Modeling Laser-Induced Incandescence of Soot Particles Produced In A Premixed Ch4/O2/N2 Flat Flame

Abstract

The present work deals with the modeling of an extensive set of laser-induced incandescence (LII) signals collected in an atmospheric CH4/O2/N2 premixed flat flame. To do so, a refined LII model built upon a comprehensive version of soot heat-and massbalance equations has been used. This latter especially includes an absorption sub-model accounting for saturation of linear, single-and multi-photon absorption processes together with terms standing for soot oxidation and particle cooling by sublimation, conduction, radiation and thermionic emission. The comparison between the simulated and the experimentally-monitored data reported herein has been achieved based on LII fluence curves and time-decays obtained at different heights above the burner as well as on the basis of measured soot temperature profiles as a function of the laser fluence. In terms of results, the theoretical model implemented within this study turns out to correctly reproduce measured LII fluence curves and soot temperature profiles although it fails to correctly simulate LII time decays collected at high fluences. An analysis of the possible improvements to be operated to the so-implemented model eventually led to the conclusion that integrating an additional energy flux standing for soot annealing could allow obtaining improved agreements between theoretical and measured signals thus giving interesting insights for complementary works to be undertaken.

Parameterization of a Refined Model Aimed at Simulating Laser-Induced Incandescence of Soot Using a Visible Excitation Wavelength of 532 nm

“…Furthermore, the results from [30] also led to the conclusion that an in-depth analysis of the formulation and parameterization of the sub-models proposed in [14,29] was necessary since, in their current form, those expressions turned out to be unsuitable to reproduce the experimental data measured by [31] in a diffusion flame of ethylene. In an attempt to simulate signals collected in an atmospheric CH4/O2/N2 premixed flat flame, [26,32] also performed advanced calculations which confirmed the relevance of considering photolytic mechanisms (e.g., photodesorption of carbon clusters) while providing interesting insights into the importance of soot annealing to properly model LII at high fluences.…”