The effect of rapeseed oil blending with ethanol on engine performance and exhaust emissions

The article presents the bench testing results of a four stroke, four cylinder, direct injection, unmodified, naturally aspirated diesel engine operating on neat rapeseed oil (RO) and its 2.5vol% (ERO2.5) and 7.5vol percent (ERO7.5) blends with ethanol. The purpose of the research was to investigate the effect of ethanol inclusion in the RO and preheating temperature on bio-fuel viscosity, engine brake power, specific fuel consumption, break thermal efficiency and emission composition changes, especially NO, NO2, NOx, CO, CO2, HC and smoke opacity of the exhausts. Inclusion in the RO 2.5 and 7.5vol% of ethanol the blend viscosity at ambient temperature of 20 centigrade diminishes by 9.2 and 28.3%. During operation under constant air-to-fuel equivalence ratio gamma = 1.6, blends ERO2.5 and ERO7.5 ensure the brake mean effective pressure (bmep) lower at the maximum torque 1800 min-1 by 0.5 and 2.3% (bmep=0.770 mpa) and at rated 2200 min1 speed by 2.4 and 9.1% (bmep=0.740 mpa), correspondingly, than that of neat RO case. The bsfc at maximum torque (248.7 g/kwh) and rated power (247.5 g/kwh) for blends ERO2.5 and ERO7.5 is higher by 1.3-4.4% and 4.2-10.7% and the brake thermal efficiency lower by 0.5-1.5% and 3.3-7.6%, respectively. The tests revealed that during operation of the fully loaded engine at rated 2200 min-1 speed, ethanol inclusion in the RO up to 7.5vol% diminishes NO, nox, HC, CO2 emissions, smoke opacity and temperature of the exhausts however it may increase simultaneously NO2, NO2/NOx and CO emissions