Sample records for flame photometry

  1. Iontophoresis and Flame Photometry: A Hybrid Interdisciplinary Experiment

    ERIC Educational Resources Information Center

    Sharp, Duncan; Cottam, Linzi; Bradley, Sarah; Brannigan, Jeanie; Davis, James

    2010-01-01

    The combination of reverse iontophoresis and flame photometry provides an engaging analytical experiment that gives first-year undergraduate students a flavor of modern drug delivery and analyte extraction techniques while reinforcing core analytical concepts. The experiment provides a highly visual demonstration of the iontophoresis technique and…

  2. Total cellular Ca2+ measurements in yeast using flame photometry.

    PubMed

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

    2015-02-01

    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

  3. Releasing effects in flame photometry: Determination of calcium

    USGS Publications Warehouse

    Dinnin, J.I.

    1960-01-01

    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.

  4. A contribution to the application of flame photometry on Ca, Sr, Ba and Li

    Microsoft Academic Search

    Tj Hollander; A. J. Borgers; C. T. J. Alkemade

    1956-01-01

    Summary  Test solutions containing Li, Ca, Sr and Ba salts were sprayed into a flame photometer of simple design. The line-to-background\\u000a ratio, the detection limit, interference effects, filter leakage and the form of the standard graphs were investigated. With\\u000a each element readings were made with a series of interference filters of varying central wavelength and with an acetylene-air\\u000a and propane-air flame,

  5. A contribution to the application of flame photometry on Ca, Sr, Ba and Li

    Microsoft Academic Search

    Tj. Hollander; A. J. Borgers; C. T. J. Alkemade

    1954-01-01

    Summary Test solutions containing Li, Ca, Sr and Ba salts were sprayed into a flame photometer of simple design. The line-to-background ratio, the detection limit, interference effects, filter leakage and the form of the standard graphs were investigated. With each element readings were made with a series of interference filters of varying central wavelength and with an acetylene-air and propane-air

  6. 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

    Hamasaki, Tetsuo

    2013-10-15

    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

  7. Asteroid Photometry

    E-print Network

    Li, Jian-Yang; Buratti, Bonnie J; Takir, Driss; Clark, Beth Ellen

    2015-01-01

    Asteroid photometry has three major applications: providing clues about asteroid surface physical properties and compositions, facilitating photometric corrections, and helping design and plan ground-based and spacecraft observations. The most significant advances in asteroid photometry in the past decade were driven by spacecraft observations that collected spatially resolved imaging and spectroscopy data. In the mean time, laboratory measurements and theoretical developments are revealing controversies regarding the physical interpretations of models and model parameter values. We will review the new developments in asteroid photometry that have occurred over the past decade in the three complementary areas of observations, laboratory work, and theory. Finally we will summarize and discuss the implications of recent findings.

  8. Basics of Photometry Photometry: Basic Questions

    E-print Network

    Masci, Frank

    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

  9. Flame dynamics

    Microsoft Academic Search

    Moshe Matalon

    2009-01-01

    This lecture describes recent theoretical developments associated with the dynamics of flames, obtained primarily by exploiting the various temporal and length scales involved in the combustion process. In premixed flames the focus is on flame–flow interactions that occur during the nonlinear development of hydrodynamically unstable large-scale flames, or during the propagation of curved flames in two-dimensional channels. The second part

  10. Stellar Populations Surface photometry

    E-print Network

    Kruit, Piet van der

    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

  11. Candle flame

    NSDL National Science Digital Library

    Victor Rocha (None; )

    2008-02-10

    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.

  12. Flame Spectra.

    ERIC Educational Resources Information Center

    Cromer, Alan

    1983-01-01

    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)

  13. Introduction to astronomical photometry

    Microsoft Academic Search

    M. Golay

    1974-01-01

    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

  14. Flame Detector

    NASA Technical Reports Server (NTRS)

    1990-01-01

    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.

  15. Surface photometry STRUCTURE OF GALAXIES

    E-print Network

    Kruit, Piet van der

    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

  16. A new approach to qualitative analysis of organophosphorus pesticide residues in cucumber using a double gas chromatographic system: GC-pulsed-flame photometry and retention time locking GC-mass spectrometry.

    PubMed

    Muñoz, J Aybar; González, E Fernández; García-Ayuso, L E; Casado, A González; Cuadros-Rodríguez, L

    2003-06-13

    A qualitative method for the screening of organophosphorus pesticides (OPs) that could present in different types of vegetables has been established and validated. A typical multi-residue extraction procedure of OPs using ethyl acetate and sodium sulphate has been applied. No clean-up was required after extraction, and concentrated extracts were analysed by gas chromatography with pulsed-flame photometric detection (GC-PFPD). Confirmation of compound identities was performed by gas chromatography with mass spectrometric detection (GC-MSD) in the electron impact (EI) mode with full scan acquisition. Retention time locking (RTL) software was used in order to improve the method capability of identification and confirmation. Spiked samples at pesticide concentrations equal to the maximum residue level (MRL) were used to check chromatographic performance and for validation studies. The proposed method allows a rapid and accurate identification of the studied OPs until the ng ml(-1) range for those whose use is forbidden, and above their MRL concentration for the rest. PMID:18969065

  17. Flame Stabilization Mechanisms in Lifted Flames

    Microsoft Academic Search

    Salvador Navarro-Martinez; Andreas Kronenburg

    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

  18. Triple flame structure and diffusion flame stabilization

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  19. Galaxy surface photometry

    E-print Network

    Bo Milvang-Jensen; Inger Jorgensen

    2000-04-04

    We describe galaxy surface photometry based on fitting ellipses to the isophotes of the galaxies. Example galaxies with different isophotal shapes are used to illustrate the process, including how the deviations from elliptical isophotes are quantified using Fourier expansions. We show how the definitions of the Fourier coefficients employed by different authors are linked. As examples of applications of surface photometry we discuss the determination of the relative disk luminosities and the inclinations for E and S0 galaxies. We also describe the color-magnitude and color-color relations. When using both near-infrared and optical photometry, the age-metallicity degeneracy may be broken. Finally we discuss the Fundamental Plane where surface photometry is combined with spectroscopy. It is shown how the FP can be used as a sensitive tool to study galaxy evolution.

