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Combustion of Methanol Droplets in Air-Diluent Environments with Reduced and Normal Gravity

Published on Jan 1, 2012in Journal of Combustion
· DOI :10.1155/2012/587987
Benjamin D. Shaw13
Estimated H-index: 13
(UC Davis: University of California, Davis),
Jingbin Wei3
Estimated H-index: 3
Cite
Abstract
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 histories of the droplets. Droplets would burn with significantly higher mole fractions of xenon than helium or carbon dioxide. In reduced gravity, droplets would burn steadily with a xenon mole fraction of 0.50 but would not burn steadily if helium or carbon dioxide mole fractions were 0.50. Comparison with previous experimental data shows that ignitability and combustion characteristics of droplets are influenced by the fuel type and also the gravitational level. Burning rates were about 40% to 70% higher in normal gravity than in reduced gravity. Methanol droplets also had burning rates that were typically larger than 1-propanol burning rates by about 20% in reduced gravity. In normal gravity, however, burning rate differences between the two fuels were significantly smaller.
  • References (23)
  • Citations (3)
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References23
Newest
Published on Jan 1, 1985
F. A. Williams1
Estimated H-index: 1
* Summary of Relevant Aspects of Fluid Dynamics and Chemical Kinetics * Rankine-Hugoniot Relations * Diffusion Flames and Droplet Burning * Reactions in Flows with Negligible Molecular Transport * Theory of Laminar Flames * Detonation Phenomena * Combustion of Solid Propellants * Ignition, Extinction, and Flammability Limits * Combustion Instabilities * Theory of Turbulent Flames * Spray Combustion * Flame Attachment and Flame Spread
Published on Oct 1, 2011in Combustion Science and Technology 1.56
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...
Published on Aug 1, 2010in Combustion and Flame 4.12
Michael C. Hicks8
Estimated H-index: 8
(Glenn Research Center),
Vedha Nayagam13
Estimated H-index: 13
(Glenn Research Center),
Forman A. Williams48
Estimated H-index: 48
(UCSD: University of California, San Diego)
Diffusive extinction of methanol droplets with initial diameters between 1.25 mm and 1.72 mm, burning in a quiescent microgravity environment at one atmosphere pressure, was obtained experimentally for varying levels of ambient carbon-dioxide concentrations with a fixed oxygen concentration of 21% and a balance of nitrogen. These experiments serve as precursors to those which are beginning to be performed on the International Space Station and are motivated by the need to understand the effectiv...
Published on Apr 1, 2008in Combustion and Flame 4.12
Manuel Arias-Zugasti7
Estimated H-index: 7
(Yale University),
Daniel E. Rosner31
Estimated H-index: 31
(Yale University)
Abstract Since, according to ideal gas kinetic theory, Ludwig–Soret species transport (temperature-gradient-driven mass transport) must be simultaneously included along with nonunity Lewis numbers [D.E. Rosner, R.S. Israel, B. La Mantia, Combust. Flame 123 (2000) 547–560], we formally consider here the influence of both effects on laminar, counterflow gaseous diffusion flames in the thin flame limit. Our deliberately idealized theoretical analysis includes cases of steady/unsteady, strained/unst...
Published on Feb 18, 2008in Combustion Science and Technology 1.56
Seul-Hyun Park7
Estimated H-index: 7
(Drexel University),
Seuk-Cheun Choi1
Estimated H-index: 1
(Drexel University)
+ 1 AuthorsAhmet Yozgatligil8
Estimated H-index: 8
(METU: Middle East Technical University)
Spherically symmetric ethanol droplet combustion experiments were performed to investigate the influence of initial droplet diameter, ambient pressure and inert substitution on the burning and sooting behaviors of ethanol droplet flames. Experiments were performed using the 2.2 sec reduced-gravity droptower facilities at the NASA Glenn Research Center. Noting the importance of transport characteristics of heat and species and their attendant effects on flame temperature and residence time on the...
Published on Dec 1, 2007in Combustion and Flame 4.12
Sridhar Palle4
Estimated H-index: 4
(Clemson University),
Richard S. Miller23
Estimated H-index: 23
(Clemson University)
Abstract Direct numerical simulations are conducted for one-dimensional laminar diffusion flames over a large range of pressures ( 1 ⩽ P 0 ⩽ 200 atm ) employing a detailed multicomponent transport model applicable to dense fluids. Reaction kinetics mechanisms including pressure dependencies and prior validations at both low and high pressures were selected and include a detailed 24-step, 12-species hydrogen mechanism (H 2 /O 2 and H 2 /air), and reduced mechanisms for methane (CH 4 /air: 11 step...
Published on May 3, 2007in Combustion Science and Technology 1.56
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)
Abstract Reduced gravity and normal gravity combustion experiments were performed with individual fiber-supported propanol droplets with initial diameters that were typically in the 1.2 to 1.3 mm range. The environment was composed of an air-inert mixture at 0.1 MPa and about 298 K, where helium, carbon dioxide and xenon were separately used as inerts. In the experiments, the amount of inert gas in the environment was progressively increased until droplets could no longer be ignited. Droplet ign...
Published on Mar 28, 2007
Michael C. Hicks8
Estimated H-index: 8
,
Vedha Nayagam4
Estimated H-index: 4
,
Forman A. Williams48
Estimated H-index: 48
Microgravity droplet combustion experiments were performed in elevated concentrations of CO2 at pressures of 1.0 atm, 3.0 atm, and 5.0 atm to examine the effects of a radiatively participating suppression agent in space applications. Methanol and n-heptane droplets, with an initial diameter of 2.0 mm supported on a quartz fiber, were used in these experiments. The ambient O2 concentration was held constant at 21% and the CO2 concentrations ranged from 0% to a maximum of 70%, by volume with the b...
Published on Jan 1, 2007
J.H. Bae1
Estimated H-index: 1
(Cornell University),
C.T. Avedisian24
Estimated H-index: 24
(Cornell University)
In this paper, we study the influence of inert concentration and initial droplet diameter on nonane (C9H20) droplet combustion in an environment that promotes spherical droplet flames. The oxygen concentration is fixed while the inert is varied between nitrogen and helium. A range of initial droplet diameters (Do) are examined in each ambient gas: 0.4 mm < Do < 0.8 mm; and an oxidizing ambiance consisting of 30% oxygen (fixed) and 70% inert (fixed), with the inert in turn composed of mixtures of...
Published on Jan 1, 2007
Ahmet Yozgatligil8
Estimated H-index: 8
(Drexel University),
Seul-Hyun Park7
Estimated H-index: 7
(Drexel University)
+ 2 AuthorsFrederick L. Dryer66
Estimated H-index: 66
(Princeton University)
Abstract The influence of oxygen (O 2 ) concentration and inert on the sooting and burning behavior of large ethanol droplets under microgravity conditions was investigated through measurements of burning rate, flame temperature, sootshell diameter, and soot volume fraction. The experiments were performed at the NASA Glenn Research Center (GRC) 2.2 s drop tower in Cleveland, OH. Argon (Ar), helium (He), and nitrogen (N 2 ) were used as the inerts and the O 2 concentration was varied between 21% ...
Cited By3
Newest
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 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 ...