantially offset the reduction of PM by DPFs during normal operation. The broad ranges of regeneration frequency per truck (3-100 h and 23-4078 miles) underscore the challenges in designing engines and associated aftertreatments that reduce emissions for all real-world duty cycles.


Subject(s)
Air Pollutants , Vehicle Emissions , Dust , Motor Vehicles , Particulate Matter
3.
Environ Sci Technol ; 47(14): 7892-8, 2013 Jul 16.
Article in English | MEDLINE | ID: mdl-23786244

ABSTRACT

The California Air Resources Board (ARB) undertook this study to characterize the in-use emissions of model year (MY) 2010 or newer diesel engines. Emissions from four trucks: one equipped with an exhaust gas recirculation (EGR) and three equipped with EGR and a selective catalytic reduction (SCR) device were measured on two different routes with three different payloads using a portable emissions measurement system (PEMS) in the Sacramento area. Results indicated that brake-specific NOx emissions for the truck equipped only with an EGR were independent of the driving conditions. Results also showed that for typical highway driving conditions, the SCR technology is proving to be effective in controlling NOx emissions. However, under operations where the SCR's do not reach minimum operating temperature, like cold starts and some low load/slow speed driving conditions, NOx emissions are still elevated. The study indicated that strategies used to maintain exhaust temperature above a certain threshold, which are used in some of the newer SCRs, have the potential to control NOx emissions during certain low-load/slow speed driving conditions.


Subject(s)
Nitric Oxide/analysis , Vehicle Emissions , Catalysis
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