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1

Total cellular Ca2+ measurements in yeast using flame photometry.  

PubMed

A photoelectric flame photometer is a device used in inorganic chemical analysis for determining the concentrations of certain metals in solution. It does this by measuring the intensity of the light emitted by the metal when the solution is sprayed under controlled conditions into a nonluminous flame. This protocol describes how to measure total cellular calcium (maximal emission at 622 nm, orange flame) in yeast using this technique. PMID:25646495

Tisi, Renata; Martegani, Enzo; Brandão, Rogelio L

2015-01-01

2

Releasing effects in flame photometry: Determination of calcium  

USGS Publications Warehouse

Strontium, lanthanum, neodymium, samarium, and yttrium completely release the flame emission of calcium from the depressive effects of sulfate, phosphate, and aluminate. Magnesium, beryllium, barium, and scandium release most of the calcium emission. These cations, when present in high concentration, preferentially form compounds with the depressing anions when the solution is evaporated rapidly in the flame. The mechanism of the interference and releasing effects is explained on the basis of the chemical equilibria in the evaporating droplets of solution and is shown to depend upon the nature of the compounds present in the aqueous phase of the solution. The need for background correction techniques is stressed. The releasing effect is used in the determination of calcium in silicate rocks without the need for separations.

Dinnin, J.I.

1960-01-01

3

A new principle applied to the determination of calcium in biological materials by flame photometry.  

PubMed

The effect of magnesium sulphate in releasing calcium emission from interference by phosphate and sulphate has been investigated. Samples were diluted in 10 mM MgSO(4), 2 mM NaCl, giving final calcium concentrations of about 0.05 to 0.10 mM. In this diluent, galvanometer readings were proportional to calcium concentrations up to 0.4 mM. The magnesium sulphate released calcium emission from depression by phosphate and sulphate. The excess sodium chloride eliminated enhancement of calcium emission by added sodium and potassium in the sample. Subtraction of background readings excluded direct interference.A 3% correction was made for the effect of the viscosity of 1: 50 plasma dilutions. Satisfactory recoveries of added calcium were obtained from plasma, urine, and faeces using the diluent described above. Results on urine and faeces correlated closely with those obtained by an EDTA titration method. Results on plasma were consistently 2% higher by flame photometry than by EDTA titration. Other methods of calcium determination, depending on the use of radiation buffers or standard addition, were found to be unsatisfactory because of variable interference by phosphate at different calcium levels. PMID:13891877

FAWCETT, J K; WYNN, V

1961-09-01

4

Simultaneous determination of organotin compounds in textiles by gas chromatography-flame photometry following liquid/liquid partitioning with tert-butyl ethyl ether after reflux-extraction.  

PubMed

A rapid and relatively clean method for determining six organotin compounds (OtC) in textile goods with a gas chromatograph equipped with a conventional flame photometric detector (GC-FPD) has been developed. After the reflux-extraction to use methanol containing 1% (v/v) of hydrochloric acid, five hydrophobic OtC (e.g. tributyltin: TBT) and slightly less hydrophobic dibutyltin (DBT) could be drawn out through partitioning between the methanolic buffer solution and tert-butyl ethyl ether instead of hazardous dichloromethane, of which usage is provided by the official-methods notified in Japan, and following the ethylation procedure to use sodium tetraethylborate, the OtC were determined with the GC-FPD. The recoveries of DBT, TBT, tetrabutyltin, triphenyltin, dioctyltin, and trioctyltin from textile products (cloth diaper, socks, and undershirt) were 60-77, 89-98, 86-94, 71-78, 85-109, and 70-79% respectively, and their coefficients of variation were 2.5-16.5%. Calibration curves for OtC were linear (0.01-0.20 ?g as Sn mL(-1)), and the correlation coefficients were 0.9922-1.0000. Their detection limits were estimated to be 2.7-9.7 n gas Sn g(-1). These data suggested that this method would be applicable to their simultaneous determination. Five retailed textile goods were analyzed by this proposed method, and 0.013-0.65 µg as Sn g(-1) of OtC (e.g. DBT) were determined in three. Moreover, a possibility that various OtC including non-targeted species in textile would be specifically detected by applying the studying speciation-technique of controlling signal intensity-flame fuel gas pressures of the GC-FPD was found. PMID:24054605

Hamasaki, Tetsuo

2013-10-15

5

Basics of Photometry Photometry: Basic Questions  

E-print Network

Basics of Photometry #12;Photometry: Basic Questions · How do you identify objects in your image type of object you're studying? #12;#12;#12;Topics 1. General Considerations 2. Stellar Photometry 3. Galaxy Photometry #12;I: General Considerations 1. Garbage in, garbage out... 2. Object Detection 3

Masci, Frank

6

Stellar Populations Surface photometry  

E-print Network

Outline Stellar Populations Surface photometry Luminosity distributions Component separation Surface photometry Luminosity distributions Component separation Photometric parameters Elliptical photometry Luminosity distributions Bulge luminosity laws Luminosity distributions in disks Component

Kruit, Piet van der

7

Candle flame  

NSDL National Science Digital Library

Your skin covers and protects your body. Your skin can also detect heat and cold. If you put one of your fingers in the flame of a candle, your brain would gather this information and send a message to your muscles to move your finger out of the flame. This is because the brain receives a signal that the flame is extremely hot and in turn the brain tells your body you are in pain and that you should move your finger.

Victor Rocha (None;)

2008-02-10

8

Flame Spectra.  

ERIC Educational Resources Information Center

When salt (NaCl) is introduced into a colorless flame, a bright yellow light (characteristic of sodium) is produced. Why doesn't the chlorine produce a characteristic color of light? The answer to this question is provided, indicating that the flame does not excite the appropriate energy levels in chlorine. (JN)

Cromer, Alan

1983-01-01

9

Introduction to astronomical photometry  

Microsoft Academic Search

General definitions and questions of energy distribution for various spectral types are considered along with photometric measurements, effects of bandwidths and interstellar absorption, the two-dimensional photometric representations of stars, multicolor and wideband photometry, intermediate and narrow passband photometry, and photometric parameters and their correlation with basic parameters describing the physical state of stellar atmospheres. Applications of photometry to various stellar

M. Golay

1974-01-01

10

Flame Detector  

NASA Technical Reports Server (NTRS)

Scientific Instruments, Inc. has now developed a second generation, commercially available instrument to detect flames in hazardous environments, typically refineries, chemical plants and offshore drilling platforms. The Model 74000 detector incorporates a sensing circuit that detects UV radiation in a 100 degree conical field of view extending as far as 250 feet from the instrument. It operates in a bandwidth that makes it virtually 'blind' to solar radiation while affording extremely high sensitivity to ultraviolet flame detection. A 'windowing' technique accurately discriminates between background UV radiation and ultraviolet emitted from an actual flame, hence the user is assured of no false alarms. Model 7410CP is a combination controller and annunciator panel designed to monitor and control as many as 24 flame detectors. *Model 74000 is no longer being manufactured.

1990-01-01

11

Flame retardants  

NASA Technical Reports Server (NTRS)

The use of flame retardants in plastics has grown only slightly in recent years and will probably grow slowly in the future. The reasons for this are slow economic growth and the absence of fundamentally new requirements for future fire prevention. The trends are toward the increasing use of easily handled, dust-free and well-dispersed flame retardant compounds and master batches; there are no spectacular new developments. In the future, questions of smoke evolution, toxicity and corrosiveness of combustion gases will become increasingly important, especially due to new regulations and rising requirements for environmental protection.

Troitzsch, J.

1988-01-01

12

Flame Stabilization Mechanisms in Lifted Flames  

Microsoft Academic Search

Flame stabilization and the mechanisms that govern the dynamics at the flame base of lifted flames have been subject to numerous\\u000a studies in recent years. A combined Large Eddy Simulation-Conditional Moment Closure (LES-CMC) approach has been successful\\u000a in predicting flame ignition and stabilization by auto-ignition, but accurate modelling of the competition between turbulent\\u000a quenching and laminar and turbulent flame propagation

Salvador Navarro-Martinez; Andreas Kronenburg

13

Surface photometry STRUCTURE OF GALAXIES  

E-print Network

Outline Surface photometry Dynamics Formation STRUCTURE OF GALAXIES 9. Elliptical galaxies Piet van van der Kruit, Kapteyn Astronomical Institute Elliptical galaxies #12;Outline Surface photometry Dynamics Formation Outline Surface photometry Luminosity distributions Shells and ripples Color gradients

Kruit, Piet van der

14

Triple flame structure and diffusion flame stabilization  

NASA Technical Reports Server (NTRS)

The stabilization of diffusion flames is studied using asymptotic techniques and numerical tools. The configuration studied corresponds to parallel streams of cold oxidizer and fuel initially separated by a splitter plate. It is shown that stabilization of a diffusion flame may only occur in this situation by two processes. First, the flame may be stabilized behind the flame holder in the wake of the splitter plate. For this case, numerical simulations confirm scalings previously predicted by asymptotic analysis. Second, the flame may be lifted. In this case a triple flame is found at longer distances downstream of the flame holder. The structure and propagation speed of this flame are studied by using an actively controlled numerical technique in which the triple flame is tracked in its own reference frame. It is then possible to investigate the triple flame structure and velocity. It is shown, as suggested from asymptotic analysis, that heat release may induce displacement speeds of the triple flame larger than the laminar flame speed corresponding to the stoichiometric conditions prevailing in the mixture approaching the triple flame. In addition to studying the characteristics of triple flames in a uniform flow, their resistance to turbulence is investigated by subjecting triple flames to different vortical configurations.

Veynante, D.; Vervisch, L.; Poinsot, T.; Linan, A.; Ruetsch, G.

1994-01-01

15

Floating Flame Balls  

NSDL National Science Digital Library

This NASA Science press release covers the discovery of tiny flame balls, a shape flames take in microgravity. The article discusses implications of the research for combustion here on Earth and includes a diagram of a flame ball.

2011-04-08

16

Candle Flames in Microgravity  

NASA Technical Reports Server (NTRS)

This work is a study of a candle flame in a microgravity environment. The purpose of the work is to determine if a steady (or quasi-steady) flame can exist in a microgravity environment, study the characteristics of the steady flame, investigate the pre-extinction flame oscillations observed in a previous experiment in more detail, and finally, determine the nature of the interactions between two closely spaced candle flames. The candle flame in microgravity is used as a model of a non-propagating, steady-state, pure diffusion flame. The present work is a continuation of two small-scale, space-based experiments on candle flames, one on the Shuttle and the other on the Mir OS. The previous studies showed nearly steady dim blue flames with flame lifetimes as high as 45 minutes, and 1 Hz spontaneous flame oscillations prior to extinction. The present paper summarizes the results of the modeling efforts to date.

Dietrich, D. L.; Ross, H. D.; T'ien, J. S.; Chang, P.; Shu, Y.

1999-01-01

17

APT: Aperture Photometry Tool  

NASA Astrophysics Data System (ADS)

Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It has a graphical user interface (GUI) which allows the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. Mouse-clicking on a source in the displayed image draws a circular or elliptical aperture and sky annulus around the source and computes the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs, including image histogram, and aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has functions for customizing calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source model, accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

Laher, Russ

2012-08-01

18

Multicolor stellar photometry  

NASA Astrophysics Data System (ADS)

The monograph describes all multicolor photometric systems which were in use for stellar photometry before 1990, particularly the UBV, Strömgren and Vilnius systems. The reviews of common properties of photometric systems, energy distribution in stellar spectra, interstellar and atmospheric extinction, photometric classification methods of stars are also given. The book includes calibrations of spectral MK types in absolute magnitudes, bolometric corrections, effective temperatures, surface gravities, masses and radii. Intrinsic color indices of the UBV, Strömgren, Vilnius and infrared systems are tabulated. The volume of the book is 570 pages. A pdf file of the book is available at: http://www.itpa.lt/MulticolorStellarPhotometry/

Straižys, Vytautas

19

Candle Flame in Microgravity  

NSDL National Science Digital Library

Investigating candle flames in microgravity can be done as either a demonstration or an activity. "Student reader" pages give background information about candle flames in microgravity. Student worksheets may be used to assess student learning.

2006-05-30

20

Aperture Photometry Tool  

NASA Astrophysics Data System (ADS)

Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It is a graphical user interface (GUI) designed to allow the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. The finely tuned layout of the GUI, along with judicious use of color-coding and alerting, is intended to give maximal user utility and convenience. Simply mouse-clicking on a source in the displayed image will instantly draw a circular or elliptical aperture and sky annulus around the source and will compute the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs with just the push of a button, including image histogram, x and y aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has many functions for customizing the calculations, including outlier rejection, pixel ""picking"" and ""zapping,"" and a selection of source and sky models. The radial-profile-interpolation source model, which is accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

Laher, Russ R.; Gorjian, Varoujan; Rebull, Luisa M.; Masci, Frank J.; Fowler, John W.; Helou, George; Kulkarni, Shrinivas R.; Law, Nicholas M.

2012-07-01

21

Candle Flames in Microgravity  

NASA Technical Reports Server (NTRS)

This work is a study of a candle flame in a microgravity environment. The purpose of the work is to determine if a steady (or quasi-steady) flame can exist in a microgravity environment, study the characteristics of the steady flame, investigate the pre-extinction flame oscillations observed in a previous experiment in more detail, and finally, determine the nature of the interactions between two closely spaced candle flames. The candle flame is used as a model combustion system, in that in microgravity it is one of the only examples of a non-propagating, steady-state, pure diffusion flame. Others have used the candle to study a number of combustion phenomena including flame flicker, flame oscillations, electric field effects and enhanced and reduced gravitational effects in flames. The present work is a continuation of a small-scale Shuttle experiment on candle flames. That study showed that the candle flame lifetimes were on the order of 40 seconds, the flames were dim blue after a transient ignition period, and that just prior to extinction the flames oscillated spontaneously for about five seconds at a frequency of 1 Hz. The authors postulated that the gas phase in the immediate vicinity of the flame was quasi-steady. Further away from the flame, however, the assertion of a quasi-steady flame was less certain, thus the authors did not prove that a steady flame could exist. They also speculated that the short lifetime of the candle flame was due to the presence of the small, weakly perforated box that surrounded the candle. The Candle Flames in Microgravity (CFM) experiment, with revised hardware, was recently flown aboard the Mir orbiting station, and conducted inside the glovebox facility by Dr. Shannon Lucid. In addition to the purposes described above, the experiments were NASA's first ability to ascertain the merits of the Mir environment for combustion science studies. In this article, we present the results of that experiment. We are also in the process of developing a numerical model of the microgravity candle flame. The status and results of the modeling efforts to date are also presented.

Dietrich, Daniel L.; Ross, Howard D.; Frate, David T.; Tien, James S.; Shu, Yong

1997-01-01

22

Unfiltered photometry of asteroids.  

NASA Astrophysics Data System (ADS)

Unfiltered Photometry of Asteroids Most asteroid search and astrometric programs use no photometric filters. Yet all these programs report magnitudes. What does this mean? What color should be reported? How accurate is it? This talk will present the results of recent calibrations against standards (Landolt) at the Grasslands Observatory (using a site CCD and a 62 cm reflector). Comparisons between filtered and unfiltered images using both the USNO-SA2.0 and GSC 1.1 catalogs will be presented.

McGaha, J.

1999-04-01

23

ESP: Extended Surface Photometry  

NASA Astrophysics Data System (ADS)

ESP (Extended Surface Photometry) determines the photometric properties of galaxies and other extended objects. It has applications that detect flatfielding faults, remove cosmic rays, median filter images, determine image statistics and local background values, perform galaxy profiling, fit 2-D Gaussian profiles to galaxies, generate pie slice cross-sections of galaxies, and display profiling results. It is distributed as part of the Starlink software collection (ascl:1110.012)

Privett, Grant; Taylor, Mark; Gray, Norman; Draper, Peter W.; Jenness, Tim

2014-05-01

24

Introduction to Astronomical Photometry  

NASA Astrophysics Data System (ADS)

This textbook for graduate students in observational astronomy, describes the methods used to measure the radiation (mostly in the optical domain) from stars. It starts with an overview, followed by definitions of the main terms encountered in the subject. This is followed by a description of the fundamental physical theory of the measurement of radiative flux. Wide ranging problems in astronomical photometry are then approached. The central chapters deal with photometer design, data handling techniques, and the generation of light curves. Many applications of photometry are then described. Users of this textbook will be able to develop an interest in the practicalities of obtaining data of good quality from photometry. The book will appeal to amateur and professional astronomers engaged in variable star observations and the measurement of stellar luminosity. It is intended to encourage interest in the practicalities of observational astronomy and an understanding of stellar astrophysics from a data-based perspective. It fills a gap between a popular approach and a research monograph.

Budding, Edwin

1993-09-01

25

ARCHANGEL: Galaxy Photometry System  

NASA Astrophysics Data System (ADS)

ARCHANGEL is a Unix-based package for the surface photometry of galaxies. While oriented for large angular size systems (i.e. many pixels), its tools can be applied to any imaging data of any size. The package core contains routines to perform the following critical galaxy photometry functions: sky determinationframe cleaningellipse fittingprofile fittingtotal and isophotal magnitudes The goal of the package is to provide an automated, assembly-line type of reduction system for galaxy photometry of space-based or ground-based imaging data. The procedures outlined in the documentation are flux independent, thus, these routines can be used for non-optical data as well as typical imaging datasets. ARCHANGEL has been tested on several current OS's (RedHat Linux, Ubuntu Linux, Solaris, Mac OS X). A tarball for installation is available at the download page. The main routines are Python and FORTRAN based, therefore, a current installation of Python and a FORTRAN compiler are required. The ARCHANGEL package also contains Python hooks to the PGPLOT package, an XML processor and network tools which automatically link to data archives (i.e. NED, HST, 2MASS, etc) to download images in a non-interactive manner.

Schombert, James

2011-07-01

26

Candle flames in microgravity  

NASA Technical Reports Server (NTRS)

The candle flame in both normal and microgravity is non-propagating. In microgravity, however, the candle flame is also non-convective where (excepting Stefan flow) pure diffusion is the only transport mode. It also shares many characteristics with another classical problem, that of isolated droplet combustion. Given their qualitatively similar flame shapes and the required heat feedback to condensed-phase fuels, the gas-phase flow and temperature fields should be relatively similar for a droplet and a candle in reduced gravity. Unless the droplet diameter is maintained somehow through non-intrusive replenishment of fuel, the quasi-steady burning characteristics of a droplet can be maintained for only a few seconds. In contrast, the candle flame in microgravity may achieve a nearly steady state over a much longer time and is therefore ideal for examining a number of combustion-related phenomena. In this paper, we examine candle flame behavior in both short-duration and long-duration, quiescent, microgravity environments. Interest in this type of flame, especially 'candle flames in weightlessness', is demonstrated by very frequent public inquiries. The question is usually posed as 'will a candle flame burn in zero gravity', or, 'will a candle burn indefinitely (or steadily) in zero gravity in a large volume of quiescent air'. Intuitive speculation suggests to some that, in the absence of buoyancy, the accumulation of products in the vicinity of the flame will cause flame extinction. The classical theory for droplet combustion with its spherically-shaped diffusion flame, however, shows that steady combustion is possible in the absence of buoyancy if the chemical kinetics are fast enough. Previous experimental studies of candle flames in reduced and microgravity environments showed the flame could survive for at least 5 seconds, but did not reach a steady state in the available test time.

Dietrich, D. L.; Ross, H. D.; Tien, J. S.

1995-01-01

27

Cool Flame Quenching  

NASA Technical Reports Server (NTRS)

Cool flame quenching distances are generally presumed to be larger than those associated with hot flames, because the quenching distance scales with the inverse of the flame propagation speed, and cool flame propagation speeds are often times slower than those associated with hot flames. To date, this presumption has never been put to a rigorous test, because unstirred, non-isothermal cool flame studies on Earth are complicated by natural convection. Moreover, the critical Peclet number (Pe) for quenching of cool flames has never been established and may not be the same as that associated with wall quenching due to conduction heat loss in hot flames, Pe approx. = 40-60. The objectives of this ground-based study are to: (1) better understand the role of conduction heat loss and species diffusion on cool flame quenching (i.e., Lewis number effects), (2) determine cool flame quenching distances (i.e, critical Peclet number, Pe) for different experimental parameters and vessel surface pretreatments, and (3) understand the mechanisms that govern the quenching distances in premixtures that support cool flames as well as hot flames induced by spark-ignition. Objective (3) poses a unique fire safety hazard if conditions exist where cool flame quenching distances are smaller than those associated with hot flames. For example, a significant, yet unexplored risk, can occur if a multi-stage ignition (a cool flame that transitions to a hot flame) occurs in a vessel size that is smaller than that associated with the hot quenching distance. To accomplish the above objectives, a variety of hydrocarbon-air mixtures will be tested in a static reactor at elevated temperature in the laboratory (1g). In addition, reactions with chemical induction times that are sufficiently short will be tested aboard NASA's KC-135 microgravity (mu-g) aircraft. The mu-g results will be compared to a numerical model that includes species diffusion, heat conduction, and a skeletal kinetic mechanism, following the work on diffusion-controlled cool flames by Fairlie et,al., 2000.

Pearlman, Howard; Chapek, Richard

2001-01-01

28

Diffusion Flame Stabilization  

NASA Technical Reports Server (NTRS)

Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (Fig. 1, left). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated (Fig. 1, right). A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

Takahashi, Fumiaki; Katta, Viswanath R.

2007-01-01

29

Diffusion Flame Stabilization  

NASA Technical Reports Server (NTRS)

Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated. A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

Takahashi, Fumiaki; Katta, V. R.

2006-01-01

30

Turbulent flame propagation in partially premixed flames  

NASA Technical Reports Server (NTRS)

Turbulent premixed flame propagation is essential in many practical devices. In the past, fundamental and modeling studies of propagating flames have generally focused on turbulent flame propagation in mixtures of homogeneous composition, i.e. a mixture where the fuel-oxidizer mass ratio, or equivalence ratio, is uniform. This situation corresponds to the ideal case of perfect premixing between fuel and oxidizer. In practical situations, however, deviations from this ideal case occur frequently. In stratified reciprocating engines, fuel injection and large-scale flow motions are fine-tuned to create a mean gradient of equivalence ratio in the combustion chamber which provides additional control on combustion performance. In aircraft engines, combustion occurs with fuel and secondary air injected at various locations resulting in a nonuniform equivalence ratio. In both examples, mean values of the equivalence ratio can exhibit strong spatial and temporal variations. These variations in mixture composition are particularly significant in engines that use direct fuel injection into the combustion chamber. In this case, the liquid fuel does not always completely vaporize and mix before combustion occurs, resulting in persistent rich and lean pockets into which the turbulent flame propagates. From a practical point of view, there are several basic and important issues regarding partially premixed combustion that need to be resolved. Two such issues are how reactant composition inhomogeneities affect the laminar and turbulent flame speeds, and how the burnt gas temperature varies as a function of these inhomogeneities. Knowledge of the flame speed is critical in optimizing combustion performance, and the minimization of pollutant emissions relies heavily on the temperature in the burnt gases. Another application of partially premixed combustion is found in the field of active control of turbulent combustion. One possible technique of active control consists of pulsating the fuel flow rate and thereby modulating the equivalence ratio (Bloxsidge et al. 1987). Models of partially premixed combustion would be extremely useful in addressing all these questions related to practical systems. Unfortunately, the lack of a fundamental understanding regarding partially premixed combustion has resulted in an absence of models which accurately capture the complex nature of these flames. Previous work on partially premixed combustion has focused primarily on laminar triple flames. Triple flames correspond to an extreme case where fuel and oxidizer are initially totally separated (Veynante et al. 1994 and Ruetsch et al. 1995). These flames have a nontrivial propagation speed and are believed to be a key element in the stabilization process of jet diffusion flames. Different theories have also been proposed in the literature to describe a turbulent flame propagating in a mixture with variable equivalence ratio (Muller et al. 1994), but few validations are available. The objective of the present study is to provide basic information on the effects of partial premixing in turbulent combustion. In the following, we use direct numerical simulations to study laminar and turbulent flame propagation with variable equivalence ratio.

Poinsot, T.; Veynante, D.; Trouve, A.; Ruetsch, G.

1996-01-01

31

ARCHANGEL Galaxy Photometry System  

E-print Network

Photometry of galaxies has typically focused on small, faint systems due to their interest for cosmological studies. Large angular size galaxies, on the other hand, offer a more detailed view into the properties of galaxies, but bring a series of computational and technical difficulties that inhibit the general astronomer from extracting all the information found in a detailed galaxy image. To this end, a new galaxy photometry system has been developed (mostly building on tools and techniques that have existed in the community for decades) that combines ease of usage with a mixture of pre-built scripts. The audience for this system is a new user (graduate student or non-optical astronomer) with a fast, built-in learning curve to offer any astronomer, with imaging data, a suite of tools to quickly extract meaningful parameters from decent data. The tools are available either by a client/server web site or by tarball for personal installation. The tools also provide simple scripts to interface with various on-line datasets (e.g. 2MASS, Sloan, DSS) for data mining capability of imaged data. As a proof of concept, we preform a re-analysis of the 2MASS Large Galaxy Atlas to demonstrate the differences in an automated pipeline, with its emphasis on speed, versus this package with an emphasis on accuracy. This comparison finds the structural parameters extracted from the 2MASS pipeline is seriously flawed with scale lengths that are too small by 50% and central surface brightness that are, on average, 1 to 0.5 mags too bright. A cautionary tale on how to reduce information-rich data such as surface brightness profiles. This document and software can be found at http://abyss.uoregon.edu/~js/archangel.

J. Schombert

2007-03-26

32

Theory of flame propagation  

NASA Technical Reports Server (NTRS)

The mechanism of flame propagation has been qualitatively formulated. In accordance with this formulation, the chemical reaction initiated in some layer brings about an increase in the temperature; because of the heat conduction, the temperature is raised in the neighboring layer where in turn the chemical reaction is initiated. In this manner the flame is propagated.

Zeldovich, Y B

1951-01-01

33

Premixed turbulent flame calculation  

NASA Technical Reports Server (NTRS)

The importance of turbulent premixed flames in a variety of applications has led to a substantial amount of effort towards improving the understanding of these flames. Although these efforts have increased the understanding, many questions still remain. The use of direct numerical simulation (DNS) in solving these questions is examined.

El-Tahry, S.; Rutland, C. J.; Ferziger, J. H.; Rogers, M. M.

1987-01-01

34

The Flame Tree  

ERIC Educational Resources Information Center

Lewis's own experiences living in Indonesia are fertile ground for telling "a ripping good story," one found in "The Flame Tree." He hopes people will enjoy the tale and appreciate the differences of an unfamiliar culture. The excerpt from "The Flame Tree" will reel readers in quickly.

Lewis, Richard

2004-01-01

35

Candle Flames in Microgravity  

NASA Technical Reports Server (NTRS)

The goal of this work is to study both experimentally and numerically the behavior of a candle flame burning in a microgravity environment. Two space experiments (Shuttle and Mir) have shown the candle flame in microgravity to be small (approximately 1.5 cm diameter), dim blue, and hemispherical. Near steady flames with very long flame lifetimes (up to 45 minutes in some tests) existed for many of the tests. Most of the flames spontaneously oscillated with a period of approximately 1 Hz just prior to extinction). In a previous model of candle flame in microgravity, a porous sphere wetted with liquid fuel simulated the evaporating wick. The sphere, with a temperature equal to the boiling temperature of the fuel, was at the end of an inert cone that had a prescribed temperature. This inert cone produces the quenching effect of the candle wax in the real configuration. Although the computed flame shape resembled that observed in the microgravity experiment, the model was not able to differentiate the effect of wick geometry, e.g., a long vs. a short wick. This paper presents recent developments in the numerical model of the candle flame. The primary focus has been to more realistically account for the actual shape of the candle.

Dietrich, D. L.; Ross, H. D.; Chang, P.; T'ien, J. S.

2001-01-01

36

Brominated Flame Retardants  

EPA Science Inventory

Brominated flame retardants (BFRs) belong to a large class of compounds known as organohalogens. BFRs are currently the largest marketed flame retardant group due to their high performance efficiency and low cost. In the commercial market, more than 75 different BFRs are recogniz...

37

Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames. Appendix K  

NASA Technical Reports Server (NTRS)

The shapes (flame-sheet and luminous-flame boundaries) of steady nonbuoyant round hydrocarbon-fueled laminar-jet diffusion flames in still and coflowing air were studied both experimentally and theoretically. Flame-sheet shapes were measured from photographs using a CH optical filter to distinguish flame-sheet boundaries in the presence of blue C02 and OH emissions and yellow continuum radiation from soot. Present experimental conditions included acetylene-, methane-, propane-, and ethylene-fueled flames having initial reactant temperatures of 300 K, ambient pressures of 4-50 kPa, jet exit Reynolds number of 3-54, initial air/fuel velocity ratios of 0-9 and luminous flame lengths of 5-55 mm; earlier measurements for propylene- and 1,3-butadiene-fueled flames for similar conditions were considered as well. Nonbuoyant flames in still air were observed at micro-gravity conditions; essentially nonbuoyant flames in coflowing air were observed at small pressures to control effects of buoyancy. Predictions of luminous flame boundaries from soot luminosity were limited to laminar smoke-point conditions, whereas predictions of flame-sheet boundaries ranged from soot-free to smoke-point conditions. Flame-shape predictions were based on simplified analyses using the boundary layer approximations along with empirical parameters to distinguish flame-sheet and luminous-flame (at the laminar smoke point) boundaries. The comparison between measurements and predictions was remarkably good and showed that both flame-sheet and luminous-flame lengths are primarily controlled by fuel flow rates with lengths in coflowing air approaching 2/3 lengths in still air as coflowing air velocities are increased. Finally, luminous flame lengths at laminar smoke-point conditions were roughly twice as long as flame-sheet lengths at comparable conditions due to the presence of luminous soot particles in the fuel-lean region of the flames.

Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

38

Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The shapes (flame-sheet and luminous-flame boundaries) of steady nonbuoyant round hydrocarbon-fueled laminar-jet diffusion flames in still and coflowing air were studied both experimentally and theoretically. Flame-sheet shapes were measured from photographs using a CH optical filter to distinguish flame-sheet boundaries in the presence of blue CO2 and OH emissions and yellow continuum radiation from soot. Present experimental conditions included acetylene-, methane-, propane-, and ethylene-fueled flames having initial reactant temperatures of 300 K, ambient pressures of 4-50 kPa, jet exit Reynolds number of 3-54, initial air/fuel velocity ratios of 0-9 and luminous flame lengths of 5-55 mm; earlier measurements for propylene- and 1,3-butadiene-fueled flames for similar conditions were considered as well. Nonbuoyant flames in still air were observed at micro-gravity conditions; essentially nonbuoyant flames in coflowing air were observed at small pressures to control effects of buoyancy. Predictions of luminous flame boundaries from soot luminosity were limited to laminar smokepoint conditions, whereas predictions of flame-sheet boundaries ranged from soot-free to smokepoint conditions. Flame-shape predictions were based on simplified analyses using the boundary layer approximations along with empirical parameters to distinguish flame-sheet and luminous flame (at the laminar smoke point) boundaries. The comparison between measurements and predictions was remarkably good and showed that both flame-sheet and luminous-flame lengths are primarily controlled by fuel flow rates with lengths in coflowing air approaching 2/3 lengths in still air as coflowing air velocities are increased. Finally, luminous flame lengths at laminar smoke-point conditions were roughly twice as long as flame-sheet lengths at comparable conditions due to the presence of luminous soot particles in the fuel-lean region of the flames.

Xu, F.; Dai, Z.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z. G. (Technical Monitor)

2001-01-01

39

Introduction Observations PSF fitting Photometry Results Defocused PSF-fitting Photometry  

E-print Network

Introduction Observations PSF fitting Photometry Results Defocused PSF-fitting Photometry Ro Parviainen Defocused PSF-fitting Photometry #12;Introduction Observations PSF fitting Photometry Results 1 Introduction The light curve Defocused PSF 2 Observations Observations 3 PSF fitting Photometry PSF model 1 PSF

Pinfield, David J.

40

Flame holes and flame disks on the surface of a diffusion flame  

Microsoft Academic Search

Flame holes and flame disks in a laminar axisymmetric counterflow configuration are numerically investigated for unity Lewis number, with the strain rate as the control parameter. The temporal evolution of the topological structure of flame holes and flame disks is described in detail for different representative strain rates. It is found that corresponding to each given strain rate, there exists

Zhanbin Lu; Sandip Ghosal

2004-01-01

41

Cylindrical premixed laminar flames  

SciTech Connect

Activation energy asymptotics are used to analyze the structure and extinction characteristics of a premixed flame in a right circular cylinder enclosing a stretching vortex line. Effects of variable density and of Lewis numbers that differ from unity are taken into account for a one-reactant system with one-step, Arrhenius chemistry. It is shown that the circulation of the vortex does not influence the flame structure, but that the stretch of the vortex alters the structure and the extinction characteristics of the flame, characteristics that involve inter alia abrupt extinction for suitably large rates of stretch at finite radii for all Lewis numbers.

Libby, P.A.; Peters, N.; Williams, F.A.

1989-03-01

42

Flame spread across liquids  

NASA Technical Reports Server (NTRS)

Recent reviews of our understanding of flame spread across liquids show that there are many unresolved issues regarding the phenomenology and causal mechanisms affecting ignition susceptibility, flame spread characteristics, and flame spread rates. One area of discrepancy is the effect of buoyancy in both the uniform and pulsating spread regimes. The approach we have taken to resolving the importance of buoyancy for these flames is: (1) normal gravity (1g) and microgravity (micro g) experiments; and (2) numerical modeling at different gravitational levels. Of special interest to this work, as discussed at the previous workshop, is the determination of whether, and under what conditions, pulsating spread occurs in micro g. Microgravity offers a unique ability to modify and control the gas-phase flow pattern by utilizing a forced air flow over the pool surface.

Ross, Howard D.; Miller, Fletcher; Schiller, David; Sirignano, William

1995-01-01

43

Flame-resistant textiles  

NASA Technical Reports Server (NTRS)

Flame resistance treatment for acid resistant polyamide fibers involving photoaddition of fluorocarbons to surface has been scaled up to treat 10 yards of commercial width (41 in.) fabric. Process may be applicable to other low cost polyamides, polyesters, and textiles.

Fogg, L. C.; Stringham, R. S.; Toy, M. S.

1980-01-01

44

An examination of flame length from vertical turbulent diffusion flames  

SciTech Connect

Literature data on the length of turbulent diffusion flames is examined for the buoyancy through momentum dominated regimes. This data is interpreted through an ad hoc dimensional analysis where the length scale is the Thring-Newby theoretical lateral flame dimension. The nondimensional flame length is shown to be a function of a density weighted Froude number (inverse Richardson number) and a flame to ambient density ratio. Experimental observations on gas turbulent diffusion flames are combined with data for condensing vapor jets and jets in liquid metal combustion. The latter measurements extend the data base and offer new insights into the mechanisms affecting turbulent diffusion flames.

Blake, T.R.; McDonald, M. (Univ. of Massachusetts, Amherst, MA (United States). Mechanical Engineering Dept.)

1993-09-01

45

Detection by Transit Photometry  

NASA Technical Reports Server (NTRS)

A periodic sequence of planetary transits provides a valid detection of an orbiting planet and provides the relative size of the planet and its orbital period. Ancillary measurements of the stellar spectrum and the variations of the star's radial velocity or position combined with stellar models allow the absolute size of the planet and its mass to be obtained. The results of this approach have already shown that the planet orbiting HD209458 has only 70% of the mass of Jupiter, but is nearly 50% larger in radius. Based on models of planetary structure, these results imply that the planet must have spent most of its lifetime so close to the star that it has not been able to cool and contract as have the giant planets in our Solar System. Thus its density is much less than Jupiter and Saturn and is actually less than that of water; i.e., about 0.4 gr/cu cm. If more sensitive measurements of the light curve of stars with closely orbiting planets can be made that provide the varying amplitude of the light reflected by the planet at various phases in its orbit, then characteristics of the planetary atmosphere can be obtained. Potentially, these data can identify major molecular species present in the atmosphere and tell us if clouds are present and yield the phase function of the aerosols. Although such detail cannot be obtained for Earth-size planets because their signal amplitudes are too small, it is possible to get data critical to the determination of the structure of extrasolar planetary systems. In particular, the size distributions and their orbital distributions can be measured by the transit photometry missions now in development. The COROT mission should be able to find large terrestrial planets in short-period orbits while the more ambitious Kepler and Eddington missions should be able to detect planets even smaller than the Earth and at orbital distances that place them in the habitable zone of their stars.

Borucki, William J.; Koch, David G.; Jenkins, Jon M.; DeVincenzi, D. (Technical Monitor)

2002-01-01

46

Flame height measurement of laminar inverse diffusion flames  

SciTech Connect

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed very well with the OH flame height. Flame height predictions using Roper's analysis for circular port burners agreed with measured reaction zone heights when using values for the characteristic diffusion coefficient and/or diffusion temperature somewhat different from those recommended by Roper. The fact that Roper's analysis applies to inverse diffusion flames is evidence that inverse diffusion flames are similar in structure to normal diffusion flames. (author)

Mikofski, Mark A. [Microgravity Combustion Laboratory, University of California, Berkeley, CA 94720 (United States); Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda G. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States)

2006-07-15

47

Flame height measurement of laminar inverse diffusion flames.  

SciTech Connect

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed very well with the OH flame height. Flame height predictions using Roper's analysis for circular port burners agreed with measured reaction zone heights when using values for the characteristic diffusion coefficient and/or diffusion temperature somewhat different from those recommended by Roper. The fact that Roper's analysis applies to inverse diffusion flames is evidence that inverse diffusion flames are similar in structure to normal diffusion flames.

Shaddix, Christopher R.; Williams, Timothy C.; Blevins, Linda Gail; Mikofski, Mark A. (University of California Berkeley)

2005-09-01

48

PHOTOM: Photometry of digitized images  

NASA Astrophysics Data System (ADS)

PHOTOM performs photometry of digitized images. It has two basic modes of operation: using an interactive display to specify the positions for the measurements, or obtaining those positions from a file. In both modes of operation PHOTOM performs photometry using either the traditional aperture method or via optimal extraction. When using the traditional aperture extraction method the target aperture can be circular or elliptical and its size and shape can be varied interactively on the display, or by entering values from the keyboard. Both methods allow the background sky level to be either sampled interactively by the manual positioning of an aperture, or automatically from an annulus surrounding the target object. PHOTOM is the photometry backend for the GAIA tool (ascl:1403.024) and is part of the Starlink software collection (ascl:1110.012).

Eaton, Nicholas; Draper, Peter W.; Allan, Alasdair; Naylor, Tim; Mukai, Koji; Currie, Malcolm J.; McCaughrean, Mark

2014-05-01

49

An examination of flame length from vertical turbulent diffusion flames  

Microsoft Academic Search

Literature data on the length of turbulent diffusion flames is examined for the buoyancy through momentum dominated regimes. This data is interpreted through an ad hoc dimensional analysis where the length scale is the Thring-Newby theoretical lateral flame dimension. The nondimensional flame length is shown to be a function of a density weighted Froude number (inverse Richardson number) and a

T. R. Blake; M. McDonald

1993-01-01

50

Dynamics of Swirling Flames  

NASA Astrophysics Data System (ADS)

In many continuous combustion processes, such as those found in aeroengines or gas turbines, the flame is stabilized by a swirling flow formed by aerodynamic swirlers. The dynamics of such swirling flames is of technical and fundamental interest. This article reviews progress in this field and begins with a discussion of the swirl number, a parameter that plays a central role in the definition of the flow structure and its response to incoming disturbances. Interaction between the swirler response and incoming acoustic perturbations generates a vorticity wave convected by the flow, which is accompanied by azimuthal velocity fluctuations. Axial and azimuthal velocities in turn define the flame response in terms of heat--release rate fluctuations. The nonlinear response of swirling flames to incoming disturbances is conveniently represented with a flame describing function (FDF), in other words, with a family of transfer functions depending on frequency and incident axial velocity amplitudes. The FDF, however, does not reflect all possible nonlinear interactions in swirling flows. This aspect is illustrated with experimental data and some theoretical arguments in the last part of this article, which concerns the interaction of incident acoustic disturbances with the precessing vortex core, giving rise to nonlinear fluctuations at the frequency difference.

Candel, Sébastien; Durox, Daniel; Schuller, Thierry; Bourgouin, Jean-François; Moeck, Jonas P.

2014-01-01

51

Flame resistant elastic elastomeric fibers  

NASA Technical Reports Server (NTRS)

Development of materials to improve flame resistance of elastic elastomeric fibers is discussed. Two approaches, synthesis of polyether based urethanes and modification of synthesized urethanes with flame ratardant additives, are described. Specific applications of both techniques are presented.

Howarth, J. T.; Massucco, A. A.

1972-01-01

52

Bigger and Brighter Flame Tests.  

ERIC Educational Resources Information Center

Describes a method for flame test demonstrations that provides a way to set up quickly, clean up, and produce a large and very intense flame that can be seen easily in a 300-seat lecture auditorium. (JRH)

Dalby, David K.; Mosher, Melvyn M.

1996-01-01

53

Rubens Flame-Tube Demonstration.  

ERIC Educational Resources Information Center

Investigates and explains the phenomenon associated with Rubens flame-tube demonstration, specifically the persistance of flames at regular intervals along the tube for few minutes after the gas is turned off. (GA)

Ficken, George W.; Stephenson, Francis C.

1979-01-01

54

A Dramatic Flame Test Demonstration.  

ERIC Educational Resources Information Center

Flame tests are used for demonstration of atomic structure. Describes a demonstration that uses spray bottles filled with methanol and a variety of salts to produce a brilliantly colored flame. (Contains 11 references.) (ASK)

Johnson, Kristin A.; Schreiner, Rodney

2001-01-01

55

Flame propagation through periodic vortices  

SciTech Connect

The discovery of a new class of Navier-Stokes solutions representing steady periodic stretched vortices offers a useful test-bed for examining interactions between flames and complex flow-fields. After briefly describing these vortex solutions and their wide-ranging parameterization in terms of wavelength and amplitude, this article examines their effect on flames of constant normal propagation speed as observed through numerical solutions of an eikonal equation. Over certain ranges of vortex amplitude and flame-speed, a corridor of enhanced flame passage is seen to be created as a leading flame-tip managers to leap-frog between successive vortices. However, for large enough amplitudes of vorticity or small enough flame-speeds, the flame fails to be able to benefit from the advection due to the vortices. It is shown that the leading tips of such flames are effectively trapped by the stretched vortices.

Dold, J.W.; Kerr, O.S. [Univ. of Bristol (United Kingdom). School of Mathematics] [Univ. of Bristol (United Kingdom). School of Mathematics; Nikolova, I.P. [Inst. of Mechanics and Biomechanics, Sofia (Bulgaria)] [Inst. of Mechanics and Biomechanics, Sofia (Bulgaria)

1995-02-01

56

Flame retardant spandex type polyurethanes  

NASA Technical Reports Server (NTRS)

Flame retardant elastomeric compositions were developed, comprised of: (1) spandex type polyurethane having incorporated into the polymer chain, halogen containing polyols; (2) conventional spandex type polyurethanes in physical admixture flame retardant additives; and (3) fluoroelastomeric resins in physical admixture with flame retardant additives. Methods of preparing fibers of the flame retardant elastomeric materials are presented and articles of manufacture comprised of the elastomeric materials are mentioned.

Howarth, J. T.; Sheth, S.; Sidman, K. R.; Massucco, A. A. (inventors)

1978-01-01

57

NOX FORMATION IN CO FLAMES  

EPA Science Inventory

The report gives results of an experimental study to determine if early NO and NO2 can be observed in CO flames, since prompt NO is not anticipated and since HO2 levels might be expected to be lower in CO flames. (Previous studies of NO and NO2 production in methane flames with a...

58

Flame resistant elastic elastomeric fiber  

NASA Technical Reports Server (NTRS)

Compositions exhibit elastomeric properties and possess various degrees of flame resistance. First material polyurethane, incorporates halogen containing polyol and is flame resistant in air; second contains spandex elastomer with flame retardant additives; and third material is prepared from fluorelastomer composition of copolymer of vinylidene fluoride and hexafluoropropylene.

Howarth, J. T.; Sheth, S.; Massucco, A. A.; Sidman, K. R.

1974-01-01

59

PSF Photometry Lecture April XX 2004  

E-print Network

PSF Photometry Lecture April XX 2004 Vitaliy Fadeyev Why do PSF-fitting The simple aperture photometry has an assumption of linearly-varying background in the aperture's vicinity. Choice of (optimal Photometry Lecture April XX 2004 Vitaliy Fadeyev Crowded field example Even when nominally well separated

Masci, Frank

60

TCP'S USER MANUAL REAL TIME PHOTOMETRY (RTP)  

E-print Network

TCP'S USER MANUAL REAL TIME PHOTOMETRY (RTP) Last modified: 2011-09-20 This version by: Jorge manual ­ Real Time Photometry (RTP) 20/09/2011 2 1. INTRODUCTION CCD images normally require a lot of calibration work to be rendered useful for high precision photometry. It is therefore not unusual to spend

61

Flame Tests Performed Safely  

NSDL National Science Digital Library

The trend toward inquiry-based learning is providing today's students with a more enriching education. When implementing inquiry it is important to recognize the great number of safety concerns that accompany this paradigm shift. Fortunately, with some consideration, teachers can shape students' laboratory experiments into safe and valuable learning experiences. One very popular demonstration is the flame test. The author provides a safe and effective alternative to the traditional flame test without the traditional use of methanol, and provides strategies that allow students to safely gain a better understanding of the atomic structure, the nature of light, and the electromagnetic spectrum.

Deborah Dogancay

2005-09-01

62

CCD Photometry of Gliese 372  

NASA Astrophysics Data System (ADS)

We present optical photometry of the M-dwarf binary Gliese 372. We have searched for the predicted eclipses of this binary (Harlow 1996) using a 16-inch telescope and a CCD camera built from "The CCD Camera Cookbook." We set limits on the presence of eclipses, and on the photometric variability outside of eclipse.

Ramseyer, T. F.; Davis, C.; Lasley, C.; Leonard, C.; Portoni, A.

1997-05-01

63

Triaxial Burke-Schumann Flames with Applications to Flame Synthesis  

NASA Technical Reports Server (NTRS)

The problem of a flame generated by three coaxial flows is solved by extending the Burke-Schumann methodology to include a third stream. The solution is particularly relevant to flame synthesis wherein multiple tubes are often employed either to introduce inert as a diffusion barrier or to introduce more than two reactants. The general problem is solved where the inner and outer tubes contain reactants and the middle tube contains either an inert or a third reactant. Relevant examples are considered and the results show that the triaxial Burke-Schumann flame can be substantially more complicated than the traditional Burke-Schumann flame. When the middle flow is inert the flame temperature is no longer constant but increases axially, reaching a maximum at the flame centerline. At the exit the flame does not sit on the tube exit but instead resides between the inner and outer tubes, resulting in an effective barrier for particle build-up on the burner rim. For the case of a third reactant in the middle flow, synthesis chemistry where the inner reaction is endothermic and the outer reaction is exothermic is considered. In addition to showing the flame temperature and flame shape, the results identify conditions wherein reaction is not possible due to insufficient heat transfer from the outer flame to support the inner flame reaction.