  20. Candle Flames in Microgravity

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  1. Photometry of M33

    NASA Astrophysics Data System (ADS)

    Schlingman, W. M.; Massey, P.

    2003-12-01

    We present UBVRI photometry of stars in the nearby Local Group galaxy M33, obtained by imaging with the Kitt Peak 4-m telescope and MOSAIC camera as part of our Local Group Galaxies survey. To obtain this photometry, we have been developing and strengthening routines that can search through images and automatically photometer these stars using point-spread-function fitting. The routines split the image into its corresponding eight CCD chips and then do automated photometry on each chip separately, so that separate color transformations can be applied in a chip-by-chip manner. Our calibration data comes from images obtained on the Lowell 1.1-m Hall telescope on Anderson Mesa, obtained on numerous pristine photometric nights. Once calibrated, our Mosaic photometry values are averaged, and a complete catalogue of positions and photometry (with errors) is obtained. In the end, we have a list of several hundred thousand stars with magnitudes and colors. These data can be used to analyze the stellar populations in M33, one of our closest neighbors. We will briefly describe our procedure, and present the first HR diagrams from our data. This work has been supported by the NSF under grant AST0093060.

  2. Combustion control with flames

    Microsoft Academic Search

    Isenberg

    1984-01-01

    A combustion control process and apparatus provides a reference flame of known or constant composition which is in ionic communication with the main flame which is to be controlled. Both the reference and main flames are supported by electrically insulated burner nozzles and the flames are in mutual electrical communication through ionized gases. The potential difference is measured between the

  3. APT: Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

    Laher, Russ

    2012-08-01

    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.

  4. Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

    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

    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.

  5. The Science of Flames.

    ERIC Educational Resources Information Center

    Cornia, Ray

    1991-01-01

    Describes an exercise using flames that allows students to explore the complexities of a seemingly simple phenomenon, the lighting of a candle. Contains a foldout that provides facts about natural gas flames and suggestions for classroom use. (ZWH)

  6. Third Workshop on Photometry

    NASA Technical Reports Server (NTRS)

    Borucki, William J. (Editor); Lasher, Lawrence E. (Editor)

    2001-01-01

    The discoveries of extrasolar planets by Wolszczan, Mayor and Queloz, Butler et al., and others have stimulated a widespread effort to obtain a body of data sufficient to understand their occurrence and characteristics. Doppler velocity techniques have found dozens of extrasolar planets with masses similar to that of Jupiter. Approximately ten percent of the stars that show planets with orbital periods of a few days to a week are expected to show transits. With the mass obtained from Doppler velocity measurements and the size from transit photometry, the densities of the planets can be determined. Theoretical models of the structure of "hot Jupiters" (i.e., those planets within a tenth of an astronomical unit (AU) of the parent star) indicate that these planets should be substantially larger in size and lower in density than Jupiter. Thus the combination of transit and Doppler velocity measurements provide a critical test of the theories of planetary structure. Furthermore, because photometry can be done with small-aperture telescopes rather than requiring the use of much larger telescopes, transit photometry should also reduce the cost of discovering extrasolar planets.

  7. ARCHANGEL: Galaxy Photometry System

    NASA Astrophysics Data System (ADS)

    Schombert, James

    2011-07-01

    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.

  8. Candle Flames in Microgravity

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  9. Candle flames in microgravity

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  10. Flame front geometry in premixed turbulent flames

    SciTech Connect

    Shepherd, I.G. [Lawrence Berkeley Lab., CA (United States); Ashurst, W.T. [Sandia National Labs., Livermore, CA (United States)

    1991-12-01

    Experimental and numerical determinations of flame front curvature and orientation in premixed turbulent flames are presented. The experimental data is obtained from planar, cross sectional images of stagnation point flames at high Damkoehler number. A direct numerical simulation of a constant energy flow is combined with a zero-thickness, constant density flame model to provide the numerical results. The computational domain is a 32{sup 3} cube with periodic boundary conditions. The two-dimensional curvature distributions of the experiments and numerical simulations compare well at similar q{prime}/S{sub L} values with means close to zero and marked negative skewness. At higher turbulence levels the simulations show that the distributions become symmetric about zero. These features are also found in the three dimensional distributions of curvature. The simulations support assumptions which make it possible to determine the mean direction cosines from the experimental data. This leads to a reduction of 12% in the estimated flame surface area density in the middle of the flame brush. 18 refs.

  11. Exoplanets photometry with remote observatory

    NASA Astrophysics Data System (ADS)

    Vanhuysse, M.; Cales, J.-P.; Technologie, C.; Santerne, A.; Moutou, C.

