March 2009
Idle Emissions from Medium Heavy-Duty Diesel and Gasoline Trucks
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ABM S. Khan, Nigel N. Clark, Mridul Gautam, W. Scott Wayne, Gregory J. Thompson, and Donald W. Lyons,
Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV
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AbstractIdle emissions data from 19 medium heavy-duty diesel and gasoline trucks are presented in this paper. Emissions from these trucks were characterized using full-flow exhaust dilution as part of the Coordinating Research Council (CRC) Project E-55/59. Idle emissions data were not available from dedicated measurements, but were extracted from the continuous emissions data on the low-speed transient mode of the medium heavy-duty truck (MHDTLO) cycle. The four gasoline trucks produced very low oxides of nitrogen (NOx) and negligible particulate matter (PM) during idle. However, carbon monoxide (CO) and hydrocarbons (HCs) from these four trucks were approximately 285 and 153 g/hr on average, respectively. The gasoline trucks consumed substantially more fuel at an hourly rate (0.84 gal/hr) than their diesel counterparts (0.44 gal/hr) during idling. The diesel trucks, on the other hand, emitted higher NOx (79 g/hr) and comparatively higher PM (4.1 g/hr), on average, than the gasoline trucks (3.8 g/hr of NOx and 0.9 g/hr of PM, on average). Idle NOx emissions from diesel trucks were high for post-1992 model year engines, but no trends were observed for fuel consumption. Idle emissions and fuel consumption from the medium heavy-duty diesel trucks (MHDDTs) were marginally lower than those from the heavy heavy-duty diesel trucks (HHDDTs), previously reported in the literature.
ImplicationsAir quality improvement programs necessitate an accurate assessment of truck idle emissions. HHDDT idle emissions were previously reported in this journal, but medium heavyduty truck (MHDT) idle emissions have not been well documented before. MHDT idle is likely to occur in local delivery in urban environments. This paper provides idle emissions of CO, HCs, NOx, PM, and carbon dioxide and idle fuel consumption from a sample of 19 medium heavy-duty diesel and gasoline vehicles with model years ranging from 1974 to 2001. These data are particularly relevant because, according to the 2002 U.S. Census Bureau, 75% of the medium-duty trucks operating in the United States were model year 1997 or older. No new data were found, but this information suggests that the data reported would cover approximately 75% of the 2006 fleet.
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