Contribution à l'étude de la Transition Déflagration Détonation (TDD) dans des Mélanges Gazeux Binaires H2/C3H8/Air

Abstract : This study analyses the processes of detonation and transition from deflagration to detonation (DDT) in the binary gaseous mixtures H2/C3H8-Air contained in squared- or circular-section tubes. Focus is on the mechanisms of flame acceleration when obstacles are positioned in the tubes. The characteristic properties of the self-sustained detonation (velocity, pressure and cell size) and the DDT distance were measured for various equivalence ratios and hydrogen proportions in the propane. In particular, the effects on the DDT of the nature and length of the obstacle and of the tube diameter were investigated. Results show that the classical correlations as the detonation cell size - the chemical induction length, and the detonation cell size - the distance to DDT - well-established for simple mixtures - also apply to the considered H2/C3H8-Air binary fuels mixtures. The addition of C3H8 to H2 decreases the detonability of the binary fuels. Visualization of flame acceleration based on a shadow technique was performed by means of high-speed camera to identify the predominant physical mechanisms under different obstacle configurations. Shadow records have evidenced two stages. The first shows the predominant role of the flame intrinsic instabilities and area increase, as well as that of the delayed turbulent combustion resulting from the recirculation zone between two successive obstacles. The second shows that acceleration is controlled by the interaction of the flame front and the shock waves reflected on the obstacles or the tube walls. This leads to a strong flame-acceleration up to the "choking" regime which, under specific conditions, results in detonation initiation.
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Submitted on : Tuesday, October 9, 2012 - 2:26:37 PM
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Guanbing Cheng. Contribution à l'étude de la Transition Déflagration Détonation (TDD) dans des Mélanges Gazeux Binaires H2/C3H8/Air. Matériaux. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2012. Français. ⟨NNT : 2012ESMA0005⟩. ⟨tel-00740126⟩

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