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Combustion chemistry of methoxymethanol. Part II : Laminar flames of methanol+formaldehyde fuel mixtures

Konnov, Alexander A. LU ; Nilsson, Elna J.K. LU ; Christensen, Moah LU and Zhou, Chong Wen (2021) In Combustion and Flame
Abstract

In the present study, the laminar burning velocities of mixtures of up to 16.4% (mol) formaldehyde in methanol, burning with air, were determined at atmospheric pressure using the heat flux method covering lean, stoichiometric and rich flames at initial gas mixture temperatures of 298, 318 and 338 K. Results published in the literature indicate that evaporation of CH2O+CH3OH fuel blends should lead to a gaseous mixture of formaldehyde, methanol and methoxymethanol, although the composition of these components in the gas phase was not well defined. To interpret the measurements performed in the present study, the detailed kinetic model developed by the group of Konnov was used. The recently updated mechanism was... (More)

In the present study, the laminar burning velocities of mixtures of up to 16.4% (mol) formaldehyde in methanol, burning with air, were determined at atmospheric pressure using the heat flux method covering lean, stoichiometric and rich flames at initial gas mixture temperatures of 298, 318 and 338 K. Results published in the literature indicate that evaporation of CH2O+CH3OH fuel blends should lead to a gaseous mixture of formaldehyde, methanol and methoxymethanol, although the composition of these components in the gas phase was not well defined. To interpret the measurements performed in the present study, the detailed kinetic model developed by the group of Konnov was used. The recently updated mechanism was further extended by the reactions of methoxymethanol with the rate constants calculated in Part I of the present study. A comparison of the predictions of this mechanism with the new experimental data indicated that between 40% and 60% of CH2O present in the investigated CH2O+CH3OH mixtures were at 473 K evaporated as gaseous formaldehyde monomer, while the rest was released within CH3OCH2OH. Laminar burning velocity results suggest partial condensation of methoxymethanol in the CH3OH+CH2O fuel mixture with 5.84% formaldehyde at rich conditions and 298 K. These observations allowed evaluation of the partial pressure of CH3OCH2OH which was found to be between 0.35 and 0.52 kPa. The sensitivity and rate-of-production analyses revealed that the reduced reactivity with the increased amount of methoxymethanol in the fuel mixtures is explained by the conversion of CH3OCH2OH to CH3OCHOH radicals due to favored H-abstraction from the secondary hydrogen atoms predicted by ab initio calculations compared to other sites of methoxymethanol. Hydroxyl-methoxyl-methyl radicals further decompose forming slowly reacting formic acid and methyl radicals.

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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
in press
subject
keywords
Burning velocity, Formaldehyde, Methanol, Methoxymethanol
in
Combustion and Flame
article number
111411
publisher
Elsevier
external identifiers
  • scopus:85103133170
ISSN
0010-2180
DOI
10.1016/j.combustflame.2021.111411
language
English
LU publication?
yes
id
bfd9defa-b656-48d3-ac39-ad9d5e2a7e45
date added to LUP
2021-04-08 12:30:33
date last changed
2021-04-08 12:30:33
@article{bfd9defa-b656-48d3-ac39-ad9d5e2a7e45,
  abstract     = {<p>In the present study, the laminar burning velocities of mixtures of up to 16.4% (mol) formaldehyde in methanol, burning with air, were determined at atmospheric pressure using the heat flux method covering lean, stoichiometric and rich flames at initial gas mixture temperatures of 298, 318 and 338 K. Results published in the literature indicate that evaporation of CH<sub>2</sub>O+CH<sub>3</sub>OH fuel blends should lead to a gaseous mixture of formaldehyde, methanol and methoxymethanol, although the composition of these components in the gas phase was not well defined. To interpret the measurements performed in the present study, the detailed kinetic model developed by the group of Konnov was used. The recently updated mechanism was further extended by the reactions of methoxymethanol with the rate constants calculated in Part I of the present study. A comparison of the predictions of this mechanism with the new experimental data indicated that between 40% and 60% of CH<sub>2</sub>O present in the investigated CH<sub>2</sub>O+CH<sub>3</sub>OH mixtures were at 473 K evaporated as gaseous formaldehyde monomer, while the rest was released within CH<sub>3</sub>OCH<sub>2</sub>OH. Laminar burning velocity results suggest partial condensation of methoxymethanol in the CH<sub>3</sub>OH+CH<sub>2</sub>O fuel mixture with 5.84% formaldehyde at rich conditions and 298 K. These observations allowed evaluation of the partial pressure of CH<sub>3</sub>OCH<sub>2</sub>OH which was found to be between 0.35 and 0.52 kPa. The sensitivity and rate-of-production analyses revealed that the reduced reactivity with the increased amount of methoxymethanol in the fuel mixtures is explained by the conversion of CH<sub>3</sub>OCH<sub>2</sub>OH to CH<sub>3</sub>OCHOH radicals due to favored H-abstraction from the secondary hydrogen atoms predicted by ab initio calculations compared to other sites of methoxymethanol. Hydroxyl-methoxyl-methyl radicals further decompose forming slowly reacting formic acid and methyl radicals.</p>},
  author       = {Konnov, Alexander A. and Nilsson, Elna J.K. and Christensen, Moah and Zhou, Chong Wen},
  issn         = {0010-2180},
  language     = {eng},
  publisher    = {Elsevier},
  series       = {Combustion and Flame},
  title        = {Combustion chemistry of methoxymethanol. Part II : Laminar flames of methanol+formaldehyde fuel mixtures},
  url          = {http://dx.doi.org/10.1016/j.combustflame.2021.111411},
  doi          = {10.1016/j.combustflame.2021.111411},
  year         = {2021},
}