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Droplet Combustion Experiments Aboard the International Space Station

Published on Oct 1, 2014in Microgravity Science and Technology 1.36
· DOI :10.1007/s12217-014-9372-2
Daniel L. Dietrich13
Estimated H-index: 13
(Glenn Research Center),
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University)
+ 9 AuthorsForman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Abstract
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 a t m and ambient environments containing oxygen and nitrogen diluted with both carbon dioxide and helium. The experiments show both radiative and diffusive extinction. For both fuels, the flames exhibited pre-extinction flame oscillations during radiative extinction with a frequency of approximately 1 H z. The results revealed that as the ambient oxygen mole fraction was reduced, the diffusive-extinction droplet diameter increased and the radiative-extinction droplet diameter decreased. In between these two limiting extinction conditions, quasi-steady combustion was observed. Another important measurement that is related to spacecraft fire safety is the limiting oxygen index (LOI), the oxygen concentration below which quasi-steady combustion cannot be supported. This is also the ambient oxygen mole fraction for which the radiative and diffusive extinction diameters become equal. For oxygen/nitrogen mixtures, the LOI is 0.12 and 0.15 for methanol and heptane, respectively. The LOI increases to approximately 0.14 (0.14 O 2/0.56 N 2/0.30 C O 2) and 0.17 (0.17 O 2/0.63 N 2/0.20 C O 2) for methanol and heptane, respectively, for ambient environments that simulated dispersing an inert-gas suppressant (carbon dioxide) into a nominally air (1.0 a t m) ambient environment. The LOI is approximately 0.14 and 0.15 for methanol and heptane, respectively, when helium is dispersed into air at 1 atm. The experiments also showed unique burning behavior for large heptane droplets. After the visible hot flame radiatively extinguished around a large heptane droplet, the droplet continued to burn with a cool flame. This phenomena was observed repeatably over a wide range of ambient conditions. These cool flames were invisible to the experiment imaging system but their behavior was inferred by the sustained quasi-steady burning after visible flame extinction. Verification of this new burning regime was established by both theoretical and numerical analysis of the experimental results. These innovative experiments have provided a wealth of new data for improving the understanding of droplet combustion and related aspects of fire safety, as well as offering important measurements that can be used to test sophisticated evolving computational models and theories of droplet combustion.
  • References (27)
  • Citations (30)
Cite
References27
Newest
Published on Feb 1, 2014in Combustion and Flame 4.49
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...
55 Citations Source Cite
Published on May 19, 2013
Vedha Nayagam13
Estimated H-index: 13
,
Daniel L. Dietrich13
Estimated H-index: 13
+ 1 AuthorsForman A. Williams48
Estimated H-index: 48
The Flame Extinguishment (FLEX) experiment that is currently underway in the Combustion Integrated Rack facility onboard the International Space Station is aimed at understanding the effects of inert diluents on the flammability of condensed phase fuels. To this end, droplets of various fuels, including alkanes and alcohols, are burned in a quiescent microgravity environment with varying amounts of oxygen and inert diluents to determine the limiting oxygen index (LOI) for these fuels. In this st...
1 Citations
Published on Dec 1, 2012in Combustion and Flame 4.49
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 ...
67 Citations Source Cite
Published on Oct 1, 2012in Combustion and Flame 4.49
Tanvir Farouk17
Estimated H-index: 17
(Princeton University),
Frederick L. Dryer66
Estimated H-index: 66
(Princeton University)
Abstract Quasi-steady burning and extinction of droplets are of interest from both fundamental and application viewpoints. The latter is related to combustor performance and fire safety issues in reduced gravity environments. Influences of diluent in the atmosphere on isolated droplet combustion characteristics including extinction provide insights to fire extinguishment phenomena and the effectiveness of various diluents as fire suppressants. Extinction of pure methanol and methanol–water dropl...