    2011-10-01

    As radial velocity data, photometry is very important in order to characterize an exoplanet. Photometry of long orbital period transiting exoplanet ,such as those discovered by space-based photometry (CoRoT, Kepler) or from radial velocity are difficult to obtain from the ground. Larger professional telescope cost a lot and generally are busy for observing in photometry for a large amount of nights. We are following up transiting exoplanets with the Oversky remote observatory, which is dedicate to exoplanet photometry and located at La Palma Island (canary), and tele-operate from France via internet. One year after the installation, we reach professionals precisions that permit us to start collaboration with professionals' astronomers. We will present our remote observatory as well as we will highlight our results and compare them with professional telescope accuracy.

  12. Combustion control with flames

    SciTech Connect

    Isenberg, A.O.

    1984-05-08

    A combustion control process and apparatus provides a reference flame of known or constant composition which is in ionic communication with the main flame which is to be controlled. Both the reference and main flames are supported by electrically insulated burner nozzles and the flames are in mutual electrical communication through ionized gases. The potential difference is measured between the flames by way of the nozzles and is used in the air-fuel ratio adjustment of the main burner. Additionally, the main burner can function as a reference point in combination with a zirconia oxygen sensor to ascertain potential differences therebetween, which differences reflect the air-fuel mixture of the main flame.

  13. Flame Holder System

    NASA Technical Reports Server (NTRS)

    Haskin, Henry H. (Inventor); Vasquez, Peter (Inventor)

    2013-01-01

    A flame holder system includes a modified torch body and a ceramic flame holder. Catch pin(s) are coupled to and extend radially out from the torch body. The ceramic flame holder has groove(s) formed in its inner wall that correspond in number and positioning to the catch pin(s). Each groove starts at one end of the flame holder and can be shaped to define at least two 90.degree.turns. Each groove is sized to receive one catch pin therein when the flame holder is fitted over the end of the torch body. The flame holder is then manipulated until the catch pin(s) butt up against the end of the groove(s).

  14. Diffusion Flame Stabilization

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2007-01-01

    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.

  15. Diffusion Flame Stabilization

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, V. R.

    2006-01-01

    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.

  16. Turbulent flame propagation in partially premixed flames

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  17. The Flame Tree

    ERIC Educational Resources Information Center

    Lewis, Richard

    2004-01-01

    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.

  18. The Photoluminescence of Flames

    Microsoft Academic Search

    E. L. Nichols; H. L. Howes

    1923-01-01

    Effect of light on the intensity of the flame spectra of Li, Na, Ca, and Sr.-The salted flame of an air-hydrogen blast lamp was illuminated with the full light from a tungsten lamp, a carbon arc, a mercury arc and an iron spark, and the intensity of the bands or lines emitted, as determined by a photometric balance method in

  19. Flame-Test Chamber

    NASA Technical Reports Server (NTRS)

    Bjorklund, R. A.

    1984-01-01

    Experimental chamber provides controlled environment for observation and measurement of flames propagating in expanding plume of flammable air/fuel mixture under atmospheric conditions. Designed to evaluate quenching capability of screen-type flame arresters in atmospheric vents of fuel cargo tanks aboard marine cargo vessels.

  20. Candle Flames in Microgravity

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  1. 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...

  2. Premixed turbulent flame calculation

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  3. Introduction Observations PSF fitting Photometry Results Defocused PSF-fitting Photometry

    E-print Network

    Pinfield, David J.

    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

  4. Precision photometry for planetary transits

    E-print Network

    Frederic Pont; Claire Moutou

    2007-02-06

    We review the state of the art in follow-up photometry for planetary transit searches. Three topics are discussed: (1) Photometric monitoring of planets discovered by radial velocity to detect possible transits (2) Follow-up photometry of candidates from photometric transit searches to weed out eclipsing binaries and false positives (3) High-precision lightcurves of known transiting planets to increase the accuracy on the planet parameters.

  5. Stratified turbulent Bunsen flames: flame surface analysis and flame surface density modelling

    Microsoft Academic Search

    W. J. S. Ramaekers; J. A. van Oijen; L. P. H. de Goey

    2012-01-01

    In this paper it is investigated whether the Flame Surface Density (FSD) model, developed for turbulent premixed combustion, is also applicable to stratified flames. Direct Numerical Simulations (DNS) of turbulent stratified Bunsen flames have been carried out, using the Flamelet Generated Manifold (FGM) reduction method for reaction kinetics. Before examining the suitability of the FSD model, flame surfaces are characterized

  6. Flame spread across liquids

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  7. Flame-resistant textiles

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  8. Photometric Redshifts and Photometry Errors

    E-print Network

    D. Wittman; P. Riechers; V. E. Margoniner

    2007-09-21

    We examine the impact of non-Gaussian photometry errors on photometric redshift performance. We find that they greatly increase the scatter, but this can be mitigated to some extent by incorporating the correct noise model into the photometric redshift estimation process. However, the remaining scatter is still equivalent to that of a much shallower survey with Gaussian photometry errors. We also estimate the impact of non-Gaussian errors on the spectroscopic sample size required to verify the photometric redshift rms scatter to a given precision. Even with Gaussian {\\it photometry} errors, photometric redshift errors are sufficiently non-Gaussian to require an order of magnitude larger sample than simple Gaussian statistics would indicate. The requirements increase from this baseline if non-Gaussian photometry errors are included. Again the impact can be mitigated by incorporating the correct noise model, but only to the equivalent of a survey with much larger Gaussian photometry errors. However, these requirements may well be overestimates because they are based on a need to know the rms, which is particularly sensitive to tails. Other parametrizations of the distribution may require smaller samples.

