MCS 7 Chia Laguna, Cagliari, Sardinia, Italy, September 11-15, 2011 ON THE EMISSION AND COMBUSTION CHARACTERISTICS OF LIMONENE INVOLVED IN ACCELERATING FOREST FIRES L. Courty*, K. Chetehouna**, F. Halter***, V. Bertin*, J.P. Garo* and C. Mounaïm- Rousselle*** leo.courty@ensma.fr *Institut P’, UPR 3346 CNRS, ENSMA, Université de Poitiers, 1 Av. Clément Ader, Téléport 2, BP 40109, 86961 Futuroscope Chasseneuil, France **ENSI de Bourges, Laboratoire PRISME UPRES EA 4229, 88 Boulevard Lahitolle, 18020 Bourges, France ***Laboratoire PRISME UPRES EA 4229, Université d’Orléans, 8 Rue Léonard de Vinci, 45072 Orléans Cedex 2, France Abstract Several researches have reported that under certain conditions forest fires with normal behaviour suddenly start to propagate at unusual and very fast rate of spread. Over the last decade, these accelerating forest fires were responsible for many fatalities in Europe. A thermochemical approach, based on the ignition of a Volatile Organic Compounds (VOCs) cloud, has been proposed previously to explain this phenomenon. Indeed, some vegetal species when heated emit volatile substances. We have shown that a typical Mediterranean plant, Rosmarinus officinalis, emit fourteen components. One of the main VOCs emitted is limonene. The acceleration of the rate of spread can be the consequence of the ignition of this emitted gas. The measurement of the laminar burning speed and combustion characteristics of limonene/air premixed flames is essential to take into account this approach in forest fire modelling. Laminar burning velocities and Markstein lengths of limonene/air premixed flames are determined using the spherical expanding flames method. Experiments are carried out in a spherical vessel at atmospheric pressure. The effects of equivalence ratio (0.7 to 1.4) and unburned gas temperature (353 to 453 K) are studied. Unstretched propagation speeds and Markstein lengths are obtained using a nonlinear methodology. A correlation is developed to calculate the laminar burning speeds as a function of equivalence ratio and temperature. The PREMIX code of the CHEMKIN package is used to compute laminar flame velocities with the San Diego chemical kinetic mechanism of JP-10, which is an isomer of limonene. The experimental results are compared to the computed ones of JP-10 as well as to those found in the literature for this compound and for n-decane. Introduction Several researches have shown that under some conditions forest fires behave in a surprising way [1,2,3], changing suddenly from an ordinary behaviour (moderate rate of spread) to an explosive propagation, characterized by a rate of spread and an energy released much more important. This phenomenon is known as accelerating forest fire for its explosive nature or eruptive fire for the continuous rise of the fire rate of spread. Fires propagating in terrain specific configurations, like canyons, can lead to such fire explosions and are responsible for many fatalities in the past. Indeed, the Sintra and La Gomera accidents occurred respectively in Portugal in 1966 and in Spain in 1984, causing the death of 25 and 20 persons [4]. More recently, in 2007, this phenomenon happened in Greece in Artemida, killing 24 persons [5]. The mechanisms which explain this type of forest fires are not totally well known yet. A thermochemical approach, based on the ignition of a Volatile Organic Compounds (VOCs)