In-cylinder study of the formation, autoignition and soot production of diesel sprays at elevated pressures

The effects of in-cylinder and injection pressures on the formation and combustion of diesel sprays at realistic automotive in-cylinder conditions was investigated. By combining the results obtained with high-speed video of the liquid phase, high-speed schlieren video of the vapour phase, high-speed video of autoignition and laser-induced incandescence (LII) of soot, a detailed observation of the combustion processes was obtained for elevated in-cylinder and injection pressures. The spray dispersion angles, tip penetrations with time, autoignition delays and relative soot concentrations were measured for a range of injection and in-cylinder pressures. The tests were performed on a single-cylinder diesel rapid compression machine with optical access to the combustion chamber. A common rail injection system was used with an injector mounted with a single-hole VCO type nozzle. The injection pressure was varied from 60 to 160 MPa, the in-cylinder pressure and temperature at top dead centre from 6 to 10 MPa and from 540 to 720 K, respectively. The results obtained from the various measurement techniques were combined in order to produce a comprehensive observation of diesel spray development and combustion.