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Three stage cool flame droplet burning behavior of n-alkane droplets at elevated pressure conditions: Hot, warm and cool flame

Published on Jan 1, 2019
· DOI :10.1016/j.proci.2018.09.015
Tanvir Farouk17
Estimated H-index: 17
(USC: University of South Carolina),
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center),
Frederick L. Dryer66
Estimated H-index: 66
(Princeton University)
Abstract
Abstract Transient, isolated n -alkane droplet combustion is simulated at elevated pressure for helium-diluent substituted-air mixtures. We report the presence of unique quasi-steady, three-stage burning behavior of large sphero-symmetric n -alkane droplets at these elevated pressures and helium substituted ambient fractions. Upon initiation of reaction, hot-flame diffusive burning of large droplets is initiated that radiatively extinguishes to establish cool flame burning conditions in nitrogen/oxygen “air” at atmospheric and elevated pressures. However, at elevated pressure and moderate helium substitution for nitrogen ( X He  > 20%), the initiated cool flame burning proceeds through two distinct, quasi-steady-state, cool flame burning conditions. The classical “ Hot flame ” (∼1500 K) radiatively extinguishes into a “ Warm flame ” burning mode at a moderate maximum reaction zone temperature (∼ 970 K), followed by a transition to a lower temperature (∼765 K), quasi-steady “ Cool flame ” burning condition. The reaction zone (“flame”) temperatures are associated with distinctly different yields in intermediate reaction products within the reaction zones and surrounding near-field, and the flame-standoff ratios characterizing each burning mode progressively decrease. The presence of all three stages first appears with helium substitution near 20%, and the duration of each stage is observed to be strongly dependent on helium substitutions level between 20–60%. For helium substitution greater than 60%, the hot flame extinction is followed by only the lower temperature cool flame burning mode. In addition to the strong coupling between the diffusive loss of both energy and species and the slowly evolving degenerate branching in the low and negative temperature coefficient (NTC) kinetic regimes, the competition between the low-temperature chain branching and intermediate-temperature chain termination reactions control the “ Warm” and “ Cool ” flame quasi-steady conditions and transitioning dynamics. Experiments onboard the International Space Station with n -dodecane droplets confirm the existence of these combustion characteristics and predictions agree favorably with these observations.
  • References (13)
  • Citations (3)
References13
Newest
#1Nour Atef (KAUST: King Abdullah University of Science and Technology)H-Index: 4
#2Goutham Kukkadapu (UConn: University of Connecticut)H-Index: 7
Last.Apurba K. Das (UConn: University of Connecticut)H-Index: 1
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#1Zhandong Wang (KAUST: King Abdullah University of Science and Technology)H-Index: 21
#2S.M. Sarathy (KAUST: King Abdullah University of Science and Technology)H-Index: 26
#1Yiguang Ju (Princeton University)H-Index: 54
#2Christopher B. Reuter (Princeton University)H-Index: 7
Last.Sang Hee Won (Princeton University)H-Index: 27
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#1Daniel L. Dietrich (Glenn Research Center)H-Index: 13
#2Vedha Nayagam (Case Western Reserve University)H-Index: 4
Last.Yu Cheng Liu (Cornell University)H-Index: 10
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#1Vedha NayagamH-Index: 13
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last.Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
view all 5 authors...
#1S.M. Sarathy (LLNL: Lawrence Livermore National Laboratory)H-Index: 26
#2Charles K. Westbrook (LLNL: Lawrence Livermore National Laboratory)H-Index: 62
Last.K. Seshadri (UCSD: University of California, San Diego)H-Index: 28
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Cited By3
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#1Yiguang Ju (Princeton University)H-Index: 54
#2Christopher B. Reuter (Princeton University)H-Index: 7
Last.Sang Hee Won (USC: University of South Carolina)H-Index: 3
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#1Mohammadhadi Hajilou (UW: University of Wyoming)H-Index: 2
#2Matthew Q. Brown (UW: University of Wyoming)
Last.Erica Belmont (UW: University of Wyoming)H-Index: 5
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#1Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
#2Vedha Nayagam (Case Western Reserve University)H-Index: 13
Last.Vedha Nayagam (Case Western Reserve University)H-Index: 4
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#1Yang Zhang (THU: Tsinghua University)H-Index: 11
#2Xiehe Yang (THU: Tsinghua University)
Last.Junfu Lyu (THU: Tsinghua University)H-Index: 3
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