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A Burke–Schumann analysis of diffusion-flame structures supported by a burning droplet

Published on Jul 4, 2017in Combustion Theory and Modelling 1.65
· DOI :10.1080/13647830.2017.1280182
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University),
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center),
Forman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Cite
Abstract
A Burke–Schumann description of three different regimes of combustion of a fuel droplet in an oxidising atmosphere, namely the premixed-flame regime, the partial-burning regime and the diffusion-flame regime, is presented by treating the fuel and oxygen leakage fractions through the flame as known parameters. The analysis shows that the burning-rate constant, the flame-standoff ratio, and the flame temperature in these regimes can be obtained from the classical droplet-burning results by suitable definitions of an effective ambient oxygen mass fraction and an effective fuel concentration in the droplet interior. The results show that increasing oxygen leakage alone through the flame lowers both the droplet burning rate and the flame temperature, whereas leakage of fuel alone leaves the burning rate unaffected while reducing the flame temperature and moving the flame closer to the droplet surface. Solutions for the partial-burning regime are shown to exist only for a limited range of fuel and oxygen leakag...
  • References (13)
  • Citations (5)
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References13
Newest
Published on Apr 1, 2016in AIAA Journal 1.95
Vedha Nayagam13
Estimated H-index: 13
,
Daniel L. Dietrich13
Estimated H-index: 13
,
Forman A. Williams48
Estimated H-index: 48
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...
Published on May 1, 2015in Combustion and Flame 4.12
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University),
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center)
+ 1 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
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...
Published on Sep 3, 2014in Combustion Theory and Modelling 1.65
Guenter Paczko2
Estimated H-index: 2
(RWTH Aachen University),
N. Peters56
Estimated H-index: 56
(RWTH Aachen University)
+ 1 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Experiments on the combustion of large n-heptane droplets, performed by the National Aeronautics and Space Administration in the International Space Station, revealed a second stage of continued quasi-steady burning, supported by low-temperature chemistry, that follows radiative extinction of the first stage of burning, which is supported by normal hot-flame chemistry. The second stage of combustion experienced diffusive extinction, after which a large vapour cloud was observed to form around th...
Published on Feb 1, 2014in Combustion and Flame 4.12
Tanvir Farouk17
Estimated H-index: 17
(USC: University of South Carolina),
Frederick L. Dryer66
Estimated H-index: 66
(Princeton University)
Abstract Recent experimentally observed two stage combustion of n -heptane droplets in microgravity is numerically studied. The simulations are conducted with detailed chemistry and transport in order to obtain insight into the features controlling the low temperature second stage burn. Predictions show that the second stage combustion occurs as a result of chemical kinetics associated with classical premixed “ Cool Flame ” phenomena. In contrast to the kinetic interactions responsible for premi...
Published on Dec 1, 2012in Combustion and Flame 4.12
Vedha Nayagam13
Estimated H-index: 13
,
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center)
+ 2 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Abstract Experimental observations of anomalous combustion of n-heptane droplets burning in microgravity are reported. Following ignition, a relatively large n-heptane droplet first undergoes radiative extinction, that is, the visible flame ceases to exist because of radiant energy loss. But the droplet continues to experience vigorous vaporization for an extended period according to a quasi-steady droplet-burning law, ending in a secondary extinction at a finite droplet diameter, after which a ...
Published on Jan 1, 1996
Stephen R. Turns20
Estimated H-index: 20
Published on Mar 1, 2000
Stephen R. Turns20
Estimated H-index: 20
Preface Preface to the Second Edition Preface to the First Edition 1: Introduction 2: Combustion and Thermochemistry 3: Introduction to Mass Transfer 4: Chemical Kinetics 5: Some Important Chemical Mechanisms 6: Coupling Chemical and Thermal Analyses of Reacting Systems 7: Simplifed Conversation Equations for Reacting Flows 8: Laminar Premixed Flames 9: Laminar Diffusion Flames 10: Droplet Evaporation and Burning 11: Introduction to Turbulent Flows 12: Turbulent Premixed Flames 13: Turbulent Non...
