The intrinsic control of carbon to oxygen ratio in Diesel spray combustion

This paper present new knowledge on combustion behaviour of ethers (Butylether) and glycolethers (Diethyldiglycol) in comparison with n-Tetradecane and n-Octane behaviour. Experiments were carried out in a single cylinder direct injection (DI) diesel engine of conventional design. Two-colour pyrometry and fast sampling technique were adopted for in-cylinder soot loading and gaseous species concentration measurements. Exhaust pollutant emissions were also measured. The very high cetane number of the oxygenated fuels produce low premixed peak rate during combustion, with low HC, CO and aldheydes emissions. Soot tendency appears strictly correlated with oxygen content of the parent fuel molecule. N-Tetradecane and Diethyldiglycol were tested and compared at high E.G.R. rates. In the whole E.G.R. range, the oxygenated fuel shows low in-cylinder soot loading with respect to n-Tetradecane. In two colour method experiments, Octylalcohol and Diethyleneglycolbutylether were tested also, to study the influence of fuel molecular structure on in-cylinder soot loading. At the same fuel oxygen content, glycol-ethers show a sooting tendency that is lower than in ether and ether-alcohol blend.