TY - JOUR
T1 - Study on cool flame radical index and oxygen concentration dependence of oxygenated fuels
AU - Wang, Ziyu
AU - Zhou, Mengni
AU - Diévart, Pascal
AU - Lin, Ying
AU - Liu, Ning
AU - Yan, Chao
AU - Ju, Yiguang
N1 - Funding Information:
This research was funded by ARO grant W911NF-16-1-0076 and DOE BES research grant DE-SC0021135. This paper is dedicated to the memory of Dr. Jim Miller who had made an exceptional contribution to gas phase kinetics. YJ would like to thank Dr. Miller for his advice to work on low temperature and high pressure kinetics at the first Flame Chemistry workshop in Warsaw in 2012. With his encouragement, we have developed the research facilities of high pressure cool flames and a supercritical pressure jet stirred reactor. We are very indebted to his advice and encouragement.
Publisher Copyright:
© 2022 The Combustion Institute
PY - 2022
Y1 - 2022
N2 - The growing utilization of alternative fuels has sparked an interest in understanding the combustion characteristics of oxygenated fuels at low temperature. Cool flame extinction limits provide direct measures of the low-temperature reactivity of fuels and critical information for advanced low-temperature combustion engine design. This paper investigates the effects of fuel and oxygen concentrations on the extinction limits of diffusion cool flames for oxygenated fuels, including dimethyl ether, methyl decanoate, and 1-dodecanol in an atmospheric counterflow burner. The cool flame radical indexes of these oxygenated fuels are developed by isolating the thermal and transport effects from the chemical contribution to diffusion cool flame extinction. The results show that the ranking of low-temperature reactivities of long carbon chain oxygenated fuels, compared with n-alkane, is ether > n-alkane > alcohol > ester for a similar carbon number. Furthermore, due to the critical role of multiple oxygen addition reactions in the low-temperature chemistry, the relationship between the cool flame extinction limit and the oxygen concentration is also explored. The results show that the cool flame extinction limits of the oxygenated fuels are proportional to a nth power of the oxygen concentration, [O2]n, due to the combined effects of multiple oxygen addition reactions and the negative temperature coefficient in low-temperature chemistry. Additionally, the measured n number of 1-dodecanol is found to be larger than 2, which suggests the existence of the third oxygen addition reactions in low-temperature chemistry for large alcohols.
AB - The growing utilization of alternative fuels has sparked an interest in understanding the combustion characteristics of oxygenated fuels at low temperature. Cool flame extinction limits provide direct measures of the low-temperature reactivity of fuels and critical information for advanced low-temperature combustion engine design. This paper investigates the effects of fuel and oxygen concentrations on the extinction limits of diffusion cool flames for oxygenated fuels, including dimethyl ether, methyl decanoate, and 1-dodecanol in an atmospheric counterflow burner. The cool flame radical indexes of these oxygenated fuels are developed by isolating the thermal and transport effects from the chemical contribution to diffusion cool flame extinction. The results show that the ranking of low-temperature reactivities of long carbon chain oxygenated fuels, compared with n-alkane, is ether > n-alkane > alcohol > ester for a similar carbon number. Furthermore, due to the critical role of multiple oxygen addition reactions in the low-temperature chemistry, the relationship between the cool flame extinction limit and the oxygen concentration is also explored. The results show that the cool flame extinction limits of the oxygenated fuels are proportional to a nth power of the oxygen concentration, [O2]n, due to the combined effects of multiple oxygen addition reactions and the negative temperature coefficient in low-temperature chemistry. Additionally, the measured n number of 1-dodecanol is found to be larger than 2, which suggests the existence of the third oxygen addition reactions in low-temperature chemistry for large alcohols.
KW - Cool flame
KW - Extinction limit
KW - Oxygen concentration dependence
KW - Oxygenated fuels
KW - Radical index
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U2 - 10.1016/j.combustflame.2022.112493
DO - 10.1016/j.combustflame.2022.112493
M3 - Article
AN - SCOPUS:85142130045
SN - 0010-2180
JO - Combustion and Flame
JF - Combustion and Flame
M1 - 112493
ER -