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Triple-point shear layers in gaseous detonation waves

Massa, L. and Austin, J. M. and Jackson, T. L. (2007) Triple-point shear layers in gaseous detonation waves. Journal of Fluid Mechanics, 586 . pp. 205-248. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:20140924-090817930

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Abstract

Recent experiments have shown intriguing regions of intense luminescence or ‘hotspots’ in the vicinity of triple-point shear layers in propagating gaseous detonation waves. Localized explosions have also been observed to develop in these fronts. These features were observed in higher effective activation energy mixtures, but not in lower effective activation energy mixtures. The increased lead shock oscillation through a cell cycle in higher activation energy mixtures may result in a significantly increased disparity in the induction time on either side of the triple-point shear layer, and thus an enhanced mixing between reacted and non-reacted streams supported by Kelvin–Helmholtz instability. The relation between the shear-layer instability and the mixture effective activation energy is analysed by carrying out a spatial linear stability study for three mixtures with different activation energies and injection conditions that correspond to the experimental conditions. The role of vortical structures associated with Kelvin–Helmholtz instability in the formation of localized ignition is investigated by performing two-dimensional Navier–Stokes simulations with detailed chemical kinetics and transport. In the low activation energy mixture, large-scale vortical structures are observed to occur downstream of the induction distance; these structures do not have a noticeable effect on the reaction. In higher effective activation energy mixtures, a thin transverse ignition front develops near the interface between the two gas streams and results in a combustion structure decoupled from the entrainment region. The decoupling leads to attenuation of the instability growth rate when compared to frozen calculations, and a reduced heat release in the high vorticity region. The analysis indicates the instability plays a modest role in ignition events for high activation energy mixtures. The formation of localized explosions observed in high activation energy systems is instead linked to the impossibility of a one-dimensional reactive combustion wave supported by the injection conditions. In the absence of curvature effects and stream-tube divergence, a system of shock waves is formed which spreads the ignition to the cold gas stream.


Item Type:Article
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http://dx.doi.org/10.1017/S0022112007007008 DOIArticle
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1299032&fileId=S0022112007007008PublisherArticle
Additional Information:© 2007 Cambridge University Press. Received 21 July 2006 and in revised form 16 April 2007. Published online: 14 August 2007. L. M. and T.L. J. were supported by the US Department of Energy through the University of California under subcontract number B523819.
Group:GALCIT
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Funding AgencyGrant Number
Department of Energy (DOE)B523819
Record Number:CaltechAUTHORS:20140924-090817930
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140924-090817930
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49977
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:29 Sep 2014 22:17
Last Modified:20 Sep 2016 23:02

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