TY - JOUR
T1 - On the controlling mechanism of the upper turnover states in the NTC regime
AU - Ji, Weiqi
AU - Zhao, Peng
AU - He, Tanjin
AU - He, Xin
AU - Farooq, Aamir
AU - Law, Chung K.
N1 - Funding Information:
This work was primarily supported by the National Natural Science Foundation of China 91441202 . The work at Princeton University was supported by the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy , Office of Basic Energy Sciences under Award number DESC0001198 . Peng Zhao was also supported by the startup funding at Oakland University . The guidance on the NUIG n-butane mechanism from Dr. Kuiwen Zhang from NUIG is very much appreciated.
Funding Information:
This work was primarily supported by the National Natural Science Foundation of China 91441202. The work at Princeton University was supported by the Combustion Energy Frontier Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences under Award number DESC0001198. Peng Zhao was also supported by the startup funding at Oakland University. The guidance on the NUIG n-butane mechanism from Dr. Kuiwen Zhang from NUIG is very much appreciated.
Publisher Copyright:
© 2015 The Combustion Institute.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - Using n-butane, n-heptane and iso-octane as representative fuels exhibiting NTC (negative temperature coefficient) behavior, comprehensive computational studies with detailed mechanisms and theoretical analysis were performed to investigate the upper stationary point, denoted as turnover states, on the NTC curve near the higher temperature regime, where the ignition delay τ exhibits a local maximum. It is found that the global behavior of the turnover states exhibits distinctive thermodynamic and kinetic characteristics under different pressures, in that the ignition delay at the turnover states shows an Arrhenius dependence on the temperature T and an approximate inverse quadratic power law dependence on the pressure P. These global behaviors imply that the temperature and pressure of the turnover states are not independent and can be correlated by Arrhenius dependence, as ln P ∞ 1/T. Further theoretical analyses demonstrate that such turnover states result from the competition between the low-temperature chain branching reactions and the decomposition of the intermediate species, and therefore correspond to a critical value, α, of the ratio of OH production from low-temperature chemistry. In addition, the ignition delay at the turnover state can be well correlated by the analytical expression derived by Peters et al., with the further demonstration that the pressure dependence of the turnover ignition delay mainly result from the H2O2 decomposition reaction. Comparison of the present results with the literature experimental data of n-heptane ignition delay time shows very good agreement.
AB - Using n-butane, n-heptane and iso-octane as representative fuels exhibiting NTC (negative temperature coefficient) behavior, comprehensive computational studies with detailed mechanisms and theoretical analysis were performed to investigate the upper stationary point, denoted as turnover states, on the NTC curve near the higher temperature regime, where the ignition delay τ exhibits a local maximum. It is found that the global behavior of the turnover states exhibits distinctive thermodynamic and kinetic characteristics under different pressures, in that the ignition delay at the turnover states shows an Arrhenius dependence on the temperature T and an approximate inverse quadratic power law dependence on the pressure P. These global behaviors imply that the temperature and pressure of the turnover states are not independent and can be correlated by Arrhenius dependence, as ln P ∞ 1/T. Further theoretical analyses demonstrate that such turnover states result from the competition between the low-temperature chain branching reactions and the decomposition of the intermediate species, and therefore correspond to a critical value, α, of the ratio of OH production from low-temperature chemistry. In addition, the ignition delay at the turnover state can be well correlated by the analytical expression derived by Peters et al., with the further demonstration that the pressure dependence of the turnover ignition delay mainly result from the H2O2 decomposition reaction. Comparison of the present results with the literature experimental data of n-heptane ignition delay time shows very good agreement.
KW - Auto-ignition
KW - Chain branching ratio
KW - Low temperature chemistry
KW - NTC
KW - Turnover
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U2 - 10.1016/j.combustflame.2015.11.028
DO - 10.1016/j.combustflame.2015.11.028
M3 - Article
AN - SCOPUS:84957441594
VL - 164
SP - 294
EP - 302
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
ER -