Effects of Biodiesel Blends and Arco EC-Diesel on Emissions from Light Heavy-Duty Diesel Vehicles

Chassis dynamometer tests were performed on seven light heavy-duty diesel trucks comparing the emissions of a California diesel fuel with emissions from four other fuels:  ARCO emissions control diesel (EC-D) and three 20% biodiesel blends (one yellow grease and two soy-based). The EC-D and the yellow grease biodiesel blend both showed significant reductions in total hydrocarbons (THC) and carbon monoxide (CO) emissions over the test vehicle fleet. EC-D also showed reductions in particulate matter (PM) emission rates. NOx emissions were comparable for the different fuel types for most of the vehicles tested. The soy-based biodiesel blends showed smaller emissions differences over the test vehicles, including some increases in PM emissions. This is somewhat in contrast to previous studies that have shown larger reductions in THC, CO, and PM for biodiesel blends. The possible influence of different fuels, fuel properties, and engine load on emissions is also discussed

Exceedances of Secondary Aerosol Formation from In-Use Natural Gas Heavy-Duty Vehicles Compared to Diesel Heavy-Duty Vehicles

This work, for the first time, assessed the secondary aerosol formation from both in-use diesel and natural gas heavy-duty vehicles of different vocations when they were operated on a chassis dynamometer while the vehicles were exercised on different driving cycles. Testing was performed on natural gas vehicles equipped with three-way catalysts (TWCs) and diesel trucks equipped with diesel oxidation catalysts, diesel particulate filters, and selective catalytic reduction systems. Secondary aerosol was measured after introducing dilute exhaust into a 30 m3 environmental chamber. Particulate matter ranged from 0.18 to 0.53 mg/mile for the diesel vehicles vs 1.4–85 mg/mile for the natural gas vehicles, total particle number ranged from 4.01 × 1012 to 3.61 × 1013 for the diesel vehicles vs 5.68 × 1012–2.75 × 1015 for the natural gas vehicles, and nonmethane organic gas emissions ranged from 0.032 to 0.05 mg/mile for the diesel vehicles vs 0.012–1.35 mg/mile for the natural gas vehicles. Ammonia formation was favored in the TWC and was found in higher concentrations for the natural gas vehicles (ranged from ∼0 to 1.75 g/mile) than diesel vehicles (ranged from ∼0 to 0.4 g/mile), leading to substantial secondary ammonium nitrate formation (ranging from 8.5 to 98.8 mg/mile for the natural gas vehicles). For the diesel vehicles, one had a secondary ammonium nitrate of 18.5 mg/mile, while the other showed essentially no secondary ammonium nitrate formation. The advanced aftertreatment controls in diesel vehicles resulted in almost negligible secondary organic aerosol (SOA) formation (ranging from 0.046 to 2.04 mg/mile), while the natural gas vehicles led to elevated SOA formation that was likely sourced from the engine lubricating oil (ranging from 3.11 to 39.7 mg/mile). For two natural gas vehicles, the contribution of lightly oxidized lubricating oil in the primary organic aerosol was dominant (as shown in the mass spectra analysis), leading to enhanced SOA mass. Heavily oxidized lubricating oil was also observed to contribute to the SOA formation for other natural gas vehicles

Effects of Fuel Ethanol Content and Volatility on Regulated and Unregulated Exhaust Emissions for the Latest Technology Gasoline Vehicles

Oxygenate content and fuel volatility (distillation) variables are important parameters affecting vehicle exhaust emissions, and data on their effects on the latest technology vehicles are quite limited. For this study, 12 California-certified LEV to SULEV vehicles were tested on a matrix of 12 fuels with varying levels of ethanol concentration (0, 5.7, and 10 vol %), T50 (195, 215, and 235 °F), and T90 (295, 330, and 355 °F). There were statistically significant interactions between ethanol and T90 for NMHC, ethanol, and T50 for CO and ethanol and T50 for NOx. NMHC emissions increased with increasing ethanol content at the midpoint and high level of T90 but were unaffected at the low T90 level. CO emissions decreased as the ethanol content increased from the low to the midpoint level for all levels of T50, but between the 5.7 and 10% ethanol levels, CO showed only an increase for the high level of T50. NOx emissions increased with ethanol content for some conditions. Non-methane organic gases (NMOG) and toxic emissions were examined for only a subset of fuels with the highest T90 level, with NMOG, acetaldehyde, benzene, and 1−,3-butadiene all found to increase with increasing ethanol content

Will Aerosol Hygroscopicity Change with Biodiesel, Renewable Diesel Fuels and Emission Control Technologies?

