The study was aimed at assessing in-use emissions of a USEPA 2010 emissions-compliant heavy-duty diesel vehicle powered by a model year (MY) 2011 engine using West Virginia University's Transportable Emissions Measurement System (TEMS). The TEMS houses full-scale CVS dilution tunnel and laboratory-grade emissions measurement systems, which are compliant with the Code of Federal Regulation (CFR), Title 40, Part 1065 [1] emissions measurement specifications. One of the specific objectives of the study, and the key topic of this paper, is the quantification of greenhouse gas (GHG) emissions (CO2, N2O and CH4) along with ammonia (NH3) and regulated emissions during real-world operation of a long-haul heavy-duty vehicle, equipped with a diesel particulate filter (DPF) and urea based selective catalytic reduction (SCR) aftertreatment system for PM and NOx reduction, respectively.
The TEMS was additionally outfitted with an MKS MultiGas® 2030-HS high-speed FTIR to quantify NH3 and N2O, along with other compounds of interest, at a frequency of 5 Hz. One of the salient features of the study is the continuous measurement of N2O and NH3 concentrations at high temporal resolution while driving across the US.
A Mack heavy-duty Class8 tractor, powered by a MY 2011, 12.8 liter diesel engine, equipped with a DOC-DPF and a urea-SCR NOx aftertreatment system was used to transport the TEMS, and ancillary measurement systems. The study was conducted over a total distance of 2,450 miles driven between Morgantown, WV and Riverside, CA, with a gross vehicle weight (GVW) of 67,000 lbs. The chosen route represented varying topography and driving conditions that included the Appalachian Mountains, flat regions of the mid-west, high altitudes of the Rocky Mountains and the busy highways of Southern California.
Results show the effect of road grade, ambient operating conditions, and on-board diagnostics (OBD) related to DPF and SCR aftertreatment systems on the GHG emissions and regulated constituents. Specifically, the results show the measured payload-distance specific CO2 emissions of a USEPA 2010 emissions-compliant Class 8 heavy-duty engine is higher than MY 2014 vehicle standards by 11% over the entire trip. The brake specific GHG emissions were lower than MY 2017 & later engine standards by a wide margin. However, the simulation tool (GEM) resulted in 13% higher CO2 emissions than measured over the entire trip. The brake specific NOx emissions were an order of magnitude higher when the engine was operating at altitudes greater than 5,500 ft.