  9. Detection by Transit Photometry

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  10. Gaia broad band photometry

    NASA Astrophysics Data System (ADS)

    Jordi, C.; Gebran, M.; Carrasco, J. M.; de Bruijne, J.; Voss, H.; Fabricius, C.; Knude, J.; Vallenari, A.; Kohley, R.; Mora, A.

    2010-11-01

    Aims: The scientific community needs to be prepared to analyse the data from Gaia, one of the most ambitious ESA space missions, which is to be launched in 2012. The purpose of this paper is to provide data and tools to predict how Gaia photometry is expected to be. To do so, we provide relationships among colours involving Gaia magnitudes (white light G, blue GBP, red GRP and GRVS bands) and colours from other commonly used photometric systems (Johnson-Cousins, Sloan Digital Sky Survey, Hipparcos and Tycho). Methods: The most up-to-date information from industrial partners has been used to define the nominal passbands, and based on the BaSeL3.1 stellar spectral energy distribution library, relationships were obtained for stars with different reddening values, ranges of temperatures, surface gravities and metallicities. Results: The transformations involving Gaia and Johnson-Cousins V - IC and Sloan DSS g - z colours have the lowest residuals. A polynomial expression for the relation between the effective temperature and the colour GBP - GRP was derived for stars with Teff ? 4500 K. For stars with Teff < 4500 K, dispersions exist in gravity and metallicity for each absorption value in g - r and r - i. Transformations involving two Johnson or two Sloan DSS colours yield lower residuals than using only one colour. We also computed several ratios of total-to-selective absorption including absorption AG in the G band and colour excess E(GBP - GRP) for our sample stars. A relationship involving AG/AV and the intrinsic (V - IC) colour is provided. The derived Gaia passbands have been used to compute tracks and isochrones using the Padova and BASTI models. Finally, the performances of the predicted Gaia magnitudes have been estimated according to the magnitude and the celestial coordinates of the star. Conclusions: The provided dependencies among colours can be used for planning scientific exploitation of Gaia data, performing simulations of the Gaia-like sky, planning ground-based complementary observations and for building catalogues with auxiliary data for the Gaia data processing and validation. Tables 11-13 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/523/A48

  11. Second Workshop on Improvements to Photometry

    NASA Technical Reports Server (NTRS)

    Borucki, William J. (editor)

    1988-01-01

    The papers in these proceedings show that a major effort is under way to improve all aspects of photometry. Astronomical multichannel photometry, photodiodes, analog-to-digital converters, data reduction techniques, interference filters and optical fibers are discussed.

  12. DETAIL VIEW IN THE FLAME TRENCH LOOKING NORTH, FLAME DEFLECTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL VIEW IN THE FLAME TRENCH LOOKING NORTH, FLAME DEFLECTOR IN THE FOREGROUND, WATER PIPES AND VALVE ASSEMBLIES ON THE FOREGROUND. - Marshall Space Flight Center, Redstone Rocket (Missile) Test Stand, Dodd Road, Huntsville, Madison County, AL

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

    E-print Network

    Farritor, Shane

    Name: NAAP ­ Variable Star Photometry 1/12 Variable Star Photometry ­ Student Guide Background) ___________________________________________________________________________ #12;Name: NAAP ­ Variable Star Photometry 2/12 Question 3: A CCD has a greatest possible pixel value. This process of alignment is known as registration. #12;Name: NAAP ­ Variable Star Photometry 3

  14. 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

  15. Strained flamelets for turbulent premixed flames II: Laboratory flame results

    SciTech Connect

    Kolla, H.; Swaminathan, N. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2010-07-15

    The predictive ability of strained flamelets model for turbulent premixed flames is assessed using Reynolds Averaged Navier Stokes (RANS) calculations of laboratory flames covering a wide range of conditions. Reactant-to-product (RtP) opposed flow laminar flames parametrised using the scalar dissipation rate of reaction progress variable are used as strained flamelets. Two turbulent flames: a rod stabilised V-flame studied by Robin et al. [Combust. Flame 153 (2008) 288-315] and a set of pilot stabilised Bunsen flames studied by Chen et al. [Combust. Flame 107 (1996) 223-244] are calculated using a single set of model parameters. The V-flame corresponds to the corrugated flamelets regime. The strained flamelet model and an unstrained flamelet model yield similar predictions which are in good agreement with experimental measurements for this flame. On the other hand, for the Bunsen flames which are in the thin reaction zones regime, the unstrained flamelet model predicts a smaller flame brush compared to experiment. The predictions of the strained flamelets model allowing for fluid-dynamics stretch induced attenuation of the chemical reaction are in good agreement with the experimental data. This model predictions of major and minor species are also in good agreement with experimental data. The results demonstrate that the strained flamelets model using the scalar dissipation rate can be used across the combustion regimes. (author)

  16. Photometry of 40 LMC Cepheids

    E-print Network

    N. R. Tanvir; A. Boyle

    1999-07-01

    We present V and I_c CCD photometry for 40 LMC Cepheids at 1 to 3 epochs. This represents a significant increase in the number of LMC Cepheids with $I$-band data, and, as we show, is a useful addition to the sample which can be used to calibrate the period--luminosity relations in these important bands.

  17. HD 52452: New BVRI Photometry

    E-print Network

    Sudhanshu Barway; S. K. Pandey

    2004-08-19

    In this paper we report the multi-band BVRI photometry of HD 52452. The comparison of our data with previous observations reported by Messina et al. (2001) shows that there is a variation in amplitude, but the phases of the two minima, thus the positions of the spot, are quite stable during our observations.

  18. CCD photometry of 625 Xenia

    NASA Astrophysics Data System (ADS)

    Worman, W. E.; Fieber, Sherry; Creason, Mary A.

    615 Xenia was observed for eight nights using CCD photometry during the months of April and May 1998. The period of rotation was 21.101 ± 0.032 hours, and the lightcurve had amplitude of 0.50 ± 0.05 magnitude.

  19. Dynamics of Swirling Flames

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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.

  20. A Dramatic Flame Test Demonstration.

    ERIC Educational Resources Information Center

    Johnson, Kristin A.; Schreiner, Rodney

    2001-01-01

    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)

  1. Blue Flame from Common Salt

    Microsoft Academic Search

    J. H. Gladstone

    1879-01-01

    At the present time any spectroscopic observations of coloured flames are peculiarly interesting, and I am glad to see the origin of the blue or violet flame produced by common salt and other chlorides again discussed in your pages.

  2. Bigger and Brighter Flame Tests.

    ERIC Educational Resources Information Center

    Dalby, David K.; Mosher, Melvyn M.

    1996-01-01

    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)

  3. Flame retardant spandex type polyurethanes

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  4. 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...

  5. Overview of GAIA Multi-Color Photometry

    NASA Astrophysics Data System (ADS)

    Høg, Erik

    Gaia will obtain multi-color photometry for astrometric and astrophysical purposes. A photometry in five broad bands and with high angular resolution will be obtained after every astrometric observation of a star, especially for the sake of correcting slight astrometric chromaticity errors of the optical system. A separate smaller telescope will obtain photometry in eleven passbands of medium width designed to serve the astrophysical analysis of the mission results. The medium-band photometry (MBP) has less angular resolution, but much longer effective integration time than the broad-band photometry (BBP).

  6. Flame Tests Performed Safely

    NSDL National Science Digital Library

    Deborah Dogancay

    2005-09-01

    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.

  7. "Magic Eraser" Flame Tests

    ERIC Educational Resources Information Center

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

    2009-01-01

    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.)

  8. Modeling turbulent flame propagation

    SciTech Connect

    Ashurst, W.T.

    1994-08-01

    Laser diagnostics and flow simulation techniques axe now providing information that if available fifty years ago, would have allowed Damkoehler to show how turbulence generates flame area. In the absence of this information, many turbulent flame speed models have been created, most based on Kolmogorov concepts which ignore the turbulence vortical structure, Over the last twenty years, the vorticity structure in mixing layers and jets has been shown to determine the entrainment and mixing behavior and these effects need to be duplicated by combustion models. Turbulence simulations reveal the intense vorticity structure as filaments and simulations of passive flamelet propagation show how this vorticity Creates flame area and defines the shape of the expected chemical reaction surface. Understanding how volume expansion interacts with flow structure should improve experimental methods for determining turbulent flame speed. Since the last decade has given us such powerful new tools to create and see turbulent combustion microscopic behavior, it seems that a solution of turbulent combustion within the next decade would not be surprising in the hindsight of 2004.

  9. Sounding and Sensitive Flames

    Microsoft Academic Search

    A. S. Herschel

    1874-01-01

    A SEVERE indisposition, which disabled me from correspondence during nearly the whole of last month, prevented me from acknowledging as soon as it appeared in NATURE (vol. x. p. 244) Prof. Barrett's excellent communication on Sounding and Sensitive Flames, replying to my letter on the same subject at page 233 of this volume. Prof. Barrett supplied me with many useful

  10. Graphene based multifunctional flame sensor.

    PubMed

    Ferry, Darim B; Pavan Kumar, R; Reddy, Siva K; Mukherjee, Anwesha; Misra, Abha

    2015-05-15

    Recently, graphene has attracted much attention due to its unique electrical and thermal properties along with its high surface area, and hence presents an ideal sensing material. We report a novel configuration of a graphene based flame sensor by exploiting the response of few layer graphene to a flame along two different directions, where flame detection results from a difference in heat transfer mechanisms. A complete sensor module was developed with a signal conditioning circuit that compensates for any drift in the baseline of the sensor, along with a flame detection algorithm implemented in a microcontroller to detect the flame. A pre-defined threshold for either of the sensors is tunable, which can be varied based on the nature of the flame, hence presenting a system that can be used for detection of any kind of flame. This finding also presents a scalable method that opens avenues to modify complicated sensing schemes. PMID:25900408

  11. Surface photometry of NGC 3077

    E-print Network

    Hamed Abdel-Hamid; Peter Notni

    2000-11-03

    We present surface photometry of the irregular galaxy NGC 3077 using two data sets: photographic plates and CCD images. Isophotal contours, luminosity and colour distributions as well as position angle and ellipticity curves show that NGC 3077 is similar to an elliptical galaxy in the outer regions with a disturbed blue centre. The outer isophotes 22-25 mag/arcsec^2 are approximately centred on the dynamical centre, the inner ones are disturbed by the dominant contribution of a reddened young population.

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

    Microsoft Academic Search

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

    2011-01-01

    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

  13. Candle Flames in Microgravity Video

    NASA Technical Reports Server (NTRS)

    1997-01-01

    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.