Chao, B. H.; Axelbaum, R. L.; Gokoglu, Suleyman (Technical Monitor)

2000-01-01

64

Vortex/Flame Interactions in Microgravity Pulsed Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

Significant differences have been observed between the structure of laminar, transitional, and turbulent flames under downward, upward, and microgravity conditions. These include flame height, jet shear layer, flame instability, flicker, lift-off height, blow-off Reynolds number, and radiative properties. The primary objective of this investigation is to identify the mechanisms involved in the generation and interaction of large-scale structures in microgravity flames. This involves a study of vortex/flame interactions in a space-flight experiment utilizing a controlled, well-defined set of disturbances imposed on a laminar diffusion flame. The results provide a better understanding of the naturally occurring structures that are an inherent part of microgravity turbulent flames. The paper presents the current progress in this program.

Bahadori, M. Y.; Hegde, U.; Stocker, D. P.

2001-01-01

65

"Magic Eraser" Flame Tests  

ERIC Educational Resources Information Center

Cleaning erasers are used to support methanol-fueled flame tests. This safe demonstration technique requires only small quantities of materials, provides clean colors for up to 45 seconds, and can be used in the classroom or the auditorium. (Contains 1 note.)

Landis, Arthur M.; Davies, Malonne I.; Landis, Linda

2009-01-01

66

RDX flame structure  

SciTech Connect

Nonintrusive diagnostics were used to measure temperature and species profiles during neat RDX deflagration at 1 atm. UV-visible absorption was measured to obtain absolute concentration profiles of NO, NO{sub 2}, CN, NH, H{sub 2}CO, and OH. Temperature and species concentrations were obtained by spectral fitting. Planar laser-induced fluorescence (PLIF) of these same species was also measured to obtain two-dimensional (2D) profiles in the flame with excellent spatial resolution. The flame structure is characterized by a dark zone close to the surface and a visible flame sheet above the dark zone. For CO{sub 2} laser-assisted deflagration, the narrow flame sheet NH profile peaks 2.3 mm above the surface at a value of 100 ppm. The CN profile is slightly wider and peaks at 2.5 mm at a value of 660 ppm. The OH profile peaks outside the CN/NH flame sheet with a mole fraction of 0.055. The dark zone species studied here were NO{sub 2} and NO. The NO{sub 2} peaks very close to the surface at about 0.17 mole fraction and decays rapidly to 0 at 1.5 mm. Close to the surface, the NO mole fraction is about 0.2 and falls sharply to 0.05 at 2.5 mm as NO is consumed in the CN/NH flame sheet. No formaldehyde was detected. Rotational temperature profiles were measured from OH PLIF and NO absorption spectra. The NO gas temperature near the surface is in good agreement with prior thermocouple measurements. The temperature rises sharply to about 1,500 K at 0.3 mm and then turns over to a much more gradual slope in the dark zone. At about 2 mm, it becomes steeper again and finally levels out to 2,600 K at 3.0 mm, at the top edge of the CN flame sheet.

Hanson-Parr, D.; Parr, T. [Naval Air Warfare Center, China Lake, CA (United States)

1994-12-31

67

33 CFR 154.822 - Detonation arresters, flame arresters, and flame screens.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Detonation arresters, flame arresters, and flame screens. 154.822 Section 154.822 Navigation...Control Systems § 154.822 Detonation arresters, flame arresters, and flame screens. (a) Each...

2010-07-01

68

UBVRI photometry of red stars  

NASA Astrophysics Data System (ADS)

A total of 50 Mira- and SR-type red variable stars were observed by means of the photoelectric photometry UBVRI Kron-Cousins system. In addition, 15 nearby red dwarf stars having spectral subtypes similar to those of Mira stars at maximum were observed in order to show that the conversion of the natural system into the Landolt (1983) standard system can be made for stars as red as the Mira variables, in spite of the shortage of standard late M-type stars. The relationship function and spectral type-color index scale on the Johnson system was converted into the present system. By means of VRI photometry, the spectral subtype can immediately be determined in different phases of the light curve. SR variables have the same color indices and spectral subclasses as Mira variables.

Celis S., L.

1986-03-01

69

Candle Flames in Microgravity Video  

NASA Technical Reports Server (NTRS)

This video of a candle flame burning in space was taken by the Candle Flames in Microgravity (CFM) experiment on the Russian Mir space station. It is actually a composite of still photos from a 35mm camera since the video images were too dim. The images show a hemispherically shaped flame, primarily blue in color, with some yellow early int the flame lifetime. The actual flame is quite dim and difficult to see with the naked eye. Nearly 80 candles were burned in this experiment aboard Mir. NASA scientists have also studied how flames spread in space and how to detect fire in microgravity. Researchers hope that what they learn about fire and combustion from the flame ball experiments will help out here on Earth. Their research could help create things such as better engines for cars and airplanes. Since they use very weak flames, flame balls require little fuel. By studying how this works, engineers may be able to design engines that use far less fuel. In addition, microgravity flame research is an important step in creating new safety precautions for astronauts living in space. By understanding how fire works in space, the astronauts can be better prepared to fight it.

1997-01-01

70

Flame height measurement of laminar inverse diffusion flames  

Microsoft Academic Search

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed

Christopher R. Shaddix; Timothy C. Williams; Linda Gail Blevins; Mark A. Mikofski

2005-01-01

71

Flame height measurement of laminar inverse diffusion flames  

Microsoft Academic Search

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed

Mark A. Mikofski; Timothy C. Williams; Christopher R. Shaddix; Linda G. Blevins

2006-01-01

72

Flame height measurement of laminar inverse diffusion flames  

Microsoft Academic Search

Flame heights of co-flowing cylindrical ethylene–air and methane–air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed

Mark A. Mikofski; Timothy C. Williams; Christopher R. Shaddix; Linda G. Blevins

2006-01-01

73

Vortex/Flame Interactions in Microgravity Pulsed Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The problem of vortex/flame interaction is of fundamental importance to turbulent combustion. These interactions have been studied in normal gravity. It was found that due to the interactions between the imposed disturbances and buoyancy induced instabilities, several overall length scales dominated the flame. The problem of multiple scales does not exist in microgravity for a pulsed laminar flame, since there are no buoyancy induced instabilities. The absence of buoyant convection therefore provides an environment to study the role of vortices interacting with flames in a controlled manner. There are strong similarities between imposed and naturally occurring perturbations, since both can be described by the same spatial instability theory. Hence, imposing a harmonic disturbance on a microgravity laminar flame creates effects similar to those occurring naturally in transitional/turbulent diffusion flames observed in microgravity. In this study, controlled, large-scale, axisymmetric vortices are imposed on a microgravity laminar diffusion flame. The experimental results and predictions from a numerical model of transient jet diffusion flames are presented and the characteristics of pulsed flame are described.

Bahadori, M. Y.; Hegde, U.; Stocker, D. P.

1999-01-01

74

Solid propellant flame structure  

SciTech Connect

Planar Laser Induced Fluorescence (PLIF), UV/Vis Absorption, and thermocouple measurements were done for HNF, RDX, HMX, and XM39 deflagration with and without CO{sub 2} laser-support. RDX and especially HNF have very short self-deflagration flame length scales. HMX and XM39 have taller self-deflagration flames. XM39 has a marked dark zone with plateau temperature about 1,400 K. RDX`s dark zone, present under laser supported deflagration, collapses when the external laser flux is removed. PLIF was used to measure the 2D NH, OH, and CN species profiles for these materials and OH temperature profile for RDX and HNF under non-laser supported conditions. The best spatial resolution for the RDX PLIF was about 4 {micro}m. Sandwiches of HNF and various binders were studied with PLIF and while obvious diffusion flames were present at low pressure, they are weak and are not expected to be burn rate controlling. 34 refs., 18 figs.

Parr, T.P.; Hanson-Parr, D.M. [Naval Air Warfare Center, China Lake, CA (United States). Combustion Diagnostics Lab.

1996-07-01

75

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Flame resistance. 14.20 Section 14...PRODUCTS REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS Technical Requirements § 14.20 Flame resistance. Conveyor belts for...

2010-07-01

76

Asteroid photometry program at Modra observatory  

NASA Astrophysics Data System (ADS)

Description of the starting CCD photometry program, parallel to NEO (Near-Earth Object) follow-up, at Modra observatory is given, targeting asteroids, especially NEO, in an effort to extend the database of their physical characteristics. With the gradual increase of observation time for photometry, there is a need for automated processing of data and observation planning. Custom photometry software implemented in Java is explained and comparison of different reduction techniques provided.

Világi, J.

2002-11-01

77

Flame holes and flame disks on the surface of a diffusion flame  

NASA Astrophysics Data System (ADS)

Flame holes and flame disks in a laminar axisymmetric counterflow configuration are numerically investigated for unity Lewis number, with the strain rate as the control parameter. The temporal evolution of the topological structure of flame holes and flame disks is described in detail for different representative strain rates. It is found that corresponding to each given strain rate, there exists a critical hole (disk) radius r_c that separates the shrinking and expanding hole (disk) regimes. The value of r_c decreases monotonically with the increase (decrease) of strain rate and reaches a finite minimum at the extinction (ignition) limit of the strain rate, which indicates that one cannot ignite a mixing layer by an infinitesimal energy source, nor can one quench a diffusion flame by making an infinitesimal extinction hole on it. An examination of the phase diagrams of flame holes (disks) justifies the existence of a unique edge-flame velocity v_f as a smooth continuous function of the hole (disk) radius r_f in the entire range 0 < r_f < infty, with the strain rate (or equivalently, Damköhler number) as a parameter. For the flame hole case, it is found that in the final stage of collapse of a hole, the edge-flame velocity is essentially proportional to the inverse of the hole radius, except when the strain rate is very close to the extinction limit. Flame interactions induced by overlapping of pre-heat zones are mainly responsible for the acceleration of the edge-flame velocity when the hole radius approaches zero, and it is further enhanced by the focusing effects of hole curvature in the plane of the stoichiometric surface. For the flame disk, the increasing heat loss rate plays a major role on the acceleration of the shrinking speed when the disk radius approaches zero.

Lu, Zhanbin; Ghosal, Sandip

2004-08-01

78

SPA, "The Stellar Photometry Assistant"  

NASA Astrophysics Data System (ADS)

SPA is a stand alone software package for high speed photometry reduction and analysis. The goal of SPA is to be simple, powerful and intuitive. SPA was born out of complications studying the pulsating DB white dwarf EC20058-5234 (QuTel) due to the proximity of its companions. SPA addresses the Whole Earth Telescope's (Nather et al. 1990) demand for large scale rapid data reduction from multiple sites. SPA is being developed in MATLAB by the Delaware Asteroseismic Research Center (DARC) in collaboration with the University of Delaware and the Mount Cuba Astronomical Observatory.

Dalessio, J.; Provencal, J. L.; Shipman, H. L.

2009-06-01

79

Effects of Flame Structure and Hydrodynamics on Soot Particle Inception and Flame Extinction in Diffusion Flames  

NASA Technical Reports Server (NTRS)

This paper summarizes recent studies of the effects of stoichiometric mixture fraction (structure) and hydrodynamics on soot particle inception and flame extinction in diffusion flames. Microgravity experiments are uniquely suited for these studies because, unlike normal gravity experiments, they allow structural and hydrodynamic effects to be independently studied. As part of this recent flight definition program, microgravity studies have been performed in the 2.2 second drop tower. Normal gravity counterflow studies also have been employed and analytical and numerical models have been developed. A goal of this program is to develop sufficient understanding of the effects of flame structure that flames can be "designed" to specifications - consequently, the program name Flame Design. In other words, if a soot-free, strong, low temperature flame is required, can one produce such a flame by designing its structure? Certainly, as in any design, there will be constraints imposed by the properties of the available "materials." For hydrocarbon combustion, the base materials are fuel and air. Additives could be considered, but for this work only fuel, oxygen and nitrogen are considered. Also, the structure of these flames is "designed" by varying the stoichiometric mixture fraction. Following this line of reasoning, the studies described are aimed at developing the understanding of flame structure that is needed to allow for optimum design.

Axelbaum, R. L.; Chen, R.; Sunderland, P. B.; Urban, D. L.; Liu, S.; Chao, B. H.

2001-01-01

80

Not Just Another Old Flame  

NSDL National Science Digital Library

This NASA website explores flames in microgravity. It shows photos of flames in space. Also, it shows a related experiment in which spiral patterns are observed when a slowly rotating disc is set aflame. Images and links to more information are provided.

2007-07-03

81

Flame retarded asphalt blend composition  

SciTech Connect

This patent describes a flame retarded asphalt composition consisting essentially of a blend of: (a) thermoplastic elastomer modified bitumen; (b) 20-30 wt % inert filler; (c) 1-20 wt % of at least one halogenated flame retardant; and (d) 1-5 wt % of at least one inorganic phosphorus containing compound selected from the group consisting of ammonium phosphate compounds and red phosphorus.

Walters, R.B.

1987-04-21

82

Statistics of premixed flame cells  

NASA Technical Reports Server (NTRS)

The statistics of random cellular patterns in premixed flames are analyzed. Agreement is found with a variety of topological relations previously found for other networks, namely, Lewis's law and Aboav's law. Despite the diverse underlying physics, flame cells are shown to share a broad class of geometric properties with other random networks-metal grains, soap foams, bioconvection, and Langmuir monolayers.

Noever, David A.

1991-01-01

83

Asteroid Analysis Using Lightcurve Photometry  

NASA Astrophysics Data System (ADS)

During the summer of 2011 data was taken of asteroid 3807 Pagels, a mid-sized asteroid located in the main asteroid belt in order to identify its rotational period. The asteroid 3807 Pagels is a poorly studied main belt asteroid that has little information recorded about its physical features. Time-series photometry of 3807 Pagels was obtained with a 16-inch telescope connected to a CCD camera located at the Texas A&M University - Commerce Observatory. CCD images were taken continuously with five minute exposure times through the standard broadband V filter. The data was then analyzed using the MPO Canopus program which utilized comparison stars within each CCD image to determine differential photometry and then generate a lightcurve for the asteroid. The final lightcurve did not show a complete rotational period for the asteroid. Thus, additional observations are needed in order to precisely determine 3807 Pagels rotational period. This research is the first steps of a long process of determining more information about the many mid-sized asteroids located in the asteroid belt for the potential of being able to classify these asteroids by their physical characteristics.

Zimmerman, Jessica

2011-10-01

84

Fast photometry with small telescopes  

NASA Astrophysics Data System (ADS)

Facility instruments on major telescopes rarely provide photometry on timescales into the sub-second range. The development of dedicated high-time resolution detectors that could be attached as guest instruments was therefore natural to follow up with optical observations on many highly time variable astronomical objects. Such sources were often discovered first in the radio range (e.g. pulsars, quasars) or with X- and gamma-ray satellites (X-ray binaries, cataclysmic variables, gamma-ray bursts). Although telescopes in the 4 - 8m class would be nice to have for high-time resolution astronomy (HTRA) the access is often oversubscribed. Many currently active HTRA instruments were started on smaller telescopes in the 1-3m class, which provide the flexibility and observation time needed for the observation of highly variable stars. We describe the basic detector types, i.e. fast imaging or photon counting, and current projects. Based on our experience with the fast timing photo-polarimeter OPTIMA (Optical Timing Analyzer), we review some observational constraints on meter-class telescopes. We demonstrate the 'scientific power' of very fast photometry, done with OPTIMA and similar systems on small telescopes, with selected results for a black hole binary, an optical transient magnetar, and the Crab pulsar. %

Kanbach, G.; Rau, A.; S?owikowska, A.

2014-03-01

85

Dynamics and structure of stretched flames  

SciTech Connect

This program aims to gain fundamental understanding on the structure, geometry, and dynamics of laminar premixed flames, and relate these understanding to the practical issues of flame extinction and stabilization. The underlying fundamental interest here is the recent recognition that the response of premixed flames can be profoundly affected by flame stretch, as manifested by flow nonuniformity, flame curvature, and flame/flow unsteadiness. As such, many of the existing understanding on the behavior of premixed flames need to be qualitatively revised. The research program consists of three major thrusts: (1) detailed experimental and computational mapping of the structure of aerodynamically-strained planar flames, with emphasis on the effects of heat loss, nonequidiffusion, and finite residence time on the flame thickness, extent of incomplete reaction, and the state of extinction. (2) Analytical study of the geometry and dynamics of stretch-affected wrinkled flame sheets in simple configurations, as exemplified by the Bunsen flame and the spatially-periodic flame, with emphasis on the effects of nonlinear stretch, the phenomena of flame cusping, smoothing, and tip opening, and their implications on the structure and burning rate of turbulent flames. (3) Stabilization and blowoff of two-dimensional inverted premixed and stabilization and determining the criteria governing flame blowoff. The research is synergistically conducted through the use of laser-based diagnostics, computational simulation of the flame structure with detailed chemistry and transport, and mathematical analysis of the flame dynamics.

Law, C.K. [Princeton Univ., NJ (United States)

1993-12-01

86

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry,  

E-print Network

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry flicker photometry (HFP), and minimally distinct border (MDB). For HBM, subjects varied the relative compared with those obtained on two other tasks: hetero- chromatic flicker photometry (HFP) and minimally

Dobkins, Karen R.

87

Flame Resistant Foam  

NASA Technical Reports Server (NTRS)

Solimide manufactured by Imi-Tech Corporation, is a lightweight fire resistant material produced under a manufacturing process that allows it to be uniformly foamed. Can be produced in a variety of densities and structural configurations and remains resilient under exposure to temperatures ranging from minus 300 to plus 500 degrees Fahrenheit. Is resistant to open flame and generates virtually no smoke or toxic by-products. Used in aircraft for its superior damping characteristics, lighter weight and fire barrier properties, it's also applicable to ships and surface transportation systems such as transit cars, trains, buses and automobiles.

1984-01-01

88

An optimal extraction algorithm for imaging photometry  

Microsoft Academic Search

This paper is primarily an investigation of whether the `optimal extraction' techniques used in CCD spectroscopy can be applied to imaging photometry. It is found that using such techniques provides a gain of around 10 per cent in signal-to-noise ratio over normal aperture photometry. Formally, it is shown to be equivalent to profile fitting, but offers advantages of robust error

Tim Naylor

1998-01-01

89

Flame retardant polyphosphazenes  

NASA Technical Reports Server (NTRS)

Six polyphosphazene compositions were prepared by reaction of three bis-tertiary phosphines with two phenyl-s-triazine derived diazides. All six polyphosphazenes produced were completely characterized, four of them were furthermore subjected to isothermal gravimetric analysis, smoke density measurements, flammability and oxidative thermal degradation testing. The results of the characterization studies indicate that only low molecular weight oligomers, possibly of a cyclic structure, were obtained in the polymerization reactions. Despite this, however, two of the materials showed no weight loss after 96 hr at 200 C, one did not autoignite at 500 C in air, and all four self extinguished when exposed to a flame as soon as contact between flame and resin was lost. The only toxic decomposition products to be concerned about were found to be hydrogen cyanide and benzene. Under the conditions employed it was proven, however, that the quantities of toxic products are greatly reduced if no ignition takes place, e.g., if thermal decomposition proceeds at a sufficiently low rate.

Paciorek, K. L.; Karle, D. W.; Kratzer, R. H.

1973-01-01

90

Candle Flames in Non-Buoyant Atmospheres  

NASA Technical Reports Server (NTRS)

This paper addresses the behavior of a candle flame in a long-duration, quiescent microgravity environment both on the space Shuttle and the Mir Orbiting Station. On the Shuttle, the flames became dim blue after an initial transient where there was significant yellow (presumably soot) in the flame. The flame lifetimes were typically less than 60 seconds. The safety-mandated candlebox that contained the candle flame inhibited oxygen transport to the flame and thus limited the flame lifetime. The flames on the Mir were similar, except that the yellow luminosity persisted longer into the flame lifetime because of a higher initial oxygen concentration, The Mir flames burned for as long as 45 minutes. The difference in the flame lifetime between the Shuttle and Mir flames was primarily the redesigned candlebox that did not inhibit oxygen transport to the flame. In both environments, the flame intensity and the height-to-width ratio gradually decreased as the ambient oxygen content in the sealed chamber slowly decreased. Both sets of experiments showed spontaneous, axisymmetric flame oscillations just prior to extinction. The paper also presents a numerical model of a candle flame. The formulation is two-dimensional and time-dependent in the gas phase with constant specific heats, thermal conductivity and Lewis number (although different species can have different Lewis numbers), one-step finite-rate kinetics, and gas-phase radiative losses from CO2 and H2O. The treatment of the liquid/wick phase assumes that the, fuel evaporates from a constant diameter sphere connected to an inert cone. The model predicts a steady flame with a shape and size quantitatively similar to the Shuttle and Mir flames. The computation predicts that the flame size will increase slightly with increasing ambient oxygen mole fraction. The model also predicts pre-extinction flame oscillations if the rate of decrease in ambient oxygen is small enough, such as that which would occur for a flame burning in a sealed ambient.

Dietrich, D. L.; Ross, H. D.; Shu, Y.; Chang, P.; Tien, J. S.

2000-01-01

91

The Cool Flames Experiment  

NASA Technical Reports Server (NTRS)

A space-based experiment is currently under development to study diffusion-controlled, gas-phase, low temperature oxidation reactions, cool flames and auto-ignition in an unstirred, static reactor. At Earth's gravity (1g), natural convection due to self-heating during the course of slow reaction dominates diffusive transport and produces spatio-temporal variations in the thermal and thus species concentration profiles via the Arrhenius temperature dependence of the reaction rates. Natural convection is important in all terrestrial cool flame and auto-ignition studies, except for select low pressure, highly dilute (small temperature excess) studies in small vessels (i.e., small Rayleigh number). On Earth, natural convection occurs when the Rayleigh number (Ra) exceeds a critical value of approximately 600. Typical values of the Ra, associated with cool flames and auto-ignitions, range from 104-105 (or larger), a regime where both natural convection and conduction heat transport are important. When natural convection occurs, it alters the temperature, hydrodynamic, and species concentration fields, thus generating a multi-dimensional field that is extremely difficult, if not impossible, to be modeled analytically. This point has been emphasized recently by Kagan and co-workers who have shown that explosion limits can shift depending on the characteristic length scale associated with the natural convection. Moreover, natural convection in unstirred reactors is never "sufficiently strong to generate a spatially uniform temperature distribution throughout the reacting gas." Thus, an unstirred, nonisothermal reaction on Earth does not reduce to that generated in a mechanically, well-stirred system. Interestingly, however, thermal ignition theories and thermokinetic models neglect natural convection and assume a heat transfer correlation of the form: q=h(S/V)(T(bar) - Tw) where q is the heat loss per unit volume, h is the heat transfer coefficient, S/V is the surface to volume ratio, and (T(bar) - Tw ) is the spatially averaged temperature excess. This Newtonian form has been validated in spatially-uniform, well-stirred reactors, provided the effective heat transfer coefficient associated with the unsteady process is properly evaluated. Unfortunately, it is not a valid assumption for spatially-nonuniform temperature distributions induced by natural convection in unstirred reactors. "This is why the analysis of such a system is so difficult." Historically, the complexities associated with natural convection were perhaps recognized as early as 1938 when thermal ignition theory was first developed. In the 1955 text "Diffusion and Heat Exchange in Chemical Kinetics", Frank-Kamenetskii recognized that "the purely conductive theory can be applied at sufficiently low pressure and small dimensions of the vessel when the influence of natural convection can be disregarded." This was reiterated by Tyler in 1966 and further emphasized by Barnard and Harwood in 1974. Specifically, they state: "It is generally assumed that heat losses are purely conductive. While this may be valid for certain low pressure slow combustion regimes, it is unlikely to be true for the cool flame and ignition regimes." While this statement is true for terrestrial experiments, the purely conductive heat transport assumption is valid at microgravity (mu-g). Specifically, buoyant complexities are suppressed at mu-g and the reaction-diffusion structure associated with low temperature oxidation reactions, cool flames and auto-ignitions can be studied. Without natural convection, the system is simpler, does not require determination of the effective heat transfer coefficient, and is a testbed for analytic and numerical models that assume pure diffusive transport. In addition, mu-g experiments will provide baseline data that will improve our understanding of the effects of natural convection on Earth.

Pearlman, Howard; Chapek, Richard; Neville, Donna; Sheredy, William; Wu, Ming-Shin; Tornabene, Robert

2001-01-01

92

Numerical investigations of gaseous spherical diffusion flames  

Microsoft Academic Search

Spherical diffusion flames have several unique characteristics that make them attractive from experimental and theoretical perspectives. They can be modeled with one spatial dimension, which frees computational resources for detailed chemistry, transport, and radiative loss models. This dissertation is a numerical study of two classes of spherical diffusion flames: hydrogen micro-diffusion flames, emphasizing kinetic extinction, and ethylene diffusion flames, emphasizing

Vivien R. Lecoustre

2009-01-01

93

Candle Flames in Non-Buoyant Atmospheres  

Microsoft Academic Search

This paper addresses the behavior of a candle flame in a long-duration, quiescent microgravity environment both on the space Shuttle and the Mir Orbiting Station. On the Shuttle, the flames became dim blue after an initial transient where there was significant yellow (presumably soot) in the flame. The flame lifetimes were typically less than 60 seconds. The safety-mandated candlebox that

D. L. DIETRICH; H. D. ROSS; Y. SHU; P. CHANG; J. S. TIEN

2000-01-01

94

The 2060 Chiron: CCD photometry  

NASA Technical Reports Server (NTRS)

R-band CCD photometry of 2060 was carried out on nine nights in Nov. and Dec. 1986. The rotation period is 5.9181 + or - 0.0003 hr and the peak to peak lightcurve amplitude is 0.088 + or - 0.0003 mag. Photometric parameters are H sub R = 6.24 + or - 0.02 mag and G sub R = + or - 0.15, though formal errors may not be realistic. The lightcurve has two pairs of extrema, but its asymmetry, as evidenced by the presence of significant odd Fourier harmonics, suggests macroscopic surface irregularities and/or the presence of some large scale albedo variegation. The observational rms residual is + or - 0.015 mag. On time scales from minutes to days there is no evidence for nonperiodic (cometary) brightness changes at the level of a few millimagnitudes.

Bus, Schelte J.; Bowell, Edward; Harris, Alan W.

1987-01-01

95

Unsteady effects on flame extinction limits during gaseous and two-phase flame\\/vortex interactions  

Microsoft Academic Search

In highly fluctuating flows, it happens that high values of the strain-rate do not induce extinction of the flame front. Unsteady effects minimize the flame response to rapidly varying strain fields. In the present study, the effects of time-dependent flows on non-premixed flames are investigated during flame\\/vortex interactions. Gaseous flames and spray flames in the external sheath combustion regime are

A. Lemaire; K. Zähringer; T. R. Meyer; J. C. Rolon

2005-01-01

96

INTRODUCTION TO BROMINATED FLAME RETARDANTS  

EPA Science Inventory

Brominated flame retardants (BFRs) are a large and diverse class of major industrial products used to provide fire safety. Tetrabromobisphenol A (TBBPA), Hexabromocylocodecane (HBCD), and Polybrominated Diphenyl Ethers (PBDEs) are the major commercial compounds. TBBPA is a react...

97

Making Thermoplastics Flame-Resistant  

NASA Technical Reports Server (NTRS)

Inorganic hydrate-salt filler coated with elastomer containing acidic groups imparts flame and smoke retardancy to thermoplastics while preventing degradation of impact resistance that results from high filler loadings in thermoplastic.

Mueller, W. A.; Ingham, J. D.; Reilly, W. W.

1984-01-01

98

Neurotoxicity of brominated flame retardants  

EPA Science Inventory

Polybrominated diphenyl ethers (PBDEs) have been commonly used as commercial flame retardants in a variety of products including plastics and textiles. Despite their decreasing usage worldwide, congeners continue to accumulate in the environment, including soil, dust, food, anima...

99

An Introduction to Astronomical Photometry Using CCDs W. Romanishin  

E-print Network

An Introduction to Astronomical Photometry Using CCDs W. Romanishin University of Oklahoma wjr astrophysics major to photometry in the optical region of the spectrum of astronomical objects using CCD telescope time as photometry. That said, it is still obvious that imaging photometry is an important part

Ellingson, Steven W.

100

An Introduction to Astronomical Photometry Using CCDs W. Romanishin  

E-print Network

An Introduction to Astronomical Photometry Using CCDs W. Romanishin University of Oklahoma wjr for the college astrophysics major to photometry in the optical region of the spectrum of astronomical objects telescope time as photometry. That said, it is still obvious that imaging photometry is an important part

Masci, Frank

101

WFPC2 Stellar Photometry with HSTphot  

NASA Technical Reports Server (NTRS)

HSTphot, a photometry package designed to handle the undersampled PSFs found in WFPC2 images, is introduced and described, as well as some of the considerations that have to be made in order to obtain accurate PSF-fitting stellar photometry with WFPC2 data. Tests of HSTphot's internal reliability are made using multiple observations of the same field, and tests of external reliability are made by comparing with DoPHOT reductions of the same data. Subject headz'ngs: techniques: photometric

Dolphin, Andrew E.

2000-01-01

102

Hyper: Hybrid photometry and extraction routine  

NASA Astrophysics Data System (ADS)

We present a new hybrid photometry and extraction routine called Hyper. It is designed to do compact source photometry, allowing for varying spatial resolution and sensitivity in multi-wavelength surveys. Hyper combines multi-Gaussian fitting with aperture photometry to provide reliable photometry in regions with variable backgrounds and in crowded fields. The background is evaluated and removed locally for each source using polynomial fits of various orders. Source deblending is done through simultaneous multi-Gaussian fitting of the main source and its companion(s), followed by the subtraction of the companion(s). Hyper also allows simultaneous multi-wavelength photometry by setting a fixed aperture size independent of the map resolution and by evaluating the source flux within the same region of the sky at multiple wavelengths at the same time. This new code has been initially designed for precise aperture photometry in complex fields such as the Galactic plane observed in the far infrared (FIR) by the Herschel infrared survey of the Galactic plane (Hi-GAL). Hyper has been tested on both simulated and real Herschel fields to quantify the quality of the source identification and photometry. The code is highly modular and fully parameterisable, therefore it can be easily adapted to different experiments. Comparison of the Hyper photometry with the catalogued sources in the Bolocam Galactic Plane Survey (BGPS), the 1.1 mm survey of the Galactic plane carried out with the Caltech Submillimeter Observatory, demonstrates the versatility of Hyper on different datasets. It is fast and light in its memory, and it is freely available to the scientific community.

Traficante, A.; Fuller, G. A.; Pineda, J. E.; Pezzuto, S.

2015-02-01

103

WFPC2 Stellar Photometry with HSTphot  

Microsoft Academic Search

HSTphot, a photometry package designed to handle the undersampled PSFs found\\u000ain WFPC2 images, is introduced and described, as well as some of the\\u000aconsiderations that have to be made in order to obtain accurate PSF-fitting\\u000astellar photometry with WFPC2 data. Tests of HSTphot's internal reliability are\\u000amade using multiple observations of the same field, and tests of external\\u000areliability

2000-01-01

104

2060 Chiron - CCD and electronographic photometry  

Microsoft Academic Search

R-band observations conducted for 2060 Chiron using CCD photometry in November-December 1986 and March 1988 are discussed. While the 1986 observations exhibit neither periodic nor nonperiodic brightness changes ascribable to comet-like activity, the 1988 observations show an 0.6 + or - 0.1 mag brightening that confirms the Tholen et al. (1988) findings and is consistent with the 1978 electronographic photometry

Schelte J. Bus; Edward Bowell; Alan W. Harris; Anthony V. Hewitt

1989-01-01

105

Meteor44 Video Meteor Photometry  

NASA Technical Reports Server (NTRS)

Meteor44 is a software system developed at MSFC for the calibration and analysis of video meteor data. The dynamic range of the (8bit) video data is extended by approximately 4 magnitudes for both meteors and stellar images using saturation compensation. Camera and lens specific saturation compensation coefficients are derived from artificial variable star laboratory measurements. Saturation compensation significantly increases the number of meteors with measured intensity and improves the estimation of meteoroid mass distribution. Astrometry is automated to determine each image's plate coefficient using appropriate star catalogs. The images are simultaneously intensity calibrated from the contained stars to determine the photon sensitivity and the saturation level referenced above the atmosphere. The camera s spectral response is used to compensate for stellar color index and typical meteor spectra in order to report meteor light curves in traditional visual magnitude units. Recent efforts include improved camera calibration procedures, long focal length 'streak' meteor photometry and two-station track determination. Meteor44 has been used to analyze data from the 2001, 2002 and 2003 MSFC Leonid observational campaigns as well as several lesser showers. The software is interactive and can be demonstrated using data from recent Leonid campaigns.

Swift, Wesley R.; Suggs, Robert M.; Cooke, William J.

2004-01-01

106

Effects of buoyancy on premixed flame stabilization  

SciTech Connect

The stabilization limits of v-flame and conical flames are investigated in normal gravity (+g) and reversed gravity (up-side-down burner, -g) to compare with observations of flame stabilization during microgravity experiments. The results show that buoyancy has most influence on the stabilization of laminar V-flames. Under turbulent conditions, the effects are less significant. For conical flames stabilized with a ring, the stabilization domain of the +g and -g cases are not significantly different. Under reversed gravity, both laminar v-flames and conical flames show flame behaviors that were also found in microgravity. The v-flames reattached to the rim and the conical flame assumed a top-hat shape. One of the special cases of -g conical flame is the buoyancy stabilized laminar flat flame that is detached from the burner. These flame implies a balance between the flow momentum and buoyant forces. The stretch rates of these flames are sufficiently low (< 20 s{sup -1}) such that the displacement speeds S{sub L} are almost equal to the laminar burning speed S{sub L}{sup 0}. An analysis based on evaluating the Richardson number is used to determine the relevant parameters that describe the buoyancy/momentum balance. A perfect balance i.e. Ri = l can be attained when the effect of heat loss from the flame zone is low. For the weaker lean cases, our assumption of adiabaticity tends to overestimate the real flame temperature. This interesting low stretch laminar flame configuration can be useful for fundamental studies of combustion chemistry.

Bedat, B.; Cheng, R.K.

1995-10-01

107

Studies of Premixed Laminar and Turbulent Flames at Microgravity  

NASA Technical Reports Server (NTRS)

Several topics relating to combustion limits in premixed flames at reduced gravity have been studied. These topics include: (1) flame balls; (2) numerical simulation of flame ball and planar flame structure and stability; (3) experimental simulation of buoyancy effects in premixed flames using aqueous autocatalytic reactions; and (4) premixed flame propagation in Hele-Shaw cells.

Abid, M.; Aung, K.; Ronney, P. D.; Sharif, J. A.; Wu, M.-S.

1999-01-01

108

NAAP Variable Star Photometry 1/12 Variable Star Photometry Student Guide  

E-print Network

Name: NAAP ­ Variable Star Photometry 1/12 Variable Star Photometry ­ Student Guide Background of Variable Stars and Properties of CCDs. Question 1: The light variation from a variable star is shown in the figure to the right. a) Identify the type of variable star and explain your criteria for classifying

Farritor, Shane

109

Flame structure of LPG-air Inverse Diffusion Flame in a backstep burner  

Microsoft Academic Search

The present experimental study characterizes the turbulent LPG Inverse Diffusion Flame (IDF) stabilized in a backstep burner in terms of visible flame length, dual flame structure, centerline temperature distribution, and oxygen concentration. The visible flame length for a fixed fuel jet velocity is found to reduce with increase in air jet velocity. Besides this, the effect of air and fuel

S. Mahesh; D. P. Mishra

2010-01-01

110

Study of “hyperbolic” diffusion flames: Appearance of instability caused by an interaction of stretched diffusion flames  

Microsoft Academic Search

An appearance of dynamic combustion instability due to the interaction of curved-stretched diffusion flames is studied experimentally. A pair of “hyperbolic” diffusion flames, made by four slot burners to form four “crossed” vertical and horizontal interfacial planes of fuel and oxidizer, is utilized for the present purpose. Two types of diffusion flame are obtained: the flames can be formed around

Yuji Nakamura; Ryosuke Nozaki; Akio Kitajima

2011-01-01

111

On the dynamics of flame edges in diffusion-flame\\/vortex interactions  

Microsoft Academic Search

We analyze the local flame extinction and reignition of a counterflow diffusion flame perturbed by a laminar vortex ring. Local flame extinction leads to the appearance of flame edges separating the burning and extinguished regions of the distorted mixing layer. The dynamics of these edges is modeled based on previous numerical results, with heat release effects fully taken into account,

Miguel Hermanns; Amable Linan; Marcos Vera

2007-01-01

112

Triple Flames: the effects of heat release  

NASA Astrophysics Data System (ADS)

Triple flames (aka tribrachial flames or edge flames) are structures that appear at the edge of diffusion flame sheets in nonpremixed combustion. Their propagation properties determine the dynamics of ignition and extinction zones on such flame sheets. An earlier AEA theory (see last years abstract) for vanishingly small heat release is extended to the case of small but finite heat release. Analytical results are presented for the curvature and propagation speeds of triple flames for global Arrhenius chemistry and unity Lewis numbers and these are compared with numerical simulations of the basic equations. The results are consistent with earlier numerical investigation and the experimental fact that triple flames can propagate faster than the corresponding stoichiometric planar premixed flame. The study is of relevance in the modeling of turbulent nonpremixed combustion where violation of the assumption of infinite rate chemistry may cause local extinction and reignition events in the turbulent field.

Ghosal, Sandip; Vervisch, Luc

1998-11-01

113

Lifted Partially Premixed Flames in Microgravity  

NASA Technical Reports Server (NTRS)

Lifted Double and Triple flames are established in the UIC-NASA Partially Premixed microgravity rig. The flames examined in this paper are established above a coannular burner because its axisymmetric geometry allows for future implementation of other non-intrusive optical diagnostic techniques easily. Both burner-attached stable flames and lifted flames are established at normal and microgravity conditions in the drop tower facility.

Lock, Andrew J.; Ganguly, Ranjan; Puri, Ishwar K.; Aggarwal, Suesh K.; Hegde, Uday

2004-01-01

114

Production of fullerenic nanostructures in flames  

DOEpatents

A method for the production of fullerenic nanostructures is described in which unsaturated hydrocarbon fuel and oxygen are combusted in a burner chamber at a sub-atmospheric pressure, thereby establishing a flame. The condensibles of the flame are collected at a post-flame location. The condensibles contain fullerenic nanostructures, such as single and nested nanotubes, single and nested nanoparticles and giant fullerenes. The method of producing fullerenic soot from flames is also described.

Howard, Jack B. (Winchester, MA); Vander Sande, John B. (Newbury, MA); Chowdhury, K. Das (Cambridge, MA)

1999-01-01

115

Structure of laminar sooting inverse diffusion flames  

Microsoft Academic Search

The flame structure of laminar inverse diffusion flames (IDFs) was studied to gain insight into soot formation and growth in underventilated combustion. Both ethylene–air and methane–air IDFs were examined, fuel flow rates were kept constant for all flames of each fuel type, and airflow rates were varied to observe the effect on flame structure and soot formation. Planar laser-induced fluorescence

Mark A. Mikofski; Timothy C. Williams; Christopher R. Shaddix; A. Carlos Fernandez-Pello; Linda G. Blevins

2007-01-01

116

Oscillatory Extinction Of Spherical Diffusion Flames  

NASA Technical Reports Server (NTRS)

Since extinction has been observed in an oscillatory manner in Le greater than 1 premixed flames, it is not unreasonable to expect that extinction could occur in an unsteady manner for diffusion flames. Indeed, near-limit oscillations have been observed experimentally under microgravity conditions for both candle flames and droplet flames. Furthermore, the analysis of Cheatham and Matalon on the unsteady behavior of diffusion flames with heat loss, identified an oscillatory regime which could be triggered by either a sufficiently large Lewis number (even without heat loss) or an appreciable heat loss (even for Le=1). In light of these recent understanding, the present investigation aims to provide a well-controlled experiment that can unambiguously demonstrate the oscillation of diffusion flames near both the transport- and radiation-induced limits. That is, since candle and jet flames are stabilized through flame segments that are fundamentally premixed in nature, and since premixed flames are prone to oscillate, there is the possibility that the observed oscillation of these bulk diffusion flames could be triggered and sustained by the oscillation of the premixed flame segments. Concerning the observed oscillatory droplet extinction, it is well-known that gas-phase oscillation in heterogeneous burning can be induced by and is thereby coupled with condensed-phase unsteadiness. Consequently, a convincing experiment on diffusion flame oscillation must exclude any ingredients of premixed flames and other sources that may either oscillate themselves or promote the oscillation of the diffusion flame. The present experiment on burner-generated spherical flames with a constant reactant supply endeavored to accomplish this goal. The results are further compared with those from computational simulation for further understanding and quantification of the flame dynamics and extinction.

Law, C. K.; Yoo, S. W.; Christianson, E. W.

2003-01-01

117

Structure of laminar sooting inverse diffusion flames  

Microsoft Academic Search

The flame structure of laminar inverse diffusion flames (IDFs) was studied to gain insight into soot formation and growth in underventilated combustion. Both ethylene-air and methane-air IDFs were examined, fuel flow rates were kept constant for all flames of each fuel type, and airflow rates were varied to observe the effect on flame structure and soot formation. Planar laser-induced fluorescence

Mark A. Mikofski; A. Carlos Fernandez-Pello; Timothy C. Williams; Christopher R. Shaddix; Linda G. Blevins

2007-01-01

118

Production Of Fullerenic Soot In Flames  

DOEpatents

A method for the production of fullerenic nanostructures is described in which unsaturated hydrocarbon fuel and oxygen are combusted in a burner chamber at a sub-atmospheric pressure, thereby establishing a flame. The condensibles of the flame are collected at a post-flame location. The condensibles contain fullerenic nanostructures, such as single and nested nanotubes, single and nested nanoparticles and giant fullerenes. The method of producing fullerenic soot from flames is also described.

Howard, Jack B. (Winchester, MA); Vander Sande, John B. (Newbury, MA); Chowdhury, K. Das (Cambridge, MA)

2000-12-19

119

Soot Formation in Purely-Curved Premixed Flames and Laminar Flame Speeds of Soot-Forming Flames  

NASA Technical Reports Server (NTRS)

The research addressed here is a collaborative project between University of Delaware and Case Western Reserve University. There are two basic and related scientific objectives. First, we wish to demonstrate the suitability of spherical/cylindrical, laminar, premixed flames in the fundamental study of the chemical and physical processes of soot formation. Our reasoning is that the flame standoff distance in spherical/cylindrical flames under microgravity can be substantially larger than that in a flat burner-stabilized flame. Therefore the spherical/cylindrical flame is expected to give better spatial resolution to probe the soot inception and growth chemistry than flat flames. Second, we wish to examine the feasibility of determining the laminar flame speed of soot forming flames. Our basic assumption is that under the adiabatic condition (in the absence of conductive heat loss), the amount and dynamics of soot formed in the flame is unique for a given fuel/air mixture. The laminar flame speed can be rigorously defined as long as the radiative heat loss can be determined. This laminar flame speed characterizes the flame soot formation and dynamics in addition to the heat release rate. The research involves two integral parts: experiments of spherical and cylindrical sooting flames in microgravity (CWRU), and the computational counterpart (UD) that aims to simulate sooting laminar flames, and the sooting limits of near adiabatic flames. The computations work is described in this report, followed by a summary of the accomplishments achieved to date. Details of the microgra+ experiments will be discussed in a separate, final report prepared by the co-PI, Professor C-J. Sung of CWRU. Here only a brief discussion of these experiments will be given.

Buchanan, Thomas; Wang, Hai

2005-01-01

120

Calibration of the MACHO Photometry Database  

NASA Astrophysics Data System (ADS)

The MACHO Project is a microlensing survey that monitors the brightnesses of ~60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, a significant fraction of all astronomical photometry. We describe the calibration of MACHO two-color photometry and transformation to the standard Kron-Cousins V and R system. Calibrated MACHO photometry may be properly compared with all other observations on the Kron-Cousins standard system, enhancing the astrophysical value of these data. For ~9 million stars in the LMC bar, independent photometric measurements of ~20,000 stars with V<~18 mag in field-overlap regions demonstrate an internal precision ?V=0.021, ?R=0.019, ?V-R=0.028 mag. The accuracy of the zero point in this calibration is estimated to be +/-0.035 mag for stars with colors in the range -0.1 magphotometry with published photometric sequences and new Hubble Space Telescope observations shows agreement. The current calibration zero-point uncertainty for the remainder of the MACHO photometry database is estimated to be +/-0.10 mag in V or R and +/-0.04 mag in V-R. We describe the first application of calibrated MACHO data: the construction of a color-magnitude diagram used to calculate our experimental sensitivity for detecting microlensing in the LMC.

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Nelson, C. A.; Quinn, P. J.; Stubbs, C. W.; Sutherland, W.; Tomaney, A. B.; Vandehei, T.; Welch, D. L.; MACHO Collaboration

1999-12-01

121

Flame and Soot Boundaries of Laminar Jet Diffusion Flames. Appendix A  

NASA Technical Reports Server (NTRS)

The shapes (flame-sheet and luminous-flame boundaries) or steady weakly buoyant round hydrocarbon-fueled laminar-jet diffusion flames in still and coflowing air were studied both experimentally and theoretically. Flame-sheet shapes were measured from photographs using a CH optical filter to distinguish flame-sheet boundaries in the presence of blue CO2 and OH emissions and yellow continuum radiation from soot. Present experimental conditions included acetylene-, methane-, propane-, and ethylene-fueled flames having initial reactant temperatures of 300 K. ambient pressures of 4-50 kPa, jet-exit Reynolds numbers of 3-54, initial air/fuel velocity ratios of 0-9, and luminous flame lengths of 5-55 mm; earlier measurements for propylene- and 1,3-butadiene-fueled flames for similar conditions were considered as well. Nonbuoyant flames in still air were observed at microgravity conditions; essentially nonbuoyant flames in coflowing air were observed at small pressures to control effects of buoyancy. Predictions of luminous flame boundaries from soot luminosity were limited to laminar smoke-point conditions, whereas predictions of flame-sheet boundaries ranged from soot-free to smoke-point conditions. Flame-shape predictions were based on simplified analyses using the boundary-layer approximations along with empirical parameters to distinguish flame-sheet and luminous-flame (at the laminar smoke point) boundaries. The comparison between measurements and predictions was remarkably good and showed that both flame-sheet and luminous-flame lengths are primarily controlled by fuel flow rates with lengths in coflowing air approaching 2/3 of the lengths in still air as coflowing air velocities are increased. Finally, luminous flame lengths at laminar smoke-point conditions were roughly twice as long as flame-sheet lengths at comparable conditions because of the presence of luminous soot particles in the fuel-lean region of the flames.

