Investigation of combustion and emissions of an SI engine with ethanol port injection and gasoline direct injection under lean burn conditions.

In order to reach the goal of energy conservation and pollution emissions reduction, the combustion and emissions of a combined injection engine with ethanol port injection and gasoline direct injection under lean burn conditions are investigated in this paper. The experiments are carried out by using different direct injection timing (DIT), gasoline addition ratio (α gasoline) and excess air ratios (λ). The results indicate that T max declines after gasoline addition at λ = 1, 1.2, while increases after gasoline addition at λ = 1.4. The IMEP reaches the maximum value at DIT = 90 or 105 °CA BTDC and 0%, 10% and 30% gasoline addition bring the highest IMEP at λ = 1, 1.2 and 1.4, respectively. The COV IMEP decreases continuously with the increase of α gasoline and the EPI+GDI mode has great advantages in improving the combustion stability under λ = 1.4 condition. As for gaseous emissions, from λ = 1 to λ = 1.4, HC emissions change from increasing trend to the decreasing trend with the increase of α gasoline , while the NOx emissions show the opposite. As for particle number, at λ = 1 and 1.2, the total particle number (TPN) shows an upward trend with the increase of α gasoline. When λ = 1.4, TPN decreases with the increase of α gasoline. • The injection mode is ethanol port injection plus gasoline direct injection. • 10% and 30% gasoline addition bring the highest IMEP at λ = 1.2, 1.4, respectively. • 10% gasoline addition with injection timing of 105°CA BTDC can be regarded as best condition at λ = 1.2 • 20% gasoline addition has significant effect on reducing COV IMEP and HC at λ = 1.4 • EPI+GDI is superior at lean condition due to the stratified mixture when ignition. [ABSTRACT FROM AUTHOR]