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The effects of dilution with nitrogen and steam on the laminar burning velocity of methanol at room and elevated temperatures

Vancoillie, J. ; Christensen, Moah LU ; Heimdal Nilsson, Elna LU orcid ; Verhelst, S. and Konnov, Alexander LU (2013) In Fuel 105. p.732-738
Abstract
Dilution of flames using recirculated exhaust gas or water vapor is an important NOx reduction technique in various combustion applications. Dilution, however, can also lead to combustion instabilities due to reduced burning velocities. For methanol/air flames this subject is largely unexplored. Therefore, the current work examines the effects of diluting methanol/air flames with nitrogen and water vapor both experimentally and by simulation. Using the heat flux method, the laminar burning velocity u(l) of methanol/air mixtures was measured at p = 1 bar, T-u = 298-358 K, phi = 0.7-1.5, molar water vapor contents up to 20% and molar excess nitrogen contents of almost 10%. Simulations were performed using the methanol oxidation mechanism of... (More)
Dilution of flames using recirculated exhaust gas or water vapor is an important NOx reduction technique in various combustion applications. Dilution, however, can also lead to combustion instabilities due to reduced burning velocities. For methanol/air flames this subject is largely unexplored. Therefore, the current work examines the effects of diluting methanol/air flames with nitrogen and water vapor both experimentally and by simulation. Using the heat flux method, the laminar burning velocity u(l) of methanol/air mixtures was measured at p = 1 bar, T-u = 298-358 K, phi = 0.7-1.5, molar water vapor contents up to 20% and molar excess nitrogen contents of almost 10%. Simulations were performed using the methanol oxidation mechanism of Li et al. (IJCK 39: 109 (2007)). Excellent agreement between experimental and computed results was found for lean mixtures. For rich mixtures the mechanism of Li et al. overestimated the laminar burning velocity up to 5%. The effect of dilution on u(l) was well predicted for both diluents. The relative impact of thermal and chemical effects of dilution was estimated computationally. For both N-2 and H2O the chemical effect was shown to be negligible for diluents ratios considered here (<20%). Based on the modeling results, an explicit correlation was proposed that describes the effect of dilution on u(l) in terms of diluent molar content, diluent specific molar heat capacity, equivalence ratio and unburned mixture temperature. Very good agreement was obtained between the correlation and the modeling data. The effects of unburned mixture temperature on the laminar burning velocity of methanol were analyzed using the correlation u(l) = u(l0) . (T-u/T-u0)(alpha). The current experimental results showed that the power exponent alpha reached a minimum for phi = 1.2, which was well reproduced by the modeling. The modeling results indicated that alpha increases as the mixture gets more diluted. (Less)
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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Methanol, Laminar burning velocity, Heat flux method, Dilution
in
Fuel
volume
105
pages
732 - 738
publisher
Elsevier
external identifiers
  • wos:000311935400081
  • scopus:84870476808
ISSN
1873-7153
DOI
10.1016/j.fuel.2012.09.060
language
English
LU publication?
yes
id
395f7500-cded-40dd-856f-877f02d25b38 (old id 3224861)
alternative location
http://www.sciencedirect.com/science/article/pii/S0016236112007739
date added to LUP
2016-04-01 13:55:36
date last changed
2022-03-21 21:15:45
@article{395f7500-cded-40dd-856f-877f02d25b38,
  abstract     = {{Dilution of flames using recirculated exhaust gas or water vapor is an important NOx reduction technique in various combustion applications. Dilution, however, can also lead to combustion instabilities due to reduced burning velocities. For methanol/air flames this subject is largely unexplored. Therefore, the current work examines the effects of diluting methanol/air flames with nitrogen and water vapor both experimentally and by simulation. Using the heat flux method, the laminar burning velocity u(l) of methanol/air mixtures was measured at p = 1 bar, T-u = 298-358 K, phi = 0.7-1.5, molar water vapor contents up to 20% and molar excess nitrogen contents of almost 10%. Simulations were performed using the methanol oxidation mechanism of Li et al. (IJCK 39: 109 (2007)). Excellent agreement between experimental and computed results was found for lean mixtures. For rich mixtures the mechanism of Li et al. overestimated the laminar burning velocity up to 5%. The effect of dilution on u(l) was well predicted for both diluents. The relative impact of thermal and chemical effects of dilution was estimated computationally. For both N-2 and H2O the chemical effect was shown to be negligible for diluents ratios considered here (&lt;20%). Based on the modeling results, an explicit correlation was proposed that describes the effect of dilution on u(l) in terms of diluent molar content, diluent specific molar heat capacity, equivalence ratio and unburned mixture temperature. Very good agreement was obtained between the correlation and the modeling data. The effects of unburned mixture temperature on the laminar burning velocity of methanol were analyzed using the correlation u(l) = u(l0) . (T-u/T-u0)(alpha). The current experimental results showed that the power exponent alpha reached a minimum for phi = 1.2, which was well reproduced by the modeling. The modeling results indicated that alpha increases as the mixture gets more diluted.}},
  author       = {{Vancoillie, J. and Christensen, Moah and Heimdal Nilsson, Elna and Verhelst, S. and Konnov, Alexander}},
  issn         = {{1873-7153}},
  keywords     = {{Methanol; Laminar burning velocity; Heat flux method; Dilution}},
  language     = {{eng}},
  pages        = {{732--738}},
  publisher    = {{Elsevier}},
  series       = {{Fuel}},
  title        = {{The effects of dilution with nitrogen and steam on the laminar burning velocity of methanol at room and elevated temperatures}},
  url          = {{http://dx.doi.org/10.1016/j.fuel.2012.09.060}},
  doi          = {{10.1016/j.fuel.2012.09.060}},
  volume       = {{105}},
  year         = {{2013}},
}