Evaluation of temporal and spatial distribution of nanometric particles in a diesel engine by broadband optical techniques

Abstract

In the last few years, there has been an increasing concern about the emissions of ultrafine particles in the atmosphere. A detailed study of the formation and oxidation of these particles in the environment of the diesel engine cylinder presents many experimental difficulties due to the high temperatures, pressures and extremely reactive intermediate species. To allow investigation of the different phases of the diesel combustion process, high temporal and spatial resolution optical techniques were applied in the optically accessible chamber of a diesel engine at fixed engine speed and air-fuel ratio. Simultaneous extinction, scattering and flame chemiluminescence measurements from the ultraviolet to the visible region were carried out in order to study the diesel combustion process from the soot inception to the formation of soot particles, through the growth of their precursors. These species were characterized as carbonaceous nanometric structures and their sizes were evaluated by the Mie theory.