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Laminar burning velocities of lean hydrogen-air mixtures at pressures up to 1.0 MPa

Bradley, D., Lawes, M., Liu, K., Verhelst, S. and Woolley, R. (2007) Laminar burning velocities of lean hydrogen-air mixtures at pressures up to 1.0 MPa. Combustion and Flame, 149 (1-2). pp. 162-172. ISSN 0010-2180

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Abstract

Values of laminar burning velocity, ul, and the associated strain rate Markstein number, Masr, of H2-air mixtures have been obtained from measurements of flame speeds in a spherical explosion bomb with central ignition. Pressures ranged from 0.1 to 1.0 MPa, with values of equivalence ratio between 0.3 and 1.0. Many of the flames soon became unstable, with an accelerating flame speed, due to Darrieus-Landau and thermodiffusive instabilities. This effect increased with pressure. The flame wrinkling arising from the instabilities enhanced the flame speed. A method is described for allowing for this effect, based on measurements of the flame radii at which the instabilities increased the flame speed. This enabled ul and Masr to be obtained, devoid of the effects of instabilities. With increasing pressure, the time interval between the end of the ignition spark and the onset of flame instability, during which stable stretched flame propagation occurred, became increasingly small and very high camera speeds were necessary for accurate measurement. Eventually this time interval became so short that first Masr and then ul could not be measured. Such flame instabilities throw into question the utility of ul for high pressure, very unstable, flames. The measured values of ul are compared with those predicted by detailed chemical kinetic models of one-dimensional flames.

Item Type: Article
Institution: The University of Leeds, The University of Sheffield
Academic Units: The University of Leeds > Faculty of Engineering (Leeds) > School of Mechanical Engineering (Leeds)
The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield)
Depositing User: Mr Christopher Hardwick
Date Deposited: 21 Aug 2009 09:40
Last Modified: 08 Feb 2013 17:08
Published Version: http://dx.doi.org/10.1016/j.combustflame.2006.12.0...
Status: Published
Publisher: Elsevier Science B.V., Amsterdam
Refereed: Yes
Identification Number: 10.1016/j.combustflame.2006.12.002
URI: http://eprints.whiterose.ac.uk/id/eprint/9195

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