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Title: Extinction and reignition in direct numerical simulations of CO/H 2 temporal plane jet flames

Abstract

Direct numerical simulations of three-dimensional turbulent temporally-evolving plane CO/H2 jet flames have been performed with skeletal chemistry at Reynolds numbers of up to 9,000 and with up to 500 million grid points (Hawkes, E.R., Sankaran, R., Sutherland, J.C., Chen, J.H., Proc. Combust. Inst. 31 (2007) 1633-1640). In the present paper, the data are analyzed to understand the processes of extinction and reignition observed in the simulations. A measure of extinction based on the amount of stoichiometric surface area having a reacting scalar less than a threshold value is used to characterize extinction. Employing this characterization leads naturally to the appearance of a local displacement speed of 'flame edges' as the primary quantity of interest. Flame edges are defined as the boundaries on the stoichiometric surface between areas having a reacting scalar less than the threshold (extinguished) and those above it (burning). The displacement speed is the speed at which these boundaries move relative to the local flow. The motion of flames edges is studied using a massively parallel analysis tool. The joint probability density function of the local edge flame speed and scalar dissipation rate has been extracted and reveals a transition in character as the simulation progresses. The transitionmore » is interpreted in the context of the physical mechanisms of extinction and reignition. Along with evidence of the alignment of the scalar and mixture fraction normal vectors, it indicates that the mechanism of folding by turbulence of burning regions onto extinguished ones is the dominant reignition mechanism for the simulated conditions.« less

Authors:
 [1];  [2];  [1]
  1. Sandia National Laboratories (SNL)
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Center for Computational Sciences
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
930891
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 5th US National Combustion Meeting, San Diego, CA, CA, USA, 20070325, 20070328
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBON MONOXIDE; HYDROGEN; FLAMES; COMBUSTION KINETICS; PROBABILITY DENSITY FUNCTIONS; REYNOLDS NUMBER; SCALARS; INHIBITION; IGNITION; COMPUTERIZED SIMULATION

Citation Formats

Hawkes, Evatt R, Sankaran, Ramanan, and Chen, Jacqueline H. Extinction and reignition in direct numerical simulations of CO/H2 temporal plane jet flames. United States: N. p., 2007. Web.
Hawkes, Evatt R, Sankaran, Ramanan, & Chen, Jacqueline H. Extinction and reignition in direct numerical simulations of CO/H2 temporal plane jet flames. United States.
Hawkes, Evatt R, Sankaran, Ramanan, and Chen, Jacqueline H. Mon . "Extinction and reignition in direct numerical simulations of CO/H2 temporal plane jet flames". United States. doi:.
@article{osti_930891,
title = {Extinction and reignition in direct numerical simulations of CO/H2 temporal plane jet flames},
author = {Hawkes, Evatt R and Sankaran, Ramanan and Chen, Jacqueline H},
abstractNote = {Direct numerical simulations of three-dimensional turbulent temporally-evolving plane CO/H2 jet flames have been performed with skeletal chemistry at Reynolds numbers of up to 9,000 and with up to 500 million grid points (Hawkes, E.R., Sankaran, R., Sutherland, J.C., Chen, J.H., Proc. Combust. Inst. 31 (2007) 1633-1640). In the present paper, the data are analyzed to understand the processes of extinction and reignition observed in the simulations. A measure of extinction based on the amount of stoichiometric surface area having a reacting scalar less than a threshold value is used to characterize extinction. Employing this characterization leads naturally to the appearance of a local displacement speed of 'flame edges' as the primary quantity of interest. Flame edges are defined as the boundaries on the stoichiometric surface between areas having a reacting scalar less than the threshold (extinguished) and those above it (burning). The displacement speed is the speed at which these boundaries move relative to the local flow. The motion of flames edges is studied using a massively parallel analysis tool. The joint probability density function of the local edge flame speed and scalar dissipation rate has been extracted and reveals a transition in character as the simulation progresses. The transition is interpreted in the context of the physical mechanisms of extinction and reignition. Along with evidence of the alignment of the scalar and mixture fraction normal vectors, it indicates that the mechanism of folding by turbulence of burning regions onto extinguished ones is the dominant reignition mechanism for the simulated conditions.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

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