Sung-Sub Kee

Effects of Aromatic Hydrocarbons on Fuel Decomposition and Oxidation Processes in Diesel Combustion

The chemical behaviors of diesel fuel and the effects of aromatic content on combustion characteristics and NO x 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 NO x 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 C 2 H 4 , C 2 H 2 and C 3 H 6 at the initial combustion phase. At the diffusion combustion phase, the low boiling-point hydrocarbons consist of mainly CH 4 . 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 NO x formation duration and high final NO x concentration than those of aromatic-free fuel.

A Study on Fluidized Bed-Type Particulate Filter for Diesel Engines

A fluidized bed-type diesel particulate filter (DPF) was applied to filter particulate matter (PM) in diesel engine exhaust gas. The effects of the fluidized bed design parameters, such as gas velocity, bed particle size, and height, on PM and smoke filtration efficiencies, and pressure drop were experimentally investigated using a single-cylinder direct injection (DI) diesel engine. High PM filtration efficiency and low pressure drop were achieved with the DPF, especially at a lower gas velocity. The PM filtration efficiency was higher with a smaller bed particle size at the lower gas velocity; however, it drastically decreased with an increase in gas velocity due to excessive fluidization of the bed particles. Increase in bed height led to higher PM filtration efficiency while causing an increase in pressure drop. The theoretical work was also conducted for further investigation of the effects of the above-mentioned parameters on PM filtration. These results indicated that diffusion filtration was the dominant mechanism for PM filtration under the conditions of this study and that the decrease in PM filtration efficiency at high gas velocity was caused by a deterioration in the diffusion filtration. The bed particle diameter and the bed height should be optimized in order to obtain a high filtration efficiency without increasing the DPF size.