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RESEARCH ARTICLE
Contents Vol 16(3)

Thermal infrared emission–transmission measurements in flames from a cylindrical forest fuel burner

Jean-Luc Dupuy A C , Philippe Vachet A , Joël Maréchal A , Juan Meléndez B and Antonio J. de Castro B
+ Author Affiliations
- Author Affiliations

A INRA UR629 Recherches Forestières Méditerranéennes, Equipe de Prévention des Incendies de Forêt, Site Agroparc, F-84914 Avignon, France.

B Universidad Carlos III de Madrid, Departamento de Fisica, E-28911 Leganés (Madrid), Spain.

C Corresponding author. Email: dupuy@avignon.inra.fr

International Journal of Wildland Fire 16(3) 324-340 https://doi.org/10.1071/WF06043
Submitted: 31 March 2006  Accepted: 24 November 2006   Published: 3 July 2007

Abstract

We describe emission–transmission measurements performed at different heights in a flame from a cylindrical forest fuel burner, using a camera operating in the thermal infrared (7.5–13 µm). The forest fuel burner was made of a cylindrical wire mesh basket filled with a forest fuel (Pinus pinaster needles), which was ignited at the base of the basket. Three diameters of basket were used (20, 28 and 40 cm). Heat release rates, as calculated from weighing of the basket and heat of combustion of the fuel, ranged between 50 and 170 kW and flame heights ranged between 1 and 2 m. The emission–transmission device allows the determination of the transmittance of the flame and of a radiometric temperature. We show that radiation was dominated by soot in the spectral range of the camera, but that radiation from gaseous products of the combustion was not negligible. Using the Mie theory in its Rayleigh limit, we deduced some average volume fractions of soot from the measurements, which peaked at 6.8 × 10−6 in the persistent region of the flame. Then the total extinction coefficient and the total emissivity of the flame due to soot were calculated according to a standard method. Measured transmittance, soot volume fraction, total extinction coefficient and total emissivity were found to scale with the normalised height of measurement Z, defined as the ratio of the height of measurement to the height of the flame (0.25 < Z < 1.6).

Additional keywords: forest fires, IR thermography, radiation, soot.


Acknowledgements

The present study has been partially funded by the European Commission in the frame of the FIRESTAR research programme (contract EVG1–2001–00041).


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1 The paper summarises the method and results of an experimental study fully reported in the following reference (out of print): Hägglund B., Persson L (1974) An experimental study of the radiation from wood flames. Försvarets Forskningsanstalt Huvudenhet, FOA Rapport C 4589-D6. (Stockholm, Sweden)

2 Unlike Knight and Sullivan (2004) and Sullivan et al. (2003) asserted, the emissivity of the surface representing the flame was not set to 1 in Albini's model (1985) and other related models they cited. Rather, the flame emissive power was set equal to some fraction of the burning zone emissive power, which was considered as a radiating surface of emissivity 1.