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Soot modelling in flames and Large-Eddy Simulation of thermo-acoustic instabilities

Hernandez Vera, Ignacio. Soot modelling in flames and Large-Eddy Simulation of thermo-acoustic instabilities. PhD, Institut National Polytechnique de Toulouse, 2011

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Official URL: http://ethesis.inp-toulouse.fr/archive/00001792/

Abstract

In the first part of the present PhD. thesis a methodology is presented that allows to predict the soot produced in one-dimensional academic flames, where a semi-empirical soot model is used in combination with a complex chemistry and a detailed radiation solver. The methodology is applied to the computation of soot in a set of ethylene/air counterflow diffusion flames. Several oxidation models are tested and the constants of the model were adjusted to retrieve the experimental results. Also, the effect of radiative losses on soot formation and the flame structure is evaluated. Finally, the performance of the soot model is evaluated on 1D premixed flames, where an alternative expression for the surface growth term is proposed to better reproduce the experimental findings. In the second part of the thesis, Large-Eddy Simulation (LES) and acoustic analysis tools are applied to the prediction of limit cycle oscillations (LCO) of a thermo-acoustic instability appearing in a partially premixed methane/air academic burner operating at atmospheric pressure. The LES captures well the appearance and development of the LCO and a good agreement is found between simulations and experiments in terms of amplitude and frequency of the LCO. Some light is shed on the mechanisms leading to the existence of such instability. Then, a preliminar uncertainty quantification (UQ) analysis is performed, where the effect on the features of the LCO of several computational parameters such as the inlets impedances, mesh refinement or heat losses is assessed. Also, the LES captures well the flame stability behaviour dependence on the operating point and the burner geometry.

Item Type:PhD Thesis
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Institution: Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
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Research Director:
Cuenot, Bénédicte and Gabriel, Staffelbach
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