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Theses

Effets des Hétérogénéités de Richesse sur la Structure
Locale des Flammes Turbulentes

Abstract : In many real situations, which goes from the field of transport (rocket, plane and car engines), the electricity production (power station) or of thermics (boiler, industrial furnaces, domestic hearths), the turbulent premixing between air and fuel lead to an heterogeneity of the mixing. Consequently, the equivalence ratio of the mixing is variable both in time and space, producing a partially premixed combustion, so far from the classical premix and diffusion cases. In this thesis, we are interested in the effects of equivalence ratio heterogeneities on local structure (in term of curvature, flame thickness and stretch, fuel mole fraction) of this kind of flame. Two experimental configurations (stationary and unstationary, presenting each one their advantages) are studied. An experimental method is proposed in order to measure simultaneously flame temperature and fuel mass fraction, whose its originality is to avoid the temperature influence on acetone PLIF efficiency. The study of laminar flames shows that the flame is strongly influenced by the stratification in particular in term of geometrical configuration for the unstationary flame. But also from the point of view of the stationary flame thickness. The flame thickness evolution as a function of stretch shows a notable modification with a break of slope as a function of the Lewis number. Moreover, it is shown that the flame propagates in poor zone (below the flammability limits) due to the support of the flame by a thermal and chemical reservoir.
The study of the behavior is continued in the second part, for two turbulence grids, where the comparison is done for homogeneous and stratified premixed flames. The study shows that the flame structure is modified by the local stretch but also by the flame speed variations with the mixing composition. This lead to an additional stretch Kpp non negligible for weak equivalence ratio.
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https://tel.archives-ouvertes.fr/tel-00137911
Contributor : Olivier Degardin <>
Submitted on : Thursday, March 22, 2007 - 2:51:54 PM
Last modification on : Tuesday, February 5, 2019 - 11:44:12 AM
Long-term archiving on: : Friday, November 25, 2016 - 2:40:48 PM

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  • HAL Id : tel-00137911, version 1

Citation

Olivier Degardin. Effets des Hétérogénéités de Richesse sur la Structure
Locale des Flammes Turbulentes. Energie électrique. INSA de Rouen, 2006. Français. ⟨tel-00137911⟩

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