Development of Multiple Injection Strategy for Gasoline Compression Ignition High Performance and Low Emissions in a Light Duty Engine

The increase in regulatory demand to reduce CO₂ emissions resulted in a focus on the development of novel combustion modes such as gasoline compression ignition (GCI). It has been shown by others that GCI can improve the overall engine efficiency while achieving soot and NO_x emissions targets. In comparison with diesel fuel, gasoline has a higher volatility and has more resistance to autoignition, therefore, it has a longer ignition delay time which facilitates better mixing of the air-fuel charge before ignition. In this study, a GCI combustion system has been tested using a 2.2L compression ignition engine as part of a US Department of Energy funded project. For this purpose, a multiple injection strategy was developed to improve the pressure rise rates and soot emission levels for the same engine out NO_x emissions. The effect of start of injection timing and fuel quantity split between injections are reported for double and triple-injection strategies with impact on cylinder pressure and heat release. The results showed that multiple injections could be utilized to obtain a more favorable heat release rate and resulted in improved fuel consumption and emissions. In this study, triple-injection strategy showed an improvement in fuel consumption by 0.5% and NO_x by 5%, comparing to double-injection strategy. Indicated thermal efficiency of 40.9% was demonstrated, while demonstrating consistent engine out NO_x and smoke emissions using 0% EGR.