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Advanced combustion regimes such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) offer benefits of reduced nitrogen oxides (NOX) and particulate matter (PM) emissions. However, these combustion strategies often generate higher carbon monoxide (CO) and hydrocarbon (HC) emissions. In addition, aldehydes and ketone emissions can increase in these modes. In this study, the engine-out emissions of a compression-ignition engine operating in a fuel reactivity-controlled PCCI combustion mode using in-cylinder blending of gasoline and diesel fuel have been characterized. The work was performed on a 1.9-liter, 4-cylinder diesel engine outfitted with a port fuel injection system to deliver gasoline to the engine. The engine was operated at 2300 rpm and 4.2 bar brake mean effective pressure (BMEP) with the ratio of gasoline-to-diesel fuel that gave the highest engine efficiency and lowest emissions.

Reactivity Controlled Compression Ignition (RCCI) has demonstrated diesel-like or better brake thermal efficiency with significant reductions in nitrogen oxide (NOX) and particulate matter (PM) emissions. Hydrocarbon (HC) and carbon monoxide (CO) emission levels, on the other hand, are higher and similar to those of port-fuel-injected (PFI) gasoline engines. The higher HC and CO emissions combined with the lower exhaust temperatures during RCCI operation present a challenge for current exhaust aftertreatment technologies. The reduction of HC and CO emissions in a lean environment is typically achieved with an oxidation catalyst. In this work, several diesel oxidation catalysts (DOC) with different precious metal loadings were evaluated for effectiveness to control HC and CO emissions from RCCI combustion in a light-duty multi-cylinder engine operating on gasoline and diesel fuels.