Xu, F.; Dai, Z.; Faeth, G. M.; Yuan, Z.-G. (Technical Monitor); Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2002-01-01

122

Spherical Diffusion Flames: Structure and Dynamics  

NASA Technical Reports Server (NTRS)

The spherical geometry is the most suitable one to study fundamental issues concerning the structure and the dynamics of diffusion flames. From a theoretical point of view, it is the only geometry that permits the existence of a truly one dimensional stationary diffusion flame. A stationary planar diffusion flame with the fuel supplied upstream, at x approaches -infinity say, and the oxidant downstream, at x approaches +infinity is not possible. For a steady diffusion flame to exist, one must have nonzero fluxes of fuel and oxidant towards the flame. However, in the unlimited region behind the planar flame the only bounded solutions to the reaction-free convective-diffusive operator are constants. Hence the oxidant concentration behind the flame remains constant and there is no mechanism to generate the necessary flux towards the flame. A one-dimensional problem can be formulated if the reactants are supplied at finite locations; but the boundary conditions in this case introduce unnecessary complications and do not appropriately model the physical reality. Indeed, a planar diffusion flame can be established in the stagnation-point flow of two opposed jets but the flame in this case is stretched and the flow is essentially two-dimensional. The only stationary one-dimensional diffusion flame in an unlimited environment is therefore the spherical flame.

Matalon, Moshe

1997-01-01

123

Soot Formation In Laminar Inverse Diffusion Flames  

Microsoft Academic Search

Soot formation in laminar ethylene inverse diffusion flames has been investigated experimentally and modeled. Soot volume fraction and temperature measurements have been made and compared to numerical predictions using a soot formation model previously applied to normal diffusion flames. The inverse flame configuration serves as a good test of the applicability of the model and is relevant to practical combustor

D. B. MAKEL; I. M. KENNEDY

1994-01-01

124

Acoustically perturbed turbulent premixed swirling flames  

Microsoft Academic Search

The dynamics of a turbulent premixed confined swirling flame is investigated using large eddy simulation. The flame response is determined by introducing an external acoustic forcing at two modulation frequencies corresponding to characteristic values of the flame transfer function obtained experimentally. These values were found to give different responses in terms of gain in a previous series of experiments. The

P. Palies; T. Schuller; D. Durox; L. Y. M. Gicquel; S. Candel

2011-01-01

125

Environmental Considerations for Flame Resistant Textiles  

Technology Transfer Automated Retrieval System (TEKTRAN)

Virtually all common textiles will ignite and burn. There are mandatory and voluntary cigarette and open-flame ignition regulations to address unreasonable fire risks associated with textile products that require them to be treated with and/or contain flame retardant chemicals to make them flame res...

126

Gaia photometry for white dwarfs  

NASA Astrophysics Data System (ADS)

Context. White dwarfs can be used to study the structure and evolution of the Galaxy by analysing their luminosity function and initial mass function. Among them, the very cool white dwarfs provide the information for the early ages of each population. Because white dwarfs are intrinsically faint only the nearby (~ 20 pc) sample is reasonably complete. The Gaia space mission will drastically increase the sample of known white dwarfs through its 5-6 years survey of the whole sky up to magnitude V = 20-25. Aims: We provide a characterisation of Gaia photometry for white dwarfs to better prepare for the analysis of the scientific output of the mission. Transformations between some of the most common photometric systems and Gaia passbands are derived. We also give estimates of the number of white dwarfs of the different galactic populations that will be observed. Methods: Using synthetic spectral energy distributions and the most recent Gaia transmission curves, we computed colours of three different types of white dwarfs (pure hydrogen, pure helium, and mixed composition with H/He = 0.1). With these colours we derived transformations to other common photometric systems (Johnson-Cousins, Sloan Digital Sky Survey, and 2MASS). We also present numbers of white dwarfs predicted to be observed by Gaia. Results: We provide relationships and colour-colour diagrams among different photometric systems to allow the prediction and/or study of the Gaia white dwarf colours. We also include estimates of the number of sources expected in every galactic population and with a maximum parallax error. Gaia will increase the sample of known white dwarfs tenfold to about 200 000. Gaia will be able to observe thousands of very cool white dwarfs for the first time, which will greatly improve our understanding of these stars and early phases of star formation in our Galaxy. Tables 6 and 7 are available in electronic form at http://www.aanda.orgFull Tables 3-5 are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/A11

Carrasco, J. M.; Catalán, S.; Jordi, C.; Tremblay, P.-E.; Napiwotzki, R.; Luri, X.; Robin, A. C.; Kowalski, P. M.

2014-05-01

127

Flame Speed and Spark Intensity  

NASA Technical Reports Server (NTRS)

This report describes a series of experiments undertaken to determine whether or not the electrical characteristics of the igniting spark have any effect on the rapidity of flame spread in the explosive gas mixtures which it ignites. The results show very clearly that no such effect exists. The flame velocity in carbon-monoxide oxygen, acetylene oxygen, and gasoline-air mixtures was found to be unaffected by changes in spark intensity from sparks which were barely able to ignite the mixture up to intense condenser discharge sparks having fifty time this energy. (author)

Randolph, D W; Silsbee, F B

1925-01-01

128

Detection of Terrestrial Planets Using Transit Photometry  

NASA Technical Reports Server (NTRS)

Transit photometry detection of planets offers many advantages: an ability to detect terrestrial size planets, direct determination of the planet's size, applicability to all main-sequence stars, and a differential brightness change of the periodic signature being independent of stellar distance or planetary orbital semi-major axis. Ground and space based photometry have already been successful in detecting transits of the giant planet HD209458b. However, photometry 100 times better is required to detect terrestrial planets. We present results of laboratory measurements of an end-to-end photometric system incorporating all of the important confounding noise features of both the sky and a space based photometer including spacecraft jitter. In addition to demonstrating an instrumental noise of less than 10 ppm (an Earth transit of a solar-like star is 80 ppm), the brightnesses of individual stars were dimmed to simulate Earth-size transit signals. These 'transits' were reliably detected as part of the tests.

Koch, David; Witteborn, Fred; Jenkins, Jon; Dunham, Edward; Boruci, William; DeVincenzi, Donald (Technical Monitor)

2001-01-01

129

Theoretical and numerical study of a symmetrical triple flame using the parabolic flame path approximation  

NASA Astrophysics Data System (ADS)

In non-premixed turbulent combustion the reactive zone is localized at the stoichiometric surfaces of the mixture and may be locally approximated by a diffusion flame. Experiments and numerical simulations reveal a characteristic structure at the edge of such a two-dimensional diffusion flame. This ‘triple flame’ or ‘edge flame’ consists of a curved flame front followed by a trailing edge that constitutes the body of the diffusion flame. Triple flames are also observed at the edge of a lifted laminar diffusion flame near the exit of burners. The speed of propagation of the triple flame determines such important properties as the rate of increase of the flame surface in non-premixed combustion and the lift-off distance in lifted flames at burners. This paper presents an approximate theory of triple flames based on an approximation of the flame shape by a parabolic profile, for large activation energy and low but finite heat release. The parabolic flame path approximation is a heuristic approximation motivated by physical considerations and is independent of the large activation energy and low heat release assumptions which are incorporated through asymptotic expansions. Therefore, what is presented here is not a truly asymptotic theory of triple flames, but an asymptotic solution of a model problem in which the flame shape is assumed parabolic. Only the symmetrical flame is considered and Lewis numbers are taken to be unity. The principal results are analytical formulas for the speed and curvature of triple flames as a function of the upstream mixture fraction gradient in the limit of infinitesimal heat release as well as small but finite heat release. For given chemistry, the solution provides a complete description of the triple flame in terms of the upstream mixture fraction gradient. The theory is validated by comparison with numerical simulation of the primitive equations.

Ghosal, Sandip; Vervisch, Luc

2000-07-01

130

Flame stabilizer for stagnation flow reactor  

DOEpatents

A method of stabilizing a strained flame in a stagnation flow reactor. By causing a highly strained flame to be divided into a large number of equal size segments it is possible to stablize a highly strained flame that is on the verge of extinction, thereby providing for higher film growth rates. The flame stabilizer is an annular ring mounted coaxially and coplanar with the substrate upon which the film is growing and having a number of vertical pillars mounted on the top surface, thereby increasing the number of azimuthal nodes into which the flame is divided and preserving an axisymmetric structure necessary for stability.

Hahn, David W. (Dublin, CA); Edwards, Christopher F. (Sunnyvale, CA)

1999-01-01

131

KSC Launch Pad Flame Trench Environment Assessment  

NASA Technical Reports Server (NTRS)

This report summarizes conditions in the Launch Complex 39 (LC-39) flame trenches during a Space Shuttle Launch, as they have been measured to date. Instrumentation of the flame trench has been carried out by NASA and United Space Alliance for four Shuttle launches. Measurements in the flame trench are planned to continue for the duration of the Shuttle Program. The assessment of the launch environment is intended to provide guidance in selecting appropriate test methods for refractory materials used in the flame trench and to provide data used to improve models of the launch environment in the flame trench.

Calle, Luz Marina; Hintze, Paul E.; Parlier, Christopher R.; Curran, Jerome P.; Kolody, Mark R.; Sampson, Jeffrey W.

2010-01-01

132

CLEA: Photoelectric Photometry of the Pleiades  

NSDL National Science Digital Library

This lab is designed to familiarize students with the technique of photoelectric filter photometry and counting statistics. The software for this exercise puts students in control of a computer-controlled telescope with sidereal tracking. It illustrates the use of equatorial coordinates for finding stars in a cluster and introduces the use of H-R diagrams for analyzing the age and distance of clusters. A student guide supplied with the software describes how to use B and V photometry of cluster members to plot an H-R diagram of the Pleiades and to determine its distance. This is part of a larger collection of simulations, Project CLEA.

Marschall, Laurence; Snyder, Glenn; Cooper, P. R.; Hayden, Michael; Good, Rhonda

2008-12-15

133

Burning Laminar Jet Diffusion Flame  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence was taken July 15, 1997, MET:14/10:34 (approximate) and shows the ignition and extinction of this flame. LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel -- like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (518KB, 20-second MPEG, screen 160 x 120 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300182.html.

2003-01-01

134

An Improved Calcium Flame Test.  

ERIC Educational Resources Information Center

Indicates that the true red color of calcium can be obtained (using the procedure described by Sorm and Logowski) if the calcium ion solution is mixed with an equal volume of saturated ammonium bromide solution. Suggestions for flame tests of other elements are also noted. (JN)

Pearson, Robert S.

1985-01-01

135

NIST Photometry Short Course September 27-30, 2011  

E-print Network

NIST Photometry Short Course September 27-30, 2011 100 Bureau Drive, Gaithersburg, MD 20899 Bldg.00 ) Registrant Information gfedc gfedc Page 1 of 3NIST Conference Registration 6/29/2011file://Z:\\My Documents\\FORMS\\photometry

Perkins, Richard A.

136

Extrasolar planet transit photometry at Wallace Astrophysical Observatory  

E-print Network

Extrasolar planet transit photometry is a relatively new astronomical technique developed over the past decade. Transit photometry is the measurement of a star's brightness as an orbiting planet passes in front of the star ...

Fong, Wen-fai

2008-01-01

137

Effect of varied air flow on flame structure of laminar inverse diffusion flames.  

SciTech Connect

The structure of laminar inverse diffusion flames (IDFs) of methane and ethylene was studied using a cylindrical co-flowing burner. Several flames of the same fuel flow-rate yet various air flow-rates were examined. Heights of visible flames were obtained using measurements of hydroxyl (OH) laser-induced fluorescence (LIF) and visible images. Polycyclic aromatic hydrocarbon (PAH) LIF and soot laser-induced incandescence (LII) were also measured. In visible images, radiating soot masks the blue region typically associated with the flame height in normal diffusion flames (NDFs). Increased air flow-rates resulted in longer flames. PAH LIF and soot LII indicated that PAh and soot are present on the fuel side of the flame and that soot is located closer to the reaction zone than PAH. Ethylene flames produced significantly higher PAH LIF and soot LII signals than methane flames, which is consistent with the sooting propensity of ethylene.

Shaddix, Christopher R.; Williams, Timothy C.; Blevins, Linda Gail; Mikofski, Mark A. (University of California Berkeley)

2004-03-01

138

Experimental study of turbulent flame kernel propagation  

SciTech Connect

Flame kernels in spark ignited combustion systems dominate the flame propagation and combustion stability and performance. They are likely controlled by the spark energy, flow field and mixing field. The aim of the present work is to experimentally investigate the structure and propagation of the flame kernel in turbulent premixed methane flow using advanced laser-based techniques. The spark is generated using pulsed Nd:YAG laser with 20 mJ pulse energy in order to avoid the effect of the electrodes on the flame kernel structure and the variation of spark energy from shot-to-shot. Four flames have been investigated at equivalence ratios, {phi}{sub j}, of 0.8 and 1.0 and jet velocities, U{sub j}, of 6 and 12 m/s. A combined two-dimensional Rayleigh and LIPF-OH technique has been applied. The flame kernel structure has been collected at several time intervals from the laser ignition between 10 {mu}s and 2 ms. The data show that the flame kernel structure starts with spherical shape and changes gradually to peanut-like, then to mushroom-like and finally disturbed by the turbulence. The mushroom-like structure lasts longer in the stoichiometric and slower jet velocity. The growth rate of the average flame kernel radius is divided into two linear relations; the first one during the first 100 {mu}s is almost three times faster than that at the later stage between 100 and 2000 {mu}s. The flame propagation is slightly faster in leaner flames. The trends of the flame propagation, flame radius, flame cross-sectional area and mean flame temperature are related to the jet velocity and equivalence ratio. The relations obtained in the present work allow the prediction of any of these parameters at different conditions. (author)

Mansour, Mohy [National Institute of Laser Enhanced Sciences, Cairo University, Giza (Egypt); Peters, Norbert; Schrader, Lars-Uve [Institute of Combustion Technology, Aachen (Germany)

2008-07-15

139

Radiant extinction of gaseous diffusion flames  

NASA Technical Reports Server (NTRS)

The absence of buoyancy-induced flows in microgravity significantly alters the fundamentals of many combustion processes. Substantial differences between normal-gravity and microgravity flames have been reported during droplet combustion, flame spread over solids, candle flames, and others. These differences are more basic than just in the visible flame shape. Longer residence time and higher concentration of combustion products create a thermochemical environment which changes the flame chemistry. Processes such as flame radiation, that are often ignored under normal gravity, become very important and sometimes even controlling. This is particularly true for conditions at extinction of a microgravity diffusion flame. Under normal-gravity, the buoyant flow, which may be characterized by the strain rate, assists the diffusion process to transport the fuel and oxidizer to the combustion zone and remove the hot combustion products from it. These are essential functions for the survival of the flame which needs fuel and oxidizer. Thus, as the strain rate is increased, the diffusion flame which is 'weak' (reduced burning rate per unit flame area) at low strain rates is initially 'strengthened' and eventually it may be 'blown-out'. Most of the previous research on diffusion flame extinction has been conducted at the high strain rate 'blow-off' limit. The literature substantially lacks information on low strain rate, radiation-induced, extinction of diffusion flames. At the low strain rates encountered in microgravity, flame radiation is enhanced due to: (1) build-up of combustion products in the flame zone which increases the gas radiation, and (2) low strain rates provide sufficient residence time for substantial amounts of soot to form which further increases the flame radiation. It is expected that this radiative heat loss will extinguish the already 'weak' diffusion flame under certain conditions. Identifying these conditions (ambient atmosphere, fuel flow rate, fuel type, etc.) is important for spacecraft fire safety. Thus, the objective is to experimentally and theoretically investigate the radiation-induced extinction of diffusion flames in microgravity and determine the effect of flame radiation on the 'weak' microgravity diffusion flame.

Atreya, Arvind; Agrawal, Sanjay; Shamim, Tariq; Pickett, Kent; Sacksteder, Kurt R.; Baum, Howard R.

1995-01-01

140

The Aperture Photometry: a Software Package for IBM Personal Computers  

NASA Astrophysics Data System (ADS)

A software package, AFO, for interactive aperture photometry is presented. Observational data of the open cluster M 67 are used to test the package. The results of our photometry are compared with those obtained by the IRAF/Apphot package. Various routines of AFO and the accuracy of the photometry are discussed. A new method of the aperture photometry based on growth-curve analysis is introduced.

Bridzius, A.; Vansevicius, V.

1997-12-01

141

Flame structure of steady and pulsed sooting inverse jet diffusion flames.  

SciTech Connect

In turbulent buoyant fire plumes, local inverse diffusion flames of air injected into gaseous fuel or fuel vapors occur, but little is known about the tendency to form soot and produce thermal radiation in these flame structures. To investigate these phenomena, steady and pulsed normal and inverse jet diffusion flames of methane/air and ethylene/air have been stabilized on a slot burner, which has advantages over a coannular flame geometry for performing flame imaging measurements in sooty flames. OH and PAH laser-induced fluorescence (LIF), soot laser-induced incandescence (LII), and soot thermal emission at 850 nm have been measured in the lower flame region of steady and pulsed flames. These measurements reveal that the relative positions of these different structural features are very similar in the normal and inverse steady flames of each fuel. Also, the OH signals are nearly identical in the normal and inverse flames. The inverse flame PAH signals and soot concentrations are somewhat smaller than for the normal flames, and the near-infrared radiation is approximately 25% lower for the inverse flame. When the central slot is pulsed, the primary buoyant vortex roll-up occurs on the fuel-rich side of inverse flames, resulting in strongly enhanced PAH signals and soot concentrations. The near-infrared radiation also increases in the pulsed flames, but not from the soot within the vortex roll-up region. In general, enhancements in peak signals from soot and near-infrared radiation similar to those in pulsed normal diffusion flames are apparent in pulsed inverse diffusion flames. PAH signals are clearly greatest in the pulsed inverse flames.

Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda Gail; Schefer, Robert W.

2004-03-01

142

Flame generation of ceramic oxides  

SciTech Connect

Large quantities of TiO{sub 2}, SiO{sub 2}, and mixed TiO{sub 2}-SiO{sub 2} powders are produced annually by combustion of their chloride precursors for use as catalysts and as paint opacifiers. We have studied the formation of flame synthesized oxides using a counterflow diffusion flame burner. It has enabled us to obtain desired morphologies and crystalline structures by varying process variables such as flame temperature and precursor concentration ratio, and by selecting the appropriate feed stream. For example, over the ranges of TiCl{sub 4} (the TiO{sub 2} precursor) concentrations tested, feeding it only into the oxidizer stream yields mainly anatase TiO{sub 2} powders, while feeding only into the fuel stream yields mainly rutile TiO{sub 2} powders. By adding TiCl{sub 4} and SiCl{sub 4} simultaneously to the same flame and choosing conditions such that the TiO{sub 2} condenses before the SiO{sub 2}, we obtained SiO{sub 2} attached to, or coated onto, TiO{sub 2} particles in a single step process. Oxide particles produced in the counterflow diffusion flame burner are in the 10 to 100 manometer range. Their high surface area makes them potentially useful as catalysts. V{sub 2}O{sub 5}-TiO{sub 2} and V{sub 2}O{sub 5}-Al{sub 2}O{sub 3} are well-known catalysts for the selective oxidation of o-xylene to phthalic anhydride, and V-P-O oxides are widely used catalysts for the selective oxidation of butene and n-butane to maleic anhydride. Several V{sub 2}O{sub 5}-based mixed oxide powders were produced in the burner. 21 refs.

Katz, J.L. [John Hopkins Univ., Baltimore, MD (United States)

1996-12-31

143

Instrument Science Report ACS 2006-01 PSFs, Photometry,  

E-print Network

Instrument Science Report ACS 2006-01 PSFs, Photometry, and Astrometry for the ACS/WFC Jay Anderson is to be interpolated for each star. Fitting these PSFs to star images gives photometry and astrometry with accuracies hurting photometry. The following sections present our modeling of the F606W PSF, and also provide PSFs

Sirianni, Marco

144

WFPC2 Photometry from Subtraction of Observed PSFs  

E-print Network

1 WFPC2 Photometry from Subtraction of Observed PSFs J. Surdej1,2 , S. Baggett3 , M. Remy1 , M of PSF subtrac- tion tests have been performed and the resulting photometry analyzed. We find that using or planets) but also provides a means of deriving accurate photometry of the primary objects

Sirianni, Marco

145

Systematic photometry of XUV solar images  

Microsoft Academic Search

Units and methods have been devised to express the photometry of solar XUV images. The source and limb-brightened fluxes are given in terms of the sun's quiet central intensity. Measurements made on this system can be meaningfully compared with solar data and with theoretical predictions. Calculations have been made of the XUV distribution for optically thin solar models and results

C. W. Allen

1969-01-01

146

M83. I - Multicolor surface photometry  

Microsoft Academic Search

UBVR surface photometry of the bright southern spiral galaxy NGC 5236 (M83) is presented. Calibrated maps of UBVR and H-alpha surface brightness and colors are compared with models of evolving mixes of stellar populations in order to establish a measurable drift velocity relative to some feature for the young associations supposedly formed in the wake of a spiral density wave.

R. J. Talbot Jr.; E. B. Jensen; R. J. Dufour

1979-01-01

147

Diffraction Losses in Radiometry and Photometry  

Microsoft Academic Search

The precision of radiometry and photometry is reaching a stage, in standardizing laboratories at least, where greater attention should be paid to losses of flux by diffraction. Otherwise errors of up to 0.5% or more may occur. This article reviews from the radiometric point of view diffraction losses at circular apertures, for both the Fraunhofer and Fresnel conditions and for

W R Blevin

1970-01-01

148

Near-Field Photometry: A New Approach  

Microsoft Academic Search

This paper presents a new approach to near-field photometry and describes a novel nearfieldgoniophotometer and illuminance calculation method. The approach is based onhelios, which is a rationalization of the luminance concept for volume sources. Thegoniophotometer measures the three-dimensional vector field of light surrounding aluminaire rather than any of its intrinsic properties. The calculation method can predictthe illuminance at any point

Ian Ashdown

1992-01-01

149

Radiative extinction of gaseous spherical diffusion flames in microgravity  

Microsoft Academic Search

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished

K. J. Santa; B. H. Chao; P. B. Sunderland; D. L. Urban; D. P. Stocker; R. L. Axelbaum

2007-01-01

150

Studies of Premixed Laminar and Turbulent Flames at Microgravity  

NASA Technical Reports Server (NTRS)

Several topics relating to premixed flame behavior at reduced gravity have been studied. These topics include: (1) flame balls; (2) flame structure and stability at low Lewis number; (3) experimental simulation of buoyancy effects in premixed flames using aqueous autocatalytic reactions; and (4) premixed flame propagation in Hele-Shaw cells.

Abid, M.; Aung, K.; Kaiser, C.; Liu, J. -B.; Ronney, P. D.; Sharif, J.

2001-01-01

151

Structure of laminar sooting inverse diffusion flames  

SciTech Connect

The flame structure of laminar inverse diffusion flames (IDFs) was studied to gain insight into soot formation and growth in underventilated combustion. Both ethylene-air and methane-air IDFs were examined, fuel flow rates were kept constant for all flames of each fuel type, and airflow rates were varied to observe the effect on flame structure and soot formation. Planar laser-induced fluorescence of hydroxyl radicals (OH PLIF) and polycyclic aromatic hydrocarbons (PAH PLIF), planar laser-induced incandescence of soot (soot PLII), and thermocouple-determined gas temperatures were used to draw conclusions about flame structure and soot formation. Flickering, caused by buoyancy-induced vortices, was evident above and outside the flames. The distances between the OH, PAH, and soot zones were similar in IDFs and normal diffusion flames (NDFs), but the locations of those zones were inverted in IDFs relative to NDFs. Peak OH PLIF coincided with peak temperature and marked the flame front. Soot appeared outside the flame front, corresponding to temperatures around the minimum soot formation temperature of 1300 K. PAHs appeared outside the soot layer, with characteristic temperature depending on the wavelength detection band. PAHs and soot began to appear at a constant axial position for each fuel, independent of the rate of air flow. PAH formation either preceded or coincided with soot formation, indicating that PAHs are important components in soot formation. Soot growth continued for some time downstream of the flame, at temperatures below the inception temperature, probably through reaction with PAHs. (author)

Mikofski, Mark A.; Fernandez-Pello, A. Carlos [Microgravity Combustion Laboratory, University of California Berkeley, Berkeley, CA 94720 (United States); Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda G. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States)

2007-06-15

152

Numerical investigations of gaseous spherical diffusion flames  

NASA Astrophysics Data System (ADS)

Spherical diffusion flames have several unique characteristics that make them attractive from experimental and theoretical perspectives. They can be modeled with one spatial dimension, which frees computational resources for detailed chemistry, transport, and radiative loss models. This dissertation is a numerical study of two classes of spherical diffusion flames: hydrogen micro-diffusion flames, emphasizing kinetic extinction, and ethylene diffusion flames, emphasizing sooting limits. The flames were modeled using a one-dimensional, time-accurate diffusion flame code with detailed chemistry and transport. Radiative losses from products were modeled using a detailed absorption/emission statistical narrow band model and the discrete ordinates method. During this work the code has been enhanced by the implementation of a soot formation/oxidation model using the method of moments. Hydrogen micro-diffusion flames were studied experimentally and numerically. The experiments involved gas jets of hydrogen. At their quenching limits, these flames had heat release rates of 0.46 and 0.25 W in air and in oxygen, respectively. These are the weakest flames ever observed. The modeling results confirmed the quenching limits and revealed high rates of reactant leakage near the limits. The effects of the burner size and mass flow rate were predicted to have a significant impact on the flame chemistry and species distribution profiles, favoring kinetic extinction. Spherical ethylene diffusion flames at their sooting limits were also examined. Seventeen normal and inverse spherical flames were considered. Initially sooty, these flames were experimentally observed to reach their sooting limits 2 s after ignition. Structure of the flames at 2 s was considered, with an emphasis on the relationships among local temperature, carbon to oxygen atom ratio (C/O), and scalar dissipation rate. A critical C/O ratio was identified, along with two different sooting limit regimes. Diffusion flames with local scalar dissipation rates below 2 s-1 were found to have temperatures near 1410 K at the location of the critical C/O ratio, whereas flames with greater local scalar dissipation rate exhibited increased temperatures. The present work sheds light on important combustion phenomenon related to flame extinction and soot formation. Applications to energy efficiency, pollutant reduction, and fire safety are expected.

Lecoustre, Vivien R.

153

Numerical Investigation of Edge Flame Structure of Counterflow Nonpremixed Flames with Local Extinction Due to Flame Stretch  

NASA Astrophysics Data System (ADS)

Laminar counterflow nonpremixed flames with local extinction caused by nonuniform inflows are numerically investigated in two-dimensions in a system governed by Lewis numbers of unity and assuming a single-step, irreversible, finite-rate reaction. A numerical method based on the SIMPLE algorithm is used. Edge flame structures are investigated through the introduction of a new progress variable defined as the normalized integral of the mass fraction of a product in the mixture fraction Z space and which expresses the progress of the chemical reaction. Calculation results reveal that the edge flame structure can be classified into three regions; fully burning flame, weakened flame with a low reaction rate, and a non-reacting preheat region. Under these conditions, and in terms of the energy balance, the edge flame structure is dependent on the Z-directional heat diffusion transport, heat consumption (given by the progress variable), and heat production by chemical reaction. It is found that each type of flame structure can be well characterized by three parameters; the mixture fraction, the stoichiometric scalar dissipation rate, and the progress variable. These three parameters are identified as important factors affecting the edge flame structure of nonpremixed flames with local extinction.

Noda, Susumu; Tsubokura, Tomonori

154

Transitional Gas Jet Diffusion Flames in Microgravity  

NASA Technical Reports Server (NTRS)

Drop tower experiments were performed to identify buoyancy effects in transitional hydrogen gas jet diffusion flames. Quantitative rainbow schlieren deflectometry was utilized to optically visualize the flame and to measure oxygen concentration in the laminar portion of the flame. Test conditions consisted of atmospheric pressure flames burning in quiescent air. Fuel from a 0.3mm inside diameter tube injector was issued at jet exit Reynolds numbers (Re) of 1300 to 1700. Helium mole percentage in the fuel was varied from 0 to 40%. Significant effects of buoyancy were observed in near field of the flame even-though the fuel jets were momentum-dominated. Results show an increase of breakpoint length in microgravity. Data suggest that transitional flames in earth-gravity at Re<1300 might become laminar in microgravity.

Agrawal, Ajay K.; Alammar, Khalid; Gollahalli, S. R.; Griffin, DeVon (Technical Monitor)

2000-01-01

155

The VLT FLAMES Tarantula Survey  

NASA Astrophysics Data System (ADS)

We introduce the VLT FLAMES Tarantula Survey, an ESO Large Programme from which we have obtained optical spectroscopy of over 800 massive stars in the spectacular 30 Doradus region of the Large Magellanic Cloud. A key feature is the use of multi-epoch observations to provide strong constraints on the binary fraction. This is the largest high quality survey of extragalactic massive stars ever assembled, and is already providing exciting new insights into their evolution, multiplicity and formation.

Evans, C.; Taylor, W.; Sana, H.; Hénault-Brunet, V.; Bagnoli, T.; Bastian, N.; Bestenlehner, J.; Bonanos, A.; Bressert, E.; Brott, I.; Campbell, M.; Cantiello, M.; Carraro, G.; Clark, S.; Costa, E.; Crowther, P.; de Koter, A.; de Mink, S. E.; Doran, E.; Dufton, P.; Dunstall, P.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I.; Izzard, R.; Köhler, K.; Langer, N.; Lennon, D.; Maíz Apellániz, J.; Markova, N.; Najarro, P.; Puls, J.; Ramirez, O.; Sabín-Sanjulián, C.; Simón-Díaz, S.; Smartt, S.; Stroud, V.; van Loon, J.; Vink, J. S.; Walborn, N.

2011-09-01

156

Laminar Jet Diffusion Flame Burning  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence, using propane fuel, was taken STS-94, July 4 1997, MET:2/05:30 (approximate). LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel-like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (983KB, 9-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300184.html.

2003-01-01

157

Flame Suppression Agent, System and Uses  

NASA Technical Reports Server (NTRS)

Aqueous droplets encapsulated in a flame retardant polymer are useful in suppressing combustion. Upon exposure to a flame, the encapsulated aqueous droplets rupture and vaporize, removing heat and displacing oxygen to retard the combustion process. The polymer encapsulant, through decomposition, may further add free radicals to the combustion atmosphere, thereby further retarding the combustion process. The encapsulated aqueous droplets may be used as a replacement to halon, water mist and dry powder flame suppression systems.

Parrish, Clyde F. (Inventor)

2013-01-01

158

Brominated flame retardants in laboratory air  

Microsoft Academic Search

During the development of a method for determination of brominated flame retardants in human plasma and serum using solid-phase extraction, several brominated flame retardants were found in the procedural blanks. The contaminants originated most probably from the laboratory air. The brominated flame retardants were found to be adsorbed on glass surfaces and to be acquired using solid-phase sampling. 2,4,6-Tribromophenol, 2,2?,4,4?-tetrabromodiphenyl

C Thomsen; H Leknes; E Lundanes; G Becher

2001-01-01

159

Kinetics of Chemical Reactions in Flames  

NASA Technical Reports Server (NTRS)

In part I of the paper the theory of flame propagation is developed along the lines followed by Frank-Kamenetsky and one of the writers. The development of chain processes in flames is considered. A basis is given for the application of the method of stationary concentrations to reactions in flames; reactions with branching chains are analyzed. The case of a diffusion coefficient different from the coefficient of temperature conductivity is considered.

Zeldovich, Y.; Semenov, N.

1946-01-01

160

A review of flame retardant polypropylene fibres  

Microsoft Academic Search

Flame retardants for polypropylene (PP) and their potential suitability for use in fibre applications are reviewed. Five principal types of generic flame retardant systems for inclusion in polypropylene fibres have been identified as phosphorus-containing, halogen-containing, silicon-containing, metal hydrate and oxide and the more recently developed nanocomposite flame retardant formulations.The most effective to date comprise halogen–antimony and phosphorus–bromine combinations, which while

Sheng Zhang; A. Richard Horrocks

2003-01-01

161

30 CFR 75.600-1 - Approved cables; flame resistance.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Approved cables; flame resistance. 75.600-1 Section 75...Cables § 75.600-1 Approved cables; flame resistance. Cables shall be accepted or approved by MSHA as flame resistant. [57 FR 61223, Dec....

2010-07-01

162

30 CFR 75.600 - Trailing cables; flame resistance.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Trailing cables; flame resistance. 75.600 Section 75...Cables § 75.600 Trailing cables; flame resistance. [Statutory Provisions...requirements established by the Secretary for flame-resistant...

2010-07-01

163

46 CFR 151.03-23 - Flame arrestor.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Flame arrestor. 151.03-23 Section 151...CARGOES Definitions § 151.03-23 Flame arrestor. Any device or assembly...type used for preventing the passage of flames into enclosed...

2010-10-01

164

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Smoking or open flames. 195.438 Section 195...Operation and Maintenance § 195.438 Smoking or open flames. Each operator shall prohibit smoking and open flames in each pump station...

2010-10-01

165

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Smoking or open flames. 195.438 Section 195...Operation and Maintenance § 195.438 Smoking or open flames. Each operator shall prohibit smoking and open flames in each pump station...

2011-10-01

166

Flow/Soot-Formation Interactions in Nonbuoyant Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

This is the final report of a research program considering interactions between flow and soot properties within laminar diffusion flames. Laminar diffusion flames were considered because they provide model flame systems that are far more tractable for theoretical and experimental studies than more practical turbulent diffusion flames. In particular, understanding the transport and chemical reaction processes of laminar flames is a necessary precursor to understanding these processes in practical turbulent flames and many aspects of laminar diffusion flames have direct relevance to turbulent diffusion flames through application of the widely recognized laminar flamelet concept of turbulent diffusion flames. The investigation was divided into three phases, considering the shapes of nonbuoyant round laminar jet diffusion flames in still air, the shapes of nonbuoyant round laminar jet diffusion flames in coflowing air, and the hydrodynamic suppression of soot formation in laminar diffusion flames.

Dai, Z.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.

2002-01-01

167

Gravitational effects on the extinction conditions for premixed flames  

NASA Technical Reports Server (NTRS)

The four particular classes of premixed flames which are of special interest include freely propagating gaseous flames, burner stabilized premixed gaseous flames, freely propagating particle-cloud flames, and burner stabilized two-phase flames. Associated gravitational effects are related to upward flame propagation, downward flame propagation, and flame propagation in microgravity. The results of theoretical and experimental studies suggest that a comprehensive approach to representation of extinction limits must deal with the full range of existence limits observed for flames. Issues awaiting solution are related to the flammability limits, extinction limit relations, and flame theories for g = 0. Attention is given to theoretical considerations, nonadiabatic features of premixed lycopodium-air flames, and general comments on the extinction conditions for premixed flames.

Berlad, A. L.; Joshi, N. D.

1984-01-01

168

Flame structure of steady and pulsed sooting inverse jet diffusion flames  

Microsoft Academic Search

In turbulent buoyant fire plumes, local inverse diffusion flames of air injected into gaseous fuel or fuel vapors occur, but little is known about the tendency to form soot and produce thermal radiation in these flame structures. To investigate these phenomena, steady and pulsed normal and inverse jet diffusion flames of methane\\/air and ethylene\\/air have been stabilized on a slot

Timothy C. Williams; Christopher R. Shaddix; Linda Gail Blevins; Robert W. Schefer

2004-01-01

169

Flame structure of steady and pulsed sooting inverse jet diffusion flames  

Microsoft Academic Search

In turbulent buoyant fire plumes, local inverse diffusion flames of air injected into gaseous fuel or fuel vapors occur, but little is known about the tendency to form soot and produce thermal radiation in these flame structures. To investigate these phenomena, steady and pulsed normal and inverse jet diffusion flames of methane\\/air and ethylene\\/air have been stabilized on a slot

Christopher R. Shaddix; Timothy C. Williams; Linda G. Blevins; Robert W. Schefer

2005-01-01

170

Heat transfer characteristics of an impinging inverse diffusion flame jet – Part I: Free flame structure  

Microsoft Academic Search

This is the first part of the experimental investigation on the feasibility of inverse diffusion flame (IDF) for impingement heating. This part is aimed to identify the favorable IDF structure for impingement heating. Seven IDF structures have been observed altogether. Among them the favorable flame structure for impingement heating is identified to comprise a short base diffusion flame and a

L. L. Dong; C. S. Cheung; C. W. Leung

2007-01-01

171

An investigation of flame zones and burning velocities of laminar unconfined methane-oxygen premixed flames  

Microsoft Academic Search

Numerical and experimental investigations of unconfined methane-oxygen laminar premixed flames are presented. In a lab-scale burner, premixed flame experiments have been conducted using pure methane and pure oxygen mixtures having different equivalence ratios. Digital photographs of the flames have been captured and the radial temperature profiles at different axial locations have been measured using a thermocouple. Numerical simulations have been

R. Sreenivasan; V. Raghavan; T. Sundararajan

2012-01-01

172

An investigation of flame zones and burning velocities of laminar unconfined methane-oxygen premixed flames  

Microsoft Academic Search

Numerical and experimental investigations of unconfined methane-oxygen laminar premixed flames are presented. In a lab-scale burner, premixed flame experiments have been conducted using pure methane and pure oxygen mixtures having different equivalence ratios. Digital photographs of the flames have been captured and the radial temperature profiles at different axial locations have been measured using a thermocouple. Numerical simulations have been

R. Sreenivasan; V. Raghavan; T. Sundararajan

2011-01-01

173

Flames in Type Ia Supernova: Deflagration-Detonation Transition in the Oxygen Burning Flame  

E-print Network

Flames in Type Ia Supernova: Deflagration-Detonation Transition in the Oxygen Burning Flame S. E. Woosley1 , A. R. Kerstein2 , and A. J. Aspden3 ABSTRACT The flame in a Type Ia supernova is a conglomerate of these regions can be supersonic and could initiate a detonation. Subject headings: supernovae: general

174

Fundamental mechanisms in premixed turbulent flame propagation via flame–vortex interactions  

Microsoft Academic Search

A combined experimental and numerical study of the interaction of a two-dimensional vortex with planar laminar premixed flames has been carried out. In such a flow, the flame is subjected to time-varying strain and curvature and, hence, the interaction may be viewed as a model of fundamental processes occurring in premixed turbulent flames. Part I of the paper describes the

J.-M. Samaniego; T. Mantel

1999-01-01

175

Numerical simulation of flame dynamics associated with negative velocity induced by deformed flame shape  

Microsoft Academic Search

In this study, the influence of the negative velocity field formed ahead of an abruptly deformed flame tip on the propagation behaviour of a laminar premixed flame is numerically investigated. A strong deformation in the flame front is induced by imposing a very narrow, in-line pre-heating zone in the unburned region. The simulation is performed under low Mach number approximation

Akter Hossain; Nobuyuki Oshima; Yuji Nakamura; Marie Oshima

2012-01-01

176

Gravitational Effects on Cellular Flame Structure  

NASA Technical Reports Server (NTRS)

An experimental investigation has been conducted of the effect of gravity on the structure of downwardly propagating, cellular premixed propane-oxygen-nitrogen flames anchored on a water-cooled porous-plug burner. The flame is subjected to microgravity conditions in the NASA Lewis 2.2-second drop tower, and flame characteristics are recorded on high-speed film. These are compared to flames at normal gravity conditions with the same equivalence ratio, dilution index, mixture flow rate, and ambient pressure. The results show that the cellular instability band, which is located in the rich mixture region, changes little under the absence of gravity. Lifted normal-gravity flames near the cellular/lifted limits, however, are observed to become cellular when gravity is reduced. Observations of a transient cell growth period following ignition point to heat loss as being an important mechanism in the overall flame stability, dominating the stabilizing effect of buoyancy for these downwardly-propagating burner-anchored flames. The pulsations that are observed in the plume and diffusion flame generated downstream of the premixed flame in the fuel rich cases disappear in microgravity, verifying that these fluctuations are gravity related.

Dunsky, C. M.; Fernandez-Pello, A. C.

1991-01-01

177

Confined superadiabatic premixed flame-flow interaction  

SciTech Connect

Laminar premixed unity-Lewis number flames are studied numerically, to examine flow-flame interaction in a two-dimensional closed domain. Two opposed planar flame fronts are perturbed sinusoidally and allowed to develop by consuming premixed reactants. Combustion heat release leads to global pressure and temperature rise in the domain, due to confinement. A superadiabatic condition, with products temperature rising with distance behind the flame front, is observed due to stagnation pressure rise. Variations in tangential strain rate behind the perturbed flame fronts, due to flame curvature and heat release, result in a modified local superadiabatic temperature gradient in the products. These variations in temperature gradients are shown to determine the net local confinement-heating rate in the products, leading to corresponding deviations in products temperature, and the local reaction rate along the flame front. These observations, which are not consistent with one-dimensional superadiabatic stagnation flame behavior, are a direct result of the unrestrained unsteady nature of two-dimensional flame-flow interaction.

Najm, H.N.

1995-12-31

178

Characteristics of Edge Flames in Microcombustors  

NASA Astrophysics Data System (ADS)

Two streams, one containing fuel and the other oxidizer, are flowing into a relatively narrow channel where they mix and support an edge flame at some distance downstream. Our analysis is based on two models; one that fully couples the fluid dynamics and transport equations, used to determine the flame shape and location, and the other that assumes a constant-density flow, used to test the steady solutions for stability. It is found that in relatively wide channels the flame has a premixed, rounded edge with a trailing diffusion flame, but when the channel width decreases the flame is located further away from the supply and has a broader edge that can span the entire channel, when its width becomes comparable to the characteristic flame thickness. The effect of thermal expansion is to relocate the edge flame closer to the reactant supply. Heat losses at the channel walls cause a drop in the overall temperature and, as a result, the edge flame is confined to the center of the channel and the trailing diffusion flame is shortened significantly. Depending on the Lewis number, the flow rate, and the extent of heat loss, the edge may either remain steady, oscillate, or be blown off by the flow. With appreciable heat losses, residual fuel and oxidizer are observed at the end of the channel, so that under appropriate conditions, they could re-ignite and support a streak of diffusion flamelets, as seen experimentally.

Bieri, Joanna; Matalon, Moshe

2010-11-01

179

Soot zone structure and sooting limit in diffusion flames: Comparison of counterflow and co-flow flames  

SciTech Connect

Soot zone structures of counterflow and co-flow diffusion flames have been studied experimentally using the soot extinction-scattering, polycyclic aromatic hydrocarbon fluorescence, and laser Doppler velocimetry measurements. The counterflow flame has been numerically modelled with detailed chemistry. Results show that two different categories of sooting flame structures can be classified depending on the relative transport of soot particles to flames. These are the soot formation-oxidation flame and the soot formation flame. The soot formation-oxidation flame characteristics are observed in counterflow flames when located on the fuel side and in normal co-flow flames. In this case, soot particles are transported toward the high temperature region or the flame and experience soot inception, coagulation-growth, and oxidation. The soot formation flame characteristics are observed in counterflow flames when located on the oxidizer side and in inverse co-flow flames. In this case, soot particles are transported away from the flame without experiencing oxidation and finally leak through the stagnation plane in counterflow flames or leave the flame in inverse co-flow flames. Sooting limit measurements in both flames also substantiate the two different sooting flame structures and their characteristics.

Kang, K.T.; Hwang, J.Y.; Chung, S.H. [Seoul National Univ. (Korea, Republic of). Dept. of Mechanical Engineering] [Seoul National Univ. (Korea, Republic of). Dept. of Mechanical Engineering; Lee, W. [Dankook Univ., Seoul (Korea, Republic of). Dept. of Mechanical Engineering] [Dankook Univ., Seoul (Korea, Republic of). Dept. of Mechanical Engineering

1997-04-01

180

2060 Chiron - CCD and electronographic photometry  

NASA Technical Reports Server (NTRS)

R-band observations conducted for 2060 Chiron using CCD photometry in November-December 1986 and March 1988 are discussed. While the 1986 observations exhibit neither periodic nor nonperiodic brightness changes ascribable to comet-like activity, the 1988 observations show an 0.6 + or - 0.1 mag brightening that confirms the Tholen et al. (1988) findings and is consistent with the 1978 electronographic photometry presented. The lightcurve amplitudes appear, however, to have remained unchanged from 1978 to 1988, and the image profiles from 1978 are indistinguishable from the stars in 1986 and 1988. It is suggested that Chiron has either been varying nonasteroidally of late, on a 1-2 month timescale, or its intrinsic brightness has been bistable over the past decade.

Bus, Schelte J.; Bowell, Edward; Harris, Alan W.; Hewitt, Anthony V.

1989-01-01

181

Introducing SPA, "The Stellar Photometry Assistant"  

NASA Astrophysics Data System (ADS)

The Stellar Photometry Assistant, SPA, is a stand alone software package for time-series photometry reduction and analysis slated for an initial test release in spring 2008. The goal of SPA is to be simple, powerful, and intuitive. SPA was born out of complications in studying the pulsating DB white dwarf EC20058-5234 (QU Tel) due to the proximity of its nearby companions. SPA also addresses the Whole Earth Telescope's (WET) demand for large scale rapid data reduction from multiple sites. SPA is being developed in Matlab by the Delaware Asteroseismologic Research Center (DARC) in collaboration with the University of Delaware and the Mount Cuba Astronomical Observatory. The need for SPA is addressed, and key features of the program are listed and discussed.

Dalessio, J.; Provencal, J. L.; Kanaan, A.

2008-06-01

182

Lightcurve Photometry Opportunities: 2015 January-March  

NASA Astrophysics Data System (ADS)

We present lists of asteroid photometry opportunities for objects reaching a favorable apparition and having either none or poorly-defined lightcurve parameters. Additional data on these objects will help with shape and spin axis modeling via lightcurve inversion. We also include lists of objects that will be the target of radar observations. Lightcurves for these objects can help constrain pole solutions and/or remove rotation period ambiguities that might not come from using radar data alone.

Warner, Brian D.; Harris, Alan W.; Durech, Josef; Benner, Lance A. M.

2015-01-01

183

One Percent Strömvil Photometry in M 67  

NASA Astrophysics Data System (ADS)

The Vatican Advanced Technology Telescope on Mt. Graham is being used in a program of CCD photometry of open and globular clusters. We are using the Ströomvil System (Straižys et al. 1996), a combination of the Strömgren and Vilnius Systems. This system allows stars to be classified as to temperature, surface gravity, metallicity and reddening from the photometric measures alone. However, to make accurate estimates of the stellar parameters the photometry should be accurate to 1 or 1.5 percent. In our initial runs on the VATT we did not achieve this accuracy. The problem turned out to be scattered light in the telescope and this has now been reduced so we can do accurate photometry. Boyle has written a routine in IRAF which allows us to correct the flats for any differences. We take rotated frames and also frames which are offset in position by one third of a frame, east-west and north-south. Measures of the offset stars give us the corrections that need to be made to the flat. Robert Janusz has written a program, the CommandLog, which allows us to paste IRAF commands in the correct order to reduce measures made on a given observing run. There is an automatic version where one can test various parameters and get a set of solutions. Now we have a set of Strömvil frames in the open cluster, M 67 and we compare our color-magnitude diagram with those of BATC (Fan et al. 1996) and Vilnius (Boyle et al. 1998). A preliminary report of the M 67 photometry will be found in Laugalys et al. (2004). Here we report on a selected set of stars in the M 67 frames, those with errors 1 percent or less.

