Particulate Matter Emissions from Diesel Engines Equipped with a Diesel Particulate Filter at Varying Temperatures, Loads, Fuels and Drive Cycles

The United States Environmental Protection Agency (EPA) has implemented emissions standards for manufactures to follow in an effort for producing efficient and clean diesel engines. The on-road diesel emission regulation for particulate matter (PM) restricts to 0.01 grams per brake-horsepower-hour (g/bhp-hr) and for nitrogen oxides (NOx) restricts to 0.02 g/bhp-hr. The current EPA regulations for PM are based on mass and to meet the regulations engine manufactures use a diesel particulate filter (DPF). PM has a wide range of impacts on the environment as well as human health and it is critical to minimize exposure to PM. Understanding PM emissions are an important step to reduce its impacts.;Two medium heavy-duty diesel trucks equipped with a DPF were tested at two ambient temperatures (70oF and 20oF), two fuels [ultra-low sulfur diesel (ULSD) and biodiesel (B20)], and two operating loads (a heavy and light weight) in a temperature controlled chassis dynamometer. The DPFs on the vehicles go through a clean out process, a regeneration, to remove the PM once it gets built up along the filter walls. Vehicle 1 was equipped with a NOx adsorber catalyst (NAC) in the aftertreatment system for NOx control and Vehicle 2 used a selective catalytic reduction (SCR) with urea. The test procedure included three driving cycles, a cold start with low transients (CSLT), the federal heavy-duty urban dynamometer driving schedule (UDDS), and a warm start with low transients (WSLT). All DPF active regenerations occurred during the UDDS cycle. PM emissions were measured second-by-second using an Aethalometer for black carbon (BC) concentrations and an Engine Exhaust Particle Sizer (EEPS) for particle count measurements between 5.6 and 560 nm. An analysis of variance (ANOVA) completed with the EEPS data showed that the DPF regeneration impacted the PM emissions during and after the DPF regeneration.;Vehicle 1 experienced increased BC and particle number concentrations during cold starts under cold ambient conditions, with concentrations two to three times higher than under warm starts at higher ambient temperatures. This vehicle also experienced decreased emissions when going from ULSD to B20, with an approximately 13% average decrease in PM number and an approximately 27% decrease in BC. Vehicle 2 had much lower emissions, with many of the BC and particle number measurements below detectable limits. Both vehicles did experience elevated emissions due to the DPF regeneration events. For the day after an active regeneration occurred both vehicles showed significant increases in particle number and BC for the CSLT drive cycle, with increases from 93 to 1380 percent for PM number emissions compared with tests following a day without an active regeneration. Vehicle 1 showed a decrease in PM emissions during the regeneration and a significant increase in PM emissions after a DPF regeneration. Vehicle 2 showed an increase of three orders of magnitude of PM emissions during the only DPF regeneration experienced. Both vehicles showed an increase in particle number count from the WSLT to the CSLT post-rgeneration which was 38% for Vehicle 1 and 113% for Vehicle 2 while still maintaining PM emissions levels below the standards.;Nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) emissions and fuel consumption data were also collected during this testing. Vehicle cold starts had the greatest impact on NOx, HC and CO emissions and fuel consumption and this impact was more significant at the colder ambient temperature. Vehicle cold starts attributed for a loss of fuel in miles per gallon by 29% and 35% for Vehicles 1 and 2, respectively.