Title: Towards the distributed burning regime in turbulent premixed flames

Abstract

Three-dimensional numerical simulations of canonical statistically steady, statistically planar turbulent flames have been used in an attempt to produce distributed burning in lean methane and hydrogen flames. Dilatation across the flame means that extremely large Karlovitz numbers are required; even at the extreme levels of turbulence studied (up to a Karlovitz number of 8767) distributed burning was only achieved in the hydrogen case. In this case, turbulence was found to broaden the reaction zone visually by around an order of magnitude, and thermodiffusive effects (typically present for lean hydrogen flames) were not observed. In the preheat zone, the species compositions differ considerably from those of one-dimensional flames based a number of different transport models (mixture averaged, unity Lewis number and a turbulent eddy viscosity model). The behaviour is a characteristic of turbulence dominating non-unity Lewis number species transport, and the distinct limit is again attributed to dilatation and its effect on the turbulence. Peak local reaction rates are found to be lower in the distributed case than in the lower Karlovitz cases but higher than in the laminar flame, which is attributed to effects that arise from the modified fuel-temperature distribution that results from turbulent mixing dominating low Lewis numbermore » thermodiffusive effects. Finally, approaches to achieve distributed burning at realisable conditions are discussed; factors that increase the likelihood of realising distributed burning are higher pressure, lower equivalence ratio, higher Lewis number and lower reactant temperature.« less

Authors:

Aspden, A. J.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-2970-4824"
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Day, M. S.  ^[2];

• Search DOE PAGES for author "Day, M. S."
• Search DOE PAGES for ORCID "0000-0002-1711-3963"
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Bell, J. B.  ^[2]

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• Search DOE PAGES for ORCID "0000-0002-5749-334X"
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+ Show Author Affiliations

1. Newcastle Univ. (United Kingdom). School of Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Center for Computational Sciences and Engineering
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Center for Computational Sciences and Engineering

Publication Date:

2019-07-25

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)

Sponsoring Org.:

USDOE

OSTI Identifier:

1526713

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Fluid Mechanics

Additional Journal Information:

Journal Volume: 871; Journal ID: ISSN 0022-1120

Publisher:

Cambridge University Press

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING