h i g h l i g h t s Emissions evaluation from ethanol and iso-butanol GDI and PFI vehicles. THC, CO, and NO x did not show strong trends with ethanol and blends. PM mass, number, and black carbon emissions were higher for the GDI vehicles. Increasing ethanol and butanol content reduced PM and number emissions. Butanol blends enhanced the formation of butyraldehyde emissions.

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 (NOx), 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.

a b s t r a c tWe examined the effects of different ethanol and iso-butanol blends on the gaseous and particulate emissions from two passenger cars equipped with spark ignition direct injection engines and with one spray-guided and one wall-guided configuration. Both vehicles were tested over triplicate FTP (Federal Test Procedure) and UC (Unified Cycles) using a chassis dynamometer. Emissions of THC (total hydrocarbons), NMHC (non-methane hydrocarbons), and CO (carbon monoxide) reduced with increasing oxygen content in the blend for some of the vehicle/fuel combinations, whereas NO x (nitrogen oxide) emissions did not show strong fuel effects. Formaldehyde and acetaldehyde were the main carbonyls in the exhaust, with the higher ethanol blends showing higher acetaldehyde emissions during the coldstart. For butyraldehyde emissions, both vehicles showed some increases with different butanol blends when compared to ethanol blends, but not for all cases. The higher ethanol and butanol blends showed reductions in PM (particulate mass), number, and soot mass emissions. Particulate emissions were significantly affected by the fuel injection design, with the wall-guided vehicle producing higher mass and number emissions compared to the spray-guided vehicle. Particle size was influenced by ethanol and iso-butanol content, with higher alcohol blends showing lower accumulation mode particles than the baseline fuel.

This study examines the hygroscopic and surface tension properties as a function of photochemical aging of the aerosol emissions from biomass burning. Experiments were conducted in a chamber setting at the UC-Riverside Center for Environmental Research and Technology (CE-CERT) Atmospheric Processes Lab using two biomass fuel sources, manzanita and chamise. Cloud condensation nuclei (CCN) measurements and off-line filter sample analysis were conducted. The water-soluble organic carbon content and surface tension of the extracted filter samples were measured. Surface tension information was then examined with Köhler theory analysis to calculate the hygroscopicity parameter, κ. Laboratory measurement of biomass burning smoke from two chaparral fuels is shown to depress the surface tension of water by 30% or more at organic matter concentrations relevant at droplet activation. Accounting for surface tension depression can lower the calculated κ by a factor of 2. This work provides evidence for surface tension depression in an important aerosol system and may provide closure for differing sub- and supersaturated κ measurements.

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 (NOx) 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.