Contribution à l'étude de la structure des détonations dans les milieux biphasiques

Abstract : Physical and chemical processes involved in propagation of detonations in solid particles-gas or liquid droplets-gas mixtures have been studied, by numerical simulations of the detonation cellular structure. In the case of suspensions of aluminium particles, two combustion models have been incorporated to the numerical code EFAE of the LCD. Calibration of only one best-fitting parameter against existing experimental results yields reasonable values of the characteristic width of the cellular structure ( = 40 cm for Al/Air and = 5-10 cm for Al/O2). The particle diameter dp0 has an influence on both induction Li and combustion Lc zone lengths (Li dp0 and Lc d1:8 p0 ) and on the cell width: d1:4 p0 . Contrary to gaseous detonations, chemical reactions do not start behind the triple points, but in the low-pressure zones, where particle concentration is lower thus enabling their fast ignition. The detonation spinning regime has been simulated for the first time in the case of suspensions of aluminium particles in a gaseous oxidizing atmosphere. The values of the critical detonation radius Rc and of the critical initiation energy Ec have been estimated (by extrapolating the correlations established for gases): Rc = 1 m and Ec = 105 J for Al/O2 mixtures while Rc = 8 m and Ec = 5.12 x 107 J for suspensions of Al in air. These values agree reasonably with available experimental data. In the case of hydrocarbon spray detonations, an evaporation model based on the "stripping" mode and on the diffusion regime has been incorporated in the code, coupled with a two-step kinetics chemistry (induction and combustion). First simulations of the cellular structure indicate that the characteristic cellular width is of the order of = 4-5 cm for octane-air mixtures, in agreement with existing experimental results.
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Arnaud Briand. Contribution à l'étude de la structure des détonations dans les milieux biphasiques. Sciences de l'ingénieur [physics]. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2009. Français. ⟨tel-00460888⟩

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