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In this paper, the impacts of Aromatic and Olefin on the formation of poly-aromatic hydrocarbons (PAHs) in the gasoline direct injection (GDI) engine were experimentally and numerically investigated. The objective of this study is to describe the formation process of the soot precursors including one ring to four ring aromatics (A1-A4). In order to better understand the effects of the fuel properties on the formations of PAHs. Three types of fuels, namely base gasoline, gasoline with higher aromatics content, and gasoline with higher olefin content were experimentally studied. At the same time, these aspects were also numerically investigated in the CHEMKIN code by using premixed laminar flame model and surrogated fuels. The results show that higher aromatics content in gasoline will lead to much higher PAHs formation. Similar trend was also found in the gasoline with higher olefin content.

Spray atomization, spray-wall impingement, and mixture formation are key factors in affecting the particulate matter (PM) emission in gasoline direct injection (GDI) engines. Current knowledge of wall-wetting phenomenon and mixture formation are mostly based on the studies that the fuel is injected at ordinary temperature and various ambient conditions. In the real GDI engine, the fuel pipe and injector are always heated up by the pump and the engine body, especially at hot engine conditions, thus the fuel temperature is always higher than the ordinary temperature, and the relevant research is still limited. The aim of this study is to numerically investigate the spray, spray-wall impingement, and mixture formation characteristics under different fuel temperature conditions, so as to provide theoretical support in optimizing the combustion performance and further reducing the PM emission of GDI engines.