Laser light scattering, emission/extinction spectroscopy and thermogravimetric analysis in the study of soot behaviour in oil spray flames

Vertical unconfined spray diesel oil flames was generated on a variable swirl burner with 90 KW power. 90° laser light scattering was employed to distinguish the fuel droplets and soot particles in the first part of the flames. Local values of the OH emission at ?=309.0 nm and of the ?=632.8 nm extinction and emission coefficients in the same region were obtained by Abel inverted chordal measurements. Profiles of soot particle size and number concentrations were obtained from scatter-extinction ratios, assuming a monodisperse spherical model; soot temperature distribution were evaluated by the Kirchhoff law. A new thermogravimetric technique, employed on the material sampled in the upper part of the flames, allowed quantitative distinction among the unburnt fuel, the heavy molecular mass products and the carbonaceous matrix. Flame development and spray penetration are studied to show the potentialities of laser light scattering and the thermogravimetric analysis. The results indicate that the two techniques can both detect and distinguish the fuel and soot particles, but they operate in different ranges of the droplet and soot volume fractions. © 1981 Combustion Institute.