Abstract
Particulate Matter (PM) emissions from gasoline direct injection (GDI) engines, particularly Particle Number (PN) emissions, have been studied intensively in both academia and industry because of the adverse effects of ultrafine PM emissions on human health and other environmental concerns. GDI engines are known to emit a higher number of PN emissions (on an engine-out basis) than Port Fuel Injection (PFI) engines, due to the reduced mixture homogeneity in GDI engines. Euro 6 emission standards have been introduced in Europe (and similarly in China) to limit PN emissions from GDI engines. This article summarises the current state of research in GDI PN emissions (engine-out) including a discussion of PN formation, and the characteristics of PN emissions from GDI engines. The effect of key GDI engine operating parameters is analysed, including air-fuel ratio, ignition and injection timing, injection pressure, and EGR; in addition the effect of fuel composition on particulate emissions is explored, including the effect of oxygenate components such as ethanol.
Highlights
Gasoline Direct Injection (GDI) engines are a key enabler for reducing CO2 emissions from gasoline-powered vehicles
Limited review work on GDI Particulate Matter (PM) emissions has been conducted previously other than a review by Überall et al [15] and one by Myung and Park, [16] which cover a wide range of topics, including the effect of particulate emissions on health, PM measurement techniques, PM chemical analysis and fuel influences
The carbon composition of PM is broken down into elemental carbon (EC) and organic carbon (OC); studies have shown that EC accounts for around 90% of PM mass emitted from GDI engines [43]
Summary
Gasoline Direct Injection (GDI) engines are a key enabler for reducing CO2 emissions from gasoline-powered vehicles. In comparison with diesel engines fitted with diesel particle filter (DPF), GDI vehicles produce more ultrafine particles [2,5] These ultrafine particles, below the size of 100 nm, have been associated with adverse impacts on human health and environment [3,6,7,8,9,10,11,12]. Ultrafine PM may contribute little to the total particle mass, they occupy a significant proportion of the total particle number This has led to the introduction of the Euro 6 regulations where. Limited review work on GDI PM emissions has been conducted previously other than a review by Überall et al [15] and one by Myung and Park, [16] which cover a wide range of topics, including the effect of particulate emissions on health, PM measurement techniques, PM chemical analysis and fuel influences. This review paper provides a comprehensive report on recent progress in GDI PM number emissions research and PM number reduction techniques
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