Effect of distillate fraction of real jet fuel on sooting propensity -Part 2: Soot formation in nonpremixed counterflow flames

For practical engines with petroleum-derived fuel being injected as a spray, the high molecular weight aromatics containing multiple rings that are present towards the hightemperature end of the distillation curve, while of trace amount, would directly allow for soot nucleation. In the Part 1 work, the variation of the sooting propensity as a function of distillate fractions was studied in a series of premixed stretch-stabilized ethylene-oxygen-nitrogen flames doped with Jet-A or a certain distillate fraction, by using a Scanning Mobility Particle Sizer to determine the changes in mobility particle size distribution functions, soot volume fraction, and number density. In this Part 2 study, the effect of distillate fraction on soot formation in nonpremixed combustion was investigated. In particular, the soot volume fraction profiles of the sooting and near-sooting ethylene counterflow nonpremixed flames doped with 2000 ppm (by mole) Jet-A or a certain distillate fraction were measured using the Laser Induced Incandescence (LII) diagnostics. The experimental results show that the maximum soot volume fractions along the centerline, f_v.max, of the doped flames are higher than that of the baseline ethylene flame, and f_v.maxincreases with increasing distillate percentage. In addition, f_v.maxof the flame doped with neat Jet-A is similar to that of the flame doped with 0-60 percent distillate fraction. Furthermore, the tail end of the distillation curve can produce more soot volume fraction than the light molecular fraction and neat Jet-A. The implication of the present experimental findings on modeling soot formation from real jet fuel combustion is also discussed.