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 (alpha(gasoline)) and excess air ratios (lambda). The results indicate that T-max declines after gasoline addition at lambda = 1, 1.2, while increases after gasoline addition at lambda = 1.4. The IMEP reaches the maximum value at DIT = 90 or 105 degrees CA BTDC and 0%, 10% and 30% gasoline addition bring the highest IMEP at lambda = 1, 1.2 and 1.4, respectively. The COVIMEP decreases continuously with the increase of alpha(gasoline) and the EPI+GDI mode has great advantages in improving the combustion stability under lambda = 1.4 condition. As for gaseous emissions, from lambda = 1 to lambda = 1.4, HC emissions change from increasing trend to the decreasing trend with the increase of alpha(gasoline). while the NOx emissions show the opposite. As for particle number, at lambda = 1 and 1.2, the total particle number (TPN) shows an upward trend with the increase of alpha(gasoline) When lambda = 1.4, TPN decreases with the increase of alpha(gasoline). (C) 2019 Elsevier Ltd. All rights reserved.