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In an optically accessible high-pressure/high-temperature (HP/HT) chamber, OH radicals, soot concentration, and OH* chemiluminescence images were captured simultaneously at a constant ambient temperature of 823 K and a gas density of 20 kg/m3, with injection pressures of 800-2000 bar using an injector with nozzle orifice having a diameter of 0.1 mm. Swedish market sold MK1 diesel fuel was used in this study. The optical diagnostic methods used were the two-dimensional laser extinction for the soot concentration measurement, planar laser induced fluorescence for the OH radical measurement, OH* chemiluminescence imaging, and the natural flame luminosity imaging. The objective of this study is to explore the diesel spray structures under the low sooting and non-sooting conditions. In this study, it was found that the OH radical zone in the jet’s upstream region expanded to the jet center and the soot concentration decreased when the fuel injection pressure increased.

The effects of nozzle geometry on diesel spray characteristics were studied in a spray chamber under evaporating conditions using three single-hole nozzles, one cylindrical and two convergent, designated N1 (outlet diameter 140 μm, k-factor 0), N2 (outlet diameter 140 μm, k-factor 2) and N3 (outlet diameter 136 μm, k-factor 2). Spray experiments were performed with each nozzle at two constant gas densities (15 and 30 kg/m3) and an ambient temperature (673 K) at which evaporation occurs, with injection pressures ranging from 800 to 1600 bar. A light absorption and scattering method using visible and UV light was implemented, and shadow images of liquid and vapor phase fuel were recorded with high-speed video cameras. The cylindrical nozzle N1 yielded larger local vapor cone angles than the convergent nozzles N2 and N3 at both gas densities, and the difference became larger as the injection pressure increased.

The influence of ethanol blending in Diesel fuel on the spray and spray combustion characteristics was investigated by performing experiments in an optically accessible high-pressure / high-temperature spray chamber under non-evaporating, evaporating and combusting conditions. Three fuels were investigated: (1) Diesel - a European Diesel based on the EN590 standard; (2) E10 - a blend of Diesel containing 10% ethanol and 2% emulsion additive; and (3) E20 - a blend of Diesel containing 20% ethanol and 2% emulsion additive. A constant gas density of 24.3 kg/m3 was maintained under non-evaporating (30 °C, 21.1 bar), evaporating (350 °C, 43.4 bar), low combustion temperature (550 °C, 57.3 bar) and high combustion temperature (600 °C, 60 bar) conditions. A single-hole injector with a nozzle diameter of 0.14 mm was used and injection pressure was held constant at 1350 bar. Various optical methods were used to characterize the non-combusting and combusting sprays.