Experimental study of n-butanol addition on performance and emissions with diesel low temperature combustion

Compared with ethanol or methanol, butanol has higher heating value and higher miscibility. Because of lower cetane number of butanol, butanol-diesel blends are more suitable for diesel low temperature combustion (LTC). In the paper, experimental study was carried out on a modified single cylinder heavy duty diesel engine to investigate the effects of n-butanol and EGR on diesel engine's combustion and emission characteristics. CA50 timing was fixed at 8 °CA ATDC and two different volume fractions (20% and 40%) of n-butanol were blended into diesel fuel. The results showed that with the increase of n-butanol fraction, ignition delay prolonged, (dp/dφ)max increased and indicated thermal efficiency (ITE) had a slight increase. Fuel properties had little effects on NOx emission, but NO proportion decreased and NO2 proportion increased with higher n-butanol fraction. With n-butanol addition, CO and THC (total hydrocarbon) emissions decreased at higher EGR levels, soot emissions reduced greatly and soot-bump was almost eliminated. With the increase of EGR rate, CH4 proportion increased, but n-butanol addition could decrease CH4 proportion.