Published on Jan 1, 1982in Progress in Energy and Combustion Science 26.47
Chung K. Law77
Estimated H-index: 77
(NU: Northwestern University)
Abstract Recent progress on understanding the fundamental mechanisms governing droplet vaporization and combustion are reviewed. Topics include the classical d 2 -Law and its limitations; the major transient processes of droplet heating and fuel vapor accumulation; effects due to variable transport property assumptions; combustion of multicomponent fuels including the miscible fuel blends, immiscible emulsions, and coal-oil mixtures, finite-rate kinetics leading to ignition and extinction; and d...
Published on Oct 1, 1977in Combustion Science and Technology 1.56
Chung K. Law77
Estimated H-index: 77
(NU: Northwestern University)
Abstract The vaporization and combustion characteristics of an oil/water emulsion droplet are investigated by analyzing the multicomponent heat and mass transport processes in the gas phase and the gasification of an immiscible liquid mixture at the gas-liquid interface. Results substantiate and quantify the potential reductions in soot and NOx formation through water emulsification and demonstrate that the embedded water micro-droplets can indeed be heated to the limit of superheat such that fr...
Published on Feb 1, 1975in Combustion and Flame 4.12
Chung K. Law77
Estimated H-index: 77
(GM: General Motors)
Abstract The quasi-steady diffusion flame structure in droplet burning is analysed, in the limit of large activation energy, for a one-step Arrhenius reaction in the gas phase. The characteristic ignition-extinction S-shaped curve is produced with segments of it corresponding to a nearly frozen flow regime, a partial burning regime, a premixed flame regime, and a nearly equilibrium regime. Critical Damkohler numbers for ignition and extinction, as well as correction factors to the mass evaporati...
Cited By5
Newest
Published on Feb 1, 2019in Acta Astronautica 2.48
V. V. Tyurenkova8
Estimated H-index: 8
(RAS: Russian Academy of Sciences),
V.V. Tyurenkova (RAS: Russian Academy of Sciences)
Abstract This paper is devoted to the burning of an isolated n-heptane droplet in microgravity and analysis of the experimental data presented by FLEX experiment. Developing the classical analytical research methodology, proposed by Forman A. Williams, and using our obtained analytical solutions for the problem of droplet equilibrium evaporation and combustion, the analytical solutions to solve the problem of two regimes of droplet burning were found. To explain the presence of the radiative fla...
Published on Sep 1, 2018in Combustion and Flame 4.12
Omar R. Yehia2
Estimated H-index: 2
(Princeton University),
Christopher B. Reuter7
Estimated H-index: 7
(Princeton University),
Yiguang Ju54
Estimated H-index: 54
(Princeton University)
Abstract We report on experimental evidence of the existence of a new self-sustaining low-temperature multistage warm diffusion flame, existing between the cool flame and hot flame, at atmospheric pressure in the counterflow geometry. The structure of multistage warm diffusion flames was examined by using thermometry, laser-induced fluorescence, and chemiluminescence measurements. It was found that the warm diffusion flame has a two-staged double flame structure, with a leading diffusion cool fl...
Published on Sep 1, 2018in Combustion and Flame 4.12
Vedha Nayagam13
Estimated H-index: 13
(Case Western Reserve University),
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University)
+ 0 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Abstract Millimeter-size fuel droplets burning in microgravity show substantial thermal expansion at earlier times in their burning history. Here, we develop a simple model that accounts for thermal expansion of the liquid fuel and compare it against experimental measurements. The results show that excellent agreement with measured droplet-diameter histories throughout the hot-flame period of combustion is obtained when the effect of thermal expansion is included.
Published on Aug 1, 2018in Combustion and Flame 4.12
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University),
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center)
+ 1 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Abstract Experimental observations are presented concerning radiative extinction of large n-alkane droplets in diluent-substituted environments at moderately varied pressures in microgravity onboard the International Space Station. The fuels considered are n-heptane, n-octane, and n-decane with carbon dioxide, helium, and xenon used as inerts, replacing nitrogen as diluents at varying amounts. It is shown that a simple scaling analysis, based on the assumptions that radiative extinction occurs w...
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University),
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center),
Forman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Abstract Droplet combustion experiments carried out onboard the International Space Station, using pure fuels and fuel mixtures, have shown that quasi-steady burning can be sustained by a non-traditional flame configuration, namely a “cool flame” burning in the “partial-burning” regime where both fuel and oxygen leak through the low-temperature-controlled flame-sheet. Recent experiments involving large, bi-component fuel ( n -decane and hexanol, 50/50 by volume) droplets at elevated pressures sh...