20 Citations Source Cite
Published on Sep 5, 2012in Image Analysis & Stereology 1.42
Christopher Dembia6
Estimated H-index: 6
(Cornell University),
Yu Cheng Liu10
Estimated H-index: 10
(Cornell University),
C. Thomas Avedisian14
Estimated H-index: 14
(Cornell University)
A simple automated image analysis algorithm has been developed that processes consecutive images from high speed, high resolution digital images of burning fuel droplets. The droplets burn under conditions that promote spherical symmetry. The algorithm performs the tasks of edge detection of the droplet’s boundary using a grayscale intensity threshold, and shape fitting either a circle or ellipse to the droplet’s boundary. The results are compared to manual measurements of droplet diameters done...
16 Citations Source Cite
Published on Jan 1, 2012in Combustion and Flame 4.49
Tanvir Farouk17
Estimated H-index: 17
(Princeton University),
Frederick L. Dryer66
Estimated H-index: 66
(Princeton University)
Abstract Tethered methanol droplet combustion in carbon dioxide enriched environment is simulated using a transient one-dimensional spherosymmetric droplet combustion model that includes the effects of tethering. A priori numerical predictions are compared against recent experimental data. The numerical predictions compare favorably with the experimental results and show significant effects of tethering on the experimental observations. The presence of a relatively large quartz fiber tether incr...
21 Citations Source Cite
Published on Jan 1, 2012in Journal of Combustion
Benjamin D. Shaw13
Estimated H-index: 13
(UC Davis: University of California, Davis),
Jingbin Wei3
Estimated H-index: 3
Reduced and normal gravity combustion experiments were performed with fiber-supported methanol droplets with initial diameters in the 1 mm size range. Experiments were performed with air-diluent mixtures at about 0.101 MPa and 298 K, where carbon dioxide, helium, or xenon was separately used as the diluent gas. Results indicate that ambient gas transport properties play an important role in determining flammability and combustion behaviors including burning rates and radiant heat output historie...
3 Citations Source Cite
Published on Oct 1, 2011in Combustion Science and Technology 1.13
Benjamin D. Shaw13
Estimated H-index: 13
(UC Davis: University of California, Davis),
J. B. Wei4
Estimated H-index: 4
(UC Davis: University of California, Davis)
Reduced gravity and normal gravity combustion experiments were performed with individual fiber-supported n-heptane and 1-propanol droplets with initial diameters in the 1-mm size range. Experiments were performed with air-inert mixtures at 0.1 MPa or 0.3 MPa and about 298 K, where helium, carbon dioxide, or xenon were separately used as inerts. The amount of inert gas required to suppress combustion was generally higher in reduced gravity than normal gravity, and higher mole fractions of xenon w...
7 Citations Source Cite
Published on Oct 15, 2001
Craig Myhre1
Estimated H-index: 1
10 Citations Source Cite
Published on Jan 1, 2001in AIAA Journal 1.56
Benjamin D. Shaw1
Estimated H-index: 1
,
Bret D. Clark1
Estimated H-index: 1
,
Difei Wang1
Estimated H-index: 1
Results are presented from experiments on reduced-gravity combustion of individual heptane/hexadecane droplets. Initial droplet diameters ranged from 0.25 to 5.2 mm, and initial hexadecane mass fractions in the droplets were 0.058, 0.10, 0.20, and 0.40. Most droplets were burned in cabin air on Spacelab with an ambient oxygen mole fraction of about 0.21 and a pressure of about 0.1 MPa. Data were also obtained for small (0.25-mm) droplets in a ground-based apparatus that provides simulated reduce...
