The Impact of Fuel Injection Strategies and Compression Ratio on Combustion and Performance of a Heavy-Duty Gasoline Compression Ignition Engine

Gasoline compression ignition using a single gasoline-type fuel has been shown as a method to achieve low-temperature combustion with low engine-out NO_x and soot emissions and high indicated thermal efficiency. However, key technical barriers to achieving low temperature combustion on multi-cylinder engines include the air handling system (limited amount of exhaust gas recirculation) as well as mechanical engine limitations (e.g. peak pressure rise rate). In light of these limitations, high temperature combustion with reduced amounts of exhaust gas recirculation appears more practical. Furthermore, for high temperature Gasoline compression ignition, an effective aftertreatment system allows high thermal efficiency with low tailpipe-out emissions. In this work, experimental testing was conducted on a 12.4 L multi-cylinder heavy-duty diesel engine operating with high temperature gasoline compression ignition combustion using EEE gasoline. Engine testing was conducted at an engine speed of 1038 rpm and a brake mean effective pressure of 14 bar. Different hardware configurations were investigated (compression ratio 17 and 20.5), as well as two sets of injectors. In addition, three injection strategies were tested in order to understand the impact of the different hardware configuration in conjunction with injection strategy on performance. A combination of port fuel and direct injection strategies were utilized to increase the premixed combustion fraction. The impact on engine performance with respect to varying injection and intake operating parameters was quantified within this study. The peak brake thermal efficiency measured was 47.2% with compression ratio 20.5 and the high flow-rate injectors. 3D computation fluid dynamics simulation was leveraged at select conditions to provide insight into the combustion process.