Effect of turbulence on flame radiative emission

Effect of turbulence on flame radiative emission A collection of radiative emissions by several flames is analyzed. Such flames have been obtained in a number of burners, either premixed or not, fed with different fuels, while radiative emission is collected by means of a photo-diode, whose sampled signal is able to carry a large quantity of information about chemistry of flames and its interaction with turbulence. All the spectra computed show a decaying trend towards high frequencies with a slope of  −5/3, that is known to be the inertial scaling of kinetic energy for homogeneous, isotropic, nonreacting turbulent flows. The aim of this work is to propose a physical model for the interpretation of the radiant energy scaling law coming from this simple instrument. To this purpose radiative emission of the flame has been splitted into two contributions, and its dynamics analyzed. The first contribution is the chemiluminescence effect, whereas the other is to be accounted for thermal emission of a gray/black body, ruled by Planck radiative equation. The time fluctuation of radiative emission is proposed to be linked to a thin reacting surface fluctuating in time and space under the constraint of turbulent fluid dynamic field. The thin reacting surface should be considered as the local flame front in premixed combustion, and as the local stoichiometric mixture fraction front in nonpremixed case. Taking into account such emission mechanisms, a physical interpretation of the  −5/3 slope is proposed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Effect of turbulence on flame radiative emission

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Publisher
Springer-Verlag
Copyright
Copyright © 2007 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-007-0415-y
Publisher site
See Article on Publisher Site

Abstract

A collection of radiative emissions by several flames is analyzed. Such flames have been obtained in a number of burners, either premixed or not, fed with different fuels, while radiative emission is collected by means of a photo-diode, whose sampled signal is able to carry a large quantity of information about chemistry of flames and its interaction with turbulence. All the spectra computed show a decaying trend towards high frequencies with a slope of  −5/3, that is known to be the inertial scaling of kinetic energy for homogeneous, isotropic, nonreacting turbulent flows. The aim of this work is to propose a physical model for the interpretation of the radiant energy scaling law coming from this simple instrument. To this purpose radiative emission of the flame has been splitted into two contributions, and its dynamics analyzed. The first contribution is the chemiluminescence effect, whereas the other is to be accounted for thermal emission of a gray/black body, ruled by Planck radiative equation. The time fluctuation of radiative emission is proposed to be linked to a thin reacting surface fluctuating in time and space under the constraint of turbulent fluid dynamic field. The thin reacting surface should be considered as the local flame front in premixed combustion, and as the local stoichiometric mixture fraction front in nonpremixed case. Taking into account such emission mechanisms, a physical interpretation of the  −5/3 slope is proposed.

Journal

Experiments in FluidsSpringer Journals

Published: Oct 24, 2007

References

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