Détonations dans les aérosols de gouttelettes liquides réactives. Etude de l'influence des propriétés physicochimiques de la phase liquide et de l'oxydant gazeux

Abstract : In heterogeneous media composed of liquid fuel sprays, influence of the physico-chemical properties of the liquid phase and of the gaseous oxidizer on conditions for detonation initiation and propagation characteristics as well as on the existence of a cellular structure, similar to that observed in homogeneous gaseous mixtures, has been studied. Experiments were performed in a square cross section (53x53mm), 4-meter long detonation tube, with 30 μm droplets. In air, with volatile fuels (heptane, isooctane), three detonation regimes have been observed with increasing equivalence ratio: spinning regime; marginal one with half a cell structure; normal multi-headed detonation regime. When the dilution ratio decreases, only the multi-headed regime was observed, and the cell size diminishes. In less volatile fuel (octane), the same detonation regimes were observed, but the cell sizes are larger than those of isooctane. In hardly volatile fuels (decane or dodecane), it was not possible to initiate a detonation, whatever the equivalent or the dilution ratios. With nitromethane (monopropellant), the initiation and propagation of a detonation was observed, and the existence of the cellular structure was displayed. A numerical model has been built on, in which only the pre-exponential factor of the chemical kinetics law is adjusted depending on chemical properties of the considered fuel. Results of 2D and 3D numerical simulations, as function of the equivalent ratio and the dilution ratio, display propagation regimes and detonation cell sizes in reasonable agreement with experimental results.
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Submitted on : Monday, February 18, 2013 - 3:41:45 PM
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Mohamed El-Amine Benmahammed. Détonations dans les aérosols de gouttelettes liquides réactives. Etude de l'influence des propriétés physicochimiques de la phase liquide et de l'oxydant gazeux. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2013. Français. ⟨NNT : 2013ESMA0001⟩. ⟨tel-00789666⟩

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