Individual particles emitted from gasoline engines: Impact of engine types, engine loads and fuel components

Abstract

Emissions from gasoline vehicles have recently become one of the main causes for urban air pollution. In this work, individual particles of particulate matter emitted from the gasoline engines on the test bench were characterised using transmission electron microscopy coupled with energy-dispersive X-ray spectrometry (TEM-EDX). Effects of the engine types (gasoline direct injection (GDI) engines and port fuel injection (PFI) engines), fuel components (F1–5), engine loads (25, 50, and 75%), and three-way catalyst (TWC) on particulate emissions were tested. The results show that there were six types of individual particles emitted from gasoline engines including soot, organic particles, Fe-rich particles, S-rich particles, Mn-rich particles, and Ca-rich particles, in which the organic, soot, and S-rich particles were predominant types. The particles emitted from GDI engines had a higher percentage of soot and lower percentage of organic particles compared to those from PFI engines. Fuel types also influenced compositions of the emitted particles. F1 produced a relatively high percentage of organic particles. Compared to F1, F2 containing more aromatics contributed a higher percentage of soot particles; F3 containing MMT (methylcyclopentadienyl manganese tricarbonyl) led to a considerably higher percentage of soot particles, and F4 gasoline (addition of 10% ethanol by volume) produced a lower percentage of soot particles. Compared to F1, F5 with a lower olefin content produced a lower percentage of organic particles. In addition, with increasing load, the relative percentages of soot increased, while the relative percentages of organic particles decreased. Finally, when TWC was used, the percentage of soot increased significantly in association with an increase in particle sizes.