Effects of Fuels Properties on Combustion and Emissions Characteristics of Light Duty GCI Engine

Our research group developed Gasoline Compression Ignition (GCI) fuel matrix based on the fuel properties, specifications and fuel sources in an effort to standardize the GCI fuel. This study attempts to experimentally validate the standardized GCI fuels to comply with the operational regimes of GCI engine. Two of the formulated GCI fuels (GCI7 and GCI8) with varying physical and chemical properties, and composition were investigated in a single cylinder compression ignition (CI) engine. In addition to fuel effects, the engine variables were parametrically varied at low (3 bar IMEP) and medium (7 bar IMEP) load conditions. At low loads, the fuel chemical effects played a crucial role in governing the combustion while physical effect had a negligible impact. Due to lower cetane number of GCI8 fuel, combustion is predominantly premixed for GCI8 fuel but GCI7 fuel shows a more pronounced diffusion combustion phase. The low temperature heat release (LTHR) is evident only for GCI8 fuel due to higher octane rating (RON = 60) whereas GCI7 fuel (diesel like) showed negligible LTHR phase. Despite improvements in engine operating parameters, the combustion performance of GCI8 is lower than GCI7 fuel. However, after improving the fuel injection strategies, GCI8 fuel showed improved peak in-cylinder pressure and heat release compared to GCI7 fuel. Double injection advanced the combustion phasing, shortened the ignition delay, and improved the burn rate when compared to single injection. Fuel composition played a crucial role in emission formation in that smoke emission is increased for GCI7 due to higher fraction of aromatics in the fuel compared to GCI8. The increased premixed effect due to lower cetane number of GCI8 decreased the fuel to air equivalence ratio and in-cylinder temperature in that NO_X emission is reduced.