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Investigation of formaldehyde enhancement by ozone addition in CH4/air premixed flames

Weng, Wubin; Heimdal Nilsson, Elna LU ; Ehn, Andreas LU ; Zhu, Jiajian LU ; Zhou, Yajun; Wang, Zhihua; Li, Zhongshan LU ; Aldén, Marcus LU and Cen, Kefa (2015) In Combustion and Flame 162(4). p.1284-1293
Abstract
Abstract The ozone (O3) decomposition in the pre-heat zone of flames can initiate and accelerate the chain-branching reactions. In the present study, formaldehyde (CH2O) was investigated by both experiment and simulation methods in methane/air laminar premixed flames under atmospheric conditions. The formaldehyde concentration profiles in the flames were measured with CH2O-PLIF. When 4500 ppm of ozone was added, the formaldehyde concentration in Bunsen type laminar flame was enhanced by 58.5% at fuel-rich condition (Ï = 1.4) and 15.5% at stoichiometric condition. In the simulation work, the most recent ozone sub-mechanism was coupled with GRI-mech 3.0 kinetic mechanism. It showed that with 4500 ppm ozone addition, the formaldehyde... (More)
Abstract The ozone (O3) decomposition in the pre-heat zone of flames can initiate and accelerate the chain-branching reactions. In the present study, formaldehyde (CH2O) was investigated by both experiment and simulation methods in methane/air laminar premixed flames under atmospheric conditions. The formaldehyde concentration profiles in the flames were measured with CH2O-PLIF. When 4500 ppm of ozone was added, the formaldehyde concentration in Bunsen type laminar flame was enhanced by 58.5% at fuel-rich condition (Ï = 1.4) and 15.5% at stoichiometric condition. In the simulation work, the most recent ozone sub-mechanism was coupled with GRI-mech 3.0 kinetic mechanism. It showed that with 4500 ppm ozone addition, the formaldehyde concentration was enhanced by about 48.1% at rich condition (Ï = 1.4) and about 14.7% in stoichiometric mixture. The simulation suggested an early production of CH2O with ozone addition, especially in rich conditions. These reactions occurred at relatively low temperature, around 500 K. In order to isolate these reactions from the flame, experiments with preheated unburned mixtures were carried out. A larger amount of formaldehyde was produced in the zone far from the flame as the preheating temperature was increased. It indicated that the combustion enhancement with ozone could be caused by the additional reactions of ozone at relatively low temperature. Simulations showed that methoxy radical (CH3O) is the key specie for production of formaldehyde at lower temperatures. Early in the pre-heat zone of the laminar flame, formaldehyde occurs via decomposition of CH3O while in the pre-heated gas mixture via reaction of CH3O with O2. Furthermore, the O3 effect on turbulent flames was investigated showing a greater enhancement in formaldehyde signal than that in the laminar cases. This difference in formaldehyde signal enhancement could be attributed to the expansion of the preheat zone, due to turbulence. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Ozone, Formaldehyde, Methane flame, Pre-heating, CH2O-PLIF
in
Combustion and Flame
volume
162
issue
4
pages
1284 - 1293
publisher
Elsevier
external identifiers
  • wos:000351794100033
  • scopus:84924272166
ISSN
0010-2180
DOI
10.1016/j.combustflame.2014.10.021
language
English
LU publication?
yes
id
498825a4-4ba9-4bcd-aa09-a06611ed0d8c (old id 4855908)
alternative location
http://www.sciencedirect.com/science/article/pii/S0010218014003423
date added to LUP
2014-12-03 03:21:49
date last changed
2017-07-23 04:17:30
@article{498825a4-4ba9-4bcd-aa09-a06611ed0d8c,
  abstract     = {Abstract The ozone (O3) decomposition in the pre-heat zone of flames can initiate and accelerate the chain-branching reactions. In the present study, formaldehyde (CH2O) was investigated by both experiment and simulation methods in methane/air laminar premixed flames under atmospheric conditions. The formaldehyde concentration profiles in the flames were measured with CH2O-PLIF. When 4500 ppm of ozone was added, the formaldehyde concentration in Bunsen type laminar flame was enhanced by 58.5% at fuel-rich condition (Ï = 1.4) and 15.5% at stoichiometric condition. In the simulation work, the most recent ozone sub-mechanism was coupled with GRI-mech 3.0 kinetic mechanism. It showed that with 4500 ppm ozone addition, the formaldehyde concentration was enhanced by about 48.1% at rich condition (Ï = 1.4) and about 14.7% in stoichiometric mixture. The simulation suggested an early production of CH2O with ozone addition, especially in rich conditions. These reactions occurred at relatively low temperature, around 500 K. In order to isolate these reactions from the flame, experiments with preheated unburned mixtures were carried out. A larger amount of formaldehyde was produced in the zone far from the flame as the preheating temperature was increased. It indicated that the combustion enhancement with ozone could be caused by the additional reactions of ozone at relatively low temperature. Simulations showed that methoxy radical (CH3O) is the key specie for production of formaldehyde at lower temperatures. Early in the pre-heat zone of the laminar flame, formaldehyde occurs via decomposition of CH3O while in the pre-heated gas mixture via reaction of CH3O with O2. Furthermore, the O3 effect on turbulent flames was investigated showing a greater enhancement in formaldehyde signal than that in the laminar cases. This difference in formaldehyde signal enhancement could be attributed to the expansion of the preheat zone, due to turbulence.},
  author       = {Weng, Wubin and Heimdal Nilsson, Elna and Ehn, Andreas and Zhu, Jiajian and Zhou, Yajun and Wang, Zhihua and Li, Zhongshan and Aldén, Marcus and Cen, Kefa},
  issn         = {0010-2180},
  keyword      = {Ozone,Formaldehyde,Methane flame,Pre-heating,CH2O-PLIF},
  language     = {eng},
  number       = {4},
  pages        = {1284--1293},
  publisher    = {Elsevier},
  series       = {Combustion and Flame},
  title        = {Investigation of formaldehyde enhancement by ozone addition in CH4/air premixed flames},
  url          = {http://dx.doi.org/10.1016/j.combustflame.2014.10.021},
  volume       = {162},
  year         = {2015},
}