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Etude expérimentale et numérique de la dispersion explosive et de la combustion de particules métalliques

Abstract : The explosive dispersion of particles and their inflammation in air along with the blast wave effects were investigated experimentally and numerically. The experimental configuration consisted in studying the free-field explosion of spherical charges made of a central booster of solid explosive surrounded by a loose-packed density shell of inert (glass spheres) or reactive (atomized and flaked aluminium) particles. The high speed cinematography of the explosions coupled with image processing by a "Background Oriented Schlieren" method, and the pressure records by piezoelectric gauges permit to plot the x-t diagrams of the explosions. A technique has been developed to capture samples of dispersed particles and to make their post-analysis. The experimental results are confronted with numerical simulations performed with LCD's reactive multiphase flows code EFAE. The boundary of the dispersed cloud is not uniform but has a spiky shape with dendrites due to the formation of particle agglomerates of several millimetres. After 1m of propagation, some of those agglomerates overcome the leading shock front due to a ballistic effect. Glass particles are disintegrated by the shock. They have a mitigating effect, making the shock propagation slower and decreasing its amplitude. The effect of aluminium particles depends on their size: with the finer ones, after an initial slowdown phase, a re-acceleration of the leading shock and an increase of the pressure impulse are observed. With coarser particles, the shock is weakened but particle combustion raises the pressure level behind the shock front and slightly increases its impulse. An analysis of the collected agglomerates reveals that, in all cases, the combustion of aluminium particles is incomplete. Numerical simulations are in reasonable agreement with experimental results in the farfield domain.
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https://tel.archives-ouvertes.fr/tel-00476994
Contributor : Bénédicte Carouge <>
Submitted on : Tuesday, April 27, 2010 - 5:03:07 PM
Last modification on : Thursday, March 7, 2019 - 3:08:06 PM
Long-term archiving on: : Tuesday, September 28, 2010 - 1:05:27 PM

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Yann Gregoire. Etude expérimentale et numérique de la dispersion explosive et de la combustion de particules métalliques. Sciences de l'ingénieur [physics]. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2009. Français. ⟨tel-00476994⟩

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