Effects of Aromatic Hydrocarbons on Fuel Decomposition and Oxidation Processes in Diesel Combustion 2005-01-2086
The chemical behaviors of diesel fuel and the effects of aromatic content on combustion characteristics and NOx histories were experimentally investigated using a rapid compression machine and a total-gas sampling device. The aromatic content was changed under constant cetane number. Composition of the individual hydrocarbons, inorganic gases and NOx under various ambient temperatures and fuel injection pressures were analyzed with aromatic-free and aromatic-containing fuels. The results indicate that injected fuel is rapidly decomposed and dehydrogenated during the ignition delay period. The decomposed low boiling-point hydrocarbons consist of mainly unsaturated hydrocarbons such as C2H4, C2H2 and C3H6 at the initial combustion phase. At the diffusion combustion phase, the low boiling-point hydrocarbons consist of mainly CH4. The aromatic-containing fuel is decomposed with difficulty because of the lower decomposition rate of not only aromatic component but also other heavy saturate hydrocarbons, resulting in higher concentration of low-boiling point hydrocarbons after the ignition than that in aromatic-free fuel. Aromatic-containing fuel gives long NOx formation duration and high final NOx concentration than those of aromatic-free fuel.