Evaporating Spray Concentration Measurementsfrom Small and Medium Bore Diesel Injectors

Vapor concentration measurements were performed for two unit injectors typically found in small- and medium-bore applications under evaporating conditions similar to those experienced in Diesel engines. Ambient gas temperatures of 800 and 1000 K and an ambient density of 15 kg/m³ were investigated using a constant volume combustion-type spray chamber. The exciplex laserinduced fluorescence technique with TMPD/naphthalene doped into the fuel was used to quantitatively determine the vapor-phase concentration and liquid-phase extent. The vapor-phase concentration was quantified using a previously developed method that includes corrections for the temperature dependence of the TMPD fluorescence, laser sheet absorption, and the laser sheet intensity profile. The effect of increasing ambient temperature (1000 vs. 800 K) was significant on intact liquid length, and on the spray-spreading angle in the early portion of the injection period. Distributions of the vapor concentration for the higher temperature showed a wider extent with higher equivalence ratios, and the edge of the jet had higher vapor concentration gradients. The effect of an increase in injection pressure (1500 vs. 900 bar peak) was minimal on intact liquid lengths and spray-spreading angle, but distributions of the vapor concentration showed faster fuel vaporization rates and larger spray head volumes. The effect of an increase in nozzle hole size (267 vs. 158 μm diameter) was to increase the intact liquid length, but minimally affected the spray-spreading angle, and distributions of the vapor concentration showed a wider extent with higher equivalence ratios and larger overall spray vapor regions.