AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Effect of Drive Cycle and Gasoline Particulate Filter on Size and Morphology of Soot Particles Produced by a Gasoline Direct Injection Vehicle
MEGHDAD SAFFARIPOUR, Fengshan Liu, Kevin Thomson, Tak Chan, Joseph Kubsh, Brezny Rasto, National Research Council Canada
Abstract Number: 412 Working Group: Combustion
Abstract To provide a better understanding of soot formation in Gasoline Direct Injection (GDI) engines and the impact of Gasoline Particulate Filters (GPF) on these emissions, a detail characterization of the size and morphology of particulates is performed by Transmission Electron Microscope (TEM) image analysis on a 2013 2.0-liter GDI vehicle at standard temperature on a chassis dynamometer. Particulate samples are collected over the U.S. Federal Test Procedure (FTP-75) and the US06 Supplemental Federal Test Procedure (US06), with and without the use of a catalytic regenerative GPF. In the absence of the GPF, TEM images exhibit fractal-like clusters of spherical primary particles (spherules), with no evidence of volatile material (organic carbon) or collapsed particles. Throughout both drive cycles, spherule size remains unchanged (about 26 nm) with a narrow size distribution. The aggregate fractal dimensions and fractal prefactors are 1.8 and 1.4, respectively, showing that these particles have morphologies similar to diesel particulates. TEM image analysis indicates no statistical difference between the sizes of soot aggregates in different phases of the FTP cycle. However, over the US06 drive cycle, particles are smaller and contain fewer spherules (15 spherules compared to 22). This is because of the higher engine speeds and lower residence times compared to the FTP cycle. When a GPF is installed, the aggregates are slightly larger, confirming that finer particles are more effectively removed by the GPF. On the other hand, the size of spherules and the morphology of aggregates do not change. In contrast to the FTP drive cycle, over the US06 cycle, post-GPF exhaust temperature is hot enough to support soot regeneration during which, additional ultrafine particles are emitted with a volatile nature. TEM images verify the presence of a considerable amount of these ultrafine and volatile particles and show that soot aggregates are coated with these materials.