  14. Soot growth in laminar premixed flames

    Microsoft Academic Search

    Fang Xu

    1999-01-01

    The objectives of the present investigation were to study soot processes in laminar premixed flames. Both experimental and computational methods were used: the experiments involved observations of the flame and soot properties of laminar premixed flames stabilized on flat-flame burners at atmospheric pressure, the computations involved predictions of flame structure using detailed mechanisms of transport and chemical kinetics as well

  15. Vortex/Flame Interactions in Microgravity Pulsed Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  16. Photocells, photomultipliers, and southern-hemisphere photometry.

    NASA Astrophysics Data System (ADS)

    Hearnshaw, J. B.

    1996-11-01

    Three aspects of the historical development of photoelectric photometry in astronomy are discussed. The first is the era of the diode photocell in astronomical photometry, which represents the forerunner of the application of the photomultiplier, and was the first serious attempt to use electronics at the telescope. Secondly, the early days of the photomultiplier are discussed, which, after World War II, brought about an instant revolution in the practice of photoelectric photometry. And finally, the arrival of photomultiplier photometry in the southern hemisphere from about 1950 will be discussed.

  17. Flame Retardant Epoxy Resins

    NASA Technical Reports Server (NTRS)

    Thompson, C. M.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; Lyon, R. E.

    2004-01-01

    As part of a program to develop fire resistant exterior composite structures for future subsonic commercial aircraft, flame retardant epoxy resins are under investigation. Epoxies and their curing agents (aromatic diamines) containing phosphorus were synthesized and used to prepare epoxy formulations. Phosphorus was incorporated within the backbone of the epoxy resin and not used as an additive. The resulting cured epoxies were characterized by thermogravimetric analysis, propane torch test, elemental analysis and microscale combustion calorimetry. Several formulations showed excellent flame retardation with phosphorous contents as low as 1.5% by weight. The fracture toughness of plaques of several cured formulations was determined on single-edge notched bend specimens. The chemistry and properties of these new epoxy formulations are discussed.

  18. Flame Spray Pyrolysis

    Microsoft Academic Search

    A. Purwanto; W.-N. Wang; K. Okuyama

    \\u000a Flame spray pyrolysis (FSP) has been applied for the production of powders industrially. FSP allows production of powders\\u000a with controlled characteristics at a high rate. In addition to the process parameters, several other factors are crucial for\\u000a nanoparticle production. Precursor type, as an example, is an important factor determining the particle size. Using metalorganic\\u000a precursors, particles in nano-sized order could

  19. Candle Flames in Non-Buoyant Atmospheres

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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 (OS). 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. 'Me flames on the Mir OS 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 candle flame. The model is detailed in the gas-phase, but uses a simplified liquid/wick phase. 'Me model predicts a steady flame with a shape and size quantitatively similar to the Shuttle and Mir flames. ne model also predicts pre-extinction flame oscillations if the decrease in ambient oxygen is small enough.

  20. Combustor flame flashback

    NASA Technical Reports Server (NTRS)

    Proctor, M. P.; Tien, J. S.

    1985-01-01

    A stainless steel, two-dimensional (rectangular), center-dump, premixed-prevaporized combustor with quartz window sidewalls for visual access was designed, built, and used to study flashback. A parametric study revealed that the flashback equivalence ratio decreased slightly as the inlet air temperature increased. It also indicated that the average premixer velocity and premixer wall temperature were not governing parameters of flashback. The steady-state velocity balance concept as the flashback mechanism was not supported. From visual observation several stages of burning were identified. High speed photography verified upstream flame propagation with the leading edge of the flame front near the premixer wall. Combustion instabilities (spontaneous pressure oscillations) were discovered during combustion at the dump plane and during flashback. The pressure oscillation frequency ranged from 40 to 80 Hz. The peak-to-peak amplitude (up to 1.4 psi) increased as the fuel/air equivalence ratio was increased attaining a maximum value just before flashback. The amplitude suddenly decreased when the flame stabilized in the premixer. The pressure oscillations were large enough to cause a local flow reversal. A simple test using ceramic fiber tufts indicated flow reversals existed at the premixer exit during flickering. It is suspected that flashback occurs through the premixer wall boundary layer flow reversal caused by combustion instability. A theoretical analysis of periodic flow in the premixing channel has been made. The theory supports the flow reversal mechanism.

  1. pysynphot: Synthetic photometry software package

    NASA Astrophysics Data System (ADS)

    STScI development Team

    2013-03-01

    pysynphot is a synthetic photometry software package suitable for either library or interactive use. Intended as a modern-language successor to the IRAF/STSDAS synphot package, it provides improved algorithms that address known shortcomings in synphot, and its object-oriented design is more easily extensible than synphot's task-oriented approach. It runs under PyRAF, and a backwards compatibility mode is provided that recognizes all spectral and throughput tables, obsmodes, and spectral expressions used by synphot, to facilitate the transition for legacy code.

  2. Photometry of astrometric reference stars

    NASA Technical Reports Server (NTRS)

    Castelaz, Michael W.; Persinger, Tim; Stein, John W.; Prosser, James; Powell, Harry D.

    1991-01-01

    UBVRI, DDO, and uvby, H-beta photometry of astrometric reference stars is presented. Spectral types and luminosity classifications made from the colors are used to determine their spectroscopic parallaxes. In this paper, colors for 309 stars in 25 regions are given, and classifications for 210 stars have been made. These stars form reference frames in the Allegheny Observatory Multichannel Astrometric Photometer astrometric program, and in the Praesepe cluster reduced by Russell (1976). It is found that the present photometric spectral types are reliable to within 2.5 spectral subclasses.

  3. Probe Diagnostics of Meteotron Flame

    Microsoft Academic Search

    A. A. Kuznetsov

    2003-01-01

    A movable double probe was used to study the large-scale naked flame of the meteotron installation. The paper gives a description of the installation and experimental technique used and the data obtained. The electron temperature and the degree of ionization of the flame plasma are obtained from current–voltage characteristics. The operation mode of the probe–flame plasma system is determined. The

  4. NCN detection in atmospheric flames

    SciTech Connect

    Sun, Z.W.; Li, Z.S.; Alden, M. [Division of Combustion Physics, Lund University, P.O. Box 118, S-221 00 Lund (Sweden); Dam, N.J. [On sabbatical leave from Radboud University of Nijmegen and Technical University of Eindhoven (Netherlands)

    2010-04-15

    The first extensive spectra of NCN in atmospheric pressure flames are reported, as well as qualitative planar LIF images of its spatial distribution. The spectra have been recorded by LIF in lifted, fuel-rich CH4/N2O/N2 and CH4/air flames, and are compared to simulations. In the CH4/air flames, the NCN LIF signal peaks around {phi} = 1.2. Planar LIF imaging illustrates the very confined NCN distribution in the CH4/N2O/N2 flame.

  5. Numerical modeling of turbulent nonpremixed lifted flames

    Microsoft Academic Search

    Hoojoong Kim; Yongmo Kim; Kook-young Ahn

    2004-01-01

    The present study has focused on numerical investigation on the flame structure, flame lift-off and stabilization in the partially\\u000a premixed turbulent lifted jet flames. Since the lifted jet flames have the partially premixed nature in the flow region between\\u000a nozzle exit and flame base, level set approach is applied to simulate the partially premixed turbulent lifted jet flames for\\u000a various

  6. Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry,

    E-print Network

    Dobkins, Karen R.

    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

  7. Fast photometry with small telescopes

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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. %

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  9. An optimal extraction algorithm for imaging photometry

    Microsoft Academic Search

    Tim Naylor

    1998-01-01

    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

  10. The Photoluminescence of Flames. II

    Microsoft Academic Search

    E. L. Nichols; H. L. Howes

    1924-01-01

    Photoluminescence of salted flames.-Study of a new flat hydrogen flame showed that the sensitiveness to excitation noted in previous work, is confined chiefly to the boundary between the oxidizing and reducing regions. When excited by exposure to light from an amalgam arc, measurements of the positions of the edges of the bands and of the intensities of the maxima and

  11. The Flame of Common Salt

    Microsoft Academic Search

    T. N. Müller

    1876-01-01

    HAVING been much interested in the progress of the investigations concerning the blue flame of common salt when thrown into a coal fire, I made the following experiments, by which I came to the conclusion that the origin of the blue flame is due to the presence of copper, which occurs in nearly every coal as an ingredient of the

  12. Flame spectra of copper salts

    Microsoft Academic Search

    Nand Lal Singh

    1947-01-01

    ]NTRODUCTION COPPER SALTS, specially the halides, like so many other salts of alkalire earths and iron group, from their natural colours and the co]ours which they impart to the flames in which they are introdueed, have been drawing the attention of workers from very early times. Most of the copper salts, when put into a flame, give a yellowish luminescence

  13. A Dramatic Flame Test Demonstration

    Microsoft Academic Search

    Kristin A. Johnson; Rodney Schreiner

    2001-01-01

    A dramatic ball of colored fire appears when a salt\\/methanol mixture is sprayed into the flame of a Meker burner. The colored fireball is highly visible, even in large lecture halls. Although the fireball has a short duration, it can easily be recreated by repeated spraying of the salt\\/methanol mixture into the burner. The equipment for these striking flame tests

  14. Flame combustion of carbonaceous fuels

    Microsoft Academic Search

    W. J. Hampton; R. L. Hatch; G. R. James

    1984-01-01

    A method for improving the flame combustion of carbonaceous fuels. The method enables the reduction of oxides of nitrogen generated by the flame combustion, and enables an improvement in boiler efficiency. An ionic sodium or potassium compound, or a combination of them, is supplied with the combustible mixture of fuel and air so as intimately and uniformly to be present

  15. LIFTED LAMINAR JET DIFFUSION FLAMES

    Microsoft Academic Search

    AMABLE LIÑÁN; EDUARDO FERNÁNDEZ-TARRAZO; MARCOS VERA; ANTONIO L. SÁNCHEZ

    2005-01-01

    This paper addresses the numerical description of lifted flames in axisymmetric laminar coflow jets. The analysis considers moderately large values of the Reynolds number, when the boundary-layer approximation can be used to describe the slender mixing region that extends between the jet exit and the flame, providing the profiles of velocity and mixture fraction that exist immediately upstream from the

  16. Statistics of premixed flame cells

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1991-01-01

    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.

  17. Statistics of premixed flame cells

    SciTech Connect

    Noever, D.A. (Universities Space Research Association, NASA Marshall Space Flight Center, ES-76, Huntsville, Alabama 35812 (US))

    1991-07-15

    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.

  18. Dynamics and structure of stretched flames

    SciTech Connect

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

    1993-12-01

    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.

