The effects of strain rate and curvature on surface density function transport in turbulent premixed methane-air and hydrogen-air flames: A comparative study
- Engineering Department, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom)
- School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)
- Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States)
- Engineering Department, Cambridge University, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)
The effects of tangential strain rate and curvature on the surface density function (SDF) and on source terms within the SDF transport equation are studied for lean methane-air and hydrogen-air flames using two-dimensional direct numerical simulations with detailed chemistry. A positive correlation is observed between the SDF and the tangential strain rate, and this is explained in terms of the interaction between the local tangential strain rate and the dilatation rate due to heat release. Curvature is also seen to affect the SDF through the curvature response of both tangential strain rate and dilatation rate on a given flame isosurface. Strain rate and curvature are found to have an appreciable effect on several terms of the SDF transport equation. The SDF straining term in both methane and hydrogen flames is correlated positively with tangential strain rate, as expected, and is also correlated negatively with curvature. For methane flames, the SDF propagation term is found to correlate negatively with flame curvature toward the reactant side of the flame and positively toward the product side. By contrast, for hydrogen flames the SDF propagation term is negatively correlated with curvature throughout the flame brush. The variation of the SDF curvature term with local flame curvature for both methane and hydrogen flames is found to be nonlinear due to the additional stretch induced by the tangential diffusion component of the displacement speed. Physical explanations are provided for all of these effects, and the modeling implications are considered in detail. (author)
- OSTI ID:
- 21044886
- Journal Information:
- Combustion and Flame, Vol. 154, Issue 1-2; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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