Effect of Combustion on Diesel Spray Penetrations in Relation to Vaporizing, Non-Reacting Sprays 2016-01-2201
Extensive studies have addressed diesel sprays under non-vaporizing, vaporizing and combusting conditions respectively, but further insights into the mechanism by which combustion alters the macroscopic characteristics including the spray penetration and the shape of the spray under diesel engine conditions are needed. Contradictory observations are reported in the literature regarding the combusting diesel spray penetration compared to the inert conditions, and it is an objective of this study to provide further insights and analyses on the combusting spray characteristics by expanding the range of operating parameters. Parameters varied in the studies are charge gas conditions including oxygen levels of 0 %, 15%, 19%, charge densities of 22.8 & 34.8 kg/m3, and charge temperatures of 800, 900 & 1050 K for injection pressures of 1200, 1500, and 1800 bar with a single-hole injector with a nozzle diameter of 100 μm. These represent conditions for operation of a modern diesel engine with a high-pressure common rail injector at high load with EGR. Optical diagnostics include near-simultaneous Schlieren/Mie scattering imaging, natural luminosity imaging, OH* chemiluminescence imaging to visualize and quantify the vapor penetration, the liquid length, the flame penetration, the lift-off length, and the ignition delay. Analyses are focused on the flame luminosity, the relative penetration ratio between the flame penetration and the vapor penetration. Additionally, the relationship between the liquid length from a vaporizing spray and the lift-off length from a combusting spray are also compared.