No abstract

Real-time solid particle number (PN), size distributions, black carbon (BC), and particulate matter (PM) mass measurements were obtained from a gasoline direct injection (GDI) vehicle with and without a catalyzed gasoline particulate filter (GPF) over the US Federal Test Procedure 75 (FTP-75) and US06 Supplemental Federal Test Procedure (US06) drive cycles. The organic and elemental carbon fractions of the carbonaceous PM and transmission electron microscope (TEM) images for the exhaust particles were examined. Particles emitted from the GDI vehicle over various moderate driving conditions have similar morphology, size, and composition. These accumulation mode particles have diameters of 50 to 90 nm, have comparable fractal structures to diesel particles, and contain mostly BC with little organic materials. Under aggressive driving conditions, many nanoparticles (<20 nm in diameter) are emitted with the accumulation mode particles. Over the FTP-75 driving conditions, the optimized GPF reaches particle filtration efficiency of over 90 % from clean condition rapidly and filtration efficiency remains unchanged as filter regeneration was not observed. Over the US06 driving condition, filter regeneration was triggered by the high exhaust temperature during which many nanoparticles with diameters smaller than 30 nm are formed downstream of the GPF. TEM image analysis suggests that BC particles collected during the filter regeneration contain a layer of semi-volatile materials on the aggregate surface while the nanoparticles were semi-volatile in nature. During filter regeneration, moderate filtration of the accumulation mode BC particles was still observed.

The influence of the aromatic hydrocarbons in gasoline on the fuel distillation parameter, as well as the particle number (PN), black carbon (BC), and other regulated gaseous emissions from a passenger car (PC) and light-duty truck (LDT), was assessed by operating two vehicles fueled with U.S. Environmental Protection Agency Tier 3 certification gasoline and two gasoline test fuels over two standard drive cycles. The two gasoline test fuels represent a range of commercial motor gasoline, with one containing less naphthalenes and lower heavy fraction volatility (T80, T90, and final boiling point) than the other. Observations showed that various gasolines have minor impact on both vehicles on regulated gaseous emissions and fuel consumption. Particulate emissions from both vehicles showed similar trends with fuel type, with lower naphthalene containing gasoline produced lower PN and BC emissions. In addition, the effect of fuel on particle emissions varied with vehicle type, drive cycle, and power to weight ratio. Results also showed that lowering the naphthalenes in gasoline produces smaller sized particles. The real-time particle emission time series from both vehicles suggested that the composition and volatility of the gasoline fuels are sensitive parameters in influencing particulate matter emissions. These results could support one possible explanation of the large variations in emission factors reported in the literature when using different gasolines in the same type of vehicle and driving conditions.

No abstract