Effects of Fuel Components on Thermal Efficiency and Emissions in Super Lean Burn S.I. Engine

To reduce CO2 emission from the vehicles equipped with internal combustion engine, it is important to combine novel fuel characteristics with combustion technology for high thermal efficiency engine. Lean boosted technology has been studied for a long time because of its potential to increase engine thermal efficiency. Super lean-burn whose excess air ratio λ is higher than 2.0 is expected to achieve both high thermal efficiency and low NOx emissions. In such high λ condition, the chemical reaction effect of fuel components becomes more important. However, it is not evaluated enough due to the difficulty of achieving super lean condition. Therefore, in this paper the effects of fuel on combustion speed, knocking, emission and thermal efficiency are analyzed with super lean burn engine. As a result, it is clarified that the fuel effect on enhancing combustion, especially latter half of combustion is important to reduce HC emission and improves thermal efficiency in super lean burn engine.