The use of biodiesel and renewable diesel fuels in compression ignition engines and aftertreatment technologies may affect vehicle exhaust emissions. In this study two 2012 light-duty vehicles equipped with direct injection diesel engines, diesel oxidation catalyst (DOC), diesel particulate filter (DPF), and selective catalytic reduction (SCR) were tested on a chassis dynamometer. One vehicle was tested over the Federal Test Procedure (FTP) cycle on seven biodiesel and renewable diesel fuel blends. Both vehicles were exercised over double Environmental Protection Agency (EPA) Highway fuel economy test (HWFET) cycles on ultralow sulfur diesel (ULSD) and a soy-based biodiesel blend to investigate the aerosol hygroscopicity during the regeneration of the DPF. Overall, the apparent hygroscopicity of emissions during nonregeneration events is consistently low (κ < 0.1) for all fuels over the FTP cycle. Aerosol emitted during filter regeneration is significantly more CCN active and hygroscopic; average κ values range from 0.242 to 0.439 and are as high as 0.843. Regardless of fuel, the current classification of “fresh” tailpipe emissions as nonhygroscopic remains true during nonregeneration operation. However, aftertreatment technologies such as DPF, will produce significantly more hygroscopic particles during regeneration. To our knowledge, this is the first study to show a significant enhancement of hygroscopic materials emitted during DPF regeneration of on-road diesel vehicles. As such, the contribution of regeneration emissions from a growing fleet of diesel vehicles will be important

Quantifying In-Use PM Measurements for Heavy Duty Diesel Vehicles

Heavy duty emissions regulations have recently expanded from the laboratory to include in-use requirements. This paradigm shift to in-use testing has forced the development of portable emissions measurement systems (PEMS) for particulate matter (PM). These PM measurements are not trivial for laboratory work, and are even more complex for in-use testing. This study evaluates five PM PEMS in comparison to UCR’s mobile reference laboratory under in-use conditions. Three on-highway, heavy-duty trucks were selected to provide PM emissions levels from 0.1 to 0.0003 g/hp-h, with varying compositions of elemental carbon (EC), organic carbon (OC), and sulfate. The on-road driving courses included segments near sea level, at elevations up to 1500 m, and coastal and desert regions. The photoacoustic measurement PEMS performed best for the non-aftertreatment system (ATS)-equipped engine, where the PM was mostly EC, with a linear regression slope of 0.91 and an R2 of 0.95. The PEMS did not perform as well for the 2007 modified ATS equipped engines. The best performing PEMS showed a slope of 0.16 for the ATS-equipped engine with predominantly sulfate emissions and 0.89 for the ATS-equipped engine with predominantly OC emissions, with the next best slope at 0.45 for the predominantly OC engine

Evaluation of the Impacts of Biodiesel and Second Generation Biofuels on NO_x Emissions for CARB Diesel Fuels

The impact of biodiesel and second generation biofuels on nitrogen oxides (NO_<i>x</i>) emissions from heavy-duty engines was investigated using a California Air Resources Board (CARB) certified diesel fuel. Two heavy-duty engines, a 2006 engine with no exhaust aftertreatment, and a 2007 engine with a diesel particle filter (DPF), were tested on an engine dynamometer over four different test cycles. Emissions from soy- and animal-based biodiesels, a hydrotreated renewable diesel, and a gas to liquid (GTL) fuel were evaluated at blend levels from 5 to 100%. NO_<i>x</i> emissions consistently increased with increasing biodiesel blend level, while increasing renewable diesel and GTL blends showed NO_<i>x</i> emissions reductions with blend level. NO_<i>x</i> increases ranged from 1.5% to 6.9% for B20, 6.4% to 18.2% for B50, and 14.1% to 47.1% for B100. The soy-biodiesel showed higher NO_<i>x</i> emissions increases compared to the animal-biodiesel. NO_<i>x</i> emissions neutrality with the CARB diesel was achieved by blending GTL or renewable diesel fuels with various levels of biodiesel or by using di-<i>tert</i>-butyl peroxide (DTBP). It appears that the impact of biodiesel on NO_<i>x</i> emissions might be a more important consideration when blended with CARB diesel or similar fuels, and that some form of NO_<i>x</i> mitigation might be needed for biodiesel blends with such fuels

Evaluation of the Impacts of Biodiesel and Second Generation Biofuels on NO_x Emissions for CARB Diesel Fuels