Philip, A. G. D.; Boyle, R. P.; Janusz, R.

2005-05-01

184

Near-Infrared Photometry of Carbon Stars  

Microsoft Academic Search

Near-infrared, JHKL, photometry of 239 Galactic carbon-rich variable stars is\\u000apresented and discussed. From these and published data the stars were\\u000aclassified as Mira or non-Mira variables and amplitudes and pulsation periods,\\u000aranging from 222 to 948 days for the Miras, were determined for most of them. A\\u000acomparison of the colour and period relations with those of similar stars

Patricia A. Whitelock; Michael W. Feast; Freddy Marang; M. A. T. Groenewegen

2006-01-01

185

Variable Star Photometry at West Challow Observatory  

NASA Astrophysics Data System (ADS)

This paper describes the facilities and observing programme of a small personal observatory set up in the UK for CCD photometry of variable stars. Its development has been driven by the belief that committed amateurs can make a valuable scientific contribution to the study of variable stars. Observing projects carried out at WCO are described including examples of Pro-Am collaboration and contributions to the observing programmes of the BAAVSS, AAVSO and CBA.

Boyd, D.

2007-05-01

186

Recalibrating SFD Using SDSS Spectroscopy And Photometry  

NASA Astrophysics Data System (ADS)

We use new measurements of reddening using SDSS photometry and spectroscopy to test the SFD dust map. We find that both the photometric and spectroscopic technique agree on a common SFD calibration that is different from the original SFD calibration by 13%. We find additionally that a Fitzpatrick 1999 reddening law provides a good fit to the reddening law derived from these techniques, while CCM and O'Donnell reddening laws are disfavored.

Schlafly, Eddie; Finkbeiner, D. P.

2011-05-01

187

Galileo photometry of Asteroid 951 Gaspra  

Microsoft Academic Search

The mean photometric properties of Gaspra's surface are derived in terms of Hapke's photometric model by combining earth-based telescopic photometry with Galileo's whole-disk and disk-resolved data. The results are used to estimate fundamental properties, such as the geometric albedo, and to compare surface materials on Gaspra with materials on other planetary surfaces. The photometric parameters and a new shape model

P. Helfenstein; J. Veverka; P. C. Thomas; D. P. Simonelli; P. Lee; K. Klaasen; T. V. Johnson; H. Breneman; J. W. Head; S. Murchie

1994-01-01

188

Material characterization by laser speckle photometry  

NASA Astrophysics Data System (ADS)

The damage and stress conditions of large industrial components have to be tested continuously. Especially welding processes in the field of coal production demand a nondestructive monitoring of internal stresses under an external load. In a first step, a new optical method, Laser Speckle Photometry was used during laboratory welding experiments under tensile and bending loads at high strength construction steels. Laser Speckle Photometry is a fast and contactless method for measuring spatial-temporal dynamics of speckle field with high temporal resolution after local heat excitation. The thermally induced change in the material structure causes changes in the speckle-field, which is formed by a probing laser. The shift of the speckle-field is analyzed by statistical methods, using correlation functions. The result of processing is the two-dimensional distribution of thermal diffusivity coefficient correlated to porosity, materials strain or hardness [1-3]. Here, the results of the welding experiments under load are presented. It is shown, that the Laser Speckle Photometry is a suitable technique for nondestructive monitoring and characterization of internal material stresses under external load.

Bendjus, Beatrice; Cikalova, Ulana; Schreiber, Juergen

2012-10-01

189

CCD Strömvil Photometry of M 37  

NASA Astrophysics Data System (ADS)

We have been working on a program of setting up standards in the Strömvil photometric system and have been doing CCD photometry of globular and open clusters. A previous paper (Boyle et al. BAAS, AAS Meeting #193, #68.08) described the results of observations made in the open cluster M 67, which we are setting up as one of the prime standard fields for Strömvil photometry. Now we discuss our observations of M 37, made on the Vatican Advanced Technology Telescope on Mt. Graham, Arizona. One of us (R.J.) has automated the data processing by a novel method. The Strömvil group is multinational. By use of this innovative automated, yet interactive processing method, one systematically applies the same processing steps to run in IRAF by capturing them as presented in html files and submitting them to the IRAF command language. Use of the mouse avoids errors and accelerates the processing from raw data frames to calibrated photometry. From several G2 V stars in M 67 we have calculated their mean color indices and compare them to stars in M 37 to identify candidate G2 V stars there. Identifying such stars relates to the search for terrestrial exoplanets. Ultimately we will use the calibrated Strömvil indices to make photometric determinations of log g and Teff.

Boyle, R. P.; Janusz, R.; Kazlauskas, A.; Philip, A. G. Davis

2001-12-01

190

Astrometry and photometry in high contrast imaging  

NASA Astrophysics Data System (ADS)

The direct exoplanet imaging field will strongly benefit from the larger aperture and the higher angular resolution achieved by next generation 30+m telescopes. To fully take advantage of these new facilities, one of the biggest challenges that ground-based adaptive optics imaging must overcome is to be able to derive accurate astrometry and photometry with realistic estimate of residual errors. The planet photometry and its astrometry are used to compare with atmospheric models and to fit orbits. If erroneous numbers are found, or if errors are underestimated, spurious fits can lead to unphysical planet characteristics or wrong/unstable orbits. Overestimating the errors also needs to be avoided as it degrades the value of the data. In the high-contrast planet imaging context, we will present various photometry/astrometry biases induced by several noise sources (anisoplanatism, non-Gaussian noise, etc.) or processing techniques (ADI/SSDI/LOCI) that we have uncovered during our ongoing direct exoplanet imaging campaign at Gemini, VLT and Keck. We will describe the procedures that we have implemented to properly estimate those biases. These solutions will be implemented in the Gemini Planet Imager campaign data pipeline and we expect that they will also play a crucial role in any future 30+m survey.

Galicher, Raphael; Marois, Christian

2011-09-01

191

Interaction of Two Micro-slot Flames: Heat Release Rate and Flame Shape  

NASA Astrophysics Data System (ADS)

This paper studies the interaction between two identical micro-slot diffusion flames. Here, we define a micro-slot flame as a slot flame of which the slot width is less than about 1 mm. Because of its smallness, a micro-slot flame has a high heating density and can be used as a small heat source. However, the heat release rate of a single micro-slot flame is limited, and therefore, multiple micro-slot flames may be used to increase total heat release rate. As a first step, this paper considers a situation in which two micro-slot flames are used with certain burner spacing. When two diffusion flames are placed closely, flame shape changes from that of an isolated flame. Studying such flame shape change and resultant change in total heat release rate is the topic of this paper. Experiment is conducted and total heat release rate is measured by integrating CH* chemiluminescence recorded using a CCD camera and an optical filter of the wavelength of 430 nm. Two different burner materials, copper and glass, are tested to study the effect of heat loss to burners. An analytical model is applied to predict flame shape. In addition to the classical Burke-Schumann assumptions, two slot flames are modeled as line sources with zero width, enabling a simple analytical solution for the critical burner spacing at which two flames touch each other. The critical burner spacing is a key parameter that characterizes the interaction between two micro-slot flames. Computational fluid dynamics (CFD) simulations are then conducted to test the validity of the present theory. CFD results are favorably compared with the theoretical prediction.

Kuwana, K.; Kato, S.; Kosugi, A.; Hirasawa, T.; Nakamura, Y.

2014-11-01

192

Unsteady planar diffusion flames: Ignition, travel, burnout  

NASA Technical Reports Server (NTRS)

In microgravity, a thin planar diffusion flame is created and thenceforth travels so that the flame is situated at all times at an interface at which the hydrogen and oxygen meet in stoichiometric proportion. If the initial amount of hydrogen is deficient relative to the initial amount of oxygen, then the planar flame will travel further and further into the half volume initially containing hydrogen, until the hydrogen is (virtually) fully depleted. Of course, when the amount of residual hydrogen becomes small, the diffusion flame is neither vigorous nor thin; in practice, the flame is extinguished before the hydrogen is fully depleted, owing to the finite rate of the actual chemical-kinetic mechanism. The rate of travel of the hydrogen-air diffusion flame is much slower than the rate of laminar flame propagation through a hydrogen-air mixture. This slow travel facilitates diagnostic detection of the flame position as a function of time, but the slow travel also means that the time to burnout (extinction) probably far exceeds the testing time (typically, a few seconds) available in earth-sited facilities for microgravity-environment experiments. We undertake an analysis to predict (1) the position and temperature of the diffusion flame as a function of time, (2) the time at which extinction of the diffusion flame occurs, and (3) the thickness of quench layers formed on side walls (i.e., on lateral boundaries, with normal vectors parallel to the diffusion-flame plane), and whether, prior to extinction, water vapor formed by burning will condense on these cold walls.

Fendell, F.; Wu, F.

1995-01-01

193

Public health implications of components of plastics manufacture. Flame retardants.  

PubMed Central

The four processes involved in the flammability of materials are described and related to the various flame retardance mechanisms that may operate. Following this the four practical approaches used in improving flame retardance of materials are described. Each approach is illustrated with a number of typical examples of flame retardants or synthetic procedures used. This overview of flammability, flame retardance, and flame retardants used is followed by a more detailed examination of most of the plastics manufactured in the United States during 1973, their consumption patterns, and the primary types of flame retardants used in the flame retardance of the most used plastics. The main types of flame retardants are illustrated with a number of typical commercial examples. Statistical data on flame retardant market size, flame retardant growth in plastics, and price ranges of common flame retardants are presented. Images FIGURE 1. FIGURE 2. FIGURE 3. FIGURE 4. PMID:1175568

Pearce, E M; Liepins, R

1975-01-01

194

Propagation of a Free Flame in a Turbulent Gas Stream  

NASA Technical Reports Server (NTRS)

Effective flame speeds of free turbulent flames were measured by photographic, ionization-gap, and photomultiplier-tube methods, and were found to have a statistical distribution attributed to the nature of the turbulent field. The effective turbulent flame speeds for the free flame were less than those previously measured for flames stabilized on nozzle burners, Bunsen burners, and bluff bodies. The statistical spread of the effective turbulent flame speeds was markedly wider in the lean and rich fuel-air-ratio regions, which might be attributed to the greater sensitivity of laminar flame speed to flame temperature in those regions. Values calculated from the turbulent free-flame-speed analysis proposed by Tucker apparently form upper limits for the statistical spread of free-flame-speed data. Hot-wire anemometer measurements of the longitudinal velocity fluctuation intensity and longitudinal correlation coefficient were made and were employed in the comparison of data and in the theoretical calculation of turbulent flame speed.

Mickelsen, William R; Ernstein, Norman E

1956-01-01

195

Jet flames of a refuse derived fuel  

SciTech Connect

This paper is concerned with combustion of a refuse derived fuel in a small-scale flame. The objective is to provide a direct comparison of the RDF flame properties with properties of pulverized coal flames fired under similar boundary conditions. Measurements of temperature, gas composition (O{sub 2}, CO{sub 2}, CO, NO) and burnout have demonstrated fundamental differences between the coal flames and the RDF flames. The pulverized coals ignite in the close vicinity of the burner and most of the combustion is completed within the first 300 ms. Despite the high volatile content of the RDF, its combustion extends far into the furnace and after 1.8 s residence time only a 94% burnout has been achieved. This effect has been attributed not only to the larger particle size of fluffy RDF particles but also to differences in RDF volatiles if compared to coal volatiles. Substantial amounts of oily tars have been observed in the RDF flames even though the flame temperatures exceeded 1300 C. The presence of these tars has enhanced the slagging propensity of RDF flames and rapidly growing deposits of high carbon content have been observed. (author)

Weber, Roman; Kupka, Tomasz; Zajac, Krzysztof [Institute of Energy Process Engineering and Fuel Technology, Clausthal University of Technology, Agicolastrasse 4, 38 678 Clausthal-Zellerfeld (Germany)

2009-04-15

196

The Structure and Propagation of Turbulent Flames  

Microsoft Academic Search

The influence of turbulence intensity, scale and vorticity on burning velocity and flame structure is examined by using premixed propane-air mixtures supplied at atmospheric pressure to a combustion chamber 31 cm long and 10 cm X 10 cm cross-section. The chamber is fitted with transparent side walls to permit flame observations and schlieren photography. Control over the turbulence level is

D. R. Ballal; A. H. Lefebvre

1975-01-01

197

The Mechanics of Vibrating Flames in Tubes  

Microsoft Academic Search

A mechanism of flame vibration is proposed which depends upon the instability of a reacting gas with respect to wave motion. A flame, steadily advancing down a tube, is represented by a narrow section of reacting gas bounded on either side by non-reacting gases at appropriate temperatures. By matching the derivatives of the velocity potentials of the reacting gas and

H. Jones

1977-01-01

198

Flame retardant cotton based highloft nonwovens  

Technology Transfer Automated Retrieval System (TEKTRAN)

Flame retardancy has been a serious bottleneck to develop cotton blended very high specific volume bulky High loft fabrics. Alternately, newer approach to produce flame retardant cotton blended High loft fabrics must be employed that retain soft feel characteristics desirable of furnishings. Hence, ...

199

Flame aerosol synthesis of ceramic powders  

Microsoft Academic Search

Flame aerosol technology is used for large-scale manufacture of ceramic commodities such as pigmentary titania, fumed silica and alumina. In addition, the introduction of this technology to the manufacture of optical fibers and its potential for cheap synthesis of ultrafine particles (e.g. nanoparticles) has renewed the research interest for better understanding of flame aerosol reactors. Here, after an overview of

Sotiris E. Pratsinis

1998-01-01

200

Thermal stability and flame retardancy of polyurethanes  

Microsoft Academic Search

The thermal stability and flame retardancy of polyurethanes is reviewed. Polyurethanes (PUs) are an important class of polymers that have wide application in a number of different industrial sectors. More than 70% of the literature that deals with PUs evaluates their thermal stability or flame retardancy and attempts to provide a structure–property correlation. The importance of studying thermal degradation, understanding

D. K. Chattopadhyay; Dean C. Webster

2009-01-01

201

Simple Flame Test Techniques Using Cotton Swabs  

ERIC Educational Resources Information Center

Three alternative methods for performing flame tests using cheaply and easily available cotton swabs are described. These flame tests are useful for chemical demonstrations or laboratory experiments because they are quick and easy to perform with easy cleanup and disposal methods.

Sanger, Michael J.; Phelps, Amy J.; Banks, Catherine

2004-01-01

202

On self-drifting flame balls  

Microsoft Academic Search

Self-drifting flame balls whose existence has recently been suggested by an ad hoc one-dimensional sandwich model are studied within the framework of a more rational multi-dimensional formulation as bifurcations of the associated stationary spherical flame balls.

L. Kagan; S. Minaev; Gregory I. Sivashinsky

2004-01-01

203

Isothermal propagation of rarefied nitrogen trichloride flames  

Microsoft Academic Search

1.Flames resulting from chain NCl3 decomposition are propagated through NCl3 + He mixtures lying outside the autoignition region.2.The fact that these are essentially isothermal flames is an indication of the important role of positive chain interaction in this process.

V. V. Azatyan; R. R. Borodulin; E. A. Markevich; N. M. Rubtsov; N. N. Semenov

1976-01-01

204

Transient Supersonic Methane-Air Flames  

E-print Network

. The combustor was designed following well-known principles of jet engine combustors. A flame holder and spark plug combination was used to encourage turbulent mixing and ignition of reactant gases, and to anchor the transient flame. Combustion created a high...

Richards, John L.

2012-07-16

205

Soot formation in laminar diffusion flames  

Microsoft Academic Search

Laminar, sooting, coflow diffusion flames at atmospheric pressure have been studied experimentally and theoretically as a function of fuel dilution by inert nitrogen. The flames have been investigated with laser diagnostics. Laser extinction has been used to calibrate the experimental soot volume fractions and an improved gating method has been implemented in the laser-induced incandescence (LII) measurements resulting in differences

M. D. Smooke; M. B. Long; B. C. Connelly; M. B. Colket; R. J. Hall

2005-01-01

206

Flame retardant cotton barrier nonwovens for mattresses  

Technology Transfer Automated Retrieval System (TEKTRAN)

According to regulation CPSC 16 CFR 1633, every new residential mattress sold in the United States since July 2007 must resist ignition by open flame. An environmentally benign “green”, inexpensive way to meet this regulation is to use a low-cost flame retardant (FR) barrier fabric. In this study, a...

207

Upward flame spread over corrugated cardboard  

Microsoft Academic Search

As part of a study of the combustion of boxes of commodities, rates of upward flame spread during early-stage burning were observed during experiments on wide samples of corrugated cardboard. The rate of spread of the flame front, defined by the burning pyrolysis region, was determined by visually averaging the pyrolysis front position across the fuel surface. The resulting best

M. J. Gollner; F. A. Williams; A. S. Rangwala

2011-01-01

208

Thermal diffusion and flame structure in a laminar hydrogen jet diffusion flames  

NASA Astrophysics Data System (ADS)

This dissertation is a combined experimental and numerical investigation of hydrogen diffusion flame structure. Several laser diagnostic techniques were applied to study laminar hydrogen jet diffusion flames. The experimental results were compared with direct numerical simulation (DNS) models of the combusting flows. Nitrogen coherent anti-Stokes Raman scattering (CARS) provided measurements of temperature. These measurements initially indicated that modeling of the flames requires the inclusion of thermal diffusion. Usually neglected, thermal diffusion was found to nearly double the diffusion velocity of light species to the flame from when compared to concentration diffusion alone. Thermal diffusion acts to increase the flame temperature by increasing the non-unity Lewis number effects in these flames, i.e. the flame becomes hotter due to the increased preferential diffusion of hydrogen. The DNS computations indicated that thermal diffusion significantly affects the hydrogen concentration profiles. Consequently, dual-pump hydrogen/nitrogen CARS was used to obtain relative hydrogen/nitrogen concentrations. With accurate temperature and hydrogen concentration measurements it was possible to evaluate the magnitude of the hydrogen thermal diffusion in the DNS model. Quantitative comparisons of detailed measurements and DNS modeling were used to analyze a wide variety of complex reacting flows, including: steady flames, the stabilization region, and driven vortex-flame interactions. The steady, undriven flames were used to evaluate the thermal diffusion model. In addition to showing a premixed area inside the flame zone of the stabilization region, temperature and concentration measurements indicated that jet flame attachment is sensitive to nozzle and flow conditions. The complex interactions of flow, flame stretch, and chemistry were found to be important in the driven vortex-flame interactions.

Schauer, Frederick R.

209

Stoichiometric flames and their stability  

SciTech Connect

The authors consider a flame in a stoichiometric combustible mixture of two reactants, A and B, having different diffusivities. They employ a thin reaction zone approximation and assume that the reaction ceases when the concentrations and temperature approach their thermodynamic equilibrium values. Thus, the analysis accounts for the possibility of a reversible stage in the combustion reactions. The authors find uniform flames and analyze both their cellular and pulsating instabilities. They compare the results with those for a one reactant flame as well as with previously obtained results for a stoichiometric mixture of two reactants. Studies of the latter assumed complete consumption of one of the reactants in the reaction front and that both Lewis numbers, L{sub A} and L{sub B}, are close to 1. They showed that the cellular stability boundary for bimolecular reactions is determined by an effective Lewis number which is the arithmetic mean of L{sub A} and L{sub B}. By considering the limiting case of a negligibly small equilibrium constant, so that the final concentrations of the reactants approach zero, the authors show that for general Lewis numbers, not limited to being close to 1, the cellular stability boundary is determined by an effective Lewis number which, for equimolecular is the harmonic mean of the Lewis numbers of the two reactants, i.e., L{sub eff} = 2/(L{sub A}{sup {minus}1} + L{sub B}{sup {minus}1}). For significantly different Lewis numbers, a case not covered by previous results, their solution shows that stability is determined by diffusion of the lighter reactant, in accord with experimental observations. Thus, the authors provide a theoretical basis for the effect of preferential diffusion. They also find that dissociation of the product is stabilizing.

Aldushin, A.P.; Matkowsky, B.J.; Volpert, V.A. [Northwestern Univ., Evanston, IL (United States). Dept. of Engineering Sciences and Applied Mathematics] [Northwestern Univ., Evanston, IL (United States). Dept. of Engineering Sciences and Applied Mathematics

1995-04-01

210

Monitoring Atmospheric Transmission with FLAME  

NASA Astrophysics Data System (ADS)

Calibration of ground-based observations in the optical and near-infrared requires precise and accurate understanding of atmospheric transmission, at least as precise and accurate as that required for the spectral energy distributions of science targets. Traditionally this has used the Langley extrapolation method, observing targets and calibrators over a range of airmass and extrapolating to zero airmass by assuming a plane-parallel homogeneous atmosphere. The technique we present uses direct measurements of the atmosphere to derive the transmission along the line of sight to science targets at a few well-chosen wavelengths. The Facility Lidar Atmospheric Monitor of Extinction (FLAME) is a 0.5m diameter three Nd:YAG wavelength (355nm, 532nm & 1064nm) elastic backscatter lidar system. Laser pulses are transmitted into the atmosphere in the direction of the science target. Photons scattered back toward the receiver by molecules, aerosols and clouds are collected and time-gated so that the backscatter intensity is measured as a function of range to the scattering volume. The system is housed in a mobile calibration lab, which also contains auxiliary instrumentation to provide a NIST traceable calibration of the transmitted laser power and receiver efficiency. FLAME was designed to create a million photons per minute signal from the middle stratosphere, where the atmosphere is relatively calm and dominated by molecules of the well-mixed atmosphere (O2 & N2). Routine radiosonde measurements of the density at these altitudes constrain the scattering efficiency in this region and, combined with calibration of the transmitter and receiver, the only remaining unknown quantity is the two-way transmission to the stratosphere. These measurements can inform atmospheric transmission models to better understand the complex and ever-changing observatory radiative transfer environment. FLAME is currently under active development and we present some of our ongoing measurements.

Zimmer, Peter C.; McGraw, J. T.; Zirzow, D. C.; Koppa, M.; Buttler-Pena, K.

2014-01-01

211

The Structure and Stability of Laminar Flames  

NASA Technical Reports Server (NTRS)

This review paper on the structure and stability of laminar flames considers such phenomena as heterogeneous mixtures, acoustic instabilities, flame balls and related phenomena, radiation effects, the iodate oxidation of arsenous acid and 'liquid flame fronts', approximate kinetic mechanisms and asymptotic approximations, and tribrachial or triple flames. The topics examined here indicate three themes that may play an important role in laminar flame theory in the coming years: microgravity experiments, kinetic modeling, and turbulence modeling. In the discussion of microgravity experiments it is pointed out that access to drop towers, the Space Shuttle and, in due course, the Space Station Freedom will encourage the development of experiments well designed to isolate the fundamental physics of combustion.

Buckmaster, John

1993-01-01

212

Edge Diffusion Flame Propagation and Stabilization Studied  

NASA Technical Reports Server (NTRS)

In most practical combustion systems or fires, fuel and air are initially unmixed, thus forming diffusion flames. As a result of flame-surface interactions, the diffusion flame often forms an edge, which may attach to burner walls, spread over condensed fuel surfaces, jump to another location through the fuel-air mixture formed, or extinguish by destabilization (blowoff). Flame holding in combustors is necessary to achieve design performance and safe operation of the system. Fires aboard spacecraft behave differently from those on Earth because of the absence of buoyancy in microgravity. This ongoing in-house flame-stability research at the NASA Glenn Research Center is important in spacecraft fire safety and Earth-bound combustion systems.

Takahashi, Fumiaki; Katta, Viswanath R.

2004-01-01

213

Interaction Between Flames and Electric Fields Studied  

NASA Technical Reports Server (NTRS)

The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

Yuan, Zeng-Guang; Hegde, Uday

2003-01-01

214

Particle Cloud Flames in Acoustic Fields  

NASA Technical Reports Server (NTRS)

Results are presented on a study of flames supported by clouds of particles suspended in air, at pressures about 100 times lower than normal. In the experiment, an acoustic driver (4-in speaker) placed at one end of a closed tube, 0.75-m long and 0.05 m in diameter, disperses a cloud of lycopodium particles during a 0.5-sec powerful acoustic burst. Properties of the particle cloud and the flame were recorded by high-speed motion pictures and optical transmission detectors. Novel flame structures were observed, which owe their features to partial confinement, which encourages flame-acoustic interactions, segregation of particle clouds into laminae, and penetration of the flame's radiative flux density into the unburned particle-cloud regimes. Results of these experiments imply that, for particles in confined spaces, uncontrolled fire and explosion may be a threat even if the Phi(0) values are below some apparent lean limit.

Berlad, A. L.; Tangirala, V.; Ross, H.; Facca, L.

1990-01-01

215

Flame-vortex interactions imaged in microgravity  

NASA Technical Reports Server (NTRS)

The scientific objective is to obtain high quality color-enhanced digital images of a vortex exerting aerodynamic strain on premixed and nonpremixed flames with the complicating effects of buoyancy removed. The images will provide universal (buoyancy free) scaling relations that are required to improve several types of models of turbulent combustion, including KIVA-3, discrete vortex, and large-eddy simulations. The images will be used to help quantify several source terms in the models, including those due to flame stretch, flame-generated vorticity, flame curvature, and preferential diffusion, for a range of vortex sizes and flame conditions. The experiment is an ideal way to study turbulence-chemistry interactions and isolate the effect of vortices of different sizes and strengths in a repeatable manner. A parallel computational effort is being conducted which considers full chemistry and preferential diffusion.

Driscoll, James F.; Dahm, Werner J. A.; Sichel, Martin

1995-01-01

216

The flaming gypsy skirt injury.  

PubMed

On review of admissions over a 12-month period, we noted a significant number of women presenting with gypsy skirt burns. We describe all six cases to highlight the unique distribution of the wounds and the circumstances in which the accidents occurred. Four skirts were ignited by open fire heaters: two skirts ignited whilst the women were standing nearby, distracted with a telephone conversation; one brushed over the flame as she was walking past the heater; other whilst dancing in the lounge. One skirt was ignited by decorative candles placed on the floor during a social gathering. Another skirt was set alight by cigarette ember, whilst smoking in the toilet. Percentage surface area burned, estimated according to the rule of nines, showed that gypsy skirt burns were significant ranging from 7 to 14% total body surface area (TBSA) and averaging 9% TBSA. Two patients required allogenic split-skin grafts. Common sense care with proximity to naked flame is all that is needed to prevent this injury. PMID:17081546

Leong, S C L; Emecheta, I E; James, M I

2007-01-01

217

Scaling of turbulent flame speed for expanding flames with Markstein diffusion considerations  

NASA Astrophysics Data System (ADS)

In this paper we clarify the role of Markstein diffusivity, which is the product of the planar laminar flame speed and the Markstein length, on the turbulent flame speed and its scaling, based on experimental measurements on constant-pressure expanding turbulent flames. Turbulent flame propagation data are presented for premixed flames of mixtures of hydrogen, methane, ethylene, n-butane, and dimethyl ether with air, in near-isotropic turbulence in a dual-chamber, fan-stirred vessel. For each individual fuel-air mixture presented in this work and the recently published iso-octane data from Leeds, normalized turbulent flame speed data of individual fuel-air mixtures approximately follow a ReT,f0.5 scaling, for which the average radius is the length scale and thermal diffusivity is the transport property of the turbulence Reynolds number. At a given ReT,f, it is experimentally observed that the normalized turbulent flame speed decreases with increasing Markstein number, which could be explained by considering Markstein diffusivity as the leading dissipation mechanism for the large wave number flame surface fluctuations. Consequently, by replacing thermal diffusivity with the Markstein diffusivity in the turbulence Reynolds number definition above, it is found that normalized turbulent flame speeds could be scaled by ReT,M0.5 irrespective of the fuel, equivalence ratio, pressure, and turbulence intensity for positive Markstein number flames.

Chaudhuri, Swetaprovo; Wu, Fujia; Law, Chung K.

2013-09-01

218

Near Infrared Photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

Subjects: Infra-Red, Nova We report RIJHKLM photometry of Nova Del 2013 taken on August 28.13 UT using an As:Si bolometer mounted on the 0.76-m infrared telescope of the University of Minnesota's O'Brien Observatory (Marine on St. Croix, Minnesota, USA). Vega (alpha Lyrae) was used as the standard star. On this date we find: R = 5.6 +/- 0.1, I = 5.2 +/- 0.1, J = 4.5 +/- 0.1, H = 4.7 +/- 0.1, K = 4.7 +/- 0.1, L = 3.3 +/- 0.2, M = +1.8 +/- 0.3.

Cass, C. A.; Carlon, L. R.; Corgan, T. D.; Dykhoff, A. D.; Gehrz, D. R.; Shenoy, P. D.

2013-08-01

219

New BVR Photometry of BL Camelopardalis  

NASA Astrophysics Data System (ADS)

New BVR photometry of the SX Phe star BL Camelopardalis has been secured with the 0.9 m reflector at the BYU West Mountain Observatory. The new data have been used to determine times of maximum light, standardize light curves in each of the three filters, and examine the frequencies that are currently detectable in the light curves from a single location.We acknowledge the Brigham Young University College of Physical and Mathematical Sciences as well as the Department of Physics and Astronomy for continued support of this and other research efforts currently being done at the West Mountain Observatory.

Joner, Michael D.

2015-01-01

220

V photometry of Titania, Oberon, and Triton  

NASA Technical Reports Server (NTRS)

The phase angle and orbital brightness variations of Titania, Oberon, and Triton are presently obtained through analysis of V filter photometry obtained at Mauna Kea in 1982-1983. While Titania and Oberon exhibit magnitude variations with phase angle comparable to those of low-to-moderate albedo asteroids observed within several deg of opposition, Triton's phase variation is distinctly different from these and has a phase coefficient consistent with either a high-albedo regolith or an optically thick nonparticulate scattering layer (perhaps an atmosphere, or an ocean). A low-albedo regolith cannot on the strength of these data be ruled out, however.

Goguen, J. D.; Hammel, H. B.; Brown, R. H.

1989-01-01

221

Charles Nordmann and Multicolour Stellar Photometry  

NASA Astrophysics Data System (ADS)

Charles Nordmann (1881-1940), an astronomer at the Paris Observatory, was the first to determine the effective temperature of stars with his photometre heterochrome, simultaneously and independently of Rosenberg, Wilsing and Scheiner in Germany. He is also the remote precursor of the multicolour photometry of Johnson and Morgan. In spite of the quality of his temperature determinations, which were as good or better than those made by spectrophotometry, he rapidly fell into oblivion because of some failures in his scientific work. We examine his activity in the international context of the time, and explain why he has been forgotten, to be rediscovered only recently.

Lequeux, James

2010-11-01

222

Photometry of six radar target asteroids  

NASA Astrophysics Data System (ADS)

Photoelectric photometry of six Earth-approaching asteroids is presented. The selection criterion was that they were close enough in 1986 to be observed by radar. Rotation periods were obtained for 1986 DA, 3199, 3103, and 1983 RD. 1986 JK and 1986 RA showed no detectable brightness variations during the monitoring time on several nights each, and therefore were either seen pole-on or have long rotation periods. Asteroids 1986 JK and 1986 RA are of taxonomic class C, 1986 DA and 3103 of class X, 1983 RD of class Q, and only 3199 of the class S that was previously believed to be predominant among Earth-approaching asteroids.

Wisniewski, W. Z.

1987-06-01

223

CCD surface photometry of galaxies with dynamical data. II. UBR photometry of 39 elliptical galaxies  

Microsoft Academic Search

Intrinsic properties of elliptical galaxies and the mechanisms of their formation and evolution are discussed on the basis of high-precision, multicolor, surface photometry of 39 elliptical galaxies and measurements of rotation curves and velocity dispersion profiles. Using the data collected, a number of correlations between the characteristic parameters of the stellar population of the galaxies have been made to explore

Reynier F. Peletier; Roger L. Davies; L. E. Davis; G. D. Illingworth; Michael Cawson

1990-01-01

224

Stability Limits and Behaviors of the Inverse Diffusion Flame  

Microsoft Academic Search

The flame stability limits essentially define the fundamental operation conditions of the combustion system. The critical conditions of the flame stability limits are highly dependent on flow configurations and species of fuels. For various species of fuels (Methane, Propane and Hydrogen), the flame-base stability mechanism for the diffusion flame holding has been studied. The nozzle diameter (curvature) at the upstream

T. Yoshimoto; Y. Kato; N. Kubo; D. Ito; T. Takagi

225

Laminar Soot Processes Experiment Shedding Light on Flame Radiation  

NASA Technical Reports Server (NTRS)

The Laminar Soot Processes (LSP) experiment investigated soot processes in nonturbulent, round gas jet diffusion flames in still air. The soot processes within these flames are relevant to practical combustion in aircraft propulsion systems, diesel engines, and furnaces. However, for the LSP experiment, the flames were slowed and spread out to allow measurements that are not tractable for practical, Earth-bound flames.

Urban, David L.

1998-01-01

226

Interaction of a vortex ring with a diffusion flame  

Microsoft Academic Search

The interaction between a laminar vortex ring and a flat diffusion flame is investigated via direct numerical simulations. The diffusion flame is generated by a ``spark'' and is implemented as initial condition for the simulations. The chemistry is modeled by an Arrhenius, single step, irreversible reaction. A heat-releasing flame sheet is also considered in addition to the finite rate flames.

C. Safta; S. Enachescu; C. K. Madnia

2002-01-01

227

Droplet and flame dynamics in combustion phenomena  

NASA Astrophysics Data System (ADS)

This dissertation presents theoretical and experimental results on binary droplet collision, flame-vortex interaction, and the structure, geometry and propagation of spherical and cylindrical premixed and diffusion flames. Regarding the study on the dynamics of binary droplet collision, it is shown that, by varying the density of the gas through its pressure and molecular weight, water and hydrocarbon droplets both exhibit five distinct regimes of collision outcomes, namely coalescences with minor and substantial deformations, bouncing, and near head-on and off-center separations after coalescences. Therefore previous observations, obtained at one atmosphere air for water droplet are extended and unified with hydrocarbon droplets. A coalescence/separation criterion was derived, which identifies the dominant factors of the impact inertia and viscous dissipation and agrees well with the experimental data. A front tracking numerical technique was then used to study the collision dynamics in detail, and the computation quantitatively simulates well the experimental outcome of the collision. It was found that the minimum gas gap between the droplets exhibits a non-monotonic dependence on the droplet kinetic energy, thereby explaining the non-monotonic transition between the collision regimes of coalescence and bouncing. Both computational and experimental results further show that the droplet collision time is close to its natural oscillation time. This front tracking method for droplet collision was then adopted to simulate the unsteady motion of a premixed flame upon its interaction with a flow vortex. It was shown that the initial vorticity field can be significantly distorted or even eliminated by the flame, being substituted by flame generated vorticity corresponding to the tilted flame element, as consequence of the flame instability development. A linear stability analysis and numerical simulation of the flame and vortex pair interaction in the presence of gravity further showed that the hydrostatic pressure can qualitatively change the vorticity development, and that the influence of gravity on the vorticity generation depends on the Froude number associated with the flame speed and the characteristic length scale of the vortex. Two auxiliary studies on the structure and dynamics of flames in the absence of gravity were performed. First the influence of flow rate and rotation on the structure and response of burner-stabilized spherical premixed flames was analyzed by the asymptotic method. The leading order solution which describes the non-rotating spherical flame was constructed, and various mechanisms for the stabilization of the curved flame were identified. Rotation was then included as a perturbation. It was found that flame is deformed into a pancake shape that may be flattened either at the poles or the equator, depending on the combined effects of Lewis number, flame stretch and ambient temperature. The second problem is concerned with the unsteady outwardly-spreading motion of a diffusion flame from a cylindrical porous burner. Laplace inversion with large or small values of time was used to show that the flame spreading is mainly controlled by the ambient oxidizer concentration relative to the fuel concentration, modified by the flow rate from the burner, and that the characteristic diffusion length can be significantly larger or smaller than the flame radius, with their ratio being related to the quasi-steady assumption.

Qian, Jun

1997-08-01

228

Laminar Premixed and Diffusion Flames (Ground-Based Study)  

NASA Technical Reports Server (NTRS)

Ground-based studies of soot processes in laminar flames proceeded in two phases, considering laminar premixed flames and laminar diffusion flames, in turn. The test arrangement for laminar premixed flames involved round flat flame burners directed vertically upward at atmospheric pressure. The test arrangement for laminar jet diffusion flames involved a round fuel port directed vertically upward with various hydrocarbon fuels burning at atmospheric pressure in air. In both cases, coflow was used to prevent flame oscillations and measurements were limited to the flame axes. The measurements were sufficient to resolve soot nucleation, growth and oxidation rates, as well as the properties of the environment needed to evaluate mechanisms of these processes. The experimental methods used were also designed to maintain capabilities for experimental methods used in corresponding space-based experiments. This section of the report will be limited to consideration of flame structure for both premixed and diffusion flames.

Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

229

Structure of Propagating and Attached Hydrocarbon Flames  

NASA Technical Reports Server (NTRS)

Direct numerical simulations with C3-chemistry and radiative heat-loss models have been performed to reveal the internal structure of propagating and attached flames in an axisymmetric fuel jet of methane, ethane, ethylene, acetylene, or propane in air under normal and zero gravity. Observations of the flames were also made at the NASA Glenn 2.2-Second Drop Tower. In computations, the fuel issued into quasi-quiescent air for a fixed mixing time before it was ignited along the centerline at stoichiometry. The edge of the flame propagated through a flammable layer at the laminar flame speed of the stoichiometric fuel-air mixture independent of gravity. For all cases, a peak reactivity spot, i.e., reaction kernel, was formed in the flame base, thereby holding a trailing diffusion flame. The location of the reaction kernel in the attached flames depended inversely on the reactivity. The reaction-kernel correlations between the reactivity and the velocity were developed further using variables related to local Damkahler and Peclet numbers.

Takahashi, Fumiaki; Katta, Viswanath

2004-01-01

230

Progress and challenges in swirling flame dynamics  

NASA Astrophysics Data System (ADS)

In many continuous combustion processes the flame is stabilized by swirling the injected flow. This is the case for example in aeroengine combustors or in gas turbines where aerodynamic injectors impart a rotating component to the flow to create a central recirculation zone which anchors the flame. Swirling flame dynamics is of technical interest and also gives rise to interesting scientific issues. Some of the recent progress in this field will be reviewed. It is first shown that the swirler response to incident acoustic perturbations generates a vorticity wave which is convected by the flow. A result of this process is that the swirl number fluctuates. It is then shown that the flame response is defined by a combination of heat release rate fluctuations induced by the incoming acoustic and convective perturbations. This is confirmed by experimental measurements and by large eddy simulations of the reactive flow. Measured flame describing functions (FDFs) are then used to characterize the nonlinear response of swirling flames to incident perturbations and determine the regimes of instability of a generic system comprising an upstream manifold, an injector equipped with a swirler and a combustion chamber confining the flame. The last part of this article is concerned with interactions of the precessing vortex core (PVC) with incoming acoustic perturbations. The PVC is formed at high swirl number and this hydrodynamic helical instability gives rise to some interesting nonlinear interactions between the acoustic frequency, the PVC frequency and their difference frequency.

Candel, Sébastien; Durox, Daniel; Schuller, Thierry; Palies, Paul; Bourgouin, Jean-François; Moeck, Jonas P.

2012-11-01

231

Premixed turbulent flame propagation in microgravity  

NASA Technical Reports Server (NTRS)

To reduce pollutant formation there is, at present, an increased interest in employing premixed fuel/air mixture in combustion devices. It is well known that greater control over local temperature can be achieved with premixed flames and with lean premixed mixtures, significant reduction of pollutants such as NO(x) can be achieved. However, an issue that is still unresolved is the predictability of the flame propagation speed in turbulent premixed mixtures, especially in lean mixtures. Although substantial progress has been made in recent years, there is still no direct verification that flame speeds in turbulent premixed flows are highly predictable in complex flow fields found in realistic combustors. One of the problems associated with experimental verification is the difficulty in obtaining access to all scales of motion in typical high Reynolds number flows, since, such flows contain scales of motion that range from the size of the device to the smallest Kolmogorov scale. The overall objective of this study is to characterize the behavior of turbulent premixed flames at reasonable high Reynolds number, Re(sub L). Of particular interest here is the thin flame limit where the laminar flame thickness is much smaller than the Kolmogorov scale. Thin flames occur in many practical combustion devices and will be numerically studied using a recently developed new formulation that is briefly described.

Menon, S.; Jagoda, J.; Sujith, R.

1995-01-01

232

Soot zone structure and sooting limit in diffusion flames: Comparison of counterflow and co-flow flames  

Microsoft Academic Search

Soot zone structures of counterflow and co-flow diffusion flames have been studied experimentally using the soot extinction-scattering, polycyclic aromatic hydrocarbon fluorescence, and laser Doppler velocimetry measurements. The counterflow flame has been numerically modelled with detailed chemistry. Results show that two different categories of sooting flame structures can be classified depending on the relative transport of soot particles to flames. These

W. Lee; J. Y. Hwang; S. H. Chung

1997-01-01

233

Investigations of heat release, extinction, and time evolution of the flame surface, for a nonpremixed flame interacting with a vortex  

Microsoft Academic Search

Flame\\/vortex interactions to a great extent govern turbulent combustion. Flame roll-up due to vortices is also one of the most important phenomena driving combustion instabilities. An experimental investigation analyzes some fundamental features of a diffusion flame interacting with a vortex ring. A steady nonpremixed counterflow flame of air and hydrogen diluted with nitrogen is first established. A vortex ring is

Paul-Henri Renard; Juan Carlos Rolon; Dominique Thévenin; Sébastien Candel

1999-01-01

234

Quasar Selection using Optical Photometry and Variability  

NASA Astrophysics Data System (ADS)

We used the Non-parametric Bayesian Classification Kernel Density Estimation (NBC KDE) quasar selection algorithm to identify 30,755 type 1 quasar candidates on the Sloan Digital Sky Survey (SDSS) Stripe 82 using the combination of optical photometry and variability. Optical photometry is taken from the SDSS-I/II, while the variability parameters are calculated by fitting the structure function of the object with a power law. Selection was based on a training sample of 13,784 spectroscopically-confirmed type 1 quasars from the SDSS-I/II and the Baryon Oscillation Spectroscopic Survey (BOSS). Using variability alone, colors alone, and combining variability and colors we achieve 85%, 90%, and 95% quasar completeness respectively, with particular improvement in the selection of quasars at 2.7

Peters, Christina M.; Richards, Gordon T.; Myers, Adam D.; Ross, Nicholas

2015-01-01

235

Speckle Interferometry and Photometry of Binary Stars  

NASA Astrophysics Data System (ADS)

Binary orbits, when combined with parallaxes, yield dynamical masses, while photometry of the components restrains astrophysical models. Both are vital to understanding stellar evolution. Speckle interferometry, which is telescope resolution limited as opposed to seeing limited, allows observation of close, short-period binaries. We will use our next-generation, ultra-portable, low cost, EMCCD based speckle camera to observe some 500 binaries. We will confirm Hipparcos/Tycho double star discoveries as candidates for new binaries, classify new pairs by determining if their motion is curved (binary) or linear (optical double), add high-accuracy speckle observations that will allow the first determination of orbits, refine existing orbits by extending orbital coverage with speckle observations, and obtain precise photometry of binary components to link photometric with dynamical masses. For a decade, PI Genet has held undergraduate astronomy research seminars at Cuesta College that feature published student observations of binary stars. This run will demonstrate that student researchers can be an integral part of speckle interferometry runs at major observatories.

Genet, Russell M.; Hartkopf, William I.; Clark, R. Kent; Hardersen, Paul; Wren, Paul; Wallace, Daniel; Gelston, Ryan

2013-08-01

236

WISE photometry of EXor sources and candidates  

NASA Astrophysics Data System (ADS)

We present a collection of WISE photometry of EXor sources and candidates (more recently identified). This represents the first complete survey of such objects in the mid-IR (3.4-22 ?m) that was carried out with the same instrumentation. Two-color diagrams constructed with WISE data evidence a clear segregation between classical and newly identified sources, being these latter characterized by colder (and less evolved) circumstellar disks. By combining 2MASS and WISE data, we obtain spectral energy distributions (SED's) that are compatible with the existence of an inner hole in the circumstellar disk. A compilation of all EXor observations given in the literature at wavelengths very similar to those of WISE is also provided. This allows us to study their mid-IR variability, which has been poorly investigated so far and without any coordination with surveys at shorter wavelengths. The presented WISE photometry and the compilation of the literature data are intended as a first step toward the construction of a significant database in this spectral regime. Preliminary indications on the mechanisms responsible for the luminosity fluctuations are provided.

Antoniucci, S.; Giannini, T.; Lorenzetti, D.

2013-10-01

237

Multicolour photometry of EO Ceti (PB 8783)  

NASA Astrophysics Data System (ADS)

We present the first-look analysis of the high-speed multicolour photometry of the bright V361 Hya-type star EO Ceti ( m V=12.3). The observations were gathered with the three-channel ULTRACAM instrument attached to the 4.2-m William Herschel Telescope. The data set has a total time span of 6.2 d and consists of 31 h simultaneous three colour photometry. The main power regions in all three colours are the same as previously reported in the white light photometric campaigns on EO Ceti. We calculate the frequencies, amplitudes and phases of the significant modes in three colours of the SDSS system, r', g' and u'. The amplitudes of the detected modes are the highest in the u' lightcurve, and the phases are the same in all three colours within the measurement accuracy. The amplitudes of the highest signal-to-noise modes show time variability in all three colours. We analyse the amplitude and phase variations of the five highest signal-to-noise modes in different colours. Even though the amplitudes show variations from night to night, the amplitude ratios are found to be constant to within 2 ? level. This result is promising as it allows us to compare the observed amplitude ratios with theoretically calculated amplitude ratios. This may further constrain the mode identification of the highest amplitude modes in EO Ceti and let us test the proposed seismic and binary evolution models.

Vu?kovi?, M.; Østensen, R. H.; Aerts, C.; Dhillon, V. S.; Marsh, T. R.

2010-10-01

238

Flame Oscillations In Non-Premixed Systems Diffusion Flames and Edge-Flames  

NASA Technical Reports Server (NTRS)

Diffusive-thermal instabilities are well known features of premixed and diffusion flames. In one of its form the instability appears as spontaneous oscillations. In premixed systems oscillations are predicted to occur when the effective Lewis number, defined as the ratio of the thermal diffusivity of the mixture to the mass diffusivity of the deficient component, is sufficiently larger than one. Oscillations would therefore occur in mixtures that are deficient in the less mobile reactant, namely in lean hydrocarbon-air or rich hydrogen-air mixtures. The theoretical predictions summarized above are in general agreement with experimental results; see for example [5] where a jet configuration was used and experiments were conducted for various inert-diluted propane and methane flames burning in inert-diluted oxygen. Nitrogen, argon and SF6 were used as inert in order to produce conditions of substantially different Lewis numbers and mixture strength. In accord with the predicted trend, it was found that oscillations arise at near extinction conditions, that for oscillations to occur it suffices that one of the two Lewis numbers be sufficiently large, and that oscillations are more likely to be observed when is relatively large.

Matalon, Moshe

2003-01-01

239

Flame-Generated Vorticity Production in Premixed Flame-Vortex Interactions  

NASA Technical Reports Server (NTRS)

In this study, we use detailed time-dependent, multi-dimensional numerical simulations to investigate the relative importance of the processes leading to FGV in flame-vortex interactions in normal gravity and microgravity and to determine if the production of vorticity in flames in gravity is the same as that in zero gravity except for the contribution of the gravity term. The numerical simulations will be performed using the computational model developed at NRL, FLAME3D. FLAME3D is a parallel, multi-dimensional (either two- or three-dimensional) flame model based on FLIC2D, which has been used extensively to study the structure and stability of premixed hydrogen and methane flames.

Patnaik, G.; Kailasanath, K.

2003-01-01

240

Studies of Premixed Laminar and Turbulent Flames at Microgravity  

NASA Technical Reports Server (NTRS)

Several topics relating to premixed flame behavior at reduced gravity have been studied. These topics include: (1) flame balls; (2) flame structure and stability at low Lewis number; (3) experimental simulation of buoyancy effects in premixed flames using aqueous autocatalytic reactions; and (4) premixed flame propagation in Hele-Shaw cells. Because of space limitations, only topic (1) is discussed here, emphasizing results from experiments on the recent STS-107 Space Shuttle mission, along with numerical modeling efforts.

Kwon, O. C.; Abid, M.; Porres, J.; Liu, J. B.; Ronney, P. D.; Struk, P. M.; Weiland, K. J.

2003-01-01

241

Numerical investigation of spherical diffusion flames at their sooting limits  

Microsoft Academic Search

Detailed numerical simulations are presented of laminar microgravity spherical diffusion flames at their experimentally observed sooting limits. Ten normal and inverse flames fueled by ethylene are considered. Observed in a drop tower, these flames were initially sooty but reached their sooting limits 2s after ignition (or slightly before). The flames span broad ranges of stoichiometric mixture fraction (0.065–0.692), adiabatic flame

V. R. Lecoustre; P. B. Sunderland; B. H. Chao; R. L. Axelbaum

242

Unsolved problems and unanswered questions in flame retardance of polymers  

Microsoft Academic Search

Some of the unsolved problems and unanswered questions in the flame retardance of polymers are reviewed. They include, durable flame-retardant systems for cotton; FR treatment of cotton–PET blends; durable, weatherable, non-water-leachable, FR treatment of lignocellulosic products, especially wood; better understanding of gas phase and condensed phase mechanisms of flame retardance; flame retardance by sulfur derivatives; weatherable flame-retardant coatings; lowering smoke

Menachem Lewin

2005-01-01

243

Premixed-flame shapes and polynomials  

NASA Astrophysics Data System (ADS)

The nonlinear nonlocal Michelson-Sivashinsky equation for isolated crests of unstable flames is studied, using pole-decompositions as starting point. Polynomials encoding the numerically computed 2 N flame-slope poles, and auxiliary ones, are found to closely follow a Meixner-Pollaczek recurrence; accurate steady crest shapes ensue for N ? 3. Squeezed crests ruled by a discretized Burgers equation involve the same polynomials. Such explicit approximate shapes still lack for finite- N pole-decomposed periodic flames, despite another empirical recurrence.

Denet, Bruno; Joulin, Guy

2015-02-01

244

Modeling of hydrogen-air diffusion flame  

NASA Technical Reports Server (NTRS)

An analytical and computational study of opposed jet diffusion flame for the purpose of understanding the effects of contaminants in the reactants and thermal diffusion of light species on extinction and reignition of diffusion flames is in progress. The methodologies that have been attempted so far are described. Results using a simple, one-step reaction for the hydrogen-air counterflow diffusion flame are presented. These results show the correct trends in the profiles of chemical species and temperature. The extinction limit can be clearly seen in the plot of temperature vs. Damkohler number.

Isaac, K. M.

1989-01-01

245

Aromatics oxidation and soot formation in flames  

SciTech Connect

This project is concerned with the kinetics and mechanisms of aromatics oxidation and soot and fullerenes formation in flames. The scope includes detailed measurements of profiles of stable and radical species concentrations in low-pressure one-dimensional premixed flames. Intermediate species identifications and mole fractions, fluxes, and net reaction rates calculated from the measured profiles are used to test postulated reaction mechanisms. Particular objectives are to identify and to determine or confirm rate constants for the main benzene oxidation reactions in flames, and to characterize fullerenes and their formation mechanisms and kinetics.

Howard, J.B.; Pope, C.J.; Shandross, R.A.; Yadav, T. [Massachusetts Institute of Technology, Cambridge (United States)

1993-12-01

246

Effect of varied air flow on flame structure of laminar inverse diffusion flames  

Microsoft Academic Search

The structure of laminar inverse diffusion flames (IDFs) of methane and ethylene was studied using a cylindrical co-flowing burner. Several flames of the same fuel flow-rate yet various air flow-rates were examined. Heights of visible flames were obtained using measurements of hydroxyl (OH) laser-induced fluorescence (LIF) and visible images. Polycyclic aromatic hydrocarbon (PAH) LIF and soot laser-induced incandescence (LII) were

Christopher R. Shaddix; Timothy C. Williams; Linda Gail Blevins; Mark A. Mikofski

2004-01-01

247

Flame temperature, fuel structure, and fuel concentration effects on soot formation in inverse diffusion flames  

Microsoft Academic Search

Insights into soot formation processes are gained from chemical sampling and thermocouple probing of co-flowing inverse diffusion flames (IDFs), with the oxidizer in the center. In this paper the transition from near-to slightly sooting flames and the effects of flame temperature, fuel concentration, and fuel structure (using methane, ethene, propene and 1-butene) are investigated. The aromatic content of IDFS scales

G. W. Sidebotham; I. Glassman

1992-01-01

248

A numerical investigation of the flame structure of an unsteady inverse partially premixed flame  

SciTech Connect

The flame structure of unsteady flickering partially premixed flames is numerically investigated, and detailed results are provided for a flame established at Fr = 0.5, Re = 500, and overall {phi} = 1. A numerical study is conducted in an inverse configuration in which a fuel-rich (CH{sub 4}-air) annular jet is sandwiched between an axisymmetric air jet (on the inside) and coflowing air (on the outside). The computations involve a time-dependent, axisymmetric model based on a direct numerical simulation methodology, and a detailed 52-step mechanism to model the CH{sub 4}-air chemistry. The calculations show that the flame structure of the partially premixed flames differs from that of a typical nonpremixed laminar jet flame. The fuel-rich annular ring close to the nozzle exit undergoes premixed combustion, but once oxygen is depleted inside the annular ring, diffusion flames are established on both sides of it due to excess fuel emerging from the premixed zone. The effect of unsteadiness on flame structure is investigated by comparing the scalar profiles at different times with respect to a conserved scalar. The predictions do not reveal significant effects of unsteadiness on the flame structure, although buoyant convection may influence the heat transfer to the unreacted flow. This is because the rollup process essentially affects the postflame, or plume, region and not the actual flame. The vortex rollup process can be delayed by increasing either the Froude (Fr) or Reynolds (Re) numbers. The shortest rollup length is for the flame corresponding to the lowest values of Fr and Re. Detailed numerical simulations of analogous counterflow flames were performed using a more detailed chemical mechanism for the sake of comparison.

Shu, Z.; Aggarwal, S.K.; Puri, I.K. [Univ. of Illinois, Chicago, IL (United States). Dept. of Mechanical Engineering] [Univ. of Illinois, Chicago, IL (United States). Dept. of Mechanical Engineering; Katta, V.R. [Innovative Scientific Solutions, Inc., Dayton, OH (United States)] [Innovative Scientific Solutions, Inc., Dayton, OH (United States)

1997-12-01

249

Large-eddy simulation of a turbulent piloted methane\\/air diffusion flame (Sandia flame D)  

Microsoft Academic Search

The Lagrangian Flamelet Model is formulated as a combustion model for large-eddy simulations of turbulent jet diffusion flames. The model is applied in a large-eddy simulation of a piloted partially premixed methane\\/air diffusion flame (Sandia flame D). The results of the simulation are compared to experimental data of the mean and RMS of the axial velocity and the mixture fraction

H. Pitsch; H. Steiner

2000-01-01

250

JHK photometry of selected Trojan and Hilda asteroids  

NASA Technical Reports Server (NTRS)

No entirely satisfactory match has been established between the present JHK photometry of selected Hilda and Trojan asteroids and photometry for both main belt asteroids and laboratory samples. It is noted that while the leading Trojans and Hildas exhibit similar and homogeneous JHK colors, the trailing Trojans appear to be more heterogeneous. Charcoal and magnetite provide the best match in terms of JHK colors.

Smith, Dale W.; Johnson, Paul E.; Buckingham, William L.; Shorthill, Richard W.

1992-01-01

251

High Speed Photometry of White Dwarfs with Small Telescopes  

NASA Astrophysics Data System (ADS)

We present high speed photometry of the white dwarfs G29-38 and GD358 obtained with the 0.6m telescope at Mt. Cuba Observatory in Greenville, DE. We also present photometry of the massive pulsating white dwarf BPM37093 obtained with the 0.9m telescope in CTIO as part of the SMARTS consortium.

Provencal, J. L.; Shipman, H. L.; Childers, D.; Nitta, A.

2005-07-01

252

DOPHOT, a CCD photometry program: Description and tests  

Microsoft Academic Search

The design considerations and operational features of DOPHOT, a point-spread function (PSF) fitting photometry program, are described. Some relevant details of the PSF fitting are discussed. The quality of the photometry returned by DOPHOT is assessed via reductions of an 'artificial' globular cluster generated from a list of stars with known magnitudes and colors. Results from comparative tests between DOPHOT

Paul L. Schechter; Mario Mateo; Abhijit Saha

1993-01-01

253

Flame resistant nontoxic polymer development  

NASA Technical Reports Server (NTRS)

A number of homopolymers, copolymers, and terpolymers were synthesized employing styrene and four derivatives of diphenyl-p-styrylphosphine. The various polymeric compositions were prepared by two processes, (1) monomer bulk polymerizations and (2) substitution of preformed polydiphenyl-p-styrylphosphine. Results indicate that the majority of the compositions exhibit superior melting and flame retardant characteristics as compared to polystyrene, but are inferior in molding and film forming capability. Terpolymerization appears to result in the materials with the best overall combination of properties. Toxicological evaluation of three representative basic compositions in the form of molded washers showed that no mortalities occurred among the test animals exposed to the products of the oxidative thermal decomposition of the three materials.

Paciorek, K. L.; Karle, D. W.; Kratzer, R. H.

1975-01-01

254

Flame Resistant Fibrous Materials Development  

NASA Technical Reports Server (NTRS)

Since 1973, Albany International Research Co. has been engaged by NASA-JSC under Contract No. NAS9-13673 to conduct studies aimed at developing fibers and flexible structures made therefrom which would provide improved flame resistance over existing commercially available materials in oxygen enriched atmospheres. A portion of the crew bay area life support system and crew equipment for the space shuttle was initially designed to function at a 30% oxygen, 70% nitrogen atmosphere at 9 psia pressure. This oxygen concentration imposed certain fire safety and smoke generation requirements which could not be completely met by commonly accepted textiles. Potentially useful new polymers were investigated both for fire safety and mechanical properties. During the course of the work, three candidate fibers were studied and evaluated and the results of each of these efforts are summarized.

Coskren, R. J.

1982-01-01

255

Experimental analysis of flashback in lean premixed swirling flames: upstream flame propagation  

NASA Astrophysics Data System (ADS)

Simultaneous 10-kHz OH-PLIF and 20-kHz two-component PIV were made in conjunction with wide-field 20-kHz flame luminescence imaging of an unconfined, swirling, lean premixed, bluff-body stabilized flame during flashback. Flashback was induced by increasing the stoichiometry or swirl number or reducing the Reynolds number. A detailed stability regime was prepared and compared to predictions. Analysis of the time-correlated flame history inside the exit nozzle during flashback and non-flashback flame events led to a new hypothesis for the flashback mechanism.

Heeger, C.; Gordon, R. L.; Tummers, M. J.; Sattelmayer, T.; Dreizler, A.

2010-10-01

256

Triple flame structure and dynamics at the stabilization point of a lifted jet diffusion flame  

SciTech Connect

A coupled Lagrangian-Eulerian low-Mach-number numerical scheme is developed, using the vortex method for the momentum equations, and a finite difference approach with adaptive mesh refinement for the scalar conservation equations. The scheme is used to study the structure and dynamics of a forced lifted buoyant planar jet flame. Outer buoyant structures, driven by baroclinic vorticity generation, are observed. The flame base is found to stabilize in a region where flow velocities are sufficiently small to allow its existence. A triple flame is observed at the flame base, a result of premixing of fuel and oxidizer upstream of the ignition point. The structure and dynamics of the triple flame, and its modulation by jet vortex structures, are studied. The spatial extent of the triple flame is small, such that it fits wholly within the rounded flame base temperature field. The dilatation rate field outlines the edge of the hot fluid at the flame base. Neither the temperature field nor the dilatation rate field seem appropriate for experimental measurement of the triple flame in this flow.

Najm, H.N.; Milne, R.B. [Sandia National Labs., Livermore, CA (United States); Devine, K.D.; Kempka, S.N. [Sandia National Labs., Albuquerque, NM (United States)

1998-03-01

257

High pressure flame system for pollution studies with results for methane-air diffusion flames  

NASA Technical Reports Server (NTRS)

A high pressure flame system was designed and constructed for studying nitrogen oxide formation in fuel air combustion. Its advantages and limitations were demonstrated by tests with a confined laminar methane air diffusion flame over the pressure range from 1 to 50 atm. The methane issued from a 3.06 mm diameter port concentrically into a stream of air contained within a 20.5 mm diameter chimney. As the combustion pressure is increased, the flame changes in shape from wide and convex to slender and concave, and there is a marked increase in the amount of luminous carbon. The height of the flame changes only moderately with pressure.

Miller, I. M.; Maahs, H. G.

1977-01-01

258

Effect of cylindrical confinement on the determination of laminar flame speeds using outwardly propagating flames  

SciTech Connect

The effect of nonspherical (i.e. cylindrical) bomb geometry on the evolution of outwardly propagating flames and the determination of laminar flame speeds using the conventional constant-pressure technique is investigated experimentally and theoretically. The cylindrical chamber boundary modifies the propagation rate through the interaction of the wall with the flow induced by thermal expansion across the flame (even with constant pressure), which leads to significant distortion of the flame surface for large flame radii. These departures from the unconfined case, especially the resulting nonzero burned gas velocities, can lead to significant errors in flame speeds calculated using the conventional assumptions, especially for large flame radii. For example, at a flame radius of 0.5 times the wall radius, the flame speed calculated neglecting confinement effects can be low by {proportional_to}15% (even with constant pressure). A methodology to estimate the effect of nonzero burned gas velocities on the measured flame speed in cylindrical chambers is presented. Modeling and experiments indicate that the effect of confinement can be neglected for flame radii less than 0.3 times the wall radius while still achieving acceptable accuracy (within 3%). The methodology is applied to correct the flame speed for nonzero burned gas speeds, in order to extend the range of flame radii useful for flame speed measurements. Under the proposed scaling, the burned gas speed can be well approximated as a function of only flame radius for a given chamber geometry - i.e. the correction function need only be determined once for an apparatus and then it can be used for any mixture. Results indicate that the flow correction can be used to extract flame speeds for flame radii up to 0.5 times the wall radius with somewhat larger, yet still acceptable uncertainties for the cases studied. Flow-corrected burning velocities are measured for hydrogen and syngas mixtures at atmospheric and elevated pressures. Flow-corrected flame speeds in the small cylindrical chamber used here agree well with previously reported flame speeds from large spherical chambers. Previous papers presenting burning velocities from cylindrical chambers report performing data analysis on flame radii less than 0.5 or 0.6 times the wall radius, where the flame speed calculated neglecting confinement effects may be low by {proportional_to}15 or 20%, respectively. For cylindrical chambers, data analysis should be restricted to flame radii less than 0.3 times the wall radius or a flow correction should be employed to account for the burned gas motions. With regard to the design of future vessels, larger vessels that minimize the flow aberrations for the same flame radius are preferred. Larger vessels maximize the relatively unaffected region of data allowing for a more straightforward approach to interpret the experimental data. (author)

Burke, Michael P.; Chen, Zheng; Ju, Yiguang; Dryer, Frederick L. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2009-04-15

259

Laminar Diffusion Flame Studies (Ground- and Space-Based Studies)  

NASA Technical Reports Server (NTRS)

Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion flames must precede understanding these processes in more complex turbulent diffusion flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar jet diffusion flame shapes (luminous flame boundaries) have been of particular interest since the classical study of Burke and Schumann because they are a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Thus, consideration of laminar flame shapes is undertaken in the following, emphasizing conditions where effects of gravity are small, due to the importance of such conditions to practical applications. Another class of interesting properties of laminar diffusion flames are their laminar soot and smoke point properties (i.e., the flame length, fuel flow rate, characteristic residence time, etc., at the onset of soot appearance in the flame (the soot point) and the onset of soot emissions from the flame (the smoke point)). These are useful observable soot properties of nonpremixed flames because they provide a convenient means to rate several aspects of flame sooting properties: the relative propensity of various fuels to produce soot in flames; the relative effects of fuel structure, fuel dilution, flame temperature and ambient pressure on the soot appearance and emission properties of flames; the relative levels of continuum radiation from soot in flames; and effects of the intrusion of gravity (or buoyant motion) on emissions of soot from flames. An important motivation to define conditions for soot emissions is that observations of laminar jet diffusion flames in critical environments, e.g., space shuttle and space station facilities, cannot involve soot emitting flames in order to ensure that test chamber windows used for experimental observations are not blocked by soot deposits, thereby compromising unusually valuable experimental results. Another important motivation to define conditions where soot is present in diffusion flames is that flame chemistry, transport and radiation properties are vastly simplified when soot is absent, making such flames far more tractable for detailed numerical simulations than corresponding soot-containing flames. Motivated by these observations, the objectives of this phase of the investigation were as follows: (1) Observe flame-sheet shapes (the location of the reaction zone near phi=1) of nonluminous (soot free) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of flame-sheet shapes for these conditions; (2) Observe luminous flame boundaries of luminous (soot-containing) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of luminous flame boundaries for these conditions. In order to fix ideas here, maximum luminous flame boundaries at the laminar smoke point conditions were sought, i.e., luminous flame boundaries at the laminar smoke point; (3) Observe effects of coflow on laminar soot- and smoke-point conditions because coflow has been proposed as a means to control soot emissions and minimize the presence of soot in diffusion flames.

Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

260

Large Eddy Simulation of a Premixed Bunsen Flame Using a Modified Thickened-Flame Model at Two Reynolds Number  

Microsoft Academic Search

A modified thickened flame (TF) model based on large eddy simulation (LES) methodology is used to investigate premixed combustion, and the model predictions are evaluated by comparing with the piloted premixed stoichiometric methane-air flame data for Reynolds numbers Re = 24,000 (flame F3) and Re = 52,000 (flame F1). The basic idea of the TF approach is that the flame front is artificially thickened

Ashoke De; Sumanta Acharya

2009-01-01

261

Ten Recent Enhancements To Aperture Photometry Tool  

NASA Astrophysics Data System (ADS)

Aperture Photometry Tool is free, multi-platform, easy-to-install software for astronomical research, as well as for learning, visualizing, and refining aperture-photometry analyses. This mature software has been under development for five years, and is a silent workhorse of the NASA/IPAC Teacher Archive Research Program. Software version 2.1.5 is described by Laher et al., Publications of the Astronomical Society of the Pacific, Vol. 124, No. 917, pp. 737-763, (July 2012). Four software upgrades have been released since the publication, which include new capabilities, increased speed, more user-friendliness, and some minor bug fixes. Visit www.aperturephotometry.org to download the latest version. The enhancements are as follows: 1) Added new Tools menu option to write selected primary-image data to a comma-separated-value file (for importing into Excel); 2) Added a new display of the color-table levels on a separate panel; 3) Added a new tool to measure the angular separation between positions on the thumbnail image, via mouse-cursor drag and release; 4) Added a new tool to overlay an aperture at user-specified coordinates (in addition to aperture overlay via mouse click); 5) Speeded up the source-list tool with optional multithreading in its automatic mode (allowed thread number is user-specifiable); 6) Added a new “Number” column to the output aperture-photometry-table file in order to track the input source order (multithreading reorders the output); 7) Upgraded the source-list tool to accept input source lists containing positions in sexagesimal equatorial coordinates (in addition to decimal degrees, or, alternatively, pixel coordinates); 8) Added a new decimal/sexagesimal converter; 9) Upgraded the source-list creation tool to compute the detection threshold using robust estimates of the local background and local data dispersion, where the user can select the grid and window sizes for these local calculations; and 10) Modified the batch mode to optionally generate a source list. These upgrades increase the software's utility, and more improvements are planned for future releases.

Laher, Russ; Rebull, L. M.; Gorjian, V.

2013-01-01

262

Characterization of acoustically forced swirl flame dynamics  

E-print Network

Characterization of acoustically forced swirl flame dynamics Sai Kumar Thumuluru *, Tim Lieuwen.05.037 * Corresponding author. Address: Ben T. Zinn Com- bustion Laboratory, Georgia Institute of Technology, 635 Strong

Lieuwen, Timothy C.

263

Brominated Flame Retardants and Perfluorinated Chemicals  

EPA Science Inventory

Brominated flame retardants (BFRs) and perfluorinated chemicals (PFCs) belong to a large class of chemicals known as organohalogens. It is believed that both BFRs and PFCs saved lives by reducing flammability of materials commonly used and bactericidal (biocidal) properties. Thes...

264

PCBs, PBBs and Brominated Flame Retardants  

EPA Science Inventory

This chapter introduces selected organohalogen chemicals such as polychlorinated biphenyls (PCB5), polychiorinated biphenyls (PBBs), and brominated flame retardants (BFRs) with emphasis on the background, physicochemical properties, environmental levels, health effects and possib...

265

HEALTH EFFECTS OF BROMINATED FLAME RETARDANTS (BFRS)  

EPA Science Inventory

Abstract Brominated flame retardant use has increased dramatically in order to provide fire safety to consumers. However, there is growing concern about widespread environmental contamination and potential health risks from some of these products. The most used products...

266

Light collection device for flame emission detectors  

DOEpatents

A light collection device for use in a flame emission detection system such as an on-line, real-time alkali concentration process stream monitor is disclosed which comprises a sphere coated on its interior with a highly diffuse reflective paint which is positioned over a flame emission source, and one or more fiber optic cables which transfer the light generated at the interior of the sphere to a detecting device. The diffuse scattering of the light emitted by the flame uniformly distributes the light in the sphere, and the collection efficiency of the device is greater than that obtainable in the prior art. The device of the present invention thus provides enhanced sensitivity and reduces the noise associated with flame emission detectors, and can achieve substantial improvements in alkali detection levels.

Woodruff, Stephen D. (Morgantown, WV); Logan, Ronald G. (Morgantown, WV); Pineault, Richard L. (Morgantown, WV)

1990-01-01

267

Flame Spread Across Liquids: Experimental Results  

NASA Technical Reports Server (NTRS)

The goal of our research on flame spread across a pool of liquid fuel is the quantitative identification of the mechanisms that control the rate and nature of flame spread when the initial temperature of the liquid pool is below the fuel's flash point temperature. Besides numerous experiments in drop towers and 1 g laboratories, we have flown five microgravity (mu-g) experiments on sounding rockets. As described in earlier papers, the first three flights examined the effect of forced opposed airflow over a 2.5 cm deep x 2 cm wide x 30 cm long pool of 1-butanol in mu-g. It was found that the flame spread is much slower and steadier than in 1 g where flame spread has a pulsating character. It was speculated that the flame spread in mu-g resembled the character of pseudo-uniform spread in 1 g; Ito et al later confirmed this conclusively in 1 g experiments. Much of the mu-g flame is also farther from the surface, dimmer, and with less soot, when compared to the 1 g flame. Three-dimensional liquid-phase flow patterns that control the liquid preheating were discovered in both 1 g and mu-g. Our numerical model, restricted to two dimensions, had predicted faster, pulsating flame spread in mu-g for opposed airflow. In examining the differences in the dimensionality of the model and experiment, it was noted that the experiment allowed gas expansion in the lateral direction (across the width of the pool), for which the model could not account. Such lateral expansion could reduce the expansion in the forward and upward directions. Because only these latter directions could be modeled, it was decided to artificially reduce the gas thermal expansion in the predictions. When this was done, satisfactory agreement could be obtained between the predicted and observed spread rates and the steadiness of the spread in microgravity. In 1 g, however, the predicted flame spread character also changed to pseudo-uniform, which disagreed with our 1 g experiments where the spread is pulsating. It was then speculated that gas-phase buoyant flow might oppose the lateral gas expansion, so that the 1 g experiments retained their pulsating flame spread character. If this speculation was valid, a difference in lateral gas expansion should be observable when comparing 1 g and mu-g experiments. Specifically, it was anticipated that greater flow divergence caused by lateral expansion would be measured in mu-g in the absence of a buoyant flow directed towards the flame.

Ross, H. D.; Miller, F. J.

1999-01-01

268

Modeling of hydrogen-air diffusion flame  

NASA Technical Reports Server (NTRS)

Work performed during the first six months of the project duration for NASA Grant (NAG-1-861) is reported. An analytical and computational study of opposed jet diffusion flame for the purpose of understanding the effects of contaminants in the reactants and thermal diffusion of light species on extinction and reignition of diffusion flames is in progress. The methodologies attempted so far are described.

Isaac, K. M.

1988-01-01

269

Aromatics oxidation and soot formation in flames  

SciTech Connect

Work during this contract period has been concerned with the mechanisms through which aromatics are formed and destroyed in flames, and the processes responsible for soot formation. Recent progress has been primarily in two areas: experiments and modeling of the soot nucleation process in low pressure benzene flames and preparation for experiments on the destruction mechanisms of benzene. In addition, we have incorporated weak collision'' formalisms into a fall-off computer code.

Howard, J.B.

1989-01-01

270

Environmentally Benign Flame Retardant Nanocoatings for Fabric  

E-print Network

of the most natural textile fibers used to produce apparel, home furnishings, and industrial products, but this cellulosic material has a low limiting oxygen index (LOI) and combustion temperature (360 ? 425 ?C) that makes it highly flammable.44 Cotton...-containing flame retardants include elemental red phosphorus,57 inorganic phosphates,58 and organophosphates.59 It is believed these flame retardants are significantly more effective in oxygen-containing polymers (e.g., cellulose and rigid polyurethane foam).60...

Li, Yu-Chin

2012-07-16

271

Thermally Stable and Flame Retardant Elastomeric Nanocomposites  

Microsoft Academic Search

\\u000a This chapter is dedicated to thermally stable and flame retardant elastomeric composites. Two approaches are considered: the\\u000a synthesis of elastomeric nanocomposites, where the nanoparticles are dispersed at the nanoscale, and the incorporation of\\u000a nanofillers at high loadings where agglomerate of nanoparticles are observed in the elastomeric matrix. The chapter is mainly\\u000a focused on the key parameter influencing the flame retardancy,

O. Cerin; G. Fontaine; S. Duquesne; S. Bourbigot

272

TERMS Photometry of Known Transiting Exoplanets  

E-print Network

The Transit Ephemeris Refinement and Monitoring Survey (TERMS) conducts radial velocity and photometric monitoring of known exoplanets in order to refine planetary orbits and predictions of possible transit times. This effort is primarily directed towards planets not known to transit, but a small sample of our targets consist of known transiting systems. Here we present precision photometry for 6 WASP planets acquired during their transit windows. We perform a Markov Chain Monte Carlo (MCMC) analysis for each planet and combine these data with previous measurements to redetermine the period and ephemerides for these planets. These observations provide recent mid-transit times which are useful for scheduling future observations. Our results improve the ephemerides of WASP-4b, WASP-5b and WASP-6b and reduce the uncertainties on the mid-transit time for WASP-29b. We also confirm the orbital, stellar and planetary parameters of all 6 systems.

Dragomir, Diana; Pilyavsky, Genady; Mahadevan, Suvrath; Ciardi, David R; Gazak, J Zachary; Gelino, Dawn M; Payne, Alan; Rabus, Markus; Ramirez, Solange V; von Braun, Kaspar; Wright, Jason T; Wyatt, Pamela

2011-01-01

273

Simplified Color Photometry Using APASS Data (Abstract)  

NASA Astrophysics Data System (ADS)

(Abstract only) APASS, the AAVSO Photometric All-Sky Survey, now contains 47 million stars and covers 97% of the Northern and Southern hemisphere sky. Its extraordinary coverage means that there are multiple APASS-calibrated stars available for color photometry in the field of view of virtually every amateur image. This paper presents a simplified spreadsheet-based procedure that combines raw photometric data with APASS data to calibrate target objects in the same field of view. The complete photometric equations are reviewed and a simplified form is obtained for use within a limited field of view. Raw photometric data and APASS data for that image from AAVSO are combined on a spreadsheet to produce calibrated photometric measurements of target objects within the field of view. The consistency of the fit to the data is shown graphically. Error terms are tracked through the equations to provide the standard deviation of each measurement.

Dunkel, N.

2014-12-01

274

A Method to Measure Flame Index in Turbulent Partially-Premixed Flames  

NASA Astrophysics Data System (ADS)

This dissertation describes the development of a diagnostic technique and data processing routine to measure the flame index in partially-premixed flames, called the Flame Index Measurement Method. Many modern combustion applications involve conditions in which the fuel and oxidizer are only partially mixed prior to entering the flame. These partially-premixed flames contain some regions of premixed and some regions of non-premixed flamelets. New computational approaches use the flame index concept: premixed regions are identified and a premixed model is applied; non-premixed regions are also identified and a non-premixed model is applied. The flame index is defined as the normalized dot product of the gradients of the fuel and oxidizer mass fractions; it is +1 in premixed flamelets and is -1 in non-premixed flamelets. Previously there had been no experimentally measured values of flame index available to assess the modeling approaches. A new method has been developed to measure the flame index using planar laser-induced fluorescence tracers to indicate the sign and direction of the fuel and oxygen gradients. Through the modeling of premixed and non-premixed flamelets, acetone was selected as a fuel tracer and nitrogen dioxide was selected as an oxygen tracer. The fluorescence properties of both acetone and nitrogen dioxide were studied. With acetone seeded into the fuel, and nitrogen dioxide seeded into the air, the Flame Index Measurement Method was evaluated in laminar premixed and non-premixed methane/acetone/air flames, as well as in a well-defined turbulent partially-premixed burner, the Gas Turbine Model Combustor (GTMC). The flame index was measured in the GTMC with methane, propane, and syngas flames. Statistics (mean, variance, and probability mass functions) of the flame index are reported for the highly-turbulent partially-premixed GTMC flames. Two new statistical quantities were developed that describe the probability for the occurrence of premixed flamelets and the degree of partial-premixing. Aspects of the new measurement technique are discussed, including: signal-to-noise ratio, tracer gas seeding levels, data analysis/gradient identification methods, and uncertainty.

Rosenberg, David Ari

275

Flame Inhibition by Phosphorus-Containing Compounds in Lean and Rich Propane Flames  

SciTech Connect

Chemical inhibition of laminar propane flames by organophosphorus compounds has been studied experimentally, using a laboratory Mache Hebra nozzle burner and a flat flame burner with molecular beam mass spectrometry (MBMS), and with a computational flame model using a detailed chemical kinetic reaction mechanism. Both fuel-lean and fuel-rich propane flames were studied to examine the role of equivalence ratio in flame inhibition. The experiments examined a wide variety of organophosphorus compounds. We report on the experimental species flame profiles for tri-methyl phosphate (TMP) and compare them with the species flame profile results from modeling of TMP and di-methyl methyl phosphonate (DMMP). Both the experiments and kinetic modeling support and illustrate previous experimental studies in both premixed and non-premixed flames that inhibition efficiency is effectively the same for all of the organophosphorus compounds examined, independent of the molecular structure of the initial inhibitor molecule. The chemical inhibition is due to reactions involving the small P-bearing species HOPO{sub 2} and HOPO that are produced by the organophosphorus compounds (OPCs). The ratios of the HOPO{sub 2} and HOPO concentrations differ between the lean and rich flames, with HOPO{sub 2} dominant in lean flames while HOPO dominates in rich flames. The resulting HOPO{sub 2} and HOPO species profiles do not depend significantly on the initial source of the HOPO{sub 2} and HOPO and thus are relatively insensitive to the initial OPC inhibitor. A more generalized form of the original Twarowski mechanism for hydrocarbon radical recombination is developed to account for the results observed, and new theoretical values have been determined for heats of formation of the important P-containing species, using the BAC-G2 method.

Curran, H; Korobeinichev, O P; Shvartsberg, V M; Shmakov, A G; Bolshova, T A; Jayaweera, T M; Melius, C F; Pitz, W J; Westbrook, C K

2003-12-19

276

An elementary discussion of propellant flame geometry  

SciTech Connect

The authors examine the geometry of diffusion flames generated by the burning of a heterogeneous solid propellant, using a simple model designed to provide qualitative insights. In the fast chemistry limit a strategy is used which has its roots in Burke and Schumann`s 1928 study of diffusion flames, albeit with different boundary conditions. This shows that the stoichiometric level surface (SLS) intersects the propellant surface at a point displaced from the fuel/oxidizer interface, and the variations of this displacement with Peclet number are discussed. The authors show that for model sandwich propellants, or their axisymmetric counterpart, the geometry of the SLS when the core is oxidizer is quite different from the geometry of the SLS when the core is fuel. Also, it is much easier to quench the flame on an oxidizer core, by reducing the Peclet number, than it is to quench the flame on a fuel core. When finite chemistry effects are accounted for, the flame only occupies a portion of the SLS, and there is a leading edge structure in which premixing plays a role. Enhancement of the burning rate due to premixing is identified, but a well-defined tribrachial structure is not observed. The authors show how a sharp reduction in pressure can lead to a detachment of the flame from the SLS, with subsequent quenching as it is swept downstream.

Buckmaster, J.; Jackson, T.L.; Yao, J. [Univ. of Illinois, Urbana, IL (United States)] [Univ. of Illinois, Urbana, IL (United States)

1999-05-01

277

Premixed Turbulent Flame Propagation in Microgravity  

NASA Technical Reports Server (NTRS)

A combined numerical-experimental study has been carried out to investigate the structure and propagation characteristics of turbulent premixed flames with and without the influence of buoyancy. Experimentally, the premixed flame characteristics are studied in the wrinkled regime using a Couette flow facility and an isotropic flow facility in order to resolve the scale of flame wrinkling. Both facilities were chosen for their ability to achieve sustained turbulence at low Reynolds number. This implies that conventional diagnostics can be employed to resolve the smallest scales of wrinkling. The Couette facility was also built keeping in mind the constraints imposed by the drop tower requirements. Results showed that the flow in this Couette flow facility achieves full-developed turbulence at low Re and all turbulence statistics are in good agreement with past measurements on large-scale facilities. Premixed flame propagation studies were then carried out both using the isotropic box and the Couette facility. Flame imaging showed that fine scales of wrinkling occurs during flame propagation. Both cases in Ig showed significant buoyancy effect. To demonstrate that micro-g can remove this buoyancy effect, a small drop tower was built and drop experiments were conducted using the isotropic box. Results using the Couette facility confirmed the ability to carry out these unique reacting flow experiments at least in 1g. Drop experiments at NASA GRC were planned but were not completed due to termination of this project.

Menon, Suresh

1999-01-01

278

NO concentration imaging in turbulent nonpremixed flames  

SciTech Connect

The importance of NO as a pollutant species is well known. An understanding of the formation characteristics of NO in turbulent hydrocarbon flames is important to both the desired reduction of pollutant emissions and the validation of proposed models for turbulent reacting flows. Of particular interest is the relationship between NO formation and the local flame zone, in which the fuel is oxidized and primary heat release occurs. Planar imaging of NO provides the multipoint statistics needed to relate NO formation to the both the flame zone and the local turbulence characteristics. Planar imaging of NO has been demonstrated in turbulent flames where NO was seeded into the flow at high concentrations (2000 ppm) to determine the gas temperature distribution. The NO concentrations in these experiments were significantly higher than those expected in typical hydrocarbon-air flames, which require a much lower detectability limit for NO measurements. An imaging technique based on laser-induced fluorescence with sufficient sensitivity to study the NO formation mechanism in the stabilization region of turbulent lifted-jet methane flames.

Schefer, R.W. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

279

The structure of particle cloud premixed flames  

NASA Technical Reports Server (NTRS)

The structure of premixed flames propagating in combustible systems containing uniformly distributed volatile fuel particles in an oxidizing gas mixture is analyzed. This analysis is motivated by experiments conducted at NASA Lewis Research Center on the structure of flames propagating in combustible mixtures of lycopodium particles and air. Several interesting modes of flame propagation were observed in these experiments depending on the number density and the initial size of the fuel particle. The experimental results show that steady flame propagation occurs even if the initial equivalence ratio of the combustible mixture based on the gaseous fuel available in the particles, phi sub u, is substantially larger than unity. A model is developed to explain these experimental observations. In the model, it is presumed that the fuel particles vaporize first to yield a gaseous fuel of known chemical composition which then reacts with oxygen in a one-step overall process. The activation energy of the chemical reaction is presumed to be large. The activation energy characterizing the kinetics of vaporization is also presumed to be large. The equations governing the structure of the flame were integrated numerically. It is shown that the interplay of vaporization kinetics and oxidation process can result in steady flame propagation in combustible mixtures where the value of phi sub u is substantially larger than unity. This prediction is in agreement with experimental observations.

Seshadri, K.; Berlad, A. L.

1992-01-01

280

Quantitative Species Measurements in Microgravity Combustion Flames  

NASA Technical Reports Server (NTRS)

Flame-vortex interactions are canonical configurations that can be used to study the underlying processes occurring in complicated turbulent reacting flows. The elegant simplicity of the flame-vortex interaction permits the study of these complex interactions under relatively controllable experimental configurations, in contrast to direct measurements in turbulent flames. The ability to measure and model the fundamental phenomena that occur in a turbulent flame, but with time and spatial scales which are amenable to our diagnostics, permits significant improvements in the understanding of turbulent combustion under both normal and reduced gravity conditions. In this paper, we report absolute mole fraction measurements of methane in a reacting vortex ring. These microgravity experiments are performed in the 2.2-sec drop tower at NASA Glenn Research Center. In collaboration with Drs. Chen and Dahm at the University of Michigan, measured methane absorbances are incorporated into a new model from which the temperature and concentrations of all major gases in the flame can be determined at all positions and times in the development of the vortex ring. This is the first demonstration of the ITAC (Iterative Temperature with Assumed Chemistry) approach, and the results of these computations and analyses are presented in a companion paper by Dahm and Chen at this Workshop. We believe that the ITAC approach will become a powerful tool in understanding a wide variety of combustion flames under both equilibrium and non-equilibrium conditions.

Silver, Joel A.; Wood, William R.; Chen, Shin-Juh; Dahm, Werner J. A.; Piltch, Nancy D.

2001-01-01

281

Quantitative Species Measurements In Microgravity Combustion Flames  

NASA Technical Reports Server (NTRS)

The capability of models and theories to accurately predict and describe the behavior of low gravity flames can only be verified by quantitative measurements. Although video imaging, simple temperature measurements, and velocimetry methods have provided useful information in many cases, there is still a need for quantitative species measurements. Over the past decade, we have been developing high sensitivity optical absorption techniques to permit in situ, non-intrusive, absolute concentration measurements for both major and minor flames species using diode lasers. This work has helped to establish wavelength modulation spectroscopy (WMS) as an important method for species detection within the restrictions of microgravity-based measurements. More recently, in collaboration with Prof. Dahm at the University of Michigan, a new methodology combining computed flame libraries with a single experimental measurement has allowed us to determine the concentration profiles for all species in a flame. This method, termed ITAC (Iterative Temperature with Assumed Chemistry) was demonstrated for a simple laminar nonpremixed methane-air flame at both 1-g and at 0-g in a vortex ring flame. In this paper, we report additional normal and microgravity experiments which further confirm the usefulness of this approach. We also present the development of a new type of laser. This is an external cavity diode laser (ECDL) which has the unique capability of high frequency modulation as well as a very wide tuning range. This will permit the detection of multiple species with one laser while using WMS detection.

Chen, Shin-Juh; Pilgrim, Jeffrey S.; Silver, Joel A.; Piltch, Nancy D.

2003-01-01

282

A Computational Investigation of Sooting Limits of Spherical Diffusion Flames  

NASA Technical Reports Server (NTRS)

Limiting conditions for soot particle inception in spherical diffusion flames were investigated numerically. The flames were modeled using a one-dimensional, time accurate diffusion flame code with detailed chemistry and transport and an optically thick radiation model. Seventeen normal and inverse flames were considered, covering a wide range of stoichiometric mixture fraction, adiabatic flame temperature, and residence time. These flames were previously observed to reach their sooting limits after 2 s of microgravity. Sooting-limit diffusion flames with residence times longer than 200 ms were found to have temperatures near 1190 K where C/O = 0.6, whereas flames with shorter residence times required increased temperatures. Acetylene was found to be a reasonable surrogate for soot precursor species in these flames, having peak mole fractions of about 0.01.

Lecoustre, V. R.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

283

Flame Detector Model: A Prototype for Detecting Flames in Social Networking Sites  

Microsoft Academic Search

Now-a-days the social Networking sites are gaining most popularity due to the ideal and efficient way of communication between two parties. However, during communication between two parties it may possible that some abusive words are to be used may be intentionally or unintentionally that is referred as Flaming during communication. This paper mainly focuses on the Flame detector model, which

Shiv Shankar Prasad Shukla; Nitin; Sandeep Pratap Singh; Navjot Singh Parande; Ankit Khare; Nilesh Kumar Pandey

2012-01-01

284

Impact of flame-wall interaction on premixed flame dynamics and transfer function characteristics  

Microsoft Academic Search

In this paper, we numerically investigate the response of a perforated-plate stabilized laminar methane–air premixed flame to imposed inlet velocity perturbations. A flame model using detailed chemical kinetics mechanism is applied and heat exchange between the burner plate and the gas mixture is incorporated. Linear transfer functions, for low mean inlet velocity oscillations, are analyzed for different equivalence ratio, mean

K. S. Kedia; H. M. Altay; A. F. Ghoniem

2011-01-01

285

Recent Research Progress on the Flame-Retardant Mechanism of Halogen-Free Flame Retardant Polypropylene  

Microsoft Academic Search

Polypropylene (PP) is one of the five kinds of universal polymers that have greatly improved our life qualities. While a pestilent limitation of PP is its flammability. Usually, halogen-containing flame retardants (FRs) are used to improve its flame retard ability. However, the halogen-containing FRs are limited more and more strictly because they would produce environment problems, such as the release

Jianjun Wang; Li Wang; Anguo Xiao

2009-01-01

286

Large eddy simulation of a turbulent nonpremixed piloted methane jet flame (Sandia Flame D)  

Microsoft Academic Search

Large eddy simulation (LES) is conducted of the Sandia Flame D [Proc. Combust. Inst. 27 (1998) 1087, Sandia National Laboratories (2004)], which is a turbulent piloted nonpremixed methane jet flame. The subgrid scale (SGS) closure is based on the scalar filtered mass density function (SFMDF) methodology [J. Fluid Mech. 401 (1999) 85]. The SFMDF is basically the mass weighted probability

M. R. H. Sheikhi; T. G. Drozda; P. Givi; F. A. Jaberi; S. B. Pope

2005-01-01

287

On the dynamics of flame edges in diffusion-flame/vortex interactions  

SciTech Connect

We analyze the local flame extinction and reignition of a counterflow diffusion flame perturbed by a laminar vortex ring. Local flame extinction leads to the appearance of flame edges separating the burning and extinguished regions of the distorted mixing layer. The dynamics of these edges is modeled based on previous numerical results, with heat release effects fully taken into account, which provide the propagation velocity of triple and edge flames in terms of the upstream unperturbed value of the scalar dissipation. The temporal evolution of the mixing layer is determined using the classical mixture fraction approach, with both unsteady and curvature effects taken into account. Although variable density effects play an important role in exothermic reacting mixing layers, in this paper the description of the mixing layer is carried out using the constant density approximation, leading to a simplified analytical description of the flow field. The mathematical model reveals the relevant nondimensional parameters governing diffusion-flame/vortex interactions and provides the parameter range for the more relevant regime of local flame extinction followed by reignition via flame edges. Despite the simplicity of the model, the results show very good agreement with previously published experimental results. (author)

Hermanns, Miguel; Linan, Amable [Departamento de Motopropulsion y Termofluidodinamica, Universidad Politecnica de Madrid, Pza. Cardenal Cisneros 3, 28040 Madrid (Spain); Vera, Marcos [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

2007-04-15

288

Modeling Candle Flame Behavior In Variable Gravity  

NASA Technical Reports Server (NTRS)

The burning of a candle, as typical non-propagating diffusion flame, has been used by a number of researchers to study the effects of electric fields on flame, spontaneous flame oscillation and flickering phenomena, and flame extinction. In normal gravity, the heat released from combustion creates buoyant convection that draws oxygen into the flame. The strength of the buoyant flow depends on the gravitational level and it is expected that the flame shape, size and candle burning rate will vary with gravity. Experimentally, there exist studies of candle burning in enhanced gravity (i.e. higher than normal earth gravity, g(sub e)), and in microgravity in drop towers and space-based facilities. There are, however, no reported experimental data on candle burning in partial gravity (g < g(sub e)). In a previous numerical model of the candle flame, buoyant forces were neglected. The treatment of momentum equation was simplified using a potential flow approximation. Although the predicted flame characteristics agreed well with the experimental results, the model cannot be extended to cases with buoyant flows. In addition, because of the use of potential flow, no-slip boundary condition is not satisfied on the wick surface. So there is some uncertainty on the accuracy of the predicted flow field. In the present modeling effort, the full Navier-Stokes momentum equations with body force term is included. This enables us to study the effect of gravity on candle flames (with zero gravity as the limiting case). In addition, we consider radiation effects in more detail by solving the radiation transfer equation. In the previous study, flame radiation is treated as a simple loss term in the energy equation. Emphasis of the present model is on the gas-phase processes. Therefore, the detailed heat and mass transfer phenomena inside the porous wick are not treated. Instead, it is assumed that a thin layer of liquid fuel coated the entire wick surface during the burning process. This is the limiting case that the mass transfer process in the wick is much faster than the evaporation process at the wick surface.

Alsairafi, A.; Tien, J. S.; Lee, S. T.; Dietrich, D. L.; Ross, H. D.

