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An experimental/numerical investigation of the role of the quarl in enhancing the blowout limits of swirl-stabilized turbulent non-premixed flames

Elbaz, A. M.; Yu, S. LU ; Liu, X. LU ; Bai, X. S. LU ; Khesho, I. and Roberts, W. L. (2019) In Fuel 236. p.1226-1242
Abstract

The blowout limits of methane/air non-premixed swirl-stabilized flames were measured with and without quarl. The addition of a quarl significantly enhances the flame blowout limits. The transition from attached flame to blowout was mapped. To explore the role of the quarl, a series of OH-PLIF/PIV experiments, coupled with large eddy simulations (LES) using a transported probability density function (PDF) model, were carried out on flames with and without quarl over a wide range of fuel jet velocity, Uf. The results show that the mean flow field is characterized by two recirculation zones. The existence of the quarl enhances this flow field by triggering a larger scale of reversal flow, penetrating deeply upstream into the... (More)

The blowout limits of methane/air non-premixed swirl-stabilized flames were measured with and without quarl. The addition of a quarl significantly enhances the flame blowout limits. The transition from attached flame to blowout was mapped. To explore the role of the quarl, a series of OH-PLIF/PIV experiments, coupled with large eddy simulations (LES) using a transported probability density function (PDF) model, were carried out on flames with and without quarl over a wide range of fuel jet velocity, Uf. The results show that the mean flow field is characterized by two recirculation zones. The existence of the quarl enhances this flow field by triggering a larger scale of reversal flow, penetrating deeply upstream into the quarl. This results in much earlier fuel, extending down into the air tube, where a diffusion flame is stabilized around the stoichiometric mixture contour and locally low scalar dissipation rates. The relative delay in fuel/air mixing in non-quarl flames results in a locally strong scalar dissipation rate layer overlapping the stoichiometric mixture contour, and thus, the flame is highly sensitive to local extinction with increasing fuel jet velocity. At high Uf, in the liftoff flame region, the existence of the quarl enhances the jet spreading and a weak recirculation zone around the highly strained jet is observed. Together with fuel jet spreading, partial oxidization of the mixture upstream the lifted flame base creates a wider range of burnable mixture along the axis in the quarl flames. On the contrary, the high scalar dissipation rate and the absence of a recirculation region in the proximity of the fuel nozzle in the non-quarl flame give rise to an earlier blowout.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
LES, Non-premixed swirl flames, PIV/OH-PLIF, Quarl swirl stabilized, Transported PDF
in
Fuel
volume
236
pages
17 pages
publisher
Elsevier
external identifiers
  • scopus:85053862817
ISSN
0016-2361
DOI
10.1016/j.fuel.2018.09.064
language
English
LU publication?
yes
id
1784a2fa-e4b0-4d45-acf8-7f0f54a3faa0
date added to LUP
2018-10-08 09:40:36
date last changed
2018-10-08 09:40:36
@article{1784a2fa-e4b0-4d45-acf8-7f0f54a3faa0,
  abstract     = {<p>The blowout limits of methane/air non-premixed swirl-stabilized flames were measured with and without quarl. The addition of a quarl significantly enhances the flame blowout limits. The transition from attached flame to blowout was mapped. To explore the role of the quarl, a series of OH-PLIF/PIV experiments, coupled with large eddy simulations (LES) using a transported probability density function (PDF) model, were carried out on flames with and without quarl over a wide range of fuel jet velocity, U<sub>f</sub>. The results show that the mean flow field is characterized by two recirculation zones. The existence of the quarl enhances this flow field by triggering a larger scale of reversal flow, penetrating deeply upstream into the quarl. This results in much earlier fuel, extending down into the air tube, where a diffusion flame is stabilized around the stoichiometric mixture contour and locally low scalar dissipation rates. The relative delay in fuel/air mixing in non-quarl flames results in a locally strong scalar dissipation rate layer overlapping the stoichiometric mixture contour, and thus, the flame is highly sensitive to local extinction with increasing fuel jet velocity. At high U<sub>f</sub>, in the liftoff flame region, the existence of the quarl enhances the jet spreading and a weak recirculation zone around the highly strained jet is observed. Together with fuel jet spreading, partial oxidization of the mixture upstream the lifted flame base creates a wider range of burnable mixture along the axis in the quarl flames. On the contrary, the high scalar dissipation rate and the absence of a recirculation region in the proximity of the fuel nozzle in the non-quarl flame give rise to an earlier blowout.</p>},
  author       = {Elbaz, A. M. and Yu, S. and Liu, X. and Bai, X. S. and Khesho, I. and Roberts, W. L.},
  issn         = {0016-2361},
  keyword      = {LES,Non-premixed swirl flames,PIV/OH-PLIF,Quarl swirl stabilized,Transported PDF},
  language     = {eng},
  month        = {01},
  pages        = {1226--1242},
  publisher    = {Elsevier},
  series       = {Fuel},
  title        = {An experimental/numerical investigation of the role of the quarl in enhancing the blowout limits of swirl-stabilized turbulent non-premixed flames},
  url          = {http://dx.doi.org/10.1016/j.fuel.2018.09.064},
  volume       = {236},
  year         = {2019},
}