%0 Journal Article
%T Direct Numerical Simulations of the Impact of High Turbulence Intensities and Volume Viscosity on Premixed Methane Flames
%A Gordon Fru
%A G¨¢bor Janiga
%A Dominique Th¨¦venin
%J Journal of Combustion
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/746719
%X 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. 1. Introduction Both the availability of electrical energy and all transportation systems are controlled to a large extent by turbulent combustion processes, such as in gas turbines or Internal Combustion engines, burning either fossil or renewable fuels. Optimizing further such well-known systems is only possible with a much better understanding of all relevant processes involved. Detailed quantitative experiments are needed and very useful, but sometimes impossible and usually limited to only a few flame quantities. As a complement, detailed (direct) numerical simulations (DNSs) are increasingly gaining grounds as a reliable tool for detailed investigations towards fundamental understanding of a variety of turbulent combustion phenomena [1]. Progress in numerical techniques as well as computational power now allows quantitative investigations of turbulent reacting flows for increasingly realistic conditions, for which practically relevant fuels are simulated at higher turbulent Reynolds numbers ( ), while employing at the same time complex physicochemical models to describe turbulence, molecular transport, and chemistry [2¨C4]. There are in fact only two possibilities to obtain statistically significant results. Ensemble
%U http://www.hindawi.com/journals/jc/2011/746719/