Authors
Peng, Qian; Rockstroh, Toby; Hall, Carrie
Abstract
Gasoline compression ignition in diesel engines has been proposed in orderto meet increasingly stringent emission regulations without sacrificing efficiency. In this study, a six-cylinder heavy-duty diesel engine was operatedin a mixing controlled gasoline compression ignition mode to investigate theinfluence of fuels and injection strategies on the combustion characteristics,emissions, and thermal efficiencies. Fuels, including ethanol (E), isobutanol(IB), and diisobutylene (DIB), were blended with a gasoline fuel to formE10, E30, IB30, and DIB30 based on volumetric fraction. These four blendsalong with gasoline formed the five test fuels. With these fuels, three injections strategies were investigated, including late pilot injection, early pilotinjection, and port fuel injection/direct injection. The impact of moderateexhaust gas recirculation on nitrogen oxides and soot emissions was examined to determine the most promising fuel/injection strategy for emissionsreduction. In addition, first and second law analyses were performed to provide insights into the efficiency, loss, and exergy destruction of the variousgasoline fuel blends at low and medium load conditions. Overall, the emission output, thermal efficiency, and combustion performances of the five fuelswere found to be similar and their differences are modest under most testconditions. E30 with the port/direct fuel injection strategy obtained thepeak brake thermal efficiency (46.9%) and gross indicated thermal efficiency(52.2%) at 14 bar. At 7 bar, the peak brake thermal efficiency (44.2%) andgross indicated thermal efficiency (52.5%) also belonged to E30 with the latepilot injection strategy. The second law analysis revealed that exergy destruction was mostly influenced by the fuel type and not by the injectionstrategy for the 14 bar operating conditions. However, the opposite trend was observed for the 7 bar case. In addition, port fuel injection in combination with oxygenated fuel blends was found to be helpful to suppress sootemissions for operation with exhaust gas recirculation.