Isopar-M spray flame forms smaller soot particles than Jet A-1 in laser incandescence tests
Authors measured soot in turbulent spray flames of Jet A-1 and the Isopar-M surrogate on a laboratory burner; Isopar-M showed weaker signals and limited particle growth.
Researchers Brendan Gachot, Cornelia Irimiea, Renaud Jalain, Nicolas Fdida and Xavier Mercier compared soot formation in turbulent spray flames of Jet A-1 kerosene and Isopar-M, a laboratory surrogate for alternative aviation fuel. The work was published in Applied Physics B and used three laser-induced incandescence (LII) configurations: time-resolved, planar and spectral. springer.com
Applied Physics Bspringer.comOpen source ↗ According to the authors, the Jet A-1 flame produced higher soot loads and longer signal decay times, while the Isopar-M flame gave weak signals.
Burner and measurement setup
Both flames were stabilized on a laboratory burner at atmospheric pressure with a nebulizer. Fuel flow was held at 100 grams per hour, atomized with 18 grams per hour of nitrogen, and the co-flowing air was 1500 grams per hour. The flames were about 270 millimeters tall. Isopar-M serves as a laboratory analog of alcohol-to-jet synthetic kerosene.
For LII, the team used a pulsed Nd:YAG laser at 532 nanometers with a fluence of 80 millijoules per square centimeter, below the soot sublimation threshold. Time-averaged planar images were compiled from 2000 instantaneous frames.
Particle size, distribution and filaments
The decay time of the incandescence signal reflects primary particle size: a longer decay indicates larger particles. In the Jet A-1 flame, decay times ranged from 50 to 550 nanoseconds and peaked between 140 and 150 millimeters above the burner. In the Isopar-M flame they stayed between 50 and 150 nanoseconds with an essentially flat axial profile, which the authors interpret as limited particle growth. springer.com
Applied Physics Bspringer.comOpen source ↗ Average incandescence intensity in Jet A-1 was roughly three times that of Isopar-M.
Planar images differed as well. The Jet A-1 flame showed a clear signal maximum between 110 and 140 millimeters. The Isopar-M signal was lower and more homogeneous, so locations where soot formation or oxidation dominates could not be distinguished. Filament intermittency was assessed with statistical image-to-image metrics. Spectral measurements revealed interfering fluorescence and allowed the soot volume fraction in the Jet A-1 flame to be inferred.
The authors conclude that soot formation in spray flames is complex and requires multi-scale, time-resolved measurements to characterize.
