Nano organic carbon and soot in turbulent non-premixed ethylene flames


D'Anna A., Commodo M., Violl S., Allouis C. G. , Kent J.

PROCEEDINGS OF THE COMBUSTION INSTITUTE, vol.31, pp.621-629, 2007 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 31
  • Publication Date: 2007
  • Doi Number: 10.1016/j.proci.2006.07.062
  • Title of Journal : PROCEEDINGS OF THE COMBUSTION INSTITUTE
  • Page Numbers: pp.621-629
  • Keywords: pollutants, nanoparticles, soot, turbulent flames, optical diagnostics, SPECTROSCOPIC CHARACTERIZATION, DIFFUSION FLAMES, NANOPARTICLES, COMBUSTION, JET, COAGULATION, PREDICTION

Abstract

Spectral optical techniques are combined to characterise the distribution of large-molecule soot precursors, nanoparticles of organic carbon, and soot in two turbulent non-premixed ethylene flames with differing residence times. Laser-induced fluorescence, laser-induced incandescence and light scattering are used to define distributions across the particle size distribution. From the scattering and laser-induced emission measurements it appears that two classes of particles are formed. The first ones are preferentially formed in the fuel-rich region of the flame closer to the nozzle, have sizes of the order of few nanometers but are not fully solid particles, because the constituent molecules still maintain their individual identity exhibiting strong broadband fluorescence in the UV. The second class of particles constituted by solid particles, with sizes of the order of tens of nanometers are able to absorb a sufficient number of photons to be heated to incandescent temperatures. These larger particles are formed at larger residence times in the flame since they are the result of slow growth processes such as coagulation or carbonization. The flames are also modeled in order to produce mixture fraction maps. A new discovery is that nanoparticles of organic carbon concentration, unlike soot, does correlate well with mixture fraction, independent of position in the flame. This is likely to be a significant benefit to future modelling of soot inception processes in turbulent nonpremixed flames. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.