TY - JOUR
T1 - First-stage ignition delay in the negative temperature coefficient behavior
T2 - Experiment and simulation
AU - Zhang, Peng
AU - Ji, Weiqi
AU - He, Tanjin
AU - He, Xin
AU - Wang, Zhi
AU - Yang, Bin
AU - Law, Chung King
N1 - Funding Information:
The authors acknowledge the valuable discussion with Professor Peng Zhao of Oakland University on the mechanisms. This work was supported by the National Natural Science Foundation of China ( 91541113 and 51476086 ).
Publisher Copyright:
© 2016 The Combustion Institute.
PY - 2016/5/1
Y1 - 2016/5/1
N2 - The existence of the first-stage ignition delay (FID) negative temperature coefficient (NTC) behavior was confirmed by rapid compression machine experiments using iso-octane and methyl-cyclohexane. The first-stage NTC behavior of iso-octane is observed in the temperature range 757-782K under 20bar and φ=1. For methyl-cyclohexane, the observed first-stage NTC temperature range is 750-785K under 15bar and φ=0.5. In further iso-octane experiments, the FID is found to be sensitive to the O2 concentration and insensitive to the dilution gas and fuel concentrations. The effects of the FID and its NTC behavior on the total ignition delay NTC were analyzed using a detailed n-heptane mechanism. The contributions to the total ignition delay NTC from the reduced second-stage initial temperature, pressure, and less reactive species pool, together with the NTC of FID were discussed quantitatively. For the first-stage NTC behavior, five competing reactions were identified as being important based on sensitivity analysis, reaction pathway analysis, and simplified mechanism method. They are the backward reaction of second O2 addition, RO2 ⇔ alkene+HO2, QOOH ⇔ cyclic-ether+OH, QOOH ⇔ alkene+HO2, and the beta scission reaction of the alkyl radical. Their competition with the low-temperature branching channel finally leads to the first-stage NTC behavior.
AB - The existence of the first-stage ignition delay (FID) negative temperature coefficient (NTC) behavior was confirmed by rapid compression machine experiments using iso-octane and methyl-cyclohexane. The first-stage NTC behavior of iso-octane is observed in the temperature range 757-782K under 20bar and φ=1. For methyl-cyclohexane, the observed first-stage NTC temperature range is 750-785K under 15bar and φ=0.5. In further iso-octane experiments, the FID is found to be sensitive to the O2 concentration and insensitive to the dilution gas and fuel concentrations. The effects of the FID and its NTC behavior on the total ignition delay NTC were analyzed using a detailed n-heptane mechanism. The contributions to the total ignition delay NTC from the reduced second-stage initial temperature, pressure, and less reactive species pool, together with the NTC of FID were discussed quantitatively. For the first-stage NTC behavior, five competing reactions were identified as being important based on sensitivity analysis, reaction pathway analysis, and simplified mechanism method. They are the backward reaction of second O2 addition, RO2 ⇔ alkene+HO2, QOOH ⇔ cyclic-ether+OH, QOOH ⇔ alkene+HO2, and the beta scission reaction of the alkyl radical. Their competition with the low-temperature branching channel finally leads to the first-stage NTC behavior.
KW - First-stage ignition
KW - Low-temperature mechanism
KW - Negative temperature coefficient
KW - Rapid compression machine
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U2 - 10.1016/j.combustflame.2016.03.002
DO - 10.1016/j.combustflame.2016.03.002
M3 - Article
AN - SCOPUS:84979463214
SN - 0010-2180
VL - 167
SP - 14
EP - 23
JO - Combustion and Flame
JF - Combustion and Flame
ER -