Natural flame luminescence of combustion in diesel engine fueled with blends of diesel and oxygenated fuels

High-speed imaging and thermodynamic analyses were applied to an optically accessible diesel engine, at engine speed of 1200 r/min and fuel-injection quantity of 20 mg per cycle, to investigate the effects of blends of 3 types of oxygenated fuels with diesel on natural flame luminosity of combustion. 20% of methyl butyrate, n-butanol and 2, 5-dimethylfuran (DMF) were blended with diesel by volume, respectively, referred to as MB 20 B 20 and DMF 20. Results show that D 100 has the largest gap between the ignition delay derived from heat release and natural luminosity. Obvious blue flame from chemiluminescence of combustion process is observed for all three blends. The ability for soot reduction of these three oxygenated fuels is in the order of DMF 20, MB 20 and B 20. Longer ignition delay plays the most important role in soot reduction in the combustion process of DMF 20, while for MB 20 and B 20, oxygen content prevails. Blending of oxygenated fuels reduces the flame area and flame temperature, and cuts down the soot formed in combustion process.