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Solid and metallic ash particle number (PN) and particulate matter (PM) mass emission measurements were performed on a heavy-duty (HD) on-highway diesel engine and a compressed natural gas (CNG) engine. Measurements were conducted under transient engine operation that included the FTP, WHTC and RMC. Both engines were calibrated to meet CARB ultra low NOX emission target of 0.02 g/hp-hr, a 90% reduction from current emissions limit. The HD diesel engine final exhaust configuration included a number of aftertreatement sub-systems in addition to a selective catalytic reduction filter (SCRF). The stoichiometric CNG engine final configuration included a closed coupled Three Way Catalyst (ccTWC) and an under floor TWC (ufTWC). The aftertreatment systems for both engines were aged for a full useful life (FUL) of 435,000 miles, prior to emissions testing. PM mass emissions from both engines were comparable and well below the US EPA emissions standard.

This paper summarizes the Heavy-Duty In-Use Testing (HDUIT) measurement allowance program for Particulate Matter Portable Emissions Measurement Systems (PM-PEMS). The measurement allowance program was designed to determine the incremental error between PM measurements using the laboratory constant volume sampler (CVS) filter method and in-use testing with a PEMS. Two independent PM-PEMS that included the Sensors Portable Particulate Measuring Device (PPMD) and the Horiba Transient Particulate Matter (TRPM) were used in this program. An additional instrument that included the AVL Micro Soot Sensor (MSS) was used in conjunction with the Sensors PPMD to be considered a PM-PEMS. A series of steady state and transient tests were performed in a 40 CFR Part 1065 compliant engine dynamometer test cell using a 2007 on-highway heavy-duty diesel engine to quantify the accuracy and precision of the PEMS in comparison with the CVS filter-based method.

Comparative exhaust emission tests were performed with five diesel fuels, namely a Sasol Fischer-Tropsch diesel, a fuel meeting the CARB diesel fuel specification, a fuel meeting the US 2-D diesel fuel specification, and two blends of the Fischer-Tropsch diesel and the 2-D diesel. Hot-start and cold-start heavy-duty transient emission tests were performed using a 1999 model year DDC series 60 engine. Regulated exhaust emissions with the Fischer-Tropsch diesel were significantly lower than with the 2-D and CARB diesel fuels, in both the hot-start and cold-start tests. When compared with test results obtained previously with a 1991 engine, it was found that the reduction in NOX with the Fischer-Tropsch fuel was smaller in the 1999 engine, while the reduction in PM was greater.

Particle number concentrations and size distributions were measured for the diluted exhaust of a 1991 diesel engine during the US FTP transient cycle for heavy-duty diesel engines. The engine was operated on US 2-D on-highway diesel fuel. The particle measurement system consisted of a full flow dilution tunnel as the primary dilution stage, an air ejector pump as the secondary dilution stage, and an electrical low pressure impactor (ELPI) for particle size distribution measurements. Particle number emission rate was the highest during the Los Angeles Non Freeway (LANF) and the Los Angeles Freeway (LAF) segments of the transient cycle. However, on brake specific number basis the LAF had the lowest emission level. The particle size distribution was monomodal in shape with a mode between 0.084 μm and 0.14 μm. The shape of the size distribution suggested no presence of nanoparticles below the lower detection limit of the instrument (0.032 μm), except during engine idle.