Comparison of Real-World and MOVES Estimated Emissions for Heavy-Duty Diesel Refuse Trucks

摘要

Real-world activity, fuel use, and emissions were measured for three refuse trucks, including one each of heavy-duty diesel front-loader, side-loader, and roll-off configurations. The trucks had engines with model years from 2003 to 2006 with similar emissions controls. Each truck was instrumented for one day of operation with a portable emissions measurement system (PEMS), Engine Control Unit (ECU) data logger, and Global Position System (GPS) receivers. Emissions of CO_2, CO, and Hydrocarbons (HC) and nitric oxide (NO) were measured. PM was measured on a relative basis using laser light scattering. Mass per time emission rates and fuel use rate were estimated on a second by second basis. Duty cycles, fuel use rates, and emission rates were quantified in terms of operating mode bins defined by the U.S. Environmental Protection Agency for the Motor Vehicle Emission Simulator (MOVES) emission factor model. The purpose of this paper is to: (1) compare fuel use and emission rates between truck configurations and cycles and (2) demonstrate a method to compare real-world and MOVES estimates of cycle average emissions rates. During the study the trucks drove 420 miles and collected 90 tons of trash from over 600 containers. The side-loader truck has the highest time spent in idle mode while the roll-off truck has the highest time spent in speeds above 25 mph. Overall, the roll-off truck has the lowest, and the side-loader truck has the highest, distance based cycle average fuel use and emissions rates. Comparing duty cycles, the roll-off cycle has a higher proportion of operation in OpModes associated both with higher engine power demand, which leads to higher time-based rates, but also with faster travel speed, which leads to lower distance-based rates. Comparing trucks, the roll-off truck has the lowest time- and distance-based fuel use and emission rates and the best fuel economy, which could be due to absence of onboard compaction and engine management that reduces idle mode fuel use. There is substantial inter-cycle and inter-truck variability. Compared to real-world, MOVES2010 under-estimates the CO_2 emission rates by 20 % to 40 % and the NO_x emission rates by 40 % to 60 %. The comparison with MOVES can be extended to include the 2014 version of the model and more trucks.