Ph-D thesis defense of Kévin Torres Monclard (EM2C, Gif-sur-Yvette) – July 5, 2021

Numerical simulation and thermal radiation analysis in sooted flames : impact of radiative properties

Keywords : combustion, soot, turbulence, radiation, modeling, thermal transfer

Abstract : Modelling soot radiation in CFD simulations is a challenging task as it strongly depends on particle size, morphology and optical properties. In the literature, all the studies related to thermal radiation in sooty flames are considering soot as spherical particles, although it is well admitted that they are clustering into complex aggregates. In this PhD work, an aggregate morphology for soot particles is considered and the impact of advanced soot radiative models (such as RDGFA) is assessed on several configurations. These models are implemented in an accurate code based on a Monte-Carlo approach, which solves the radiative transfer equation to retrieve key thermal radiation quantities. Numerical strategies are developed to reduce the computational cost due to the Monte-Carlo method while preserving a high accuracy. These strategies are applied on two turbulent flames: a diffusion coflow ethylene-air jet-flame and a swirled non-premixed ethylene-air flame. The radiative model RDGFA is then compared with experimental data obtained on laminar flames to assess its accuracy. A multi-physics coupled calculation is performed on the diffusion laminar ethylene-air Santoro’s flame. This coupled approach accounts for soot dynamics, radiation, and ethylene pre-heating due to the hot burner walls. The thermal radiation analysis demonstrates the capability of the RDGFA model to retrieve experimental data with a good accuracy. Finally, an application of based on the numerical synthetization of laser scattering signals due to soot particles is proposed and applied on Santoro’s flame.

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