Effects of wall wetting and in-cylinder fuel distribution in an advanced turbo-charged engine

One of the proposed concepts for spark ignition engines is advanced port fuel injection(APFI),which suggests using two port injectors for each cylinder.In this research,we numerically examine the capabilities of this concept in reducing fuel consumption and increasing engine performance.The results demonstrated that the use of this concept is very effective due to the use of two injectors and the possibility of reducing the spraying time and bringing the injection start time closer to the air inlet valve opening time.The maximum amount of fuel film formed on the walls is reduced by about 75%,naturally,which leads to better and more homogeneous fuel distribution inside the combustion chamber and increases combustion efficiency.The results showed that under the same boundary conditions and engine operating point,the use of two port injectors for each cylinder leads to an increase of more than 20%of the maximum combustion chamber pressure and about 4%combustion efficiency.On the other hand,fuel film formation becomes worse in cold conditions.So in this study,the capabilities of this concept in cold conditions were investigated too.Investigations have shown that the advanced port fuel injection,unlike conventional engines,is almost insensitive to inlet temperature changes.

Potential of secondary aerosol formation from Chinese gasoline engine exhaust

Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol（SOA） production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.