Physical and chemical characteristics of soot particles from GDI engines: Roles of fuels, lubricants, and transient driving cycles

Particulate matter emissions from gasoline direct injection (GDI) engines have become a growing environmental and health concern due to their ultrafine particle sizes, high reactivity, and potential toxicity. As global emission regulations become increasingly stringent, a deeper understanding of the physical and chemical characteristics of GDI soot is critical for developing effective control strategies, particularly in optimizing gasoline particulate filter (GPF) performance. This review investigates the physical and chemical properties of soot particles emitted from GDI engines, focusing on the roles of fuel composition, lubricating oil, and transient driving conditions. GDI soot exhibits unique characteristics, including smaller particle sizes and higher oxidative reactivity, which are critical for understanding its environmental and health impacts. The study examines the influence of oxygenated fuels, such as ethanol and dimethyl carbonate, on soot morphology, nanostructure, and oxidation reactivity, highlighting their potential to enhance particulate filter regeneration. Additionally, the impact of lubricating oils on soot formation and the interaction between soot particles and oil additives are analyzed, revealing significant effects on soot morphology and chemical composition. The review also explores soot properties under transient driving cycles, emphasizing variations in particle size, surface chemistry, and polycyclic aromatic hydrocarbon content. These findings provide essential insights into the physical and chemical characteristics of GDI soot, offering a scientific basis for improving soot oxidation processes and optimizing GPF regeneration strategies.