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Deflagration-to-detonation transition in highly reactive combustible mixtures
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
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2010 (English)In: Acta Astronautica, ISSN 0094-5765, Vol. 67, no 7-8, 688-701 p.Article in journal (Refereed) Published
Abstract [en]

The paper presents experimental, theoretical, and numerical studies of deflagration-to-detonation transition (DDT) in highly reactive hydrogen-oxygen and ethylene-oxygen mixtures. Two-dimensional reactive Navier-Stokes equations for a hydrogen-oxygen gaseous mixture including the effects of viscosity, thermal conduction, molecular diffusion, and a detailed chemical reaction mechanism are solved numerically. It is found that mechanism of DDT is entirely determined by the features of the flame acceleration in tubes with no-slip walls. The experiments and computations show three distinct stages of the process: (1) the flame accelerates exponentially producing shock waves far ahead from the flame, (2) the flame acceleration decreases and shocks are formed directly on the flame surface, and (3) the final third stage of the actual transition to a detonation. During the second stage a compressed and heated pocket of unreacted gas adjacent ahead to the flame the preheat zone is forming and the compressed unreacted mixture entering the flame produces large amplitude pressure pulse. The increase of pressure enhances reaction rate and due to a positive feedback between the pressure peak and the reaction the pressure peak grows exponentially, steepens into a strong shock that is coupled with the reaction zone forming the overdriven detonation wave. The proposed new physical mechanism of DDT highlights the features of flame acceleration in tubes with no-slip walls, which is the key factor of the DDT origin.

Place, publisher, year, edition, pages
2010. Vol. 67, no 7-8, 688-701 p.
Keyword [en]
Deflagration, Detonation, Transition to detonation, Shock waves, Temperature gradient
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-134816DOI: 10.1016/j.actaastro.2010.05.024ISI: 000281923600005OAI: oai:DiVA.org:uu-134816DiVA: diva2:373909
Available from: 2010-12-02 Created: 2010-12-01 Last updated: 2010-12-02Bibliographically approved

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