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Reaction zones in highly unstable detonations

Austin, J. M. and Pintgen, F. and Shepherd, J. E. (2005) Reaction zones in highly unstable detonations. Proceedings of the Combustion Institute, 30 (2). pp. 1849-1857. ISSN 1540-7489. https://resolver.caltech.edu/CaltechAUTHORS:20140924-093117980

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Abstract

Experimental images of detonation fronts are made for several fuel-oxidizer mixtures, including hydrocarbon–air systems. Schlieren and planar laser induced fluorescence techniques are used to image both the shock configurations and the OH reaction front structure in a single experiment. The experiments are carried out in a narrow rectangular channel. The degree of instability of detonation fronts in different mixtures is evaluated by comparing calculated mixture parameters with the longitudinal neutral stability curve. The images reveal that the structure of the front increases dramatically in complexity as the mixture parameters move away from the neutral stability curve into the unstable region. Of the mixtures studied, nitrogen-diluted hydrocarbon mixtures are predicted to be the most unstable, and these show the greatest degree of wrinkling in the shock and OH fronts, with distortion occurring over a wide range of spatial scales. In the most unstable cases, separation of the shock and OH front occurs, and localized explosions in these regions are observed in a high-speed schlieren movie. This is in dramatic contrast to the weakly unstable waves that have smooth reaction fronts and quasi-steady reaction zones with no evidence of localized explosions. A key feature of highly unstable waves is very fine scale wrinkling of the OH and shock fronts, which is absent in the low-activation energy cases. This may be due to the superposition of cellular structures with a wide range of cell sizes. In contrast to soot foils, images of the OH front have a more stochastic appearance, and organized cellular structure is not as apparent.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.proci.2004.08.157 DOIArticle
http://www.sciencedirect.com/science/article/pii/S0082078404002097PublisherArticle
ORCID:
AuthorORCID
Shepherd, J. E.0000-0003-3181-9310
Additional Information:© 2004 The Combustion Institute. Published by Elsevier Inc. This work was supported in part by funding from the ONR and the Caltech ASCI ASAP Center for Simulation of the Dynamic Response of Materials.
Group:GALCIT
Funders:
Funding AgencyGrant Number
Office of Naval Research (ONR)UNSPECIFIED
Caltech ASCI ASAP Center for Simulation of the Dynamic Response of MaterialsUNSPECIFIED
Subject Keywords:Detonation; Unstable; Planar laser induced fluorescence; Cellular structure
Issue or Number:2
Record Number:CaltechAUTHORS:20140924-093117980
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140924-093117980
Official Citation:J.M. Austin, F. Pintgen, J.E. Shepherd, Reaction zones in highly unstable detonations, Proceedings of the Combustion Institute, Volume 30, Issue 2, January 2005, Pages 1849-1857, ISSN 1540-7489, http://dx.doi.org/10.1016/j.proci.2004.08.157. (http://www.sciencedirect.com/science/article/pii/S0082078404002097)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49980
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Sep 2014 18:45
Last Modified:03 Oct 2019 07:19

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