2003-01-01

289

Flame Propagation in Low-Intensity Turbulence under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

The goal of the research is to understand the influences of the hydrodynamic instability on premixed-flame propagation. It is known that coupling between flame and flow-field dynamics in association with the hydrodynamic instability may lead to flame-generated turbulence, flame acceleration and enhancement of burning rates. As a result of such hydrodynamic coupling the transition from initially planar or wrinkled laminar flames to fast turbulent flames or detonations is possible, even when diffusive-thermal effects associated with non-unity reactant Lewis numbers are not destabilizing. It is important to identify methods of suppressing the hydrodynamic instability so as to insure fire safety, particularly in space.

Aldredge, R. C.

2001-01-01

290

Visual and Near-IR Photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

We report Visual and Near-IR photometry of Nova Del 2013 taken at the University of Minnesota's O'Brien Observatory (Marine-on-St-Croix, Minnesota, USA). VRIJHKLM photometry were obtained on two successive nights using an AsSi bolometer. Vega (alpha Lyrae) was used as the standard star. Our photometry show: August 16.2 UT: V = 4.8 +/- 0.1, R = 5.4 +/- 0.1, I = 5.2 +/- 0.1, J = 4.4 +/- 0.1, H = 4.3 +/- 0.1, K = 4.3 +/- 0.1, L = 4.5 +/- 0.2.

Gehrz, R. D.; Dykhoff, D. A.; Shenoy, D. P.

2013-08-01

291

UBVI CCD Photometry of the Open Cluster NGC 559  

NASA Astrophysics Data System (ADS)

We have conducted UBVI CCD photometry of an intermediate-age open cluster NGC 559 to investigate the effect of dynamical evolution on the stellar distributions in NGC 559. Our photometry allows better estimates of distance and age of the cluster owing to much deeper photometry (V <= 21) than previous ones. It is found that the luminosity function and mass function as well as the spatial stellar distributions are affected by the dynamical evolution. Mass segregation leads to the central concentration of the high mass stars, which results in the flattened mass function inside the half mass radius.

Ann, Hong Bae; Lee, Sang Hyun

2002-03-01

292

Gravity Effects Observed In Partially Premixed Flames  

NASA Technical Reports Server (NTRS)

Partially premixed flames (PPFs) contain a rich premixed fuel air mixture in a pocket or stream, and, for complete combustion to occur, they require the transport of oxidizer from an appropriately oxidizer-rich (or fuel-lean) mixture that is present in another pocket or stream. Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions. Partial premixing, therefore, represents that condition when the equivalence ratio (phi) in one portion of the flowfield is greater than unity, and in another section its value is less than unity. In general, for combustion to occur efficiently, the global equivalence ratio is in the range fuel-lean to stoichiometric. These flames can be established by design by placing a fuel-rich mixture in contact with a fuel-lean mixture, but they also occur otherwise in many practical systems, which include nonpremixed lifted flames, turbulent nonpremixed combustion, spray flames, and unwanted fires. Other practical applications of PPFs are reported elsewhere. Although extensive experimental studies have been conducted on premixed and nonpremixed flames under microgravity, there is a absence of previous experimental work on burner stabilized PPFs in this regard. Previous numerical studies by our group employing a detailed numerical model showed gravity effects to be significant on the PPF structure. We report on the results of microgravity experiments conducted on two-dimensional (established on a Wolfhard-Parker slot burner) and axisymmetric flames (on a coannular burner) that were investigated in a self-contained multipurpose rig. Thermocouple and radiometer data were also used to characterize the thermal transport in the flame.

Puri, Ishwar K.; Aggarwal, Suresh K.; Lock, Andrew J.; Gauguly, Ranjan; Hegde, Uday

2003-01-01

293

Laminar Flame Speeds of Moist Syngas Mixtures  

SciTech Connect

This work experimentally investigates the effect of the presence of water vapor on the laminar flame speeds of moist syngas/air mixtures using the counterflow twin-flame configuration. The experimental results presented here are for fuel lean syngas mixtures with molar percentage of hydrogen in the hydrogen and carbon monoxide mixture varying from 5% to 100%, for an unburned mixture temperature of 323 K, and under atmospheric pressure. At a given equivalence ratio, the effect of varying amount of water vapor addition on the measured laminar flame speed is demonstrated. The experimental laminar flame speeds are also compared with computed values using chemical kinetic mechanisms reported in the literature. It is found that laminar flame speed varies non-monotonically with addition of water for the carbon monoxide rich mixtures. It first increases with increasing amount of water addition, reaches a maximum value, and then decreases. An integrated reaction path analysis is further conducted to understand the controlling mechanism responsible for the non-monotonic variation in laminar flame speed due to water addition. On the other hand, for higher values of H{sub 2}/CO ratio the laminar flame speed monotonically decreases with increasing water addition. It is shown that the competition between the chemical and thermal effects of water addition leads to the observed response. Furthermore, reaction rate sensitivity analysis as well as binary diffusion coefficient sensitivity analysis are conducted to identify the possible sources of discrepancy between the experimental and predicted values. The sensitivity results indicate that the reaction rate constant of H{sub 2} + OH = H{sub 2}O + H is worth revisiting and refinement of binary diffusion coefficient data of N{sub 2}–H{sub 2}O, N{sub 2}–H{sub 2}, and H{sub 2}–H{sub 2}O pairs can be considered.

Das, A. K.; Kumar, K.; Zhang, Z.; Sung, C. J.

2011-01-01

294

Ultraviolet imaging of hydrogen flames  

SciTech Connect

We have assembled an ultraviolet-sensitive intensified camera for observing hydrogen combustion by imaging the OH, A/sup 2/..sigma.. - X/sup 2//Pi/ bandhead emissions near 309 nm. The camera consists of a quartz and CaF achromat lense-coupled to an ultraviolet image intensifier which is in turn fiber-coupled to a focus projection scan (FPS) vidicon. The emission band is selected with interference filters which serve to discriminate against background. The camera provides optical gain of 100 to 1000 and is capable of being shuttered at nanosecond speeds and of being framed at over 600 frames per second. We present data from observations of test flames in air at standard RS-170 video rates with varying background conditions. Enhanced images using background subtraction are presented. Finally, we discuss the use of polarizaton effects to further discrimination against sky background. This work began as a feasibility study to investigate ultraviolet technology to detect hydrogen fires for the NASA space program. 6 refs., 7 figs, 2 tabs.

Yates, G.J.; Wilke, M.; King, N.

1988-01-01

295

Engineering Flame Retardant Biodegradable Nanocomposites  

NASA Astrophysics Data System (ADS)

Cellulose-based PLA/PBAT polymer blends can potentially be a promising class of biodegradable nanocomposites. Adding cellulose fiber reinforcement can improve mechanical properties of biodegradable plastics, but homogeneously dispersing hydrophilic cellulose in the hydrophobic polymer matrix poses a significant challenge. We here show that resorcinol diphenyl phosphates (RDP) can be used to modify the surface energy, not only reducing phase separation between two polymer kinds but also allowing the cellulose particles and the Halloysite clay to be easily dispersed within polymer matrices to achieve synergy effect using melt blending. Here in this study we describe the use of cellulose fiber and Halloysite clay, coated with RDP surfactant, in producing the flame retardant polymer blends of PBAT(Ecoflex) and PLA which can pass the stringent UL-94 V0 test. We also utilized FTIR, SEM and AFM nanoindentation to elucidate the role RDP plays in improving the compatibility of biodegradable polymers, and to determine structure property of chars that resulted in composites that could have optimized mechanical and thermal properties.

He, Shan; Yang, Kai; Guo, Yichen; Zhang, Linxi; Pack, Seongchan; Davis, Rachel; Lewin, Menahem; Ade, Harald; Korach, Chad; Kashiwagi, Takashi; Rafailovich, Miriam

2013-03-01

296

Turbulent Premixed Flames in Microgravity  

NASA Technical Reports Server (NTRS)

The experimental cold-flow facility is now full operational and is currently being used to obtain baseline turbulence data in a Couette flow. The baseline turbulence data is necessary to confirm the capability of the chosen device to generate and maintain the required turbulence intensity. Subsequent reacting flow studies will assume that a similar turbulent flow field exists ahead of the premixed flame. Some modifications and refinements had to be made to enable accurate measurements. It consists of two rollers, one (driven by a motor) which drives a continuous belt and four smaller rollers used to set the belt spacing and tension to minimize belt flutter. The entire assemble is enclosed in a structure that has the dimensions to enable future drop tower experiments of the hot facility. All critical dimensions are the same as the original plans except for the pulley ratio which has been changed to enable a wider operating regime in terms of the Reynolds number. With the current setup, Reynolds numbers as low as 100 and as high as 14,000 can be achieved. This is because the in-between belt spacing can be varied from 1 cm to 7.6 cm, and the belt speed can be accurately varied from .15 m/sec to 3.1 m/sec.

Menon, Suresh

1996-01-01

297

The VLT-FLAMES Tarantula Survey. I. Introduction and observational overview  

NASA Astrophysics Data System (ADS)

The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, including optical and near-infrared photometry and comprehensive details of the data reduction. One of the principal objectives was to detect massive binary systems via variations in their radial velocities, thus shaping the multi-epoch observing strategy. Spectral classifications are given for the massive emission-line stars observed by the survey, including the discovery of a new Wolf-Rayet star (VFTS 682, classified as WN5h), 2' to the northeast of R136. To illustrate the diversity of objects encompassed by the survey, we investigate the spectral properties of sixteen targets identified by Gruendl & Chu from Spitzer photometry as candidate young stellar objects or stars with notable mid-infrared excesses. Detailed spectral classification and quantitative analysis of the O- and B-type stars in the VFTS sample, paying particular attention to the effects of rotational mixing and binarity, will be presented in a series of future articles to address fundamental questions in both stellar and cluster evolution. Figures 10-12, Tables 5 and 6, and Appendix A are available in electronic form at http://www.aanda.org

Evans, C. J.; Taylor, W. D.; Hénault-Brunet, V.; Sana, H.; de Koter, A.; Simón-Díaz, S.; Carraro, G.; Bagnoli, T.; Bastian, N.; Bestenlehner, J. M.; Bonanos, A. Z.; Bressert, E.; Brott, I.; Campbell, M. A.; Cantiello, M.; Clark, J. S.; Costa, E.; Crowther, P. A.; de Mink, S. E.; Doran, E.; Dufton, P. L.; Dunstall, P. R.; Friedrich, K.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I. D.; Izzard, R. G.; Langer, N.; Lennon, D. J.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Puls, J.; Ramirez, O. H.; Sabín-Sanjulián, C.; Smartt, S. J.; Stroud, V. E.; van Loon, J. Th.; Vink, J. S.; Walborn, N. R.

2011-06-01

298

The VLT-FLAMES Tarantula Survey I: Introduction and observational overview  

E-print Network

The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, including optical and near-infrared photometry and comprehensive details of the data reduction. One of the principal objectives was to detect massive binary systems via variations in their radial velocities, thus shaping the multi-epoch observing strategy. Spectral classifications are given for the massive emission-line stars observed by the survey, including the discovery of a new Wolf-Rayet star (VFTS 682, classified as WN5h), 2' to the northeast of R136. To illustrate the diversity of objects encompassed by the survey, we investigate the spectral properties of sixteen targets identified by Gruendl & Chu from Spitzer photometry as candidate young stellar objects or stars with notable mid-infrared excesses. Detailed ...

Evans, C J; Henault-Brunet, V; Sana, H; de Koter, A; Simon-Diaz, S; Carraro, G; Bagnoli, T; Bastian, N; Bestenlehner, J M; Bonanos, A Z; Bressert, E; Brott, I; Campbell, M A; Cantiello, M; Clark, J S; Costa, E; Crowther, P A; de Mink, S E; Doran, E; Dufton, P L; Dunstall, P R; Friedrich, K; Garcia, M; Gieles, M; Graefener, G; Herrero, A; Howarth, I D; Izzard, R G; Langer, N; Lennon, D J; Apellaniz, J Maiz; Markova, N; Najarro, F; Puls, J; Ramirez, O H; Sabin, C; Smartt, S J; Stroud, V E; van Loon, J Th; Vink, J S; Walborn, N R

2011-01-01

299

Simulations of normal and inverse laminar diffusion flames under oxygen enhancement and gravity variation  

Microsoft Academic Search

Steady-state global chemistry calculations for 20 different flames were carried out using an axisymmetric Computational Fluid Dynamics (CFD) code. Computational results for 16 flames were compared with flame images obtained at the NASA Glenn Research Center. The experimental flame data for these 16 flames were taken from Sunderland et al. [4] which included normal and inverse diffusion flames of ethane

P. Bhatia; V. R. Katta; S. S. Krishnan; Y. Zheng; P. B. Sunderland; J. P. Gore

2012-01-01

300

Detection of Extrasolar Planets by Transit Photometry  

NASA Technical Reports Server (NTRS)

A knowledge of other planetary systems that includes information on the number, size, mass, and spacing of the planets around a variety of star types is needed to deepen our understanding of planetary system formation and processes that give rise to their final configurations. Recent discoveries show that many planetary systems are quite different from the solar system in that they often possess giant planets in short period orbits. The inferred evolution of these planets and their orbital characteristics imply the absence of Earth-like planets near the habitable zone. Information on the properties of the giant-inner planets is now being obtained by both the Doppler velocity and the transit photometry techniques. The combination of the two techniques provides the mass, size, and density of the planets. For the planet orbiting star HD209458, transit photometry provided the first independent confirmation and measurement of the diameter of an extrasolar planet. The observations indicate a planet 1.27 the diameter of Jupiter with 0.63 of its mass (Charbonneau et al. 1999). The results are in excellent agreement with the theory of planetary atmospheres for a planet of the indicated mass and distance from a solar-like star. The observation of the November 23, 1999 transit of that planet made by the Ames Vulcan photometer at Lick Observatory is presented. In the future, the combination of the two techniques will greatly increase the number of discoveries and the richness of the science yield. Small rocky planets at orbital distances from 0.9 to 1.2 AU are more likely to harbor life than the gas giant planets that are now being discovered. However, new technology is needed to find smaller, Earth-like planets, which are about three hundred times less massive than Jupiter-like planets. The Kepler project is a space craft mission designed to discover hundreds of Earth-size planets in and near the habitable zone around a wide variety of stars. To demonstrate that the technology exists to find such small planets, our group has conducted an end-to-end system test. The results of the laboratory tests are presented and show that we are ready to start the search for Earth-size planets.

Borucki, William; Koch, David; Webster, Larry; Dunham, Edward; Witteborn, Fred; Jenkins, Jon; Caldwell, Douglas; Showen, Robert; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

301

Launch Pad Flame Trench Refractory Materials  

NASA Technical Reports Server (NTRS)

The launch complexes at NASA's John F. Kennedy Space Center (KSC) are critical support facilities for the successful launch of space-based vehicles. These facilities include a flame trench that bisects the pad at ground level. This trench includes a flame deflector system that consists of an inverted, V-shaped steel structure covered with a high temperature concrete material five inches thick that extends across the center of the flame trench. One side of the "V11 receives and deflects the flames from the orbiter main engines; the opposite side deflects the flames from the solid rocket boosters. There are also two movable deflectors at the top of the trench to provide additional protection to shuttle hardware from the solid rocket booster flames. These facilities are over 40 years old and are experiencing constant deterioration from launch heat/blast effects and environmental exposure. The refractory material currently used in launch pad flame deflectors has become susceptible to failure, resulting in large sections of the material breaking away from the steel base structure and creating high-speed projectiles during launch. These projectiles jeopardize the safety of the launch complex, crew, and vehicle. Post launch inspections have revealed that the number and frequency of repairs, as well as the area and size of the damage, is increasing with the number of launches. The Space Shuttle Program has accepted the extensive ground processing costs for post launch repair of damaged areas and investigations of future launch related failures for the remainder of the program. There currently are no long term solutions available for Constellation Program ground operations to address the poor performance and subsequent failures of the refractory materials. Over the last three years, significant liberation of refractory material in the flame trench and fire bricks along the adjacent trench walls following Space Shuttle launches have resulted in extensive investigations of failure mechanisms, load response, ejected material impact evaluation, and repair design analysis (environmental and structural assessment, induced environment from solid rocket booster plume, loads summary, and repair integrity), assessment of risk posture for flame trench debris, and justification of flight readiness rationale. Although the configuration of the launch pad, water and exhaust direction, and location of the Mobile Launcher Platform between the flame trench and the flight hardware should protect the Space Vehicle from debris exposure, loss of material could cause damage to a major element of the ground facility (resulting in temporary usage loss); and damage to other facility elements is possible. These are all significant risks that will impact ground operations for Constellation and development of new refractory material systems is necessary to reduce the likelihood of the foreign object debris hazard during launch. KSC is developing an alternate refractory material for the launch pad flame trench protection system, including flame deflector and flame trench walls, that will withstand launch conditions without the need for repair after every launch, as is currently the case. This paper will present a summary of the results from industry surveys, trade studies, life cycle cost analysis, and preliminary testing that have been performed to support and validate the development, testing, and qualification of new refractory materials.

Calle, Luz M.; Hintze, Paul E.; Parlier, Christopher R.; Bucherl, Cori; Sampson, Jeffrey W.; Curran, Jerome P.; Kolody, Mark; Perusich, Steve; Whitten, Mary

2010-01-01

302

Acoustic characterization of flame blowout phenomenon  

NASA Astrophysics Data System (ADS)

Combustor blowout is a very serious concern in modern land-based and aircraft engine combustors. The ability to sense blowout precursors can provide significant payoffs in engine reliability and life. The objective of this work is to characterize the blowout phenomenon and develop a sensing methodology which can detect and assess the proximity of a combustor to blowout by monitoring its acoustic signature, thus providing early warning before the actual blowout of the combustor. The first part of the work examines the blowout phenomenon in a piloted jet burner. As blowout was approached, the flame detached from one side of the burner and showed increased flame tip fluctuations, resulting in an increase in low frequency acoustics. Work was then focused on swirling combustion systems. Close to blowout, localized extinction/re-ignition events were observed, which manifested as bursts in the acoustic signal. These events increased in number and duration as the combustor approached blowout, resulting an increase in low frequency acoustics. A variety of spectral, wavelet and thresholding based approaches were developed to detect precursors to blowout. The third part of the study focused on a bluff body burner. It characterized the underlying flame dynamics near blowout in greater detail and related it to the observed acoustic emissions. Vorticity was found to play a significant role in the flame dynamics. The flame passed through two distinct stages prior to blowout. The first was associated with momentary strain levels that exceed the flame's extinction strain rate, leading to flame "holes". The second was due to large scale alteration of the fluid dynamics in the bluff body wake, leading to violent flapping of the flame front and even larger straining of the flame. This led to low frequency acoustic oscillations, of the order of von Karman vortex shedding. This manifested as an abrupt increase in combustion noise spectra at 40-100 Hz very close to blowout. Finally, work was also done to improve the robustness of lean blowout detection by developing integration techniques that combined data from acoustic and optical sensors.

Nair, Suraj

303

WIYN Open Cluster Study: UBVRI Photometry of NGC 2158  

NASA Astrophysics Data System (ADS)

We present WIYN 0.9m HDI UBVRI photometry of NGC 2158, a very rich, intermediate-aged, open cluster located near the galactic anti-center. We report derived values for the cluster age, distance, reddening.

Taverne, Luke T.; Steinhauer, Aaron J.; Deliyannis, Constantine P.

2015-01-01

304

Photoelectric Photometry of Asteriods 29 Amphitrite and 88 Thisbe  

Microsoft Academic Search

Photoelectric photometry observations of the asteroids 29 Amphitrite and 88 Thisbe were made from North Valley Stream Observatory during the period August 29 to September 1, 1986 UT. The lightcurves for both asteroids are consistent with previously determined rotation periods.

F. J. Melillo

1987-01-01

305

Photometry and transit-timing analysis for eleven transiting exoplanets  

E-print Network

This thesis presents time-series photometry of transits of 11 different extrasolar planets. Observations were conducted with the Fred L. Whipple Observatory 1.2m telescope and the Wise Observatory im telescope, in standard ...

De Kleer, Katherine Rebecca

2009-01-01

306

A catalogue of IJK photometry of Planetary Nebulae with DENIS  

E-print Network

Near-infrared photometry of planetary nebulae (PNe) allows the classification of those objects. We present the largest homogeneous sample so far, obtained with the Deep Near Infrared Southern Sky Survey (DENIS).

S. Schmeja; S. Kimeswenger

2001-05-15

307

Flame-vortex interaction and mixing behaviors of turbulent non-premixed jet flames under acoustic forcing  

SciTech Connect

This study examines the effect of acoustic excitation using forced coaxial air on the flame characteristics of turbulent hydrogen non-premixed flames. A resonance frequency was selected to acoustically excite the coaxial air jet due to its ability to effectively amplify the acoustic amplitude and reduce flame length and NO{sub x} emissions. Acoustic excitation causes the flame length to decrease by 15% and consequently, a 25% reduction in EINO{sub x} is achieved, compared to coaxial air flames without acoustic excitation at the same coaxial air to fuel velocity ratio. Moreover, acoustic excitation induces periodical fluctuation of the coaxial air velocity, thus resulting in slight fluctuation of the fuel velocity. From phase-lock PIV and OH PLIF measurement, the local flow properties at the flame surface were investigated under acoustic forcing. During flame-vortex interaction in the near field region, the entrainment velocity and the flame surface area increased locally near the vortex. This increase in flame surface area and entrainment velocity is believed to be a crucial factor in reducing flame length and NO{sub x} emission in coaxial jet flames with acoustic excitation. Local flame extinction occurred frequently when subjected to an excessive strain rate, indicating that intense mass transfer of fuel and air occurs radially inward at the flame surface. (author)

Kim, Munki; Choi, Youngil; Oh, Jeongseog; Yoon, Youngbin [School of Mechanical and Aerospace Engineering, Seoul National University, Seoul (Korea)

2009-12-15

308

Pulsating instability and self-acceleration of fast turbulent flames  

E-print Network

(Abridged) A series of three-dimensional numerical simulations is used to study the intrinsic stability of high-speed turbulent flames. Calculations model the interaction of a fully-resolved premixed flame with a highly subsonic, statistically steady, homogeneous, isotropic turbulence. We consider a wide range of turbulent intensities and system sizes, corresponding to the Damk\\"ohler numbers Da = 0.1-6.0. These calculations show that turbulent flames in the regimes considered are intrinsically unstable. In particular, we find three effects. 1) Turbulent flame speed develops pulsations with the observed peak-to-peak amplitude > 10 and a characteristic time scale close to a large-scale eddy turnover time. Such variability is caused by the interplay between turbulence, which continuously creates the flame surface, and highly intermittent flame collisions, which consume the flame surface. 2) Unstable burning results in the periodic pressure build-up and the formation of pressure waves or shocks, when the flame s...

Poludnenko, A Y

2015-01-01

309

EFFECT OF ORGANOPHOSPHORUS FLAME RETARDANTS ON NEURONAL DEVELOPMENT IN VITRO  

EPA Science Inventory

The increased use of organophosphorus compounds as alternatives to brominated flame retardants (BFRs) has led to widespread human exposure, There is, however, limited information on their potential health effects. This study compared the effects of nii ne organophosphorus flame...

310

Development of video processing based on coal flame detector system  

SciTech Connect

The principle and development of a set of pulverized coal combustion flame detection system, which is called intelligent image flame detector device based on digital video processing, is addressed in this paper. The system realizes multi-burner flame detection and processing using a distributive structure of engineering workstation and flame detectors via multi-serial-port communication. The software can deal with multi-tasks in a parallel way based on multi-thread mechanism. Streaming video capture and storage is provided to safe and playback the accidental Audio and Visual Interfaces (AVI) clips. The layer flame detectors can give the flame on/off signal through image processing. Pseudo-color visualization of flame temperature calculated from chromatic CCD signal is integrated into the system. The image flame detector system has been successfully used in thermal power generation units in China.

He Wanqing; Yu Yuefeng; Xu Weiyong; Ma Liqun

1999-07-01

311

Flashback flame arrester devices for fuel cargo tank vapor vents  

NASA Technical Reports Server (NTRS)

The flame quenching capability of four types of flame arresting devices suitable for installation on fuel cargo tank vents of marine transport vessels is evaluated. A single 30 mesh screen, a dual 20 mesh screen, a spiral wound crimped metal ribbon, and a packed bed of ballast rings were tested. Flame speed and flame penetration of the test arresters were determined. Eight fuels representative of bulk cargoes were tested. The test arresters quenched a minimum of three flashback flames from all eight fuels, with one exception: high speed ethylene flames penetrated the dual 20 mesh screen on three tests. The arresters withstood the sustained flame from a propane/air mixture for 30 minutes. None of the arresters withstood the sustained flame from an ethylene/air mixture for more than 7 minutes.

Bjorklund, R. A.; Kushida, R. O.

1981-01-01

312

Modeling of NOx formation in circular laminar jet flames  

E-print Network

into the relative importance of NOx reaction pathways in non premixed combustion for various flame conditions. The existing models include detailed chemistry kinetics for various species involved in the flame. These detailed models involve very complex integration...

Siwatch, Vivek

2007-04-25

313

Binary Star Synthetic Photometry and Distance Determination Using BINSYN  

NASA Astrophysics Data System (ADS)

This paper extends synthetic photometry to components of binary star systems. The paper demonstrates accurate recovery of single star photometric properties for four photometric standards, Vega, Sirius, GD153, and HD209458, ranging over the HR diagram, when their model synthetic spectra are placed in fictitious binary systems and subjected to synthetic photometry processing. Techniques for photometric distance determination have been validated for all four photometric standards.

Linnell, Albert P.; DeStefano, Paul; Hubeny, Ivan

2013-09-01

314

BINARY STAR SYNTHETIC PHOTOMETRY AND DISTANCE DETERMINATION USING BINSYN  

SciTech Connect

This paper extends synthetic photometry to components of binary star systems. The paper demonstrates accurate recovery of single star photometric properties for four photometric standards, Vega, Sirius, GD153, and HD209458, ranging over the HR diagram, when their model synthetic spectra are placed in fictitious binary systems and subjected to synthetic photometry processing. Techniques for photometric distance determination have been validated for all four photometric standards.

Linnell, Albert P. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); DeStefano, Paul [8508B Midvale Ave. North, Seattle, WA 98103 (United States); Hubeny, Ivan, E-mail: linnell@astro.washington.edu, E-mail: pdestefa@uw.edu, E-mail: hubeny@as.arizona.edu [Steward Observatory and Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States)

2013-09-15

315

DOPHOT, a CCD photometry program: Description and tests  

NASA Technical Reports Server (NTRS)

The design considerations and operational features of DOPHOT, a point-spread function (PSF) fitting photometry program, are described. Some relevant details of the PSF fitting are discussed. The quality of the photometry returned by DOPHOT is assessed via reductions of an 'artificial' globular cluster generated from a list of stars with known magnitudes and colors. Results from comparative tests between DOPHOT and DAOPHOT using this synthetic cluster and real data are also described.

Schechter, Paul L.; Mateo, Mario; Saha, Abhijit

1993-01-01

316

Deep CCD Photometry of Old Open Clusters  

NASA Astrophysics Data System (ADS)

Ages and distance moduli for the open clusters NGC 2204, Berkeley 39, NGC 2477, and Melotte 66 are constrained by comparing the theoretical models developed by Bertelli et al. (1994, A&A, 106, 235) to the observed cluster color-magnitude diagrams which are based on deep CCD photometry. Out of a set of comparison models, no single isochrone was superior to the others in describing an observed color-magnitude diagram. Thus, a best fitting model was selected based not only on the match to an observed color-magnitude diagram, but also on the isochrone's agreement with adopted values for the cluster's metallicity and reddening. The range of otherwise acceptable models help quantify the age and distance modulus uncertainty of each cluster. Based on the best fitting models NGC 2204 is 1.6(+0.9}_{-0.3) Gyrs old with (m-M)_o = 13.0(+0.5}_{-0.4) , Berkeley 39 has an age of 6(+2}_{-1) Gyrs with (m-M)_o = 12.9+/-0.2, NGC 2477 is 1(+0.3}_{-0.2) Gyr old with (m-M)_o = 10.5(+0.4}_{-0.3) , and Melotte 66 has an age of 4+/-1 Gyrs with (m-M)_o = 13.2(+0.3}_{-0.1) .

Kassis, Marc; Janes, Kenneth A.; Friel, Eileen D.; Phelps, Randy L.

1997-05-01

317

Recent Advances in Video Meteor Photometry  

NASA Technical Reports Server (NTRS)

One of the most common (and obvious) problems with video meteor data involves the saturation of the output signal produced by bright meteors, resulting in the elimination of such meteors from photometric determinations. It is important to realize that a "bright" meteor recorded by intensified meteor camera is not what would be considered "bright" by a visual observer - indeed, many Generation II or III camera systems are saturated by meteors with a visual magnitude of 3, barely even noticeable to the untrained eye. As the relatively small fields of view (approx.30 ) of the camera systems captures at best modest numbers of meteors, even during storm peaks, the loss of meteors brighter than +3 renders the determination of shower population indices from video observations even more difficult. Considerable effort has been devoted by the authors to the study of the meteor camera systems employed during the Marshall Space Flight Center s Leonid ground-based campaigns, and a calibration scheme has been devised which can extend the useful dynamic range of such systems by approximately 4 magnitudes. The calibration setup involves only simple equipment, available to amateur and professional, and it is hoped that use of this technique will make for better meteor photometry, and move video meteor analysis beyond the realm of simple counts.

Swift, Wesley R.; Suggs, Robert M.; Meachem, Terry; Cooke, William J.

2003-01-01

318

Dynamics of Isolated and Interacting Flame Structures in Strongly-Pulsed, Turbulent Jet Flames  

NASA Astrophysics Data System (ADS)

The dynamics of the large-scale structures in strongly-pulsed, turbulent diffusion flames were studied in normal- and microgravity. Cross-correlation of temperature measurements and high-speed flame imaging were used to estimate the celerity of the flame structures. Both diagnostics indicate a marked increase in celerity with the increasing flame puff interaction as the jet off-time decreases. The celerity is also generally higher for shorter injection times, which yield more compact flame puffs. These trends are seen both for the case of fixed injection velocity as well as for the case of fixed fueling rate. The celerity correlates well with the inverse downstream distance scaled with an appropriate injection parameter, suggesting that the impact of buoyancy can be partially accounted for by the corresponding changes in the mean flame length. Differences in the values of celerity determined by the temperature and visual techniques can be attributed to nature of the evolution of the flame puffs with downstream distance.

Fregeau, Mathieu; Liao, Ying-Hao; Hermanson, James; Stocker, Dennis; Hegde, Uday

2007-11-01

319

Fundamental mechanisms in premixed flame propagation via vortex-flame interactions: Numerical simulations  

NASA Technical Reports Server (NTRS)

The goal of the present study is to assess numerically the ability of single-step and two-step chemical models to describe the main features encountered during the interaction between a two-dimensional vortex pair and a premixed laminar flame. In the two-step mechanism, the reaction kinetics are represented by a first chain branching reaction A + X yields 2X and a second chain termination reaction X + X yields P. This paper presents the fundamental mechanisms occurring during vortex-flame interactions and the relative impact of the major parameters encountered in turbulent premixed flames and suspected of playing a role in quenching mechanism: (1) Influence of stretch is investigated by analyzing the contribution of curvature and tangential strain on the local structure of the flame. The effect of Lewis number on the flame response to a strained field is analyzed. (2) Radiative heat losses which are suspected to be partially or totally responsible for quenching are also investigated. (3) The effect of the diffusion of the radicals is studied using a two-step mechanism in which an intermediate species is present. The parameters of the two-step mechanism are entirely determined from physical arguments. (4) Precise quantitative comparisons between the DNS and the experimental results of Samaniego et al are performed. These comparisons concern the evolution of the minimum heat release rate found along the flame front during the interaction and the distribution of the heat release rate along the flame front.

Mantel, Thierry

1994-01-01

320

Point-to-plane pulsed discharge initiated flame structure modification in propane-air flame  

NASA Astrophysics Data System (ADS)

The effect of a point-to-plane pulsed discharge on a propane/air flame has been investigated by phase-locked simultaneous measurements of the change in gas temperature and OH planar laser-induced-fluorescence (PLIF). Phase-locked simultaneous measurement of gas temperature through spontaneous Raman scattering and OH PLIF with the variation of pulsed plasma energy and plasma generation location with respect to the flame holder and flame reaction zone have been performed. A fast rise time (15 ns) and a slower rise time (150 ns) high voltage pulsers are used to produce OH radical densities 50% greater than the ambient flame produced OH radicals in both lean and rich premixed flames. The excess OH radical densities were found to decay to the 50% level with time constants greater than 100 µs in the burnt gas regions with gas temperatures greater than 1000 K. The flame perturbation was dependent on the pulse repetition rates as well as on the pulse rise time for similar energy deposition per pulse. A laser photo-deflection measurement of acoustic pressure pulse generation by the pulsed discharge suggests that flame perturbation by the downstream plasma is caused mostly by flow perturbation.

Schmidt, Jacob B.; Ganguly, Biswa N.

2012-02-01

321

Flame-Vortex Studies to Quantify Markstein Numbers Needed to Model Flame Extinction Limits  

NASA Technical Reports Server (NTRS)

This has quantified a database of Markstein numbers for unsteady flames; future work will quantify a database of flame extinction limits for unsteady conditions. Unsteady extinction limits have not been documented previously; both a stretch rate and a residence time must be measured, since extinction requires that the stretch rate be sufficiently large for a sufficiently long residence time. Ma was measured for an inwardly-propagating flame (IPF) that is negatively-stretched under microgravity conditions. Computations also were performed using RUN-1DL to explain the measurements. The Markstein number of an inwardly-propagating flame, for both the microgravity experiment and the computations, is significantly larger than that of an outwardy-propagating flame. The computed profiles of the various species within the flame suggest reasons. Computed hydrogen concentrations build up ahead of the IPF but not the OPF. Understanding was gained by running the computations for both simplified and full-chemistry conditions. Numerical Simulations. To explain the experimental findings, numerical simulations of both inwardly and outwardly propagating spherical flames (with complex chemistry) were generated using the RUN-1DL code, which includes 16 species and 46 reactions.

Driscoll, James F.; Feikema, Douglas A.

2003-01-01

322

Flame photometric detector for thin-layer chromatography  

Microsoft Academic Search

A new flame photometric detector for thin-layer chromatography (TLC) was studied to determine sulfur and phosphorus containing compounds in materials with a high boiling point. The detector was integrated with a flame ionization detector into the Iatroscan TLC–flame ionization detection analyzer. The principle of the detector is based on the photometric detection of flame emission of heteroatom in a hydrogen–air

Minoru Ogasawara; Kyoko Tsuruta; Shinsuke Arao

2002-01-01

323

Spatial resolution of temperature and chemical species in a flame  

E-print Network

Committee: Dr. Glenn J. Bastiaans This work describes the use of an individual technique to measure both temperature and species concentration in a combustion device such as a flame. The spatial distri- bution of two flame species, hydroxyl radical... recombination process which takes place with the hydroxyl radical. The known i'luorescence emission spectrum at 308 nm was used to locate OH radical in the flame. Even though a nitrogen sheath was used to protect the flame from outside air penetration, OH...

Albahadily, Fakhrildeen Niema

2012-06-07

324

On stability of premixed flames in stagnation - Point flow  

NASA Technical Reports Server (NTRS)

A quantitative description of flame stabilization in stagnation-point flow is proposed. Asymptotic and stability analyses are made for a flame model where the density of the gas is assumed to be constant and the reaction zone is assumed to be narrow and concentrated over the flame front. It is shown that, if blowing is sufficiently strong, the corrugations disappear and a plane flame results. The phenomena cannot be fully described by means of classical linear stability analysis.

Sivashinsky, G. I.; Law, C. K.; Joulin, G.

1982-01-01

325

The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars  

E-print Network

Context: The commonly used extinction laws of Cardelli et al. (1989) have limitations that, among other issues, hamper the determination of the effective temperatures of O and early B stars from optical+NIR photometry. Aims: We aim to develop a new family of extinction laws for 30 Doradus, check their general applicability within that region and elsewhere, and apply them to test the feasibility of using optical+NIR photometry to determine the effective temperature of OB stars. Methods: We use spectroscopy and NIR photometry from the VLT-FLAMES Tarantula Survey and optical photometry from HST/WFC3 of 30 Doradus and we analyze them with the software code CHORIZOS using different assumptions such as the family of extinction laws. Results: We derive a new family of optical+NIR extinction laws for 30 Doradus and confirm its applicability to extinguished Galactic O-type systems. We conclude that by using the new extinction laws it is possible to measure the effective temperatures of OB stars with moderate uncertain...

Apellániz, J Maíz; Barbá, R H; Gräfener, G; Bestenlehner, J M; Crowther, P A; García, M; Herrero, A; Sana, H; Simón-Díaz, S; Taylor, W D; van Loon, J Th; Vink, J S; Walborn, N R

2014-01-01

326

The VLT-FLAMES Tarantula Survey. XVI. The optical and NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars  

NASA Astrophysics Data System (ADS)

Context. The commonly used extinction laws of Cardelli et al. (1989, ApJ, 345, 245) have limitations that, among other issues, hamper the determination of the effective temperatures of O and early B stars from optical and near-infrared (NIR) photometry. Aims: We aim to develop a new family of extinction laws for 30 Doradus, check their general applicability within that region and elsewhere, and apply them to test the feasibility of using optical and NIR photometry to determine the effective temperature of OB stars. Methods: We use spectroscopy and NIR photometry from the VLT-FLAMES Tarantula Survey and optical photometry from HST/WFC3 of 30 Doradus and we analyze them with the software code CHORIZOS using different assumptions, such as the family of extinction laws. Results: We derive a new family of optical and NIR extinction laws for 30 Doradus and confirm its applicability to extinguished Galactic O-type systems. We conclude that by using the new extinction laws it is possible to measure the effective temperatures of OB stars with moderate uncertainties and only a small bias, at least up to E(4405-5495) ~ 1.5 mag. Appendices are available in electronic form at http://www.aanda.org

Maíz Apellániz, J.; Evans, C. J.; Barbá, R. H.; Gräfener, G.; Bestenlehner, J. M.; Crowther, P. A.; García, M.; Herrero, A.; Sana, H.; Simón-Díaz, S.; Taylor, W. D.; van Loon, J. Th.; Vink, J. S.; Walborn, N. R.

2014-04-01

327

FIXING THE U-BAND PHOTOMETRY OF TYPE Ia SUPERNOVAE  

SciTech Connect

We present previously unpublished photometry of supernovae 2003gs and 2003hv. Using spectroscopically derived corrections to the U-band photometry, we reconcile U-band light curves made from imagery with the Cerro Tololo 0.9 m, 1.3 m, and Las Campanas 1 m telescopes. Previously, such light curves showed a 0.4 mag spread at one month after maximum light. This gives us hope that a set of corrected ultraviolet light curves of nearby objects can contribute to the full utilization of rest-frame U-band data of supernovae at redshift {approx}0.3-0.8. As pointed out recently by Kessler et al. in the context of the Sloan Digital Sky Survey supernova search, if we take the published U-band photometry of nearby Type Ia supernovae at face value, there is a 0.12 mag U-band anomaly in the distance moduli of higher redshift objects. This anomaly led the Sloan survey to eliminate from their analyses all photometry obtained in the rest-frame U-band. The Supernova Legacy Survey eliminated observer frame U-band photometry, which is to say nearby objects observed in the U-band, but they used photometry of high-redshift objects no matter in which band the photons were emitted.

Krisciunas, Kevin; Bastola, Deepak; Suntzeff, Nicholas B. [Department of Physics and Astronomy, Texas A and M University, 4242 TAMU, College Station, TX 77843-4242 (United States); Espinoza, Juan; Gonzalez, David [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Gonzalez, Luis; Gonzalez, Sergio; Hsiao, Eric Y.; Morrell, Nidia; Phillips, Mark M. [Las Campanas Observatory, Casilla 601, La Serena (Chile); Hamuy, Mario, E-mail: krisciunas@physics.tamu.edu, E-mail: suntzeff@physics.tamu.edu, E-mail: jespinoza@ctio.noao.edu, E-mail: hsiao@lco.cl, E-mail: nmorrell@lco.cl, E-mail: mmp@lco.cl, E-mail: mhamuy@das.uchile.cl [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile)

2013-01-01

328

NEW UBVRI PHOTOMETRY OF 234 M33 STAR CLUSTERS  

SciTech Connect

This is the second paper of our series. In this paper, we present UBVRI photometry for 234 star clusters in the field of M33. For most of these star clusters, there is photometry in only two bands in previous studies. The photometry of these star clusters is performed using archival images from the Local Group Galaxies Survey, which covers 0.8 deg{sup 2} along the major axis of M33. Detailed comparisons show that, in general, our photometry is consistent with previous measurements, and in particular that our photometry is in good agreement with that of Zloczewski and Kaluzny. Combined with star cluster photometry in previous studies, we present some results: none of the M33 youngest clusters ({approx}10{sup 7} yr) have masses approaching 10{sup 5} M{sub Sun }, and comparisons with models of simple stellar populations suggest a large range of ages for M33 star clusters and some as old as the Galactic globular clusters.

Ma Jun, E-mail: majun@nao.cas.cn [National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012 (China); Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2013-04-15

329

Nonlinear dynamic characteristics of flame stripes formed in strained diffusion flames by diffusional-thermal instability  

NASA Astrophysics Data System (ADS)

The nonlinear dynamics of striped diffusion flames, formed in the two-dimensional counterflow field by the diffusional-thermal instability with Lewis numbers sufficiently less than unity, is investigated numerically by examining the nonlinear two-dimensional transient flame-structure solutions bifurcating from the one-dimensional steady solution by various initial perturbations. The Lewis numbers for the fuel and oxidizer are assumed to be identical and an overall single-step Arrhenius-type chemical reaction rate is employed as the chemistry model. Attention is focused on two nonlinear phenomena, namely the development of the two-dimensional flame-stripe structure and the extension of the flammability limit beyond the static extinction condition of a one-dimensional flame. A time-dependent solution, carried out for a Damköhler number slightly above the static extinction Damköhler number, exhibited the developmental procedure of flame stripes with the most unstable wavelength from a long-wave initial perturbation with a small amplitude. In contrast to the chaotic cellular premixed-flame structures predicted from numerical integration of the Kuramoto-Sivashinsky equation, the stripe structure in diffusion flames is found to be stationary, consequently leading to the conclusion that the nonlinear term in the corresponding nonlinear bifurcation equation would be a simple cubic term. Two-dimensional flame-stripe solutions are also found to be able to survive Damköhler numbers significantly below the static extinction Damköhler number of the one-dimensional flame structure. Extension of the flammability is found to be greatest if the imposed initial perturbation possesses the wavenumber of the fastest growing mode.

Lee, S. R.; Kim, J. S.

2000-03-01

330

The Flame Challenge and Communicating Science  

NASA Astrophysics Data System (ADS)

When famed actor and science enthusiast Alan Alda was 11 years-old he was itching to know the science behind a flame. He asked his science teacher but her blunt response didn't exactly satisfy his curiosity. ``It's oxidation,'' she said. 65 years later, Alan Alda launched ``The Flame Challenge,'' an annual contest encouraging scientists to improve their communication to the general public. In this talk, last year's winner discusses his approach to successfully explaining the science behind a flame to a wide audience. Because communicating science is a pillar of the scientific method, he shares key elements of successful communication important for engaging funders, policy-makers, students, the general public, and even other scientists.

Ames, Ben

2013-04-01

331

Flame trench analysis of NLS vehicles  

NASA Technical Reports Server (NTRS)

The present study takes the initial steps of establishing a better flame trench design criteria for future National Launch System vehicles. A three-dimensional finite element computer model for predicting the transient thermal and structural behavior of the flame trench walls was developed using both I-DEAS and MSC/NASTRAN software packages. The results of JANNAF Standardized Plume flowfield calculations of sea-level exhaust plume of the Space Shuttle Main Engine (SSME), Space Transportation Main Engine (STME), and Advanced Solid Rocket Motors (ASRM) were analyzed for different axial distances. The results of sample calculations, using the developed finite element model, are included. The further suggestions are also reported for enhancing the overall analysis of the flame trench model.

Zeytinoglu, Nuri

1993-01-01

332

Pentan isomers compound flame front structure  

SciTech Connect

The fuels (hexane, pentane, diethyl ether) and conditions investigated in this study are relevant to engine knock in spark- ignition engines. A review is provided of the field of low temperature hydrocarbon oxidation. Studies were made of radical and stable intermediate distribution in the front of cool flames: Maximum concentrations of H atoms and peroxy radicals were observed in the luminous zone of the cool flame front. Peroxy radicals appear before the luminous zone at 430 K due to diffusion. H atoms were found in cool flames of butane and hexane. H atoms diffuses from the luminous zone to the side of the fresh mixture, and they penetrate into the fresh mixture to a small depth. Extension of action sphear of peroxy radicals in the fresh mixture is much greater than that of H atoms due to their small activity and high concentrations.

Mansurov, Z.A.; Mironenko, A.W.; Bodikov, D.U.; Rachmetkaliev, K.N. [Kazakh Al-Farabi State National Univ., Almaty (Kazakhstan)

1995-08-13

333

49 CFR 392.24 - Emergency signals; flame-producing.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Emergency signals; flame-producing. 392.24 Section 392...Vehicles § 392.24 Emergency signals; flame-producing. No driver shall attach...person to attach a lighted fusee or other flame-producing emergency signal to any...

2010-10-01

334

49 CFR 392.25 - Flame producing devices.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Flame producing devices. 392.25 Section...Commercial Motor Vehicles § 392.25 Flame producing devices. No driver shall use or permit the use of any flame-producing emergency signal...

2010-10-01

335

30 CFR 56.7805 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Smoking and open flames. 56.7805 Section... Rotary Jet Piercing § 56.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2010-07-01

336

30 CFR 57.6904 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

... 1 2010-07-01 2010-07-01 false Smoking and open flames. 57.6904 Section 57.6904...Requirements-Surface and Underground § 57.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2010-07-01

337

30 CFR 56.6904 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

... 1 2010-07-01 2010-07-01 false Smoking and open flames. 56.6904 Section 56.6904...Explosives General Requirements § 56.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2010-07-01

338

30 CFR 57.7805 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Smoking and open flames. 57.7805 Section...Piercing-Surface Only § 57.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2010-07-01

339

30 CFR 56.6904 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

... 1 2011-07-01 2011-07-01 false Smoking and open flames. 56.6904 Section 56.6904...Explosives General Requirements § 56.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2011-07-01

340

30 CFR 57.6904 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

... 1 2011-07-01 2011-07-01 false Smoking and open flames. 57.6904 Section 57.6904...Requirements-Surface and Underground § 57.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2011-07-01

341

30 CFR 56.7805 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Smoking and open flames. 56.7805 Section... Rotary Jet Piercing § 56.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2011-07-01

342

30 CFR 57.7805 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Smoking and open flames. 57.7805 Section...Piercing-Surface Only § 57.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2011-07-01

343

Effect of microgravity on flame spread over a thin fuel  

SciTech Connect

A flame spreading over a thermally thin cellulose fuel was studied in a quiescent microgravity environment. Flame spread over two different fuel thicknesses was studied in ambient oxygen-nitrogen environments from the limiting oxygen concentration to 100 percent oxygen at 1 atm pressure. Comparative normal-gravity tests were also conducted. Gravity was found to play an important role in the mechanism of flame spread. In lower oxygen environments, the buoyant flow induced in normal gravity was found to accelerate the flame spread rate as compared to the microgravity flame spread rates. It was also found to stabilize the flame in oxidizer environments, where microgravity flames in a quiescent environment extinguish. In oxygen-rich environments, however, it was determined that gravity does not play an important role in the flame spread mechanism. Fuel thickness influences the flame spread rate in both normal gravity and microgravity. The flame spread rate varies inversely with fuel thickness in both normal gravity and in an oxygen-rich microgravity environment. In lower oxygen microgravity environments, however, the inverse relationship breaks down because finite-rate kinetics and heat losses become important. Two different extinction limits were found in microgravity for the two thicknesses of fuel. This is in contrast to the normal-gravity extinction limit, which was found to be independent of fuel thickness. In microgravity the flame is quenched because of excessive thermal losses, whereas in normal gravity the flame is extinguished by blowoff.

