Partially Premixed Combustion (PPC) is a combustion concept that aims to\nprovide combustion with low smoke and NOx emissions and a high thermal efficiency.\nExtending the ignition delay to enhance premixing, avoiding spray-driven combustion, and\ncontrolling temperature at an optimum level through use of suitable dilution levels has been\nrecognized as a key factor to achieve such a concept. Fuels with high auto-ignition resistance\ndo extend ignition delay. In this work three ternary blends of an alcohol (ethanol or\nn-butanol), n-heptane and iso-octane with a target research octane number (RON) of 70 are\nstudied. RON70 was earlier found to be close to optimal for PPC over a large load range.\nThe objective of this research is to analyze the sensitivity of the combustion parameters\nto changes in air-excess ratio when using these three blends. The engine was operated at\n1250 rpm and 1000 bar injection pressure with a single injection strategy. Results revealed\nthat efficiency was increased from rich to lean combustion, and these three blends show\ndistinct premixed combustion even in lean PPC operation. The premixed fraction of combustion\nhowever reduces with the increase of air-excess ratio, which is especially apparent\nfor PRF70 which consists of n-heptane and iso-octane alone.
Loading....