The effects of distillation characteristics and aromatic content on low-load gasoline compression ignition (GCI) performance and soot emissions in a multi-cylinder engine

摘要

The DOE Co-Optima initiative focuses on investigating the ability of fuel properties to work in tandem with advanced combustion engines to increase fuel economy. One of the most promising advanced compression ignition strategies (ACI) is gasoline compression ignition (GCI). GCI leverages the relative auto-ignition resistance of gasoline-like fuels to enable highly premixed combustion processes at a range of air-fuel stratifications. In practical applications, engines must operate over a wide range of conditions, which associated with the inherent limitations and benefits of different ACI modes, suggests the engine should be capable of operating across multiple combustion modes. Operating the engine in multiple combustion modes effectively requires a fundamental understanding of fuel composition effects. The fact that GCI can operate with fuels designed for spark ignition engines enables the engine to be operated in either combustion mode when most suitable. This effort investigates the effects of fuel physical properties and aromatic content on GCI NOx, unburned hydrocarbons (HC), CO and particulate emissions. Three fuels with the same research octane number (RON) but different distillation curves and aromatic content are compared to isolate the impact of the two properties in a production, multi-cylinder engine. Different injection strategies targeting increasing levels of fuel stratification (100%, 70% and 0% premixed fuel) at a constant combustion phasing are utilized. Results showed that changes in fuel stratification had little impact on emissions of NOx, HC and CO until the fuel was injected completely near top dead center (TDC). Particulate sampling showed that the aromatic content of the fuel had greater impact on elemental carbon particulate matter (PM) emissions than the fuel distillation characteristics.