Olson, S.L.

1987-12-01

344

Detection of Organophosphate Flame Retardants in Furniture Foam  

E-print Network

Detection of Organophosphate Flame Retardants in Furniture Foam and U.S. House Dust H E A T H E R M in the increased use of alternate flame retardant chemicals to meet flammability standards. However in a new flame retardant mixture called Firemaster 550 (4.2% by weight), and one foam sample collected from

345

Advanced 3D Emission Tomography Flame Temperature Sensor  

Microsoft Academic Search

An optical diagnostic technique for measuring 3D temperature distributions in a flame, making use of new emission tomography reconstruction algorithms, is presented. The new approach aims to overcome the limitations of previous applications of emission tomography to flames, which did not consider radiation absorption inside the flame, mainly because reconstruction algorithms used did not allow for the inclusion of an

D. P. CORREIA; P. FERRÃO; A. CALDEIRA-PIRES

2001-01-01

346

TURBULENCE-FLAME MODIFICATION IN PARTICLE LADEN REACTING SHEAR FLOW  

E-print Network

, marked thin- ning of the flame and, under certain conditions, local flame extinction in the braids. In contrast, combus- tion proceeds robustly within vortex cores which have relatively dilute particle distributions; particularly at moderate Stokes numbers. The extent of global flame suppression and extinction

Miller, Richard S.

347

Large Scale Flame Spread Environmental Characterization Testing  

NASA Technical Reports Server (NTRS)

Under the Advanced Exploration Systems (AES) Spacecraft Fire Safety Demonstration Project (SFSDP), as a risk mitigation activity in support of the development of a large-scale fire demonstration experiment in microgravity, flame-spread tests were conducted in normal gravity on thin, cellulose-based fuels in a sealed chamber. The primary objective of the tests was to measure pressure rise in a chamber as sample material, burning direction (upward/downward), total heat release, heat release rate, and heat loss mechanisms were varied between tests. A Design of Experiments (DOE) method was imposed to produce an array of tests from a fixed set of constraints and a coupled response model was developed. Supplementary tests were run without experimental design to additionally vary select parameters such as initial chamber pressure. The starting chamber pressure for each test was set below atmospheric to prevent chamber overpressure. Bottom ignition, or upward propagating burns, produced rapid acceleratory turbulent flame spread. Pressure rise in the chamber increases as the amount of fuel burned increases mainly because of the larger amount of heat generation and, to a much smaller extent, due to the increase in gaseous number of moles. Top ignition, or downward propagating burns, produced a steady flame spread with a very small flat flame across the burning edge. Steady-state pressure is achieved during downward flame spread as the pressure rises and plateaus. This indicates that the heat generation by the flame matches the heat loss to surroundings during the longer, slower downward burns. One heat loss mechanism included mounting a heat exchanger directly above the burning sample in the path of the plume to act as a heat sink and more efficiently dissipate the heat due to the combustion event. This proved an effective means for chamber overpressure mitigation for those tests producing the most total heat release and thusly was determined to be a feasible mitigation strategy to incorporate into the microgravity experiment.

Clayman, Lauren K.; Olson, Sandra L.; Gokoghi, Suleyman A.; Brooker, John E.; Ferkul, Paul V.; Kacher, Henry F.

2013-01-01

348

Stabilization mechanism of lifted jet diffusion flames  

SciTech Connect

Flame lift and stabilization are studied using numerical simulations of diffusion flames resulting from a methane jet injected into an air background. The numerical model solves the time-dependent, axisymmetric, multidimensional Navier-Stokes equations coupled to submodels for chemical reaction and heat release, soot formation and radiation transport. Simulations are conducted for an undiluted methane jet and for two nitrogen-diluted jets (CH{sub 4}:N{sub 2}/3:1 and CH{sub 4}:N{sub 2}/1:1). The jet exit velocities range from 20 to 50 m/s through a 1-cm-diameter nozzle, coflowing into a 30-cm/s air stream. The flame liftoff height increases linearly with jet exit velocity and the stabilization height increases as the nitrogen dilution of the jet increases. The computations show that the flame is stabilized on a vortical structure in the inner shear layer, which is on the stoichiometric surface at a height where the local axial velocity is approximately equal to the turbulent burning velocity. There is no appreciable chemical heat release in the region below the stabilization point, although a stoichiometric surface exists in that region. The flame base moves upward with the vortical structure to which it is attached, and then quickly jumps down to attach to a new, lower vortex, resulting in an oscillating (1--2 cm) flame liftoff height. The results corroborate parts of both the premixedness and extinction stabilization theories, and suggest that the liftoff mechanisms is a result of complex fluid-chemical interactions, parts of which are incorporated in the simplified theories.

Kaplan, C.R.; Oran, E.S. [Naval Research Lab., Washington, DC (United States); Baek, S.W. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Aerospace Engineering

1994-12-31

349

Edge-Flames in Von Karman Swirling Flows  

NASA Technical Reports Server (NTRS)

Classical understanding of diffusion flames dictates that they, unlike the premixed flames, do not possess a characteristic propagation velocity and are constrained by stoichiometric requirements at the flame surface. However, it has been commonly observed that when local extinction occurs within a diffusion flame sheet, the edges that are formed propagate with distinct speeds. In general, the propagation speed of these edges depend on their geometrical shape (concave, convex, or straight) among other factors. Recently, Buckmaster investigated the dynamics of straight diffusion flame edges separating burning and quenched regions using simplified one-dimensional models. He showed that these flame edges can have positive, negative, or zero velocity depending on the Damkoehler number of the equilibrium diffusion flame that support them. It was also shown that this unsteady flame-edge behavior is intrinsically linked to S-curve behavior of the diffusion flame with varying Damkoehler number. When the system Damkoehler number lies between the extinction and ignition limits, flame edges can propagate as an "ignition wave" or as a "failure wave," and for a critical Damkoehler number remain as a stationary flame-edge. We have extend Buckmaster's 1-d model to more general edge-flame configurations where the edges appear as "flame holes" or as "flame disks". These two configurations along with the straight-edge case cover the entire range of possible edge-flame geometry observable in planar diffusion-flame sheets. A generalized map of edge-flame propagation velocities as a function of the system Damkoehler number and the edge-flame radius is presented. Experimentally we show that edge flames can be created using diffusion flames embedded in von Karman boundary layers. In a von Karman boundary layer, the flow is generated by spinning a solid (fuel) disk in a quiescent ambient gas. Under normal gravity we were able to produce "flame disks" over a range of fuel-disk rotational velocities varying from 0 to 20 revolutions per second, by orienting the burning surface of the fuel disk facing downward.

Nayagam, Vedha; Williams, Forman A.

1999-01-01

350

Underwater application of flame jet cutting method  

SciTech Connect

For drilling undersea rocks and for dismantling old structures or underwater concrete structures, the authors have been engaged in the development of the flame jet method, which is one of the thermal drilling and cutting methods. In this report the structure of a met burner, operation system of the flame jet cutting method and the following underwater (undersea) cutting results are reported: (1) cutting of undersea structures (double steel tube concrete piles); (2) dismantling of old bridge piers; (3) dismantling of old water supply pipes; (4) cutting of dam-screen for receiving dam water and sea water.

Shimada, Sohei [Univ. of Tokyo (Japan); Nakajima, Taiitsu [Sumitomo Construction Co., Ltd., Tokyo (Japan)

1994-12-31

351

Computatonal and experimental study of laminar flames  

SciTech Connect

This research has centered on an investigation of the effects of complex chemistry and detailed transport on the structure and extinction of hydrocarbon flames in counterflow, cylindrical and coflowing axisymmetric configurations. The authors have pursued both computational and experimental aspects of the research in parallel. The computational work has focused on the application of accurate and efficient numerical methods for the solution of the one and two-dimensional nonlinear boundary value problems describing the various reacting systems. Detailed experimental measurements were performed on axisymmetric coflow flames using two-dimensional imaging techniques. In particular, spontaneous Raman scattering and laser induced fluorescence were used to measure the temperature, major and minor species profiles.

Smooke, M.D.; Long, M.B. [Yale Univ., New Haven, CT (United States)

1993-12-01

352

Flame synthesis of high Tc superconductors  

NASA Astrophysics Data System (ADS)

High-temperature superconducting particles of the 1:2:3 yttrium-barium-copper oxide systems were synthesized in an inverted configuration coannular diffusion flame. The particles were produced from a spray pyrolysis technique, employing aerosolized nitrate salts of Y, Ba, and Cu. The product showed a transition temperature of 92 K as determined from magnetic susceptibility measurements. The particles were shown to have a wide size distribution, ranging from 10 to 1000 nm. Due to the effects of water vapor reactions at high temperatures, only a diffusion flame successfully produced the correct phase.

Zachariah, Michael R.; Huzarewicz, Serge

1991-10-01

353

Studies in Counterflow Laminar Flame Theory  

NASA Astrophysics Data System (ADS)

This dissertation describes asymptotic analyses of counterflow laminar diffusion and premixed flames with density changes and swirl taken into account. The employed asymptotic methods are based on large Reynolds numbers and Zel'dovich numbers to resolve thin viscous and reactive layers. Three different types of laminar flames in counterflow are analyzed to show that the density changes associated with heat release result in significant displacement effects and thus in significant alterations of the rate of strain attributed to the flow external to the flame. The analysis involves the classical sequence of calculating the first order inviscid flow which yields the standard expression for the rate of strain, the first order inner flow describing the structure of the flame and the displacement of the flame on the inviscid flow and finally the second order outer flow yielding the correction to the rate of strain. Comparison is made with some experimental results to demonstrate the significant alterations to that rate by displacement effects. A parametric analysis is performed of the counterflow mixing of two gas streams having different temperatures, with density changes taken into account. Numerical integrations of the similarity equations for counterflow mixing are completed to provide velocity, temperature and mixture -fraction fields. Results are applicable to obtain the better prediction of the structure and extinction of counterflow diffusion flames. The characteristics of isenthalpic planar premixed flames in counterflowing streams involving either corotating or counterrotating swirl of large magnitudes are analyzed. The method of activation energy asymptotics is applied to a one step Arrhenius reaction with small departures from unity Lewis numbers. Density changes resulting from heat release are fully taken into account. High swirl is shown to lead to three stagnation points and regions of radial inflow in agreement with experiment. It is shown that the character of the viscous layers containing the flames and their extinction behavior are significantly influenced by swirl for strong rate of swirl. The resonances found in an earlier inviscid calculation are shown not to be realizable and the reversal of the lean flammability limit with rotation found experimentally is explained.

Kim, Jong Soo

354

Pdf prediction of supersonic hydrogen flames  

NASA Technical Reports Server (NTRS)

A hybrid method for the prediction of supersonic turbulent flows with combustion is developed consisting of a second order closure for the velocity field and a multi-scalar pdf method for the local thermodynamic state. It is shown that for non-premixed flames and chemical equilibrium mixture fraction, the logarithm of the (dimensionless) density, internal energy per unit mass and the divergence of the velocity have several advantages over other sets of scalars. The closure model is applied to a supersonic non-premixed flame burning hydrogen with air supplied by a supersonic coflow and the results are compared with a limited set of experimental data.

Eifler, P.; Kollmann, W.

1993-01-01

355

Velocity profiles in laminar diffusion flames  

NASA Technical Reports Server (NTRS)

Velocity profiles in vertical laminar diffusion flames were measured by using laser Doppler velocimetry (LDV). Four fuels were used: n-heptane, iso-octane, cyclohexane, and ethyl alcohol. The velocity profiles were similar for all the fuels, although there were some differences in the peak velocities. The data compared favorably with the theoretical velocity predictions. The differences could be attributed to errors in experimental positioning and in the prediction of temperature profiles. Error in the predicted temperature profiles are probably due to the difficulty in predicting the radiative heat losses from the flame.

Lyons, Valerie J.; Margle, Janice M.

1986-01-01

356

Interactions between flames on parallel solid surfaces  

NASA Technical Reports Server (NTRS)

The interactions between flames spreading over parallel solid sheets of paper are being studied in normal gravity and in microgravity. This geometry is of practical importance since in most heterogeneous combustion systems, the condensed phase is non-continuous and spatially distributed. This spatial distribution can strongly affect burning and/or spread rate. This is due to radiant and diffusive interactions between the surface and the flames above the surfaces. Tests were conducted over a variety of pressures and separation distances to expose the influence of the parallel sheets on oxidizer transport and on radiative feedback.

Urban, David L.

1995-01-01

357

Effect of a novel charring–foaming agent on flame retardancy and thermal degradation of intumescent flame retardant polypropylene  

Microsoft Academic Search

A new triazine polymer was synthesized by using cyanuric chloride, ethanolamine and ethylenediamine as raw materials. It is used both as a charring agent and as a foaming agent in intumescent flame retardants, designated as charring–foaming agent (CFA). Effect of CFA on flame retardancy, thermal degradation and mechanical properties of intumescent flame retardant polypropylene (PP) system (IFR–PP system) has been

Bin Li; Miaojun Xu

2006-01-01

358

Flow and Mixing Fields for Transported Scalar PDF Simulations of a Piloted Jet Diffusion Flame (‘Delft Flame III’)  

Microsoft Academic Search

Numerical simulation results are presented for ‘Delft Flame III’, a piloted jet diffusion flame with strong turbulence–chemistry interaction. While pilot flames emerge from 12 separate holes in the experiments, the simulations are performed on a rectangular grid, under the assumption of axisymmetry. In the first part of the paper, flow and mixing field results are presented with a non-linear first

Bart Merci; Bertrand Naud; Dirk Roekaerts

2005-01-01

359

Flame temperature, fuel structure, and fuel concentration effects on soot formation in inverse diffusion flames  

SciTech Connect

Insights into soot formation processes are gained from chemical sampling and thermocouple probing of co-flowing inverse diffusion flames (IDFs), with the oxidizer in the center. In this paper the transition from near-to slightly sooting flames and the effects of flame temperature, fuel concentration, and fuel structure (using methane, ethene, propene and 1-butene) are investigated. The aromatic content of IDFS scales with the fuel's sooting tendency, and suggests that the formation of the aromatic ring is a controlling step in soot formation. In addition to the relatively well-established reactions involving C4 and C2 species, benzene may form directly from two C3 species for fuels that readily produce C3 species during pyrolysis and/or oxidative pyrolysis. The total concentration of growth species increases almost linearly with fuel concentration, but depends more weakly on flame temperature than would be expected if pure pyrolysis governed the intermediate hydrocarbon behavior.

Sidebotham, G.W.; Glassman, I. (Dept. of Mechanical and Aerospace Engineering, Princeton Univ., Princeton, NJ (US))

1992-09-01

360

Flame Structure and Scalar Properties in Microgravity Laminar Fires  

NASA Technical Reports Server (NTRS)

Recent results from microgravity combustion experiments conducted in the Zero Gravity Facility (ZGF) 5.18 second drop tower are reported. Emission mid-infrared spectroscopy measurements have been completed to quantitatively determine the flame temperature, water and carbon dioxide vapor concentrations, radiative emissive power, and soot concentrations in a microgravity laminar ethylene/air flame. The ethylene/air laminar flame conditions are similar to previously reported experiments including the Flight Project, Laminar Soot Processes (LSP). Soot concentrations and gas temperatures are in reasonable agreement with similar results available in the literature. However, soot concentrations and flame structure dramatically change in long duration microgravity laminar diffusion flames as demonstrated in this paper.

Feikema, D. A.; Lim, J.; Sivathanu, Y.

2006-01-01

361

Analytical Study of Gravity Effects on Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

A mathematical model is presented for the description of axisymmetric laminar-jet diffusion flames. The analysis includes the effects of inertia, viscosity, diffusion, gravity and combustion. These mechanisms are coupled in a boundary layer type formulation and solutions are obtained by an explicit finite difference technique. A dimensional analysis shows that the maximum flame width radius, velocity and thermodynamic state characterize the flame structure. Comparisons with experimental data showed excellent agreement for normal gravity flames and fair agreement for steady state low Reynolds number zero gravity flames. Kinetics effects and radiation are shown to be the primary mechanisms responsible for this discrepancy. Additional factors are discussed including elipticity and transient effects.

Edelman, R. B.; Fortune, O.; Weilerstein, G.

1972-01-01

362

An experimental study of air-assist atomizer spray flames  

NASA Technical Reports Server (NTRS)

It is noted that air-assisted atomizer spray flames encountered in furnaces, boilers, and gas turbine combustors possess a more complex structure than homogeneous turbulent diffusion flames, due to the swirling motion introduced into the fuel and air flows for the control of flame stability, length, combustion intensity, and efficiency. Detailed comparisons are presented between burning and nonburning condition measurements of these flames obtained by nonintrusive light scattering phase/Doppler detection. Spray structure is found to be drastically changed within the flame reaction zone, with changes in the magnitude and shape of drop number density, liquid flux, mean drop size diameter, and drop mean axial velocity radial distributions.

Mao, Chien-Pei; Wang, Geng; Chigier, Norman

1988-01-01

363

Characteristics of transitional and turbulent jet diffusion flames in microgravity  

NASA Technical Reports Server (NTRS)

This paper presents the ground-based results obtained to date in preparation of a proposed space experiment to study the role of large-scale structures in microgravity transitional and turbulent gas-jet diffusion flames by investigating the dynamics of vortex/flame interactions and their influence on flame characteristics. The overall objective is to gain an understanding of the fundamental characteristics of transitional and turbulent gas-jet diffusion flames. Understanding of the role of large-scale structures on the characteristics of microgravity transitional and turbulent flames will ultimately lead to improved understanding of normal-gravity turbulent combustion.

Bahadori, Yousef M.; Small, James F., Jr.; Hegde, Uday G.; Zhou, Liming; Stocker, Dennis P.

1995-01-01

364

Radiative Structures of Lycopodium-Air Flames in Low Gravity  

NASA Technical Reports Server (NTRS)

Initially uniform clouds of fuel particulates in air sustain processes which may lead to particle cloud nonuniformities. In low gravity, flame-induced Kundt's Tube phenomena are observed to form regular patterns of nonuniform particle concentrations. Irregular patterns of particle concentrations also are observed to result from selected nonuniform mixing processes. Low gravity flame propagation for each of these classes of particle cloud flames has been found to depend importantly on the flame-generated infrared radiative fields. The spatial structures of these radiative fields are described. Application is made for the observed clases of lycopodium-air flames.

Berlad, A. L.; Tangirala, V.; Ross, H.; Facca, L.

1989-01-01

365

On the dynamics of flame-edges in diffusion-flame\\/vortex interactions  

Microsoft Academic Search

We present a simple model for the dynamics of the flame-edges that form after the local extinction by a vortex ring of a diffusion flame between two counterflowing gaseous fuel and air streams of the same density. The analysis is confined to the near-stagnation point region, where the strain rate of the unperturbed velocity field, A_0, is constant. We restrict

Miguel Hermanns; Marcos Vera; Amable Liñán

2004-01-01

366

Effects of Swirl on Strongly-Pulsed Turbulent Diffusion Flames  

NASA Astrophysics Data System (ADS)

The dynamics of large-scale structures in strongly-pulsed, swirling, turbulent jet diffusion flames were examined experimentally. The combustor used a combination of axial and tangentially-injected air to produce a range of swirl numbers. Gaseous ethylene fuel was injected through a 2 mm diameter nozzle on the combustor centerline with a jet-on Reynolds number of 5000. The flames were fully-modulated, with the fuel flow completely shut off between pulses. High-speed imaging of the flame luminosity was employed to examine the flame dimensions and the celerity of the large-scale flame structures. The flames were found to be approximately 15-20% shorter when swirl was imposed, depending on the injection time. The more compact flames in swirl appear to be due to the presence of recirculation inside the flames. For longer injection times, the celerity of the flame structures generally decreases as the swirl intensity increases. This is evidently due to the reversed velocity in the recirculation zone. For shorter injection times, the flame celerity has an increasing trend with increased swirl intensity due to flames being closer to the fuel nozzle at burnout.

Liao, Y.-H.; Hermanson, J. C.

2009-11-01

367

Laser-saturated fluorescence measurements in laminar sooting diffusion flames  

NASA Technical Reports Server (NTRS)

The hydroxyl radical is known to be one of the most important intermediate species in the combustion processes. The hydroxyl radical has also been considered a dominant oxidizer of soot particles in flames. In this investigation the hydroxyl concentration profiles in sooting diffusion flames were measured by the laser-saturated fluorescence (LSF) method. The temperature distributions in the flames were measured by the two-line LSF technique and by thermocouple. In the sooting region the OH fluorescence was too weak to make accurate temperature measurements. The hydroxyl fluorescence profiles for all four flames presented herein show that the OH fluorescence intensities peaked near the flame front. The OH fluorescence intensity dropped sharply toward the dark region of the flame and continued declining to the sooting region. The OH fluorescence profiles also indicate that the OH fluorescence decreased with increasing height in the flames for all flames investigated. Varying the oxidizer composition resulted in a corresponding variation in the maximum OH concentration and the flame temperature. Furthermore, it appears that the maximum OH concentration for each flame increased with increasing flame temperature.

Wey, Changlie

1993-01-01

368

The effects of gravity on wrinkled laminar flames  

SciTech Connect

Laminar and turbulent conical Bunsen type flames were used. The study compares results from normal gravity with the burner in an up-right orientation (+g), the burner inverted (-g), and in microgravity ([mu]g) by using the NASA Lewis drop tower facility. The primary diagnostic is a laser schlieren system and some LDA measurements were taken for the +g condition to measure the flow field. The +g laminar flame experiences a large amount of instabilities and results in an unsteady flame tip; cause is torroidal vortex rolling up between products and stagnate surrounding air. Comparison between LDA measurements in reactants and schlieren images shows that velocity fluctuation are induced at the same frequency as the roll up vortices are formed. This pumping of the reactant stream by the product/air interface instability in the +g case is also observed in the turbulent flames. In the -g arrangement the product/air interface is stable so there is no large pumping of the flame tip. At low flow rates the -g flames have flattened tips, but at higher flow rates they become conical in shape. When both flames. appear conical, the -g flames are longer for the same flow rate. In [mu]g the larger instabilities in the flame no longer exist as the product/air interface is believed to become stable. The laminar flames in [mu]g still show small instabilities over the entire flame.

Kostiuk, L.W.; Zhou, L.; Cheng, R.K.

1992-09-01

369

The effects of gravity on wrinkled laminar flames  

SciTech Connect

Laminar and turbulent conical Bunsen type flames were used. The study compares results from normal gravity with the burner in an up-right orientation (+g), the burner inverted (-g), and in microgravity ({mu}g) by using the NASA Lewis drop tower facility. The primary diagnostic is a laser schlieren system and some LDA measurements were taken for the +g condition to measure the flow field. The +g laminar flame experiences a large amount of instabilities and results in an unsteady flame tip; cause is torroidal vortex rolling up between products and stagnate surrounding air. Comparison between LDA measurements in reactants and schlieren images shows that velocity fluctuation are induced at the same frequency as the roll up vortices are formed. This pumping of the reactant stream by the product/air interface instability in the +g case is also observed in the turbulent flames. In the -g arrangement the product/air interface is stable so there is no large pumping of the flame tip. At low flow rates the -g flames have flattened tips, but at higher flow rates they become conical in shape. When both flames. appear conical, the -g flames are longer for the same flow rate. In {mu}g the larger instabilities in the flame no longer exist as the product/air interface is believed to become stable. The laminar flames in {mu}g still show small instabilities over the entire flame.

Kostiuk, L.W.; Zhou, L.; Cheng, R.K.

1992-09-01

370

Freely propagating open premixed turbulent flames stabilized by swirl  

SciTech Connect

A novel means has been developed for using weak swirl to stabilize freely propagating open premixed turbulent flames (swirl numbers between 0.05 to 0.3). By injecting a small amount of air tangentially into the co-flow of a concentric burner, stationary flames can be maintained above the burner exit for a large range of mixture, turbulence and flow conditions. The absence of physical surfaces in the vicinity of the flame provides free access to laser diagnostics. Laser Doppler anemometry and laser Mie scattering measurements of four flames with and without incident turbulence show that their features are typical of wrinkled laminar flames. The most distinct characteristics is that flame stabilization does not rely on flow recirculation. Centrifugal force induced by swirl causes flow divergence, and the flame is maintained at where the local mass flux balances the burning rate. The flame speeds can be estimated based on the centerline velocity vector, which is locally normal to the flame brush. This flame geometry is the closest approximation to the 1-D planar flame for determining fundamental properties to advance turbulent combustion theories. 18 refs.

Chan, C.K.; Lau, K.S.; Chin, W.K. (Hong Kong Polytechnic, Kowloon (Hong Kong)); Cheng, R.K. (Lawrence Berkeley Lab., CA (United States))

1991-12-01

371

Computational predictions of flame spread over alcohol pools  

NASA Technical Reports Server (NTRS)

The effects of buoyancy and thermocapillarity on pulsating and uniform flame spread above n-propanol fuel pools have been studied using a numerical model. Data obtained indicate that the existence of pulsating flame spread is dependent upon the formation of a gas-phase recirculation cell which entrains evaporating fuel vapor in front of the leading edge of the flame. The size of the recirculation cell which is affected by the extent of liquid motion ahead of the flame, is shown to dictate whether flame spread is uniform or pulsating. The amplitude and period of the flame pulsations are found to be proportional to the maximum extent of the flow head. Under conditions considered, liquid motion was not affected appreciably by buoyancy. Horizontal convection in the liquid is the dominant mechanism for transporting heat ahead of the flame for both the pulsating and uniform regimes.

Schiller, D. N.; Ross, H. D.; Sirignano, W. A.

1993-01-01

372

Numerical study on lateral movements of cellular flames  

NASA Astrophysics Data System (ADS)

The lateral movements of cellular premixed flames for the Lewis number unity or smaller are studied by means of numerical simulation. The numerical model includes compressibility, viscosity, heat conduction, molecular diffusion, body force, chemical reaction, and convection. We superimpose the disturbances with peculiar wavelengths on the plane flames and calculate the evolution of disturbed flames. When the hydrodynamic and body-force instabilities are dominant (the Lewis number is unity), stationary cellular flames are formed. When the diffusive-thermal instability has a great influence (the Lewis number is smaller than unity), laterally moving cellular flames are obtained. The numerical simulation shows that the Lewis number effect and the nonlinear effect of the flame front are the essential factors in the lateral movements of cellular flames.

Kadowaki, Satoshi

1997-09-01

373

Shapes of buoyant and nonbuoyant laminar jet diffusion flames  

SciTech Connect

Flame shapes were measured for buoyant and nonbuoyant laminar gas jet diffusion flames burning, methane, ethane, and propane in quiescent air. Test conditions involved burner diameters of 0.19--5.5 mm, ambient pressures of 0.25--2 atm, and fuel flowrates of 0.04--4.6 mg/s. Care was taken to minimize interference from soot emissions and from ignition disturbances. Microgravity conditions were obtained in the 2.2-s drop tower at the NASA Lewis Research Center. Normalized lengths of both buoyant and nonbuoyant flames were proportional to source Reynolds number, but the nonbuoyant flames were 40% longer on average. Normalized widths of the nonbuoyant flames were constant for Re {ge} 100, whereas buoyant flame widths scaled with source Froude number. Several nonbuoyant flame models are evaluated with the present shape data.

Sunderland, P.B. [National Research Council, Cleveland, OH (United States)] [National Research Council, Cleveland, OH (United States); Mendelson, B.J. [Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering] [Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering; Yuan, Z.G. [National Center for Microgravity Research, Cleveland, OH (United States)] [National Center for Microgravity Research, Cleveland, OH (United States); Urban, D.L. [NASA Lewis Research Center, Cleveland, OH (United States)] [NASA Lewis Research Center, Cleveland, OH (United States)

1999-02-01

374

Flame propagation and extinction in large-scale vortical flows  

SciTech Connect

It is shown that the propagation speed of the premixed gas flame spreading through a time-independent, space-periodic array of large-scale vorticities is a nonmonotonic function of their intensity. for moderately strong vorticities their intensification results in the flame speed enhancement accompanied by shedding of islands of unburned gas. Yet there is a certain level of stirring at which the flame speed reaches its maximum. Any further increase in the stirring intensity leads to a drop in the flame speed, followed, for mildly nonadiabatic systems, by flame extinction. The relation of these findings to the classical theory of planar counterflow flames is discussed. The study is motivated by the experimentally known phenomenon of flame extinction by turbulence.

Kagan, L.; Sivashinsky, G.

2000-01-01

375

On the dynamics of flame-edges in diffusion-flame/vortex interactions  

NASA Astrophysics Data System (ADS)

We present a simple model for the dynamics of the flame-edges that form after the local extinction by a vortex ring of a diffusion flame between two counterflowing gaseous fuel and air streams of the same density. The analysis is confined to the near-stagnation point region, where the strain rate of the unperturbed velocity field, A_0, is constant. We restrict our attention to cases where the typical vortex ring radius, r_0, is large compared to both the size, ?_v, of the vorticity core and the characteristic thickness, ?_m0 ˜ (?/A_0)^1/2, of the mixing layer. The dynamics of the flame-edges is modeled using previous numerical results, where heat release effects are fully taken into account, which provide the propagation velocity of triple- and edge-flames in mixing layers in terms of the local Damköhler number, Da = (?m /?_L)^2, based on the local thickness, ?_m, of the mixing layer at the flame front position and the laminar flame thickness, ?_L. The results agree qualitatively well with experimental observations in the same parameter range.

Hermanns, Miguel; Vera, Marcos; Liñán, Amable

2004-11-01

376

BROMINATED FLAME RETARDANTS: CAUSE FOR CONCERN?  

EPA Science Inventory

Brominated flame retardants (BFRs) have routinely been added to consumer products for several decades in a successful effort to reduce fire-related injury and property damage. Recently, concern for this emerging class of chemicals has risen due to the occurrence of several class...

377

New Developments with Flame Resistant Cottons  

Technology Transfer Automated Retrieval System (TEKTRAN)

It is our desire to develop new crosslinking agents for cotton woven, nonwoven, and knitted textiles that afford flame protection regardless of construction. Our first step towards this goal was to design, prepare, and characterize two new epoxy phosphonate crosslinkers. Our next step was to assay t...

378

Brominated flame retardants and endocrine disruption  

Microsoft Academic Search

From an environmental point of view, an increasing important group of organohalogen compounds are the brominated flame retardants (BFRs), which are widely used in polymers and textiles and applied in construction materials, furniture, and electronic equipment. BFRs with the highest production volume are the polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBP-A), and hexabromocyclododecane (HBCD). Because of their persistence and low

Joseph G. Vos; Georg Becher; Martin van den Berg; Jacob de Boer; Pim E. G. Leonards

2003-01-01

379

BROMINATED FLAME RETARDANTS: WHY DO WE CARE?  

EPA Science Inventory

Brominated flame retardants (BFRs) save lives and property by preventing the spread of fires or delaying the time of flashover, enhancing the time people have to escape. The worldwide production of BFRs exceeded 200,000 metric tons in 2003 placing them in the high production vol...

380

The onset of oscillations in diffusion flames  

Microsoft Academic Search

We present a theoretical study aimed at understanding the basic mechanisms responsible for the onset of oscillations in diffusion flames. A simple one-dimensional configuration is considered with one reactant supplied in a uniform stream and the other diffusing against the stream. The analysis allows for unequal non-unity Lewis numbers as well as for incomplete combustion. It is found that oscillations

S. Kukuck; M. Matalon

2001-01-01

381

Brominated flame retardants as food contaminants  

Technology Transfer Automated Retrieval System (TEKTRAN)

This book chapter reviews analytical methods for the three major brominated flame retardant (BFR) classes in use today, tetrabromobisphenol-A (TBBP-A), hexabromocyclododecanes (HBCDs), and polybrominated diphenyl ethers (PBDEs), a "legacy" BFR no longer in use, polybrominated biphenyls (PBBs), and a...

382

CARS application in measurement of flame temperature  

NASA Astrophysics Data System (ADS)

Flame temperature distribution is very important for combustion diagnosis, but it is very hard to measure it because of the instability of flame and possible transient variability. Classical method used for measurement of flame temperature is always a contact method utilizing a thermocouple. Limitations on the use of thermocouples include long response time, disturbance on target temperature field, inelasiticity in rigorous measurement circumstance. Only coarse qualitative results can be acquired. A potential laser spectrum diagnostic technology was therefore introduced. The method of coherent anti-stokes Raman spectroscopy (CARS) in the measurement of temperature distribution was discussed using CARS theory. The design of measurement system was put forward and preliminary experiment results are shown. Theoretical CARS spectrums at 2000K were calculated utilizing the model of molecule transition in CARS process. Experimental results were compared to those of thermocouple measurement, and since results of two methods are close, feasibility of CARS application in the measurement of flame temperature was verified. Although the resolution of this method is not applicable for real-time measurement, a single measurement can be accomplished in a few nanoseconds. The resolution of temperature measurement is 5% better than results of measurement by thermocouple. Furthermore, future research is suggested to overcome the insufficiency of this method was pointed out with direction suggested.

Zhang, Hu; Dai, Jing-min

2008-10-01

383

Polybrominated diphenyl ether (PBDE) flame retardants  

Microsoft Academic Search

Polybrominated diphenyl ether, PBDE, flame retardants are now a world-wide pollution problem reaching even remote areas. They have been found to bioaccumulate and there are concerns over the health effects of exposure to PBDEs, they also have potential endocrine disrupting properties. They are lipophilic compounds so are easily removed from the aqueous environment and are predicted to sorb onto sediments

Frank Rahman; Katherine H Langford; Mark D Scrimshaw; John N Lester

2001-01-01

384

Are brominated flame retardants endocrine disruptors?  

Microsoft Academic Search

Brominated flame retardants (BFRs) are a group of compounds that have received much attention recently due to their similarity with “old” classes of organohalogenated compounds such as polychlorinated biphenyls (PCBs), in terms of their fate, stability in the environment and accumulation in humans and wildlife. Toxic effects, including teratogenicity, carcinogenicity and neurotoxicity, have been observed for some BFR congeners, in

Juliette Legler; Abraham Brouwer

2003-01-01

385

Analytic modeling of a spray diffusion flame  

NASA Technical Reports Server (NTRS)

A detailed model for a spray diffusion flame is described. The model is based on the boundary layer form of the equations of motion, with droplet transport accounted for using a discretized droplet size distribution function. Interphase transport of mass and energy are accounted for, with a flame-sheet model used to describe the combustion process on a droplet scale. Near dynamic equilibrium is assumed for the description of droplet transport; droplets can diffuse relative to the gas phase. Gas-phase mixing is accounted for using a two-equation turbulence model; buoyancy effects are included, with a temperature fluctuation equation used to account for buoyancy effects on turbulence structure. Thermal radiation from gas-phase CO2 and H2O is included. Gas-phase chemical kinetics are modeled using a 20-reaction, 10-species version of the advanced quasi-global chemical kinetics formulation. Results are compared with data for a vaporizing Freon spray and a pentane spray flame. It is shown that the computational approach provides a reasonably valid picture of the overall development of a spray diffusion flame, and, furthermore, provides a useful tool for the parametric examination of the spray combustion process.

Harsha, P. T.; Edelman, R. B.

1984-01-01

386

Stability of lifted flames in centerbody burner  

Microsoft Academic Search

The centerbody burner was designed with the objective of understanding the coupled processes of formation, growth, and burn-off of soot through decoupling them using recirculation zones (RZs). Experimentally it was found that the sooting characteristics of the centerbody burner could be altered dramatically via simple changes in the operating conditions. One of the interesting operating regimes in which a flame

V. R. Katta; Scott Stouffer; W. M. Roquemore

2011-01-01

387

HEALTH ASPECTS OF BROMINATED FLAME RETARDANTS (BFRS)  

EPA Science Inventory

In order to reduce the societal costs of fires, flammability standards have been set for consumer products and equipment. Flame retardants containing bromine have constituted the largest share of this market due both to their efficiency and cost. While there are at least 75 dif...

388

The Flame Challenge What is Time?  

E-print Network

The Flame Challenge What is Time? Alan Alda, the Center for Communicating Science -- and 11- year-olds around the country ­ are seeking answers from scientists to a timeless question: What is time're asking a very deep question this year ("What is Time?!). It's going to be fun to see how scientists

389

Extinction and relight in opposed flames  

Microsoft Academic Search

The nature of extinction of turbulent unforced and forced symmetric opposed methane-air flames with lean equivalence ratios was examined qualitatively with photographs and chemiluminescence images. Thermocouples and a laser Doppler velocimeter quantified the temperature and velocity in the stagnation plane. Thus, local and complete extinction were related to high local mean strain rates deduced from the velocity measurements. A preliminary

E. Korusoy; J. H. Whitelaw

2002-01-01

390

Premixed Flame-Vortex Interactions Imaged in Microgravity  

NASA Technical Reports Server (NTRS)

A unique experiment makes it now possible to obtain detailed images in microgravity showing how an individual vortex causes the wrinkling, stretching, area increase, and eventual extinction of a premixed flame. The repeatable, controllable flame-vortex interaction represents the fundamental building block of turbulent combustion concepts. New information is provided that is central to turbulent flame models, including measurements of all components of flame stretch, strain, and vorticity. Simultaneous measurements of all components of these quantities are not possible in fully turbulent flames but are possible in the present axisymmetric, repeatable experiment. Advanced PIV diagnostics have been used at one-g and have been developed for microgravity. Numerical simulations of the interaction are being performed at NRL. It is found that microgravity conditions greatly augment the flame wrinkling process. Flame area and the amplitude of wrinkles at zero-g are typically twice that observed at one-g. It is inferred that turbulent flames in microgravity could have larger surface area and thus propagate significantly faster than those in one-g, which is a potential safety hazard. A new mechanism is identified by PIV images that shows how buoyancy retards flame wrinkling at one-g; buoyancy produces new vorticity (due to baroclinic torques) that oppose the wrinkling and the stretch imposed by the original vortex. Microgravity conditions remove this stabilizing mechanism and the amplitude of flame wrinkling typically is found to double. Microgravity also increases the flame speed by a factor of 1.8 to 2.2. Both methane and propane-air flames were studied at the NASA Lewis drop tower. Results indicate that it is important to add buoyancy to models of turbulent flames to simulate the correct flame wrinkling, stretch and burning velocity.

Driscoll, J. F.; Sichel, M.; Sinibaldi, J. O.

1997-01-01

391

Photometry Of The Semi-regular Variable Tx Tau  

NASA Astrophysics Data System (ADS)

We report V-band and I-band photometry for the SRA type variable TX Tau. Photometry was obtained using the robotic telescope GORT at the Hume Observatory (NASA funded through Sonoma State University) and the PROMPT robotic telescopes at Cerro Tololo Inter-American Observatory (NSF and NASA funded through the University of North Carolina). Photometry was also obtained using the PI of the Sky optical transient search system at Las Campanas Observatory developed by a consortium of institutions in Poland. Modern periods are determined, the V-band and I-band light curves are compared, and V-I colors are derived. It is possible that the classification for this variable should be reconsidered.

Wyman, Katherine; Spear, G.; McLin, K.; Cominsky, L.; Mankiewicz, L.; Reichart, D.; Ivarsen, K.

2009-12-01

392

Near-IR Photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

Subjects: Infra-Red, Nova We report Near-IR photometry of Nova Del 2013 taken with the 0.76-m infrared telescope at the University of Minnesota's O'Brien Observatory (Marine on St. Croix, Minnesota, USA). RIJHKLM photometry were obtained on August 21.17 and 23.13 UT using an AsSi bolometer. Vega (alpha Lyrae) was used as the standard star. Our photometry show: August 21.17 UT: R = 5.1 +/- 0.1, I = 4.6 +/- 0.1, J = 4.6 +/- 0.1, H = 4.1 +/- 0.1, K = 3.9 +/- 0.1, L = 2.7 +/- 0.2, M = +2.2 +/- 0.2.

Cass, C. A.; Carlon, L. R.; Corgan, T. D.; Dykhoff, A. D.; Gehrz, D. R.; Shenoy, P. D.

2013-08-01

393

UBV CCD Photometry of the Open Cluster Berkeley 2  

NASA Astrophysics Data System (ADS)

We present UBV CCD photometry of Be 2, previously unstudied open cluster. Our photometry covers a field of 3'.2 X 3'.8 of the sky centered on the cluster, which is slightly smaller than the cluster diameter estimated to be about 260". We have determined the reddening, distance, age and metallicity of the cluster by fitting the Padova isochrones to the observed stellar distributions in color-magnitude diagram as well as main sequence fitting: E(B-V) = 0.8 +/- 0.05, (m-M)_o = 13.6 +/- 0.1, log(t) = 8.9 +/- 0.1, and Z =0.008. The present photometry shows that Be 2 is a distant open cluster of intermediate age. that it is a distant intermediate-age open cluster.

Ann, Hong Bae; Park, Yoon Ho; Kang, Yong Woo

1998-04-01

394

Temperature distribution and heat transfer characteristics of an inverse diffusion flame with circumferentially arranged fuel ports  

Microsoft Academic Search

Experiments were conducted on IDFs burning butane. The flame holder has a central air jet surrounded by 12 circumferentially arranged fuel jets. The flame consisted of a short entrainment zone and a long mixing and combustion zone with intense combustion. The temperature profiles of the flame showed a cool core at low flame heights, which disappeared at high flame heights.

L. K Sze; C. S Cheung; C. W Leung

2004-01-01

395

Synthesis of carbon nanotubes on a catalytic metal substrate by using an ethylene inverse diffusion flame  

Microsoft Academic Search

Recently, a number of researchers have published results relating to the flame synthesis of carbon na- notubes. The flame synthesis of carbon nanotubes em- ploys a flame as a heat source. The production of carbon nanomaterials, like carbon nanofibers and nanotubes, by a flame, has advantages over the other production methods that use electricity. First, with a flame, there is

Gyo Woo Lee; Jongsoo Jurng; Jungho Hwang

2004-01-01

396

Nonlinear dynamics of flame in a narrow channel with a temperature gradient  

Microsoft Academic Search

The non-stationary behaviour of near-limit premixed flame propagating in a microchannel with temperature gradient was theoretically investigated. A one-dimensional (1D) nonlinear evolutionary equation of the flame front was obtained. The nonlinear model outlined the flame stabilization, nonlinear flame oscillations and flames with repetitive extinction and ignition processes that were observed in experiments.

S. Minaev; K. Maruta; R. Fursenko

2007-01-01

397

Flame Stabilization Enhancement and NOx Production using Ultra Short Repetitively Pulsed Plasma Discharges  

Microsoft Academic Search

This paper examines the use of plasma discharges in flame stabilization. Three different types of plasma discharges are applied to a lifted jet diffusion flame in a coflow configuration, and evaluated for their abilities to enhance flame stabilization. A single electrode corona discharge (SECD) between a platinum electrode and the flame base is found to maintain the flame at a

W. Kim; M. G. Mungal

2006-01-01

398

Turbulent premixed flames on fractal-grid-generated turbulence  

NASA Astrophysics Data System (ADS)

A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent flame stabilized by a rod. The study compares the flame behaviour with a fractal grid to the behaviour when a standard square mesh grid with the same effective mesh size and solidity as the fractal grid is used. The isothermal gas flow turbulence characteristics, including mean flow velocity and rms of velocity fluctuations and Taylor length, were evaluated from hot-wire measurements. The behaviour of the flames was assessed with direct chemiluminescence emission from the flame and high-speed OH-laser-induced fluorescence. The characteristics of the two flames are considered in terms of turbulent flame thickness, local flame curvature and turbulent flame speed. It is found that, for the same flow rate and stoichiometry and at the same distance downstream of the location of the grid, fractal-grid-generated turbulence leads to a more turbulent flame with enhanced burning rate and increased flame surface area.

Soulopoulos, N.; Kerl, J.; Sponfeldner, T.; Beyrau, F.; Hardalupas, Y.; Taylor, A. M. K. P.; Vassilicos, J. C.

2013-12-01

399

Forced and natural convection in laminar-jet diffusion flames  

NASA Astrophysics Data System (ADS)

An experimental investigation was conducted on methane, laminar-jet, diffusion flames with coaxial, forced-air flow to examine flame shapes in zero-gravity and in situations where buoyancy aids (normal-gravity flames) or hinders (inverted-gravity flames) the flow velocities. Fuel nozzles ranged in size from 0.051 to 0.305 cm inside radius, while the coaxial, convergent, air nozzle had a 1.4 cm inside radius at the fuel exit plane. Fuel flows ranged from 1.55 to 10.3 cu cm/sec and air flows from 0 to 597 cu cm/sec. A computer program developed under a previous government contract was used to calculate the characteristic dimensions of normal and zero-gravity flames only. The results include a comparison between the experimental data and the computed axial flame lengths for normal gravity and zero gravity which showed good agreement. Inverted-gravity flame width was correlated with the ratio of fuel nozzle radius to average fuel velocity. Flame extinguishment upon entry into weightlessness was studied, and it was found that relatively low forced-air velocities (approximately 10 cm/sec) are sufficient to sustain methane flame combustion in zero gravity. Flame color is also discussed.

Haggard, J. B., Jr.

1981-06-01

400

Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity  

NASA Technical Reports Server (NTRS)

Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.

Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.

2007-01-01

401

Suppression and Structure of Low Strain Rate Nonpremixed Flames  

NASA Technical Reports Server (NTRS)

The agent concentration required to achieve suppression of low strain rate nonpremixed flames is an important fire safety consideration. In a microgravity environment such as a space platform, unwanted fires will likely occur in near quiescent conditions where strain rates are very low. Diffusion flames typically become more robust as the strain rate is decreased. When designing a fire suppression system for worst-case conditions, low strain rates should be considered. The objective of this study is to investigate the impact of radiative emission, flame strain, agent addition, and buoyancy on the structure and extinction of low strain rate nonpremixed flames through measurements and comparison with flame simulations. The suppression effectiveness of a suppressant (N2) added to the fuel stream of low strain rate methane-air diffusion flames was measured. Flame temperature measurements were attained in the high temperature region of the flame (T greater than 1200 K) by measurement of thin filament emission intensity. The time varying temperature was measured and simulated as the flame made the transition from normal to microgravity conditions and as the flame extinguished.

