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Quasi-steady combustion of normal-alkane droplets supported by Cool-Flame chemistry near diffusive extinction

Published on Jul 4, 2019in Combustion Theory and Modelling1.654
· DOI :10.1080/13647830.2019.1588380
Forman A. Williams54
Estimated H-index: 54
(UCSD: University of California, San Diego),
Vedha Nayagam15
Estimated H-index: 15
(Case Western Reserve University)
Abstract
Two steady-state chemical-kinetic approximations are introduced into the apparently most relevant five cool-flame steps of the latest San Diego mechanism for n-heptane, supplemented by a sixth step...
  • References (28)
  • Citations (0)
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References28
Newest
#1Tanvir Farouk (USC: University of South Carolina)H-Index: 18
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last. Frederick L. Dryer (Princeton University)H-Index: 68
view all 3 authors...
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/o...
5 CitationsSource
#1Daniel L. Dietrich (Glenn Research Center)H-Index: 13
#2R. CalabriaH-Index: 1
Last. Forman A. Williams (UCSD: University of California, San Diego)H-Index: 54
view all 5 authors...
ABSTRACTThis article presents the results of experiments conducted aboard the International Space Station involving the combustion of large bi-component droplets of decane and hexanol (50/50 by volume) in air ambients with ambient pressures between 0.05 and 0.30 MPa. The experiments showed the presence of sustained low-temperature or cool-flame burning following radiative extinction of large droplets at ambient pressures greater than or equal to 0.10 MPa. The droplet diameters at cool-flame exti...
8 CitationsSource
#1Tanvir Farouk (USC: University of South Carolina)H-Index: 18
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last. Frederick L. Dryer (Princeton University)H-Index: 68
view all 4 authors...
Abstract Observations of “ Cool Flame ” burning for large diameter isolated droplets on board the International Space Station have stimulated interest in combustion initiation/generation of non-premixed combustion modes. For a number of n -alkane fuels at large initial droplet diameters, the initiation process was observed to first establish a hot flame condition that radiatively extinguished, followed by a quasi-steady, “ Cool Flame ” droplet burning mode. However, recent large diameter n -deca...
13 CitationsSource
#1Alberto Cuoci (Polytechnic University of Milan)H-Index: 30
#2Abd Essamade Saufi (Polytechnic University of Milan)H-Index: 1
Last. Tiziano Faravelli (Polytechnic University of Milan)H-Index: 45
view all 6 authors...
Abstract A recent set of experiments carried out onboard the International Space Station (ISS) have shown that large n-alkane droplets, after the radiative extinction of the visible flame, can burn quasi-steadily in a low-temperature regime, up to a diffusive extinction accompanied by the formation of a vapor cloud. The experiments have also demonstrated that small droplets are unable to exhibit radiative extinction, but instead burn to completion or disruptively extinguish. In this work, we app...
7 CitationsSource
#1Kalyanasundaram Seshadri (UCSD: University of California, San Diego)H-Index: 30
#2Norbert Peters (RWTH Aachen University)H-Index: 57
Last. Guenter Paczko (RWTH Aachen University)H-Index: 2
view all 5 authors...
A skeletal chemical-kinetic mechanism for n-heptane cool flames is simplified to the maximum extent possible by introduction of steady-state approximations for intermediaries, following procedures employed previously in addressing two-stage ignition. A pair of ordinary differential equations in mixture-fraction space is thereby obtained, describing the quasi-steady structures of the temperature and heptylketohydroperoxide fields. Application of activation-energy asymptotics for the partial-burni...
7 CitationsSource
#1Yu Cheng Liu (UM: University of Michigan)H-Index: 11
#2Yuhao Xu (Cornell University)H-Index: 7
Last. C. Thomas Avedisian (Cornell University)H-Index: 14
view all 4 authors...
Abstract This paper reports the results of a comprehensive experimental study on the effect of initial droplet diameter ( D o ) over a very wide range (0.5 mm D o n -heptane, n -octane and n -decane – that are representative of components found in petroleum-based transportation fuels and their surrogates. Spherical symmetry in the burning process was promoted by carrying out the experiments in a reduced convection (stagnant ambience) and buoyancy (low gravity) environment using the facilities of...
18 CitationsSource
#1Vedha NayagamH-Index: 15
#2Daniel L. DietrichH-Index: 13
Last. Forman A. WilliamsH-Index: 54
view all 3 authors...
A simplified model for droplet combustion in the partial-burning regime is applied to the cool-flame regime observed in droplet-burning experiments performed in the International Space Station with normal-alkanes fuels resulting in expressions for the quasi-steady droplet burning rate and for the flame standoff ratio. The simplified predictions are found to produce reasonable agreement with the experimentally measured values of burning-rate constants but not with their apparent dependencies on p...
12 CitationsSource
8 CitationsSource
#1Juan C. PrinceH-Index: 5
#2Forman A. Williams (UCSD: University of California, San Diego)H-Index: 54
Last. Guillermo E. OvandoH-Index: 1
view all 3 authors...
Abstract The low-temperature ignition of mixtures of n-heptane and air at elevated pressures (13–40 bar) is addressed. A base mechanism of 272 elementary reactions among 45 species, which models the ignition time of this fuel under a wide range of conditions for initial temperatures above about 1000 K is revised and augmented to produce the two-stage ignition and negative-temperature-coefficient (NTC) behavior seen experimentally for this fuel below 1000 K. By using available kinetic data, it is...
17 CitationsSource
#1Vedha Nayagam (Case Western Reserve University)H-Index: 15
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last. Forman A. Williams (UCSD: University of California, San Diego)H-Index: 54
view all 4 authors...
Abstract Recent droplet-combustion experiments onboard the International Space Station (ISS) have revealed that large n-alkane droplets, following radiative extinction of the visible flame, can continue to burn quasi-steadily in a low-temperature regime, characterized by negative-temperature-coefficient (NTC) chemistry. In this study we report experimental observations of n-heptane, n-octane, and n-decane droplets of varying initial size burning in oxygen/nitrogen, oxygen/nitrogen/carbon dioxide...
31 CitationsSource
Cited By0
Newest
#1Yinhu Kang (Chongqing University)H-Index: 10
#2Qiang Wang (Chongqing University)
Last. Quanhai Wang (Chongqing University)H-Index: 10
view all 6 authors...
Abstract Flame extinction which belongs to one of the most important limit combustion phenomena plays a vital role in the combustion safety, efficiency, and stability, and additionally, it is also important for fire safety research. Hence studies on the flame extinction mechanism is of fundamental and practical significances in the combustion science. In this paper, the structure dynamics and extinction mechanism of dimethyl ether (DME) hot and cool spherical diffusion flames are studied by expe...
Source
#1Forman A. Williams (UCSD: University of California, San Diego)H-Index: 54
#2Vedha Nayagam (Case Western Reserve University)H-Index: 15
Abstract Previously published simplified n-alkane cool-flame chemistry is re-evaluated for n-dodecane. Comparison with experimental results produces improved rate-parameter estimates for n-dodecane and indicates deterioration of the simplified chemistry with increasing pressure in predictions of droplet diameters at cool-flame extinction.
1 CitationsSource