Abstract
A novel concept of fuelling a diesel engine with biofuels - rapeseed oil methyl ester (RME) and ethanol was proposed, developed, and investigated. The idea of the concept depends on standard fuelling with RME and additional injection of ethanol into the inlet port during the inlet stroke. After ignition from burning RME droplets, the ethanol-air mixture burns very quickly and promotes combustion of the main fuel droplets. This results in a shorter combustion period. Experiments were carried out with the use of a one-cylinder direct injection diesel engine adapted to ethanol injection at three speeds and two loads: low and high and for three injection timings. At each experimental point the proportion of ethanol to RME was changed from zero to the value at which diesel knock occurred in such a way that the engine load was kept constant. This showed the influence of the ethanol energy to total fuel energy ratio (ΩE) on effciency and emissions (ΩE was a main independent variable parameter). A considerable decrease in CO2 and the smoke level was obtained and, for high loads also CO and HC emissions. At low loads the NOx emissions were reduced. The optimum ratio of ethanol energy to total fuel energy, in terms of brake fuel conversion effciency and benefit of emission decrease, was found to be about 25 per cent.
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