Hamins, Anthony; Bundy, Matthew; Park, Woe Chul; Lee, Ki Yong; Logue, Jennifer

2003-01-01

402

Structure of Microgravity Transitional and Pulsed Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

This paper describes results obtained in a study of pulsed gas jet diffusion flames to better characterize the recently observed vortex/flame interactions in microgravity transitional and turbulent diffusion flames, and to improve the understanding of large-scale structures in corresponding normal-gravity flames. In preparation for a space experiment, tests were conducted in the 5.18-Second Zero-Gravity Facility of the NASA Lewis Research Center. Both unpulsed and pulsed laminar flames were studied and numerical modeling of these flames was carried out for data comparison and model validation. In addition, complementary tests for a series of unpulsed flames were conducted on-board the NASA KC-135 research aircraft. The microgravity transitional and turbulent gas-jet diffusion flames have been observed to be dominated by large-scale disturbances, or structures. These structures first appear intermittently in the flame at Reynolds numbers (based on the cold jet injection properties) of about 2100. With increase in injection Reynolds number, the rate of intermittent disturbances increases until the generation becomes continuous at Reynolds numbers of 3000 and higher. The behavior of these structures depends upon the velocity and temperature characteristics of the jet/flame shear layer. These characteristics are different in normal gravity and microgravity.

Bahadori, M. Yousef; Hegde, Uday; Stocker, Dennis P.

1997-01-01

403

Flame quality monitor system for fixed firing rate oil burners  

DOEpatents

A method and apparatus for determining and indicating the flame quality, or efficiency of the air-fuel ratio, in a fixed firing rate heating unit, such as an oil burning furnace, is provided. When the flame brightness falls outside a preset range, the flame quality, or excess air, has changed to the point that the unit should be serviced. The flame quality indicator output is in the form of lights mounted on the front of the unit. A green light indicates that the flame is about in the same condition as when the burner was last serviced. A red light indicates a flame which is either too rich or too lean, and that servicing of the burner is required. At the end of each firing cycle, the flame quality indicator goes into a hold mode which is in effect during the period that the burner remains off. A yellow or amber light indicates that the burner is in the hold mode. In this mode, the flame quality lights indicate the flame condition immediately before the burner turned off. Thus the unit can be viewed when it is off, and the flame condition at the end of the previous firing cycle can be observed.

Butcher, Thomas A. (Pt. Jefferson, NY); Cerniglia, Philip (Moriches, NY)

1992-01-01

404

Upward Flame Spread Over Thin Solids in Partial Gravity  

NASA Technical Reports Server (NTRS)

The effects of partial-gravity, reduced pressure, and sample width on upward flame spread over a thin cellulose fuel were studied experimentally and the results were compared to a numerical flame spread simulation. Fuel samples 1-cm, 2-cm, and 4-cm wide were burned in air at reduced pressures of 0.2 to 0.4 atmospheres in simulated gravity environments of 0.1-G, 0.16-G (Lunar), and 0.38-G (Martian) onboard the NASA KC-135 aircraft and in normal-gravity tests. Observed steady flame propagation speeds and pyrolysis lengths were approximately proportional to the gravity level. Flames spread more quickly and were longer with the wider samples and the variations with gravity and pressure increased with sample width. A numerical simulation of upward flame spread was developed including three-dimensional Navier-Stokes equations, one-step Arrhenius kinetics for the gas phase flame and for the solid surface decomposition, and a fuel-surface radiative loss. The model provides detailed structure of flame temperatures, the flow field interactions with the flame, and the solid fuel mass disappearance. The simulation agrees with experimental flame spread rates and their dependence on gravity level but predicts a wider flammable region than found by experiment. Some unique three-dimensional flame features are demonstrated in the model results.

Feier, I. I.; Shih, H. Y.; Sacksteder, K. R.; Tien, J. S.

2001-01-01

405

Detailed Multidimensional Simulations of the Structure and Dynamics of Flames  

NASA Technical Reports Server (NTRS)

Numerical simulations in which the various physical and chemical processes can be independently controlled can significantly advance our understanding of the structure, stability, dynamics and extinction of flames. Therefore, our approach has been to use detailed time-dependent, multidimensional, multispecies numerical models to perform carefully designed computational experiments of flames on Earth and in microgravity environments. Some of these computational experiments are complementary to physical experiments performed under the Microgravity Program while others provide a fundamental understanding that cannot be obtained from physical experiments alone. In this report, we provide a brief summary of our recent research highlighting the contributions since the previous microgravity combustion workshop. There are a number of mechanisms that can cause flame instabilities and result in the formation of dynamic multidimensional structures. In the past, we have used numerical simulations to show that it is the thermo-diffusive instability rather than an instability due to preferential diffusion that is the dominant mechanism for the formation of cellular flames in lean hydrogen-air mixtures. Other studies have explored the role of gravity on flame dynamics and extinguishment, multi-step kinetics and radiative losses on flame instabilities in rich hydrogen-air flames, and heat losses on burner-stabilized flames in microgravity. The recent emphasis of our work has been on exploring flame-vortex interactions and further investigating the structure and dynamics of lean hydrogen-air flames in microgravity. These topics are briefly discussed after a brief discussion of our computational approach for solving these problems.

Patnaik, G.; Kailasanath, K.

1999-01-01

406

High-Precision Stellar Photometry with the K2 Mission  

NASA Astrophysics Data System (ADS)

The K2 mission is a repurposed use of the Kepler spacecraft to perform high-precision photometry of selected fields in the ecliptic. We have developed an aperture photometry pipeline for K2 data which performs dynamic automated aperture mask selection, background estimation and subtraction, and positional decorrelation to minimize the effects of spacecraft pointing jitter. Here we describe that pipeline and the photometric precision we are capable of achieving with K2, illustrated by application to Campaign 0 data, and suggest future improvements in our algorithm.

Carboneau, Lindsey; Buzasi, Derek L.; Hessler, Carly; Lezcano, Andy; Preston, Heather L.

2015-01-01

407

The Structure of Galaxies I: Surface Photometry Techniques  

NASA Astrophysics Data System (ADS)

This project uses the 2MASS all-sky image database to study the structure of galaxies over a range of luminosities, sizes and morphological types. This first paper in this series will outline the techniques, reliability and data products to our surface photometry program. Our program will analyze all acceptable galaxies (meeting our criteria for isolation from companions and bright stars) from the Revised Shapley-Ames and Uppsala galaxy catalogs. Resulting photometry and surface brightness profiles are released using a transparent scheme of data storage which includes not only all the processed data but knowledge of the processing steps and calibrating parameters.

Schombert, J.; Smith, A. K.

2012-04-01

408

Transit and secondary eclipse photometry in the near-infrared  

E-print Network

Near-infrared photometry of transiting extrasolar planets can be of great scientific value. It is however not straightforward to reach the necessary millimagnitude precision. Here we report on our attempts to observe transits and secondary eclipses of several extrasolar planets at 2.2 micron. Best results have been obtained on OGLE-TR-113b using the SOFI near-infrared camera on ESO's New Technology Telescope. Its K-band transit shows a remarkably flat bottom indicating low stellar limb darkening. Secondary eclipse photometry has resulted in a formal 3 sigma detection, but residual systematic effects make this detection rather uncertain.

Ignas Snellen

2007-05-02

409

Effect of Wind Velocity on Flame Spread in Microgravity  

NASA Technical Reports Server (NTRS)

A three-dimensional, time-dependent model is developed describing ignition and subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. A low Mach number approximation to the Navier Stokes equations with global reaction rate equations describing combustion in the gas phase and the condensed phase is numerically solved. The effects of a slow external wind (1-20 cm/s) on flame transition are studied in an atmosphere of 35% oxygen concentration. The ignition is initiated at the center part of the sample by generating a line-shape flame along the width of the sample. The calculated results are compared with data obtained in the 10s drop tower. Numerical results exhibit flame quenching at a wind speed of 1.0 cm/s, two localized flames propagating upstream along the sample edges at 1.5 cm/s, a single line-shape flame front at 5.0 cm/s, three flames structure observed at 10.0 cm/s (consisting of a single line-shape flame propagating upstream and two localized flames propagating downstream along sample edges) and followed by two line-shape flames (one propagating upstream and another propagating downstream) at 20.0 cm/s. These observations qualitatively compare with experimental data. Three-dimensional visualization of the observed flame complex, fuel concentration contours, oxygen and reaction rate isosurfaces, convective and diffusive mass flux are used to obtain a detailed understanding of the controlling mechanism, Physical arguments based on lateral diffusive flux of oxygen, fuel depletion, oxygen shadow of the flame and heat release rate are constructed to explain the various observed flame shapes.

Prasad, Kuldeep; Olson, Sandra L.; Nakamura, Yuji; Fujita, Osamu; Nishizawa, Katsuhiro; Ito, Kenichi; Kashiwagi, Takashi; Simons, Stephen N. (Technical Monitor)

2002-01-01

410

Galileo Photometry of Asteroid 951 Gaspra  

USGS Publications Warehouse

Galileo images of Gaspra make it possible for the first time to determine a main-belt asteroid's photometric properties accurately by providing surface-resolved coverage over a wide range of incidence and emission angles and by extending the phase angle coverage to phases not observable from Earth. We combine Earth-based telescopic photometry over phase angles 2?? ??? ?? ??? 25?? with Galileo whole-disk and disk-resolved data at 33?? ??? ?? ??? 51?? to derive average global photometric properties in terms of Hapke's photometric model. The microscopic texture and particle phase-function behavior of Gaspra's surface are remarkably like those of other airless rocky bodies such as the Moon. The macroscopic surface roughness parameter, ??? = 29??, is slightly larger than that reported for typical lunar materials. The particle single scattering albedo, ???0 = 0.36 ?? 0.07, is significantly larger than for lunar materials, and the opposition surge amplitude, B0 = 1.63 ?? 0.07, is correspondingly smaller. We determine a visual geometric albedo pv = 0.22 ?? 0.06 for Gaspra, in close agreement with pv = 0.22 ?? 0.03 estimated from Earth-based observations. Gaspra's phase integral is 0.47, and the bolometric Bond albedo is estimated to be 0.12 ?? 0.03. An albedo map derived by correcting Galileo images with our average global photometric function reveals subdued albedo contrasts of ??10% or less over Gaspra's northern hemisphere. Several independent classification algorithms confirm the subtle spectral heterogeneity reported earlier (S. Mottola, M. DiMartino, M. Gonano-Beurer, H. Hoffman, and G. Neukum, 1993, Asteroids, Comets, Meteors, pp. 421-424; M. J. S. Belton et al., 1992, Science 257, 1647-1652). Whole-disk colors (0.41 ??? ?? ??? 0.99 ??m) vary systematically with longitude by about ??5%, but color differences as large as 30% occur locally. Colors vary continuously between end-member materials whose areal distribution correlates with regional topography. Infrared: violet (0.99:0.41-??m) color ratios on Gaspra are strongly correlated with local elevation, being largest at lower elevations and smaller at higher elevations. No correlation was detected between elevation and the green:violet (0.56:0.41-??m) color ratio. Bright materials with a strong 1-??m absorption occur primarily in association with craters along ridges, while darker materials with 30% weaker 1-??m signatures occur downslope. The variations of color and albedo cannot be easily explained by grain-size effects alone or by differences in photometric geometry. The trends observed are consistent with those revealed by laboratory studies of the effects of comminution, glass formation, and segregation of metal from silicate components in chondritic meteorites and also in some silicate mixtures. The relative importance of these various processes on Gaspra remains to be determined. ?? 1994 Academic Press. All rights reserved.

Helfenstein, P.; Veverka, J.; Thomas, P.C.; Simonelli, D.P.; Lee, P.; Klaasen, K.; Johnson, T.V.; Breneman, H.; Head, J.W.; Murchie, S.; Fanale, F.; Robinson, M.; Clark, B.; Granahan, J.; Garbeil, H.; McEwen, A.S.; Kirk, R.L.; Davies, M.; Neukum, G.; Mottola, S.; Wagner, R.; Belton, M.; Chapman, C.; Pilcher, C.

1994-01-01

411

The VLT-FLAMES Tarantula Survey. XV. VFTS\\,822: a candidate Herbig B[e] star at low metallicity  

E-print Network

We report the discovery of the B[e] star VFTS 822 in the 30 Doradus star-forming region of the Large Magellanic Cloud, classified by optical spectroscopy from the VLT-FLAMES Tarantula Survey and complementary infrared photometry. VFTS 822 is a relatively low-luminosity (log $L$ = 4.04 $\\pm$ 0.25 $L_{\\odot}$) B8[e] star. In this Letter, we evaluate the evolutionary status of VFTS 822 and discuss its candidacy as a Herbig B[e] star. If the object is indeed in the pre-main sequence phase, it would present an exciting opportunity to measure mass accretion rates at low metallicity spectroscopically, to understand the effect of metallicity on accretion rates.

Kalari, V M; Dufton, P L; Evans, C J; Dunstall, P R; Sana, H; Clark, J S; Ellerbroek, L; de Koter, A; Lennon, D J; Taylor, W D

2014-01-01

412

A Method for Transferring Photoelectric Photometry Data from Apple II+ to IBM PC  

Microsoft Academic Search

A method is presented for transferring photoelectric photometry data files from an Apple II computer to an IBM PC computer in a form which is compatible with the AAVSO Photoelectric Photometry data collection process.

Harry D. Powell; James R. Miller; Kipp Stephenson

1989-01-01

413

A Method for Transferring Photoelectric Photometry Data from Apple II+ to IBM PC  

NASA Astrophysics Data System (ADS)

A method is presented for transferring photoelectric photometry data files from an Apple II computer to an IBM PC computer in a form which is compatible with the AAVSO Photoelectric Photometry data collection process.

Powell, Harry D.; Miller, James R.; Stephenson, Kipp

1989-06-01

414

Retrieval of cirrus properties by Sun photometry: A new perspective on an old issue  

E-print Network

Retrieval of cirrus properties by Sun photometry: A new perspective on an old issue Michal Segal. Ramachandran, J. Redemann, and B. A. Baum (2013), Retrieval of cirrus properties by Sun photometry: A new

Baum, Bryan A.

415

VizieR Online Data Catalog: Radial velocity and photometry for GJ3470 (Bonfils+, 2012)  

NASA Astrophysics Data System (ADS)

The tables contain radial-velocity and photometry time series of GJ3470. Radial velocities were obtained with he HARPS spectrograph. Photometry was obtained with TRAPPIST, EulerCam and NITES telescopes. (5 data files).

Bonfils, X.; Gillon, M.; Udry, S.; Armstrong, D.; Bouchy, F.; Delfosse, X.; Forveille, T.; Fumel, A.; Jehin, E.; Lendl, M.; Lovis, C.; Mayor, M.; McCormac, J.; Neves, V.; Pepe, F.; Perrier, C.; Pollaco, D.; Queloz, D.; Santos, N. C.

2012-11-01

416

Edges of flames that do not exist: flame-edge dynamics in a non-premixed counterflow  

NASA Astrophysics Data System (ADS)

A counterflow diffusion flame model is studied revealing that, at least as a part of the quenching boundary is approached in parameter space at low-enough Lewis numbers, an edge of a diffusion flame, or triple flame, has a propagation speed that still advances the burning solution into regions that are not burning. In crossing the quenching boundary, the advancing flame edge remains a robust part of the solution but the flame behind the edge is found to break up into periodic regions, resembling `tubes' of burning and non-burning, accompanied by the appearance of an oscillatory component in the speed of propagation of the edge. In crossing a second boundary the propagation speed of the flame edge disappears altogether. The only unbounded, non-periodic stationary solution then consists of an isolated flame tube, although stationary periodic flame tubes can also exist under the same conditions. In passing back through parameter space, starting with a single flame tube already present, there is no sign of hysteresis and the oscillatory edge propagation reappears at the same point where it disappears. On the other hand, in continuing forwards across a third, final boundary the flame tube is extinguished leaving no combustion whatever. Boundaries in parameter space where different solutions arise are mapped out.

Thatcher, R. W.; Dold, J. W.

2000-12-01

417

Correlation of flame speed with stretch in turbulent premixed methane/air flames  

SciTech Connect

Direct numerical simulations of two-dimensional unsteady premixed methane/air flames are performed to determine the correlation of flame speed with stretch over a wide range of curvatures and strain rates generated by intense two-dimensional turbulence. Lean and stoichiometric premixtures are considered with a detailed C{sub 1}-mechanism for methane oxidation. The computed correlation shows the existence of two distinct stable branches. It further shows that exceedingly large negative values of stretch can be obtained solely through curvature effects which give rise to an overall nonlinear correlation of the flame speed with stretch. Over a narrower stretch range, {minus}1 {le} Ka {le} 1, which includes 90% of the sample, the correlation is approximately linear, and hence, the asymptotic theory for stretch is practically applicable. Overall, one-third of the sample has negative stretch. In this linear range, the Markstein number associated with the positive branch is determined and is consistent with values obtained from comparable steady counterflow computations. In addition to this conventional positive branch, a negative branch is identified. This negative branch occurs when a flame cusp, with a center of curvature in the burnt gases, is subjected to intense compressive strain, resulting in a negative displacement speed. Negative flame speeds are also encountered for extensive tangential strain rates exceeding a Karlovitz number of unity, a value consistent with steady counterflow computations.

Chen, J.H.; Im, H.G.

1998-03-01

418

Brominated flame retardants: cause for concern?  

PubMed Central

Brominated flame retardants (BFRs) have routinely been added to consumer products for several decades in a successful effort to reduce fire-related injury and property damage. Recently, concern for this emerging class of chemicals has risen because of the occurrence of several classes of BFRs in the environment and in human biota. The widespread production and use of BFRs; strong evidence of increasing contamination of the environment, wildlife, and people; and limited knowledge of potential effects heighten the importance of identifying emerging issues associated with the use of BFRs. In this article, we briefly review scientific issues associated with the use of tetrabromobisphenol A, hexabromocyclododecane, and three commercial mixtures of polybrominated diphenyl ethers and discuss data gaps. Overall, the toxicology database is very limited; the current literature is incomplete and often conflicting. Available data, however, raise concern over the use of certain classes of brominated flame retardants. PMID:14698924

Birnbaum, Linda S; Staskal, Daniele F

2004-01-01

419

NOx Formation in a Premixed Syngas Flame  

SciTech Connect

Reduction of NOx is a subject of significant current interest in stationary gas turbines. The objective of this study is to examine the effects of turbulence on non-thermal NOx formation in a syngas flame. This is archived by a detailed parametric study via PDF simulations of a partially stirred reactor and a dumped axisymmetric premixed flame. Several different detailed and reduced kinetics schemes are considered. The simulated results demonstrate the strong dependence of combustion process on turbulence. It is shown that the amount of NOx formation is significantly influenced by the inlet conditions. That is, the turbulence intensity can be tweaked to attain optimal ultra-low NOx emissions at a given temperature.

Yilmaz, S.L. (University of Pittsburgh, Pittsburgh, PA); Givi, P. (University of Pittsburgh, Pittsburgh, PA); Strakey, P.; Casleton, K.

2006-11-01

420

A thermal equation for flame quenching  

NASA Technical Reports Server (NTRS)

An approximate thermal equation was derived for quenching distance based on a previously proposed diffusional treatment. The quenching distance was expressed in terms of the thermal conductivity, the fuel mole fraction, the heat capacity, the rate of the rate-controlling chemical reaction, a constant that depends on the geometry of the quenching surface, and one empirical constant. The effect of pressure on quenching distance was shown to be inversely proportional to the pressure dependence of the flame reaction, with small correction necessitated by the effect of pressure on flame temperature. The equation was used with the Semenov equation for burning velocity to show that the quenching distance was inversely proportional to burning velocity and pressure at any given initial temperature and equivalence ratio.

Potter, A E , Jr; Berlad, A I

1956-01-01

421

Approaches to flame resistant polymeric materials  

NASA Technical Reports Server (NTRS)

Four research and development areas are considered for further exploration in the quest of more flame-resistant polymeric materials. It is suggested that improvements in phenolphthalein polycarbonate processability may be gained through linear free energy relationship correlations. Looped functionality in the backbone of a polymer leads to both improved thermal resistance and increased solubility. The guidelines used in the pyrolytic carbon production constitute a good starting point for the development of improved flame-resistant materials. Numerous organic reactions requiring high temperatures and the techniques of protected functionality and latent functionality constitute the third area for exploration. Finally, some well-known organic reactions are suggested for the formation of polymers that were not made before.

Liepins, R.

1975-01-01

422

Studying Flame Structures in Free Fall.  

NASA Astrophysics Data System (ADS)

We are studying the effects of acoustics on a flame in microgravity. Our research is meant to provide a new approach to reducing and extinguishing a combustion reaction in space (where a conventional fire extinguisher is hazardous). Our setup includes an interior cage, inside of which is a candle; four speakers surround the cage, which are used to manipulate the flame. A video camera, infrared camera, light sensor, and microphone are placed in various locations throughout the setup to collect data. The master computer records all data and is later used for data analysis. We will describe the experimental apparatus in more detail, which will be flown aboard a NASA DC-9 Aircraft. We will show 1g data collected with the apparatus and briefly describe NASA's Reduced Gravity Student Flight Opportunities Program (RGSFOP).

Plaks, Dmitriy

2005-04-01

423

Stability analysis of near-limit stretched premixed flames  

NASA Astrophysics Data System (ADS)

The dynamics of radiative, near-limit, stretched premixed flames was investigated analytically and numerically, with emphasis on pulsating stability for sub-unity Lewis numbers. The analysis includes both flame stretch and order-unity heat loss, and yields a dispersion equation for the stability of radiative stretched flames subjected to symmetrical and asymmetrical perturbations. The dispersion equation reduces to that of the classical thermo-diffusional stability analysis of Sivashinsky in the limit of small heat loss, small stretch rate, and infinite flame separation distance. Results show that sub-limit flames are stable near both radiation and stretch extinction limits, and that oscillation occurs only at moderate flame stretch rates. The unstable regime and the stability diagram were obtained. Numerical simulation with detailed chemical kinetics and transport models yielded results that are in good agreement with theory. The present work also provides a satisfactory explanation of the experimental results obtained in microgravity.

Minaev, S.; Fursenko, R.; Ju, Y.; Law, C. K.

2003-08-01

424

Gravitational effects on the extinction conditions for premixed flames  

NASA Astrophysics Data System (ADS)

Theory and experiment for premixed gaseous and premixed particle-cloud flames are discussed. The roles of low-temperature endothermicities in both kinds of premixed flames are found to be important determinants of flame properties, including extinction limits. Such findings are not found where truncated, overall reaction rate laws are used. Premixed stabilized lycopodium-air flames have been studied for upward ( g = +1) and downward ( g = -1) propagation under normal gravitational conditions, as well as under microgravity ( g = 0) conditions. A single, self-contained apparatus was used in all studies. The roles of cold-boundary heat losses, flame structure, competing energy transport processes and gravitational conditions are identified and discussed. In general, gravitationally induced processes and omnidirectional radiative loss rates are found to be more significant flame structure determinants than are molecular conductive losses to cold boundaries.

Berlad, A. L.; Joshi, N. D.

425

Flame inhibition by hydrogen halides - Some spectroscopic measurements  

NASA Technical Reports Server (NTRS)

The far-ultraviolet absorption spectrum of an air-propane diffusion flame inhibited with hydrogen halides has been studied. Plots of the absorption of light by hydrogen halides as a function of position in the flame and also as a function of the amount of hydrogen halide added to the flame have been obtained. The hydrogen halides are shown to be more stable on the fuel side of the reaction zone than they are on the air side. Thermal diffusion is seen to be important in determining the concentration distribution of the heavier hydrogen halides in diffusion flames. The relationship between the concentration distribution of the hydrogen halides in the flame and the flame inhibition mechanism is discussed.

Lerner, N. R.; Cagliostro, D. E.

1973-01-01

426

Stretch-induced quenching in flame-vortex interactions  

NASA Technical Reports Server (NTRS)

The flame-vortex interaction problem is a natural configuration in which several issues relevant to turbulent combustion can be addressed: effect of strain-rate and curvature, effect of the Lewis number, effect of heat losses, effect of complex chemistry, and flame-generated turbulence. In such an approach, the interaction of an isolated vortex with a laminar premixed flame is viewed as a unit process of a turbulent premixed flame in which the reaction zone keeps a laminar like structure locally; this is precisely the case of the wrinkled flame or flamelet regime in turbulent combustion. The present work complements previous studies and involves the study of the interaction of a vortex pair and a laminar premixed flame in a planar two-dimensional geometry, together with numerical simulations. This geometry is quite unique since most studies have considered axisymmetric vortex rings. Such a geometry offers several advantages over previous studies.

Samaniego, J.-M.

1993-01-01

427

The advanced flame quality indicator system  

SciTech Connect

By combining oil tank monitoring, systems diagnostics and flame quality monitoring in an affordable system that communicates directly with dealers by telephone modem, Insight Technologies offers new revenue opportunities and the capability for a new order of customer relations to oil dealers. With co-sponsorship from New York State Energy Research and Development Authority, we have incorporated several valuable functions to a new product based on the original Flame Quality Indicator concept licensed from the US DOE`s Brookhaven National Laboratory. The new system is the Advanced Flame Quality Indicator, or AFQI. As before, the AFQI monitors and reports the intensity of the burner flame relative to a calibration established when the burner is set up at AFQI installation. Repairs or adjustments are summoned by late-night outgoing telephone calls when limits are exceeded in either direction, indicating an impending contamination or other malfunction. A independently, a pressure transducer for monitoring oil tank level and filter condition, safety lockout alarms and a temperature monitor; all reporting automatically at instructed intervals via an on-board modem to a central station PC computer (CSC). Firmware on each AFQI unit and Insight-supplied software on the CSC automatically interact to maintain a customer database for an oil dealer, an OEM, or a regional service contractor. In addition to ensuring continuously clean and efficient operation, the AFQI offers the oil industry a new set of immediate payoffs, among which are reduced outages and emergency service calls, shorter service calls from cleaner operation, larger oil delivery drops, the opportunity to stretch service intervals to as along as three years in some cases, new selling features to keep and attract customers, and greatly enhanced customer contact, quality and reliability.

Oman, R.; Rossi, M.J.; Calia, V.S.; Davis, F.L.; Rudin, A. [Insight Technologies, Inc., Bohemia, NY (United States)

1997-09-01

428

Flame and acid resistant polymide fibers  

NASA Technical Reports Server (NTRS)

Economical process improves flame resistance and resistance to acids of polyamide fibers, without modifying colors of mechanical properties. Process improves general safety of garments and other items made from polyamide fibers and makes them suitable for applications requiring exposure to oxygen-rich atmosphere or corrosive acids. Halo-olefins are added to surface of fibers by photoadditon in sealed chamber. Process could be used with films and other forms of polyamide.

Stringham, R. S.; Toy, M. S.

1977-01-01

429

Selective remote diagnostics of gaseous hydrocarbon flames  

NASA Astrophysics Data System (ADS)

An optoelectronic remote method of gaseous flame parameters determination is suggested. It is based on the principles of passive optical spectroscopy with the use of a receiving radiation of tongues followed by electronic digital data processing. The radiation is registered in green-blue range of spectrum by multielement semiconductor photodetector with a predominant use of one spatial coordinate and optical integration along the other coordinate. The digital data processing is performed by means of local and pointwise image processing operators.

Antsygin, Valery D.; Borzov, Sergei M.; Kozik, Victor I.; Potaturkin, Oleg I.; Shushkov, Nikolai N.; Vaskov, S. T.

1997-05-01

430

Fractals and turbulent premixed engine flames  

Microsoft Academic Search

The fractal nature of premixed turbulent flames in an internal combustion engine is examined. A sheet of laser light, approximately 200μm thick is shone through the cylinder of a single-cylinder ported internal combustion engine. The homogeneous charge of propane and air is seeded with submicron TiOâ particles and the scattered light is collected through a quartz window in the engine

J. Mantzaras; P. G. Felton; F. V. Bracco

1989-01-01

431

PDF calculations of piloted premixed jet flames  

Microsoft Academic Search

A series of piloted premixed jet flames with strong finite-rate chemistry effects is studied using the joint velocity-turbulence frequency-composition PDF method. The numerical accuracy of the calculations is demonstrated, and the calculations are compared to experimental data. It is found that all calculations show good agreement with the measurements of mean and rms mixture fraction fields, while the reaction progress

David H. Rowinski; Stephen B. Pope

2011-01-01

432

A Series of Laminar Jet Flame  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence, using propane fuel, was taken STS-94, July 4 1997, MET:2/05:30 (approximate). LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel-like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (249KB JPEG, 1350 x 1524 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300185.html.

2003-01-01

433

Instabilities of diffusion flames near extinction  

NASA Astrophysics Data System (ADS)

The linear spatio-temporal stability of a diffusion flame, represented by a simplified one-dimensional model, located in a mixing layer is investigated. The analysis focuses on recently discovered `heat release' or combustion modes reported for flames near the extinction limit, i.e. for low Damköhler number. Numerical simulations of the two-dimensional linearized impulse response are performed to uncover the convective versus absolute nature of these combustion modes. To complement these two-dimensional simulations, the convective absolute transitions of these modes are confirmed with spatio-temporal linear stability calculations. The effects of initial reactant temperature, flow shear Reynolds number, as well as low fuel Lewis number, are explored. In addition to the Kelvin Helmholtz mode, the generalized model predicts a variety of instabilities near the extinction state, such as travelling and stationary cellular modes, zero wavenumber instabilities or `pulsations', and coupled hydrodynamic-combustion modes. The results elucidate the fundamental destabilizing mechanisms for these near-extinction flames and their relationship to previous work.

Papas, Paul; Rais, Redha M.; Monkewitz, Peter A.; Tomboulides, Ananias G.

2003-12-01

434

Flames in fractal grid generated turbulence  

NASA Astrophysics Data System (ADS)

Twin premixed turbulent opposed jet flames were stabilized for lean mixtures of air with methane and propane in fractal grid generated turbulence. A density segregation method was applied alongside particle image velocimetry to obtain velocity and scalar statistics. It is shown that the current fractal grids increase the turbulence levels by around a factor of 2. Proper orthogonal decomposition (POD) was applied to show that the fractal grids produce slightly larger turbulent structures that decay at a slower rate as compared to conventional perforated plates. Conditional POD (CPOD) was also implemented using the density segregation technique and the results show that CPOD is essential to segregate the relative structures and turbulent kinetic energy distributions in each stream. The Kolmogorov length scales were also estimated providing values ?0.1 and ?0.5 mm in the reactants and products, respectively. Resolved profiles of flame surface density indicate that a thin flame assumption leading to bimodal statistics is not perfectly valid under the current conditions and it is expected that the data obtained will be of significant value to the development of computational methods that can provide information on the conditional structure of turbulence. It is concluded that the increase in the turbulent Reynolds number is without any negative impact on other parameters and that fractal grids provide a route towards removing the classical problem of a relatively low ratio of turbulent to bulk strain associated with the opposed jet configuration.

Goh, K. H. H.; Geipel, P.; Hampp, F.; Lindstedt, R. P.

2013-12-01

435

Baltic Astronomy, vol. 8, 535{574, 1999. GALAXY SURFACE PHOTOMETRY  

E-print Network

Baltic Astronomy, vol. 8, 535{574, 1999. GALAXY SURFACE PHOTOMETRY Bo Milvang-Jensen 1;2 and Inger@gemini.edu Received March 3, 2000 Abstract. We describe galaxy surface photometry based on #12;tting ellipses. As examples of applications of surface photometry we discuss the determination of the relative disk

436

The Gaia Mission and the Asteroids. A perspective from space astrometry and photometry  

E-print Network

The Gaia Mission and the Asteroids. A perspective from space astrometry and photometry to perform high accuracy astrometry and photometry. More specifically it will provide physical and dynamical the dynamical model in general. Key words: Gaia ; astrometry ; photometry ; asteroid physical properties ; dy

437

Aperture Photometry in Practice AST337 In-Class Exercise (hand me in before you leave!)  

E-print Network

Aperture Photometry in Practice AST337 In-Class Exercise (hand me in before you leave!) 7 April in pixels, its brightness in ADU ("Object Counts" in "atv aperture photometry" window), its FWHM in pixels FWHM (ie. aperture radius = FWHM)? Part III: PhotVis, an IDL Photometry and Visualization Tool 1. Run

Lowenthal, James D.

438

ON THE AGE AND METALLICITY ESTIMATION OF SPIRAL GALAXIES USING OPTICAL AND NEAR-INFRARED PHOTOMETRY  

E-print Network

ON THE AGE AND METALLICITY ESTIMATION OF SPIRAL GALAXIES USING OPTICAL AND NEAR-INFRARED PHOTOMETRY-infrared photometry show surprisingly orthogonal grids as age and metallicity are varied, and they are coming headinggs: galaxies: abundances -- galaxies: evolution -- galaxies: photometry -- galaxies: spiral

Lee, Hyun-chul

439

Notes for KINGFISH on SPIRE Photometry DRAFT: v8 2013.3.16.759  

E-print Network

Notes for KINGFISH on SPIRE Photometry DRAFT: v8 2013.3.16.759 B. T. Drainea ABSTRACT Some notes on interpretation of SPIRE photometry of extended sources, and recommendations for use by the KINGFISH collaboration photometry to be sometimes confusing: the distinction between beam sizes to use for point sources or extended

Draine, Bruce T.

440

An Improved Technique for the Photometry and Astrometry of Faint Companions  

E-print Network

An Improved Technique for the Photometry and Astrometry of Faint Companions DANIEL BURKE School to differential astrometry and photometry of faint companions in adap- tive optics images. It is based ratio (SR) data (SR 0:5), the differential photometry of a binary star with a m ¼ 4:5 and a separation

Dainty, Chris

441

New Aperture and PSF Photometry QSO 0957+561A,B  

E-print Network

New Aperture and PSF Photometry of QSO 0957+561A,B Application to Time Delay and Microlensing Aperture and PSF Photometry of QSO 0957+561A,B", is distributed under the terms of the Public Library was initiated with the aim of developing a photometry program to reduce the CCD frames. The results were

Ovaldsen, Jan-Erik

442

NOVEL METHODS FOR PREDICTING PHOTOMETRIC REDSHIFTS FROM BROADBAND PHOTOMETRY USING VIRTUAL SENSORS  

E-print Network

NOVEL METHODS FOR PREDICTING PHOTOMETRIC REDSHIFTS FROM BROADBAND PHOTOMETRY USING VIRTUAL SENSORS, and the Two Micron All Sky Survey using two new training-set methods. We utilize the broadband photometry from material: color figures 1. INTRODUCTION Using broadband photometry in multiple filters to estimate

443

Optical properties of boreal forest fire smoke derived from Sun photometry  

E-print Network

Optical properties of boreal forest fire smoke derived from Sun photometry N. T. O'Neill,1 T. F 2001; published 13 June 2002. [1] Aerosol optical properties derived from Sun photometry were: Aerosols (0305); KEYWORDS: aerosols, forest fire smoke, Sun photometry, optics 1. Introduction [2] Smoke

Li, Zhanqing

444

Application Note (A14) A guide to photometry and  

E-print Network

is the science and technology of the measurement of electromagnetic radiant energy. It is more commonly referred radiant energy emitted by the radiating source over the entire optical spectrum (1 nm to 1000 µm, photometry relates to the measurement of radiant energy in the "visible " spectrum as perceived

Johnsen, Sönke

445

Time Series Photometry Data: Standard Access, Standard Formats  

E-print Network

the IAU Archives of Unpublished Observations of Variable Stars, Breger et al., 1990) and in journals (e.g. IBVS or A&A tables at CDS, see Fig. 1). The VO technology for locating data providers is the registry (Plante et al., 2004). A registry should be set up for time series photometry data. A well established VO

Holl, András

446

Effective temperature scale and bolometric corrections from 2MASS photometry  

Microsoft Academic Search

We present a method to determine effective temperatures, angular semi-diameters and bolometric corrections for population I and II FGK type stars based on V and 2MASS IR photometry. Accurate calibration is accomplished by using a sample of solar analogues, whose average temperature is assumed to be equal to the solar effective temperature of 5777 K. By taking into account all

E. Masana; C. Jordi; I. Ribas

2006-01-01

447

Solar type stars: Spectral energy distribution and JHKLM photometry  

NASA Astrophysics Data System (ADS)

Energy distribution data in the range 3400-7500Å obtained by means of the scanner installed at the 60-cm Zeiss reflector and JHKLM photometry provided at the 1.25 m reflector of the Sternberg Institute Crimean Station for eight stars of spectral types G1.5-G3 of V and IV luminosity classes are presented. The accuracy of the spectrophotometric data is about 2% in the range 3400-4000Å, 1% in the range 4000-6000Å and about 1.5-2% in the range 6000-7500Å. The accuracy of JHKLM photometry is 2% in the bands J, H, K and L and 5% in the M band. A comparison of the energy distribution in the spectra of stars with three reliable sets of spectrophotometric data of the Sun is presented. The differences between stellar and solar energy distribution data are at a minimum for BS 6060 and HD 213575. Comparison of stellar JHKLM photometry with synthetic solar photometry in these IR bands was done. The colour indices J - H, J - K, J - L, and J - M of the Sun and solar-type stars were analysed.

Glushneva, I. N.; Borisov, G. V.; Shenavrin, V. I.; Roshchina, I. A.

448

A Laboratory of Photometry and Radiometry of Light Pollution (LPLAB)  

Microsoft Academic Search

We present the Laboratory of Photometry and Radiometry of Light Pollution (LPLAB) that we set up to provide the Light Pollution Science and Technology Institute (ISTIL) of instruments and calibration services to support its scientific and technological research on light pollution and related environmental effects. The laboratory equipments are characterized by low light intensity measurement and calibration capabilities and by

P. Cinzano

2003-01-01

449

Readmefirst_planetary_photometry_data Purpose of this archive  

E-print Network

b ,y photometry of Uranus, Neptune, and Saturn's satellite Titan. While nearly all the data (except_by_season.txt and subsidiary files: Titan_nights.txt Titan_summary.txt Uranus_by_season.txt and subsidiary files: Uranus_nights.txt Uranus_summary.txt Neptune_by_season.txt and subsidiary files: Neptune_nights.txt Neptune _summary

Lockwood, Wes

450

Error analysis of multi-wavelength sun photometry  

Microsoft Academic Search

The error terms involved in precision multi-wavelength sun photometry, as used to study atmospheric aerosols, are analyzed. The error terms treated include instrumental errors, calibration errors, and errors imposed by the atmosphere. It is shown that in order to derive accurate aerosol parameters, one must exercise great care in the photometer calibration. A procedure for accurate calibration is described, based

Glenn E. Shaw

1976-01-01

451

Comet Kohoutek. [proceedings - astronomical photometry/astronomical spectroscopy  

NASA Technical Reports Server (NTRS)

A compilation of scientific observations (workshop) is presented. Topics discussed are: (1) tail form, structure, and evolution; (2) hydroxyl related observations; (3) molecules and atoms in the coma and tail; (4) photometry and radiometry; and (5) spacecraft and ground based observation data. Color photographs are shown.

Gary, G. A. (editor)

1975-01-01

452

Low cost robotic imaging system for high precision photometry  

E-print Network

Low cost robotic imaging system for high precision photometry Olivier Guyon (Subaru Telescope (etendue = 1m telescope, 1deg diam FOV) 10" per pixel photon-noise limited on sky background Low cost, use, observe, choose target) Easy to duplicate and upgrade, low cost ­ scalable to multiple units, higher

Guyon, Olivier

453

Extended Proper Orthogonal Decomposition for Analysis of Unsteady Flames  

Microsoft Academic Search

The aim of this work is to present the use of proper orthogonal decomposition (POD) and extended proper orthogonal decomposition\\u000a (EPOD) for revealing flame dynamics as a set of statistical quantities referred as modes. The flame fluctuations are used\\u000a to derive an empirical functions base representing the most important features of the flame. The capabilities of the technique\\u000a are exemplified

Christophe Duwig; Piero Iudiciani

2010-01-01

454

Effect of Intense Sound Waves on a Stationary Gas Flame  

NASA Technical Reports Server (NTRS)

Intense sound waves with a resonant frequency of 5000 cycles per second were imposed on a stationary propane-air flame issuing from a nozzle. In addition to a slight increase of the flame velocity, a fundamental change both in the shape of the burning zone and in the flow pattern could be observed. An attempt is made to explain the origin of the variations in the flame configuration on the basis of transition at the nozzle from jet flow to potential flow.

Hahnemann, H; Ehret, L

1950-01-01

455

Flame structure in aluminized wide-distribution AP composite propellants  

Microsoft Academic Search

Flame structure in wide-distribution ammonium-perchlorate (AP), hydroxyl-terminated-polybutadiene (HTPB) binder, aluminum (Al) composite propellants is studied using 2-D laminates with oxygenated binder. Very fine (2-?m) AP (FAP) is used to produce fuel-rich, matrix propellant (oxygenated binder) with a FAP\\/binder ratio of 75\\/25. Coarse AP (CAP) is simulated by pressed AP lamina. A flame-structure regime map for the CAP\\/oxy-fuel matrix interaction flame

M. Q. Brewster; J. C. Mullen

2010-01-01

456

Experiments on Diffusion Flame Structure of a Laminar Vortex Ring  

NASA Technical Reports Server (NTRS)

The study of flame-vortex interactions provides one of the means to better understand turbulent combustion, and allows for canonical configurations that contain the fundamental elements found in turbulent flames, These include concentrated vorticity, entrainment and mixing, strain and nonequilibrium phenomena, diffusion and differential diffusion, partial premixing and diluent effects, and heat release effects. In flame- vortex configurations, these fundamental elements can be studied under more controlled conditions than is possible in direct investigations of turbulent flames. Since the paper of Marble, the problem of the flame-vortex interaction has received considerable attention theoretically, numerically and experimentally. Several configurations exist for study of the premixed flame/vortex ring interaction but more limited results have been obtained to date for the diffusion flame/vortex ring case. The setup of Chen and Dahm, which is conceptually similar to that of Karagozian and Manda and Karagozian, Suganuma and Strom where the ring is composed of fuel and air and combustion begins during the ring formation process, is used in the current study. However, it is essential to conduct the experiments in microgravity to remove the asymmetries caused by buoyancy and thus obtain highly symmetric and repeatable interactions. In previous studies it was found that the flame structure of the vortex ring was similar to that obtained analytically by Karagozian and Manda. Dilution of propane with nitrogen led mainly to a reduction in flame luminosities, flame burnout times were affected by both fuel volumes and amount of dilution, and a simple model of the burnout times was developed. In this paper, a discussion on reacting ring displacement and flame burnout time will be given, and the flame structures of vortex rings containing ethane and air will be compared to those of propane reacting in air.

Chen, Shin-Juh; Dahm, Werner J. A.

1999-01-01

457

Candle Flames in Microgravity: USML-1 Results - 1 Year Later  

NASA Technical Reports Server (NTRS)

We report on the sustained behavior of a candle flame in microgravity determined in the glovebox facility aboard the First United States Microgravity Labomtofy. In a quiescent, microgmvjfy environment, diffusive transport becomes the dominant mode of heat and mass transfer; whether the diffusive transport rate is fast enough to sustain low-gravity candle flames in air was unknown to this series of about 70 tests. After an initial transient in which soot is observed, the microgravity candle flame in air becomes and remains hemispherical and blue (apparently soot-Ne) with a large flame standoff distance. Near flame extinction, spontaneous flame oscillations are regularly observed; these are explained as a flashback of flame through a premixed combustible gas followed by a retreat owed to flame quenching. The frequency of oscillations can be related to diffusive transport rates, and not to residual buoyant convective flow. The fact that the flame tip is the last point of the flame to survive suggests that it is the location of maximum fuel reactivity; this is unlike normal gravity, where the location of maximum fuel reactivity is the flame base. The flame color, size, and shape behaved in a quasi-steady manner; the finite size of the glovebox, combined with the restricted passages of the candlebox, inhibited the observation of true steady-state burning. Nonetheless, through calculations, and inference from the series of shuttle tests, if is concluded that a candle can burn indefinitely in a large enough ambient of air in microgravity. After igniting one candle, a second candle in close pximity could not be lit. This may be due to wax coating the wick and/or local oxygen depletion around the second, unlit candle. Post-mission testing suggests that simultaneous ignition may overcome these behaviors and enable both candles to be ignited.

Ross, H. D.; Dietrich, D. L.; Tien, J. S.

1994-01-01

458

Nonlinear Response of Diffusion Flames to Uniform Velocity Disturbances  

Microsoft Academic Search

This article presents an investigation of the nonlinear response of a diffusion flame to unsteady velocity disturbances. The infinite rate chemistry flame model is employed to study unsteady two-dimensional co-flow non-premixed combustion. In this model, the flame geometry is given by the stoichiometric level surface, which is obtained by the equation for the Schvab-Zeldovich variable. In this article, this equation

Koushik Balasubramanian; R. I. Sujith

2008-01-01

459

Unsteady extinction mechanism of nonpremixed flame interacting with a vortex  

Microsoft Academic Search

The extinction mechanism of a CH4\\/N2–air counterflow nonpremixed flame interacting with a single vortex was numerically studied. An augmented reduced mechanism was used to treat the CH4 oxidation reactions. The contribution of each term in the energy and the OH species equations were evaluated to investigate the unsteady extinction mechanism of nonpremixed flame. The flame temperature began to decrease due

Chang Bo Oh; Cheol-Hong Hwang; Chang-Eon Lee; Jeong Park

2006-01-01

460

Structure Of Flame Balls At Low Lewis-number (SOFBALL)  

NASA Technical Reports Server (NTRS)

The work has encompassed several topics related to the experimental and theoretical study of combustion limits in premixed flames at microgravity. These topics include (1) flame structure and stability at low Lewis number (which is the basis for the SOFBALL space flight experiment), (2) flame propagation and extinction in cylindrical tubes, and (3) experimental simulation of combustion processes using autocatalytic chemical reactions. Progress on each of these topics is outlined.

Ronney, Paul D.

1995-01-01

461

46 CFR 167.45-60 - Emergency breathing apparatus and flame safety lamps.  

Code of Federal Regulations, 2010 CFR

...false Emergency breathing apparatus and flame safety lamps. 167.45-60 Section...45-60 Emergency breathing apparatus and flame safety lamps. Each nautical-school...Charge, Marine Inspection. (b) One flame safety lamp approved by the Coast...

2010-10-01

462

30 CFR 77.1102 - Warning signs; smoking and open flame.  

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Warning signs; smoking and open flame. 77.1102 Section 77...Protection § 77.1102 Warning signs; smoking and open flame. Signs warning against smoking and open flames shall be posted so they...

2011-07-01

463

30 CFR 77.1102 - Warning signs; smoking and open flame.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Warning signs; smoking and open flame. 77.1102 Section 77...Protection § 77.1102 Warning signs; smoking and open flame. Signs warning against smoking and open flames shall be posted so they...

2010-07-01

464

The flame retardant properties of cyanuric chloride derivatives in cotton textile applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cyanuric chloride derivatives are promising flame retardants in cotton textile applications due to their ease of synthesis, high yield, and excellent flame retardant properties as measured by thermogravimetric analyses, limiting oxygen index, and vertical flame testing. Scanning electron microscopic...