Abstract
The scalar mixing time scale, a key quantity in many turbulent combustion models, is investigated for reactive scalars in premixed combustion. Direct numerical simulations (DNS) of three-dimensional, turbulent Bunsen flames with reduced methane-air chemistry have been analyzed in the thin reaction zones regime. Previous conclusions from single step chemistry DNS studies are confirmed regarding the role of dilatation and turbulence-chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species is found to be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional premixed laminar flames. According to this analysis, mixing rates are governed by the strong gradients which are imposed by flamelet structures at high Damköhler numbers. This suggests a modeling approach to estimate the mixing rate of individual species which can be applied, for example, in transported probability density function simulations. Flame-turbulence interactions which modify the flamelet based representation are analyzed.
Original language | English |
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Pages (from-to) | 506-515 |
Number of pages | 10 |
Journal | Combustion and Flame |
Volume | 157 |
Issue number | 3 |
DOIs | |
State | Published - Mar 2010 |
Funding
The authors are grateful to Prof. S.B. Pope (Cornell University, Ithaca, NY) for his comments on this work. The work at SNL was supported by the Division of Chemical Sciences, Geosciences and Bio-sciences, the Office of Basic Energy Sciences (BES), the US Department of Energy (DOE) and also by the US DOE, BES, SciDAC Computational Chemistry program. SNL is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US DOE under Contract No. DE-AC04-94-AL85000. This research used resources of the National Center for Computational Sciences (NCCS) at Oak Ridge National Laboratory (ORNL), which is supported by the Office of Science of the US DOE under Contract No. DE-AC05-00OR22725.
Keywords
- Direct numerical simulation
- Premixed flame
- Scalar dissipation rate
- Turbulent mixing time scale