The effect of butanol isomers on diesel engine performance, emission and combustion characteristics under different load conditions

The effect of a high proportion of butanol on combustion and emission of common rail diesel engine was studied. The four butanol isomers, n-butanol, iso-butanol, sec-butanol and tert-butanol were mixed with pure diesel at a volume ratio of 50%, and were named NB50, IB50, SB50 and TB50. Experiments were carried out under a wide range of engine (0.4 MPa-1.2 MPa). The results show that compared with pure diesel, the cylinder pressure and heat release rate of butanol/diesel mixture increased, and the peak heat release rate of SB50 was the highest under the large load. The order of ignition delays of butanol blends is IB50 > SB50 > TB50 > NB50. TB50 has the highest brake thermal efficiency under high loads, increasing by 3% compared to diesel. Butanol can effectively reduce soot emissions but also will produce higher NOx and CO emission under the low load. For higher load, butanol can improve the particulate matter (PM) emission, but at lower load, butanol significantly increases particulate matter (PM) emission. In summary, high proportion of tert-butanol has good application potential for heavy diesel engines.