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Radiative extinction of large n-alkane droplets in oxygen-inert mixtures in microgravity

Published on Aug 1, 2018in Combustion and Flame 4.12
· DOI :10.1016/j.combustflame.2018.04.023
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)
Cite
Abstract
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 when the flame temperature drops to a critical value and that the radiative heat loss rate is a fraction of the heat-release rate at the flame, is able to correlate the measured droplet diameter at extinction as a function of its initial diameter and of the ambient gas-mixture properties.
  • References (22)
  • Citations (0)
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References22
Newest
Published on Jul 4, 2017in Combustion Theory and Modelling 1.65
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)
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 suitabl...
Published on Mar 4, 2017in Combustion Science and Technology 1.56
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center),
R. Calabria1
Estimated H-index: 1
+ 2 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
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...
Published on Sep 1, 2016in Combustion and Flame 4.12
Yu Cheng Liu10
Estimated H-index: 10
(UM: University of Michigan),
Yuhao Xu7
Estimated H-index: 7
(Cornell University)
+ 1 AuthorsC. Thomas Avedisian14
Estimated H-index: 14
(Cornell University)
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...
Published on Feb 1, 2016in Combustion Science and Technology 1.56
Fahd E. Alam4
Estimated H-index: 4
(USC: University of South Carolina),
Frederick L. Dryer4
Estimated H-index: 4
(Princeton University),
Tanvir I. Farouk4
Estimated H-index: 4
(USC: University of South Carolina)
ABSTRACTThe ‘FLame EXtinguishment’ (FLEX) program conducted by NASA on board the International Space Station (ISS) has been assisting in developing fire-safety protocols for low gravity applications through microgravity droplet combustion experiments. A wide range of fuels, including alcohols and alkanes, have been studied in different ambient conditions that also encompass the use of various diluent species and concentrations. A prime focus of the work has been to observe the relative effective...
Published on Jan 2, 2016in Combustion Science and Technology 1.56
Benjamin D. Shaw13
Estimated H-index: 13
(UC Davis: University of California, Davis),
Chang L. Vang1
Estimated H-index: 1
(UC Davis: University of California, Davis)
ABSTRACTReduced gravity combustion experiments were performed aboard the International Space Station with individual methanol and n-heptane droplets that had initial diameters in the 1.2–5.0-mm-size range. Experiments were performed with air-inert mixtures at 0.1 and 0.07 MPa and about 298 K, where the monatomic gases helium and xenon were separately used as the added inert. These two gases have the same thermodynamic properties on a molar basis, but their transport properties are significantly ...
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 Oct 1, 2014in Microgravity Science and Technology 1.97
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center),
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University)
+ 9 AuthorsYu Cheng Liu10
Estimated H-index: 10
(Cornell University)
This paper summarizes the first results from isolated droplet combustion experiments performed on the International Space Station (ISS). The long durations of microgravity provided in the ISS enable the measurement of droplet and flame histories over an unprecedented range of conditions. The first experiments were with heptane and methanol as fuels, initial droplet droplet diameters between 1.5 and 5.0 m m, ambient oxygen mole fractions between 0.1 and 0.4, ambient pressures between 0.7 and 3.0 ...
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 ...
Cited By0
Newest
Published on Oct 1, 2019in Combustion and Flame 4.12
Mohammadhadi Hajilou2
Estimated H-index: 2
(UW: University of Wyoming),
Matthew Q. Brown (UW: University of Wyoming)+ 1 AuthorsErica Belmont5
Estimated H-index: 5
(UW: University of Wyoming)
Abstract Low temperature combustion of n-heptane was investigated through an experimental and numerical study of laminar cool flame structure and propagation speeds. Lean and stoichiometric n-heptane cool flames of equivalence ratios 0.4–1.0 were stabilized using a Hencken burner at sub-atmospheric pressures. Characterization of cool flame lift-off heights in burner-stabilized and freely propagating regimes was performed using broadband chemiluminescence and formaldehyde planar laser-induced flu...
Published on Jul 1, 2019in Combustion and Flame 4.12
Vedha Nayagam13
Estimated H-index: 13
,
Daniel L. Dietrich13
Estimated H-index: 13
,
Forman A. Williams48
Estimated H-index: 48
Abstract A scaling analysis of burner-supported spherical-diffusion-flame extinction brought about by radiative heat loss is presented. The results are compared against earlier microgravity experimental data and unsteady numerical computations with detailed chemistry available in the literature, for normal and inverse flames. The flame diameter at extinction is shown to correlate well with the present model, in which the extinction radius scales with one-third power of gas flow rate times reacta...