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Interactions turbulence-combustion lors des explosions de mélanges hybrides vapeurs/poussières - Combustion-turbulence interactions in hybrid mixtures flames

Abstract : Gas/dust explosions have been studied for years, but very few researches have been carried out on the hydrodynamic behavior of such flames. However, recently, the specific behaviors of such mixtures as regard to their ignition sensitivity and explosion severity have been demonstrated. Experiments have shown that concentration of gas/vapours as low as 1% vol. causes a significant decrease of the minimum ignition energy and induces changes in the rate-limiting step of the combustion reaction. They also confirmed that a hybrid mixture explosion is possible even when both dust and vapour concentrations are respectively lower than their minimum explosion concentration and lower explosivity limit. Addition of small amounts of gaseous compounds has also a strong effect on the explosion severity and could lead to explosivities of hybrid mixtures, which could be greater than those of the pure compounds themselves. This work also focuses on the effect of combustion/turbulence interactions on the flame propagation in hybrid mixtures. As regard to gaseous mixtures, the presence of particles strongly modifies the turbulence level, bringing new hydrodynamic instabilities. The impact of flame stretching on the flame velocity has also been studied. Two parameters of hybrid mixtures methane/wheat starch and hexane/sunflower oilcakes have notably been determined for: S u °, the fundamental unstretched burning velocity (ranging between 22 and 36 cm.s-1) and L, the Markstein length (from 0.2 to 1.9 mm). This study allows the determination of specific means of prevention and protection for such mixtures.
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Khalili Imad, Dufaud Olivier, Perrin Laurent, Nicolas Cuervo, Laurent André. Interactions turbulence-combustion lors des explosions de mélanges hybrides vapeurs/poussières - Combustion-turbulence interactions in hybrid mixtures flames. Récents Progrès en Génie des Procédés, 2011, pp.1-6. ⟨hal-01925947⟩

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