The impact of biodiesel and second generation biofuels on nitrogen oxides (NO_<i>x</i>) emissions from heavy-duty engines was investigated using a California Air Resources Board (CARB) certified diesel fuel. Two heavy-duty engines, a 2006 engine with no exhaust aftertreatment, and a 2007 engine with a diesel particle filter (DPF), were tested on an engine dynamometer over four different test cycles. Emissions from soy- and animal-based biodiesels, a hydrotreated renewable diesel, and a gas to liquid (GTL) fuel were evaluated at blend levels from 5 to 100%. NO_<i>x</i> emissions consistently increased with increasing biodiesel blend level, while increasing renewable diesel and GTL blends showed NO_<i>x</i> emissions reductions with blend level. NO_<i>x</i> increases ranged from 1.5% to 6.9% for B20, 6.4% to 18.2% for B50, and 14.1% to 47.1% for B100. The soy-biodiesel showed higher NO_<i>x</i> emissions increases compared to the animal-biodiesel. NO_<i>x</i> emissions neutrality with the CARB diesel was achieved by blending GTL or renewable diesel fuels with various levels of biodiesel or by using di-<i>tert</i>-butyl peroxide (DTBP). It appears that the impact of biodiesel on NO_<i>x</i> emissions might be a more important consideration when blended with CARB diesel or similar fuels, and that some form of NO_<i>x</i> mitigation might be needed for biodiesel blends with such fuels

Evaluating the Effects of Aromatics Content in Gasoline on Gaseous and Particulate Matter Emissions from SI-PFI and SIDI Vehicles

We assessed the emissions response of a fleet of seven light-duty gasoline vehicles for gasoline fuel aromatic content while operating over the LA92 driving cycle. The test fleet consisted of model year 2012 vehicles equipped with spark-ignition (SI) and either port fuel injection (PFI) or direct injection (DI) technology. Three gasoline fuels were blended to meet a range of total aromatics targets (15%, 25%, and 35% by volume) while holding other fuel properties relatively constant within specified ranges, and a fourth fuel was formulated to meet a 35% by volume total aromatics target but with a higher octane number. Our results showed statistically significant increases in carbon monoxide, nonmethane hydrocarbon, particulate matter (PM) mass, particle number, and black carbon emissions with increasing aromatics content for all seven vehicles tested. Only one vehicle showed a statistically significant increase in total hydrocarbon emissions. The monoaromatic hydrocarbon species that were evaluated showed increases with increasing aromatic content in the fuel. Changes in fuel composition had no statistically significant effect on the emissions of nitrogen oxides (NO_<i>x</i>), formaldehyde, or acetaldehyde. A good correlation was also found between the PM index and PM mass and number emissions for all vehicle/fuel combinations with the total aromatics group being a significant contributor to the total PM index followed by naphthalenes and indenes

Investigation of NH₃ Emissions from New Technology Vehicles as a Function of Vehicle Operating Conditions

The objective of this study was to measure ammonia (NH3) emissions from modern technology vehicles since information is scarce about this important source of particulate matter (PM) precursors. Test variables included the emission level to which the vehicle was certified, the vehicle operating conditions, and catalyst age. Eight vehicles with low-emission vehicle (LEV) to super-ultralow-emission vehicle (SULEV) certification levels were tested over the Federal Test Procedure (FTP75), a US06 cycle, a hot running 505, a New York City Cycle (NYCC), and a specially designed Modal Emissions Cycle (MEC01v7) using both as-received and bench-aged catalysts. NH3 emissions in the raw exhaust were measured by tunable diode laser (TDL) absorption spectroscopy. The results show that NH3 emissions depend on driving mode and are primarily generated during acceleration events. More specifically, high NH3 emissions were found for high vehicle specific power (VSP) events and rich operating conditions. For some vehicles, NH3 emissions formed immediately after catalyst light-off during a cold start

Assessing the Impacts of Ethanol and Isobutanol on Gaseous and Particulate Emissions from Flexible Fuel Vehicles

This study investigated the effects of higher ethanol blends and an isobutanol blend on the criteria emissions, fuel economy, gaseous toxic pollutants, and particulate emissions from two flexible-fuel vehicles equipped with spark ignition engines, with one wall-guided direct injection and one port fuel injection configuration. Both vehicles were tested over triplicate Federal Test Procedure (FTP) and Unified Cycles (UC) using a chassis dynamometer. Emissions of nonmethane hydrocarbons (NMHC) and carbon monoxide (CO) showed some statistically significant reductions with higher alcohol fuels, while total hydrocarbons (THC) and nitrogen oxides (NO_<i>x</i>) did not show strong fuel effects. Acetaldehyde emissions exhibited sharp increases with higher ethanol blends for both vehicles, whereas butyraldehyde emissions showed higher emissions for the butanol blend relative to the ethanol blends at a statistically significant level. Particulate matter (PM) mass, number, and soot mass emissions showed strong reductions with increasing alcohol content in gasoline. Particulate emissions were found to be clearly influenced by certain fuel parameters including oxygen content, hydrogen content, and aromatics content