TY - JOUR
T1 - Self-sustaining n-heptane cool diffusion flames activated by ozone
AU - Won, Sang Hee
AU - Jiang, Bo
AU - Diévart, Pascal
AU - Sohn, Chae Hoon
AU - Ju, Yiguang
N1 - Funding Information:
This work was supported by the AFOSR MURI research grant FA9550-07-1-0136 and AFOSR plasma assisted mild combustion research grant FA9550-13-1-0119 . PD was supported by the Combustion Energy Frontier Research Center , funded by the United States Department of Energy, Office of Science, Office of Basic Energy Sciences under the Award Number De-SC0001198 . BJ was supported by the China Scholarship Council . CHS was supported by the National Research Foundation of Korea Grant funded by the Korean Government ( NRF-2012S1A2A1A01031450 ) and the Research Year Program provided by Sejong University .
Publisher Copyright:
© 2014 The Combustion Institute.
PY - 2015
Y1 - 2015
N2 - A novel method to establish self-sustaining cool diffusion flames with well-defined boundary conditions is experimentally demonstrated by adding ozone to the oxidizer stream in counterflow configuration. It is found that the atomic oxygen produced through the decomposition of ozone dramatically shortens the induction timescale of the low temperature chemistry, extending the flammable region of cool flames. Thus, it enables the establishment of self-sustaining cool flames at the pressure and timescales at which normal cool flames may not be observable. The present method, for the first time, provides an opportunity to study cool flame dynamics, structure, and chemistry simultaneously in well-known flame geometry. Extinction limits of n-heptane/oxygen cool diffusion flames are measured and a cool diffusion flame diagram is experimentally determined. Numerical simulations reveal that the extinction limits of cool diffusion flames are strongly governed by species transport and low temperature chemistry activated by ozone decomposition. The structure of cool diffusion flame is further investigated by measuring the temperature and species distributions with a micro-probe sampling technique. The kinetic model over-predicts the rate of n-heptane oxidation, the heat release rate, and the flame temperature. Measurements of intermediate species, such as CH2O, acetaldehyde, C2H4, and CH4, suggest that the model over-predicts the QOOH thermal decomposition reactions to form olefins, resulting in substantial over-estimation of C2H4, and CH4 concentrations. The new method and data of the present study will contribute to promote understandings of cool flame chemistry.
AB - A novel method to establish self-sustaining cool diffusion flames with well-defined boundary conditions is experimentally demonstrated by adding ozone to the oxidizer stream in counterflow configuration. It is found that the atomic oxygen produced through the decomposition of ozone dramatically shortens the induction timescale of the low temperature chemistry, extending the flammable region of cool flames. Thus, it enables the establishment of self-sustaining cool flames at the pressure and timescales at which normal cool flames may not be observable. The present method, for the first time, provides an opportunity to study cool flame dynamics, structure, and chemistry simultaneously in well-known flame geometry. Extinction limits of n-heptane/oxygen cool diffusion flames are measured and a cool diffusion flame diagram is experimentally determined. Numerical simulations reveal that the extinction limits of cool diffusion flames are strongly governed by species transport and low temperature chemistry activated by ozone decomposition. The structure of cool diffusion flame is further investigated by measuring the temperature and species distributions with a micro-probe sampling technique. The kinetic model over-predicts the rate of n-heptane oxidation, the heat release rate, and the flame temperature. Measurements of intermediate species, such as CH2O, acetaldehyde, C2H4, and CH4, suggest that the model over-predicts the QOOH thermal decomposition reactions to form olefins, resulting in substantial over-estimation of C2H4, and CH4 concentrations. The new method and data of the present study will contribute to promote understandings of cool flame chemistry.
KW - Cool flame
KW - Counterflow diffusion flame
KW - Extinction
KW - Low temperature chemistry
KW - Ozone
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U2 - 10.1016/j.proci.2014.05.021
DO - 10.1016/j.proci.2014.05.021
M3 - Article
AN - SCOPUS:84947543760
SN - 1540-7489
VL - 35
SP - 881
EP - 888
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
ER -