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Journal of Combustion
Volume 2011, Article ID 746719, 12 pages
http://dx.doi.org/10.1155/2011/746719
Research Article

Direct Numerical Simulations of the Impact of High Turbulence Intensities and Volume Viscosity on Premixed Methane Flames

Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg “Otto von Guericke”, Universitätsplatz 2, 39106 Magdeburg, Germany

Received 14 January 2011; Accepted 20 April 2011

Academic Editor: Tatsuya Hasegawa

Copyright © 2011 Gordon Fru et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Parametric direct numerical simulations (DNS) of turbulent premixed flames burning methane in the thin reaction zone regime have been performed relying on complex physicochemical models and taking into account volume viscosity (). The combined effect of increasing turbulence intensities () and on the resulting flame structure is investigated. The turbulent flame structure is marred with numerous perforations and edge flame structures appearing within the burnt gas mixture at various locations, shapes and sizes. Stepping up from 3 to 12 m/s leads to an increase in the scaled integrated heat release rate from 2 to 16. This illustrates the interest of combustion in a highly turbulent medium in order to obtain high volumetric heat release rates in compact burners. Flame thickening is observed to be predominant at high turbulent Reynolds number. Via ensemble averaging, it is shown that both laminar and turbulent flame structures are not modified by . These findings are in opposition to previous observations for flames burning hydrogen, where significant modifications induced by were found for both the local and global properties of turbulent flames. Therefore, to save computational resources, we suggest that the volume viscosity transport term be ignored for turbulent combustion DNS at low Mach numbers when burning hydrocarbon fuels.