9 Citations Source Cite
Cited By30
Newest
Published on Mar 21, 2019in Combustion Theory and Modelling 1.74
Forman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego),
Vedha Nayagam4
Estimated H-index: 4
(Case Western Reserve University)
Source Cite
Published on Mar 1, 2019in International Journal of Heat and Mass Transfer 3.89
A.E. Saufi (Leonardo), Alessio Frassoldati34
Estimated H-index: 34
(Leonardo)
+ 1 AuthorsAlberto Cuoci27
Estimated H-index: 27
(Leonardo)
Abstract This paper aims at presenting the DropletSMOKE++ solver, a comprehensive multidimensional computational framework for the evaporation of fuel droplets, under the influence of a gravity field and an external fluid flow. The Volume Of Fluid (VOF) methodology is adopted to dynamically track the interface, coupled with the solution of energy and species equations. The evaporation rate is directly evaluated based on the vapor concentration gradient at the phase boundary, with no need of semi...
Source Cite
Published on Feb 1, 2019in Acta Astronautica 2.23
V. V. Tyurenkova8
Estimated H-index: 8
(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...
Source Cite
Published on Jan 1, 2019
Fahd E. Alam4
Estimated H-index: 4
(USC: University of South Carolina),
Ali Charchi Aghdam (USC: University of South Carolina)+ 1 AuthorsTanvir Farouk17
Estimated H-index: 17
(USC: University of South Carolina)
Abstract This paper reports simulation results of oscillatory cool flame burning of an isolated, submillimeter sized n-heptane (n-C 7 H 16 ) droplet in a selectively ozone (O 3 ) seeded nitrogen-oxygen (N 2 -O 2 ) environments at atmospheric pressure. An evolutionary one-dimensional droplet combustion code encompassing relevant physics and detailed chemistry was employed to explore the roles of low-temperature chemistry, O 3 seeding, and dynamic flame structure on burning behaviors. For X O2 = 2...
Source Cite
Published on Jan 1, 2019
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 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...
1 Citations Source Cite
Published on Dec 1, 2018in AIAA Journal 1.56
C. L. Vang (UC Davis: University of California, Davis), B. D. Shaw (UC Davis: University of California, Davis)
Combustion experiments on heptane–hexadecane mixture droplets were conducted onboard the International Space Station. The ambient consisted of oxygen mixed with either helium or nitrogen at 1 atm. Initial droplet diameters were in the 1.7–4.8 mm range with initial heptane mass fractions of 0.95 or 0.80. Because of limitations on resources, only fiber-supported experiments were possible. Vaporization of the more volatile fuel component (heptane) was favored during the droplet combustion process, ...
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Published on Oct 1, 2018in Journal of Computational Physics 2.86
Changxiao Shao4
Estimated H-index: 4
(ZJU: Zhejiang University),
LUOKun23
Estimated H-index: 23
(ZJU: Zhejiang University)
+ 2 AuthorsJianren Fan27
Estimated H-index: 27
(ZJU: Zhejiang University)
Abstract A computational framework for interface-resolved direct numerical simulations (DNS) of simultaneous atomization, evaporation and combustion process is proposed. The present work utilizes a level set method to implicitly capture the gas–liquid interface and the ghost fluid method (GFM) to accurately address jump conditions across the interface. Specific care has been devoted to the discretization of the convective term and diffusive term for the species and energy equations. The level se...
1 Citations Source Cite
Published on Sep 1, 2018in Combustion and Flame 4.49
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 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.
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Published on Aug 1, 2018in Combustion and Flame 4.49
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...
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Published on Aug 1, 2018in Microgravity Science and Technology 1.36
Masato Mikami14
Estimated H-index: 14
(Yamaguchi University),
Yasuko Yoshida1
Estimated H-index: 1
(Yamaguchi University)
+ 4 AuthorsMasaki Nokura1
Estimated H-index: 1
This research conducted microgravity experiments on the flame spread over randomly distributed n-decane-droplet clouds aboard the Japanese Experiment Module “Kibo” on the International Space Station. 67-152 droplets were distributed at intersections of a 30 × 30 square lattice with 14-micron SiC fibers placed in a combustion chamber. One droplet on the bottom side of lattice was ignited by a hot-wire igniter to start the flame spread. The burning behavior was observed by a digital camera. This p...
1 Citations Source Cite