TY - JOUR
T1 - Effect of non-equilibrium plasma on two-stage ignition of n-heptane
AU - Nagaraja, Sharath
AU - Sun, Wenting
AU - Yang, Vigor
N1 - Funding Information:
This work was supported by MURI research Grant FA9550-07-1-0136 from the Air Force Office of Scientific Research, with Dr. Chiping Li as the technical monitor. Wenting Sun is grateful for faculty startup support from the Georgia Institute of Technology.
Publisher Copyright:
© 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
PY - 2015
Y1 - 2015
N2 - The effect of pulsed nanosecond dielectric barrier plasma discharges on the ignition characteristics of n-heptane and air mixtures is investigated through self-consistent simulations in a plane-to-plane geometry at reduced pressures (20.3 kPa). The present work represents one of the first attempts in understanding the kinetic and thermal effects of nanosecond pulsed discharges on the two-stage ignition process of n-heptane. A plasma-fluid formulation is developed with ions and neutral species at gas temperature, and electrons in non-equilibrium. The work makes use of an optimized chemical kinetics mechanism consisting of 166 species and 611 reactions, obtained by combining a reduced n-heptane kinetic model, a non-equilibrium plasma chemistry scheme, and a NOx kinetic model. The catalytic effect from plasma-generated radicals on the first stage of the n-heptane ignition process has been identified. Production of radicals such as O, H and OH from the plasma initiates and accelerates the H abstraction of fuel molecules, and dramatically reduces the induction time of the exothermic cycle (RH → R → RO2 → OROOH) by a factor of 10. Furthermore, the plasma action on low temperature chemistry is found to be nearly independent of the equivalence ratio and more pronounced at lower temperatures (550-650 K). A staggered application of nanosecond voltage pulses (2-4 pulses at the beginning and 20-30 pulses after the first stage heat release) is shown to be optimal, resulting in a reduction of the ignition delay by approximately a factor of 2. NO production from the plasma via electron impact and quenching processes at low temperatures plays an important role in promoting chain-branching reactions and contributes to shortening the ignition delay by approximately 10%.
AB - The effect of pulsed nanosecond dielectric barrier plasma discharges on the ignition characteristics of n-heptane and air mixtures is investigated through self-consistent simulations in a plane-to-plane geometry at reduced pressures (20.3 kPa). The present work represents one of the first attempts in understanding the kinetic and thermal effects of nanosecond pulsed discharges on the two-stage ignition process of n-heptane. A plasma-fluid formulation is developed with ions and neutral species at gas temperature, and electrons in non-equilibrium. The work makes use of an optimized chemical kinetics mechanism consisting of 166 species and 611 reactions, obtained by combining a reduced n-heptane kinetic model, a non-equilibrium plasma chemistry scheme, and a NOx kinetic model. The catalytic effect from plasma-generated radicals on the first stage of the n-heptane ignition process has been identified. Production of radicals such as O, H and OH from the plasma initiates and accelerates the H abstraction of fuel molecules, and dramatically reduces the induction time of the exothermic cycle (RH → R → RO2 → OROOH) by a factor of 10. Furthermore, the plasma action on low temperature chemistry is found to be nearly independent of the equivalence ratio and more pronounced at lower temperatures (550-650 K). A staggered application of nanosecond voltage pulses (2-4 pulses at the beginning and 20-30 pulses after the first stage heat release) is shown to be optimal, resulting in a reduction of the ignition delay by approximately a factor of 2. NO production from the plasma via electron impact and quenching processes at low temperatures plays an important role in promoting chain-branching reactions and contributes to shortening the ignition delay by approximately 10%.
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U2 - 10.1016/j.proci.2014.05.123
DO - 10.1016/j.proci.2014.05.123
M3 - Article
AN - SCOPUS:84947900518
SN - 1540-7489
VL - 35
SP - 3497
EP - 3504
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 3
ER -