Characterization of Real-Time Particle Emissions from a Gasoline Direct Injection Vehicle Equipped with a Catalyzed Gasoline Particulate Filter During Filter Regeneration

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.