LES/PDF modeling of swirl-stabilized non-premixed methane/air flames with local extinction and re-ignition
(2020) In Combustion and Flame 219. p.102-119- Abstract
Turbulent non-premixed flames with local extinction and re-ignition exhibit multiple combustion modes including ignition waves, diffusion flames, partially premixed flames, and ignition-assisted partially premixed flames. The mechanisms of local extinction and re-ignition are not well understood and numerical modeling of multi-mode combustion is a challenging task. In this work, a specially designed swirl-burner was used to study local extinction and re-ignition of non-premixed turbulent methane/air flames. High speed Particle Image Velocimetry (PIV) and laser induced fluorescence of OH radicals (OH-PLIF) measurements along with Large Eddy Simulation (LES) were carried out to investigate the mechanisms of extinction and re-ignition... (More)
Turbulent non-premixed flames with local extinction and re-ignition exhibit multiple combustion modes including ignition waves, diffusion flames, partially premixed flames, and ignition-assisted partially premixed flames. The mechanisms of local extinction and re-ignition are not well understood and numerical modeling of multi-mode combustion is a challenging task. In this work, a specially designed swirl-burner was used to study local extinction and re-ignition of non-premixed turbulent methane/air flames. High speed Particle Image Velocimetry (PIV) and laser induced fluorescence of OH radicals (OH-PLIF) measurements along with Large Eddy Simulation (LES) were carried out to investigate the mechanisms of extinction and re-ignition processes in the burner. LES is based on a transported probability density function model within the framework of Eulerian Stochastic Fields (PDF-ESF). It is found that local extinction occurs when the scalar dissipation rate around the stoichiometric mixture fraction is high. The characteristic time scale for local extinction and re-ignition in the present flames is an order of magnitude longer than the characteristic time scale of diffusion/extinction of laminar flamelets. There are two mechanisms for flame hole re-ignition in the present flames. First, under low degree of local extinction conditions (i.e., for small flame holes surrounded by flames) the flame hole re-ignition is due to the mechanism of turbulent flame folding. Second, under high degree of extinction conditions (i.e., with large regions of extinction and lifted flames), re-ignition of the locally extinguished flame is due to the mechanism of ignition assisted partially premixed flame propagation. The results show that the PDF-ESF model is capable of simulating the quenching and re-ignition process found in the experiments.
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- author
- Yu, S. LU ; Liu, X. LU ; Bai, X. S. LU ; Elbaz, A. M. and Roberts, W. L.
- organization
- publishing date
- 2020
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- LES, Local extinction, Non-premixed swirl flames, PDF-ESF, Re-ignition
- in
- Combustion and Flame
- volume
- 219
- pages
- 18 pages
- publisher
- Elsevier
- external identifiers
-
- scopus:85086085878
- ISSN
- 0010-2180
- DOI
- 10.1016/j.combustflame.2020.05.018
- language
- English
- LU publication?
- yes
- id
- 3a7b5a69-fdd0-4b46-9c4a-64adbd04b81a
- date added to LUP
- 2020-06-30 10:09:04
- date last changed
- 2022-04-18 23:10:02
@article{3a7b5a69-fdd0-4b46-9c4a-64adbd04b81a,
abstract = {{<p>Turbulent non-premixed flames with local extinction and re-ignition exhibit multiple combustion modes including ignition waves, diffusion flames, partially premixed flames, and ignition-assisted partially premixed flames. The mechanisms of local extinction and re-ignition are not well understood and numerical modeling of multi-mode combustion is a challenging task. In this work, a specially designed swirl-burner was used to study local extinction and re-ignition of non-premixed turbulent methane/air flames. High speed Particle Image Velocimetry (PIV) and laser induced fluorescence of OH radicals (OH-PLIF) measurements along with Large Eddy Simulation (LES) were carried out to investigate the mechanisms of extinction and re-ignition processes in the burner. LES is based on a transported probability density function model within the framework of Eulerian Stochastic Fields (PDF-ESF). It is found that local extinction occurs when the scalar dissipation rate around the stoichiometric mixture fraction is high. The characteristic time scale for local extinction and re-ignition in the present flames is an order of magnitude longer than the characteristic time scale of diffusion/extinction of laminar flamelets. There are two mechanisms for flame hole re-ignition in the present flames. First, under low degree of local extinction conditions (i.e., for small flame holes surrounded by flames) the flame hole re-ignition is due to the mechanism of turbulent flame folding. Second, under high degree of extinction conditions (i.e., with large regions of extinction and lifted flames), re-ignition of the locally extinguished flame is due to the mechanism of ignition assisted partially premixed flame propagation. The results show that the PDF-ESF model is capable of simulating the quenching and re-ignition process found in the experiments.</p>}},
author = {{Yu, S. and Liu, X. and Bai, X. S. and Elbaz, A. M. and Roberts, W. L.}},
issn = {{0010-2180}},
keywords = {{LES; Local extinction; Non-premixed swirl flames; PDF-ESF; Re-ignition}},
language = {{eng}},
pages = {{102--119}},
publisher = {{Elsevier}},
series = {{Combustion and Flame}},
title = {{LES/PDF modeling of swirl-stabilized non-premixed methane/air flames with local extinction and re-ignition}},
url = {{http://dx.doi.org/10.1016/j.combustflame.2020.05.018}},
doi = {{10.1016/j.combustflame.2020.05.018}},
volume = {{219}},
year = {{2020}},
}