  19. What's Next in Asteroid Photometry

    NASA Astrophysics Data System (ADS)

    Vander Haagen, Gary A.

    2009-05-01

    Our knowledge of an asteroid starts with determination of its position over time using astrometry, calculation of orbital parameters, and collection of time-series photometry data to reveal its lightcurve, rotational period, and amplitude. Selectively, radar studies are performed by Arecibo and Goldstone to obtain orbital, size, shape, and surface data. Further insight into asteroid populations, general taxonomic class, albedos, estimated diameters and shape require knowledge of their absolute magnitude (H) and phase slope parameter (G) values. The H-G values are determined through reduced photometric data as the asteroid passes through its opposition or 0° phase angle. Collection of these data is ideally suited to smaller observatories since the time required is considerable and therefore costly for larger facilities. The H-G parameters were determined for 901 Brunsia and 946 Poesia thereby yielding new insight into their absolute magnitudes, albedos, diameter, and general taxonomic classification.

  20. Turbulent Flame Processes Via Diffusion Flame-Vortex Ring Interactions

    NASA Technical Reports Server (NTRS)

    Dahm, Werner J. A.; Chen, Shin-Juh; Silver, Joel A.; Piltch, Nancy D.; VanderWal, Randall L.

    2001-01-01

    Flame-vortex interactions are canonical configurations that can be used to study the underlying processes occurring in turbulent reacting flows. This configuration contains many of the fundamental aspects of the coupling between fluid dynamics and combustion that could be investigated with more controllable conditions than are possible under direct investigations of turbulent flames. Diffusion flame-vortex ring interaction contains many of the fundamental elements of flow, transport, combustion, and soot processes found in turbulent diffusion flames. Some of these elements include concentrated vorticity, entrainment and mixing, strain and nonequilibrium phenomena, diffusion and differential diffusion, partial premixing and diluent effects, soot formation and oxidation, and heat release effects. Such simplified flowfield allows the complex processes to be examined more closely and yet preserving the physical processes present in turbulent reacting flows. Furthermore, experimental results from the study of flame-vortex interactions are useful for the validation of numerical simulations and more importantly to deepen our understanding of the fundamental processes present in reacting flows. Experimental and numerical results obtained under microgravity conditions of the diffusion flame-vortex ring interaction are summarized in this paper. Results are obtained using techniques that include Flame Luminosity Imaging (FLI), Laser Soot-Mie Scattering (LSMS), Computational Fluid Dynamics and Combustion (CFDC), and Diode Laser Spectroscopy/Iterative Temperature with Assumed Chemistry (DLS/ITAC).

  1. Flame retardant polyphosphazenes

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  2. The Cool Flames Experiment

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  3. Candle Flames in Non-Buoyant Atmospheres

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  4. Conditions for a split diffusion flame

    Microsoft Academic Search

    Jean R. Hertzberg

    1997-01-01

    An unusual phenomenon has been observed in a methane jet diffusion flame subjected to axial acoustic forcing. At specific excitation frequencies and amplitudes, the driven flame splits into a central jet and one or two side jets. The splitting is accompanied by a partial detachment of the flame from the nozzle exit, a shortening of the flame by a factor

  5. Candle Flames in Non-Buoyant Atmospheres

    Microsoft Academic Search

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

    2000-01-01

    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

  6. An Introduction to Astronomical Photometry Using CCDs W. Romanishin

    E-print Network

    Masci, Frank

    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

  7. An Introduction to Astronomical Photometry Using CCDs W. Romanishin

    E-print Network

    Ellingson, Steven W.

    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

  8. Flame combustion of carbonaceous fuels

    SciTech Connect

    Hampton, W.J.; Hatch, R.L.; James, G.R.

    1984-05-08

    A method for improving the flame combustion of carbonaceous fuels. The method enables the reduction of oxides of nitrogen generated by the flame combustion, and enables an improvement in boiler efficiency. An ionic sodium or potassium compound, or a combination of them, is supplied with the combustible mixture of fuel and air so as intimately and uniformly to be present where and when the flame exists. Preferably the compound is supplied in an aqueous solution, and can be intimately mixed with the fuel, or with the atomizing air or steam, or with the combustion air. The process is useful with both single-stage and staged (multiple-staged) combustion systems.

  9. WFPC2 aperture photometry and PSF modelling

    E-print Network

    N. R. Tanvir; D. R. T. Robinson; T. von Hippel

    1995-03-22

    Since the WFPC-2 undersamples the PSF, aperture photometry can produce results which are competetive with profile fitting in many situations. This article reports and investigation of aperture corrections using both real data and PSF models.

  10. WFPC2 Stellar Photometry with HSTphot

    E-print Network

    Andrew E. Dolphin

    2000-06-15

    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.

  11. WFPC2 Stellar Photometry with HSTphot

    Microsoft Academic Search

    2000-01-01

    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

  12. WFPC2 Stellar Photometry with HSTphot

    NASA Technical Reports Server (NTRS)

    Dolphin, Andrew E.

    2000-01-01

    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

  13. Hyper: Hybrid photometry and extraction routine

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  14. Meteor44 Video Meteor Photometry

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    Meteor44 is a software system developed at MSFC for the calibration and analysis of video meteor data. The photometric range of the (8 bit) video data is extended from a visual magnitude range of from 8 to 3 to from 8 to -8 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 and long focal length "streak" meteor photometry. Meteor44 has been used to analyze data from the 2001, 2002 and 2003 MSFC Leonid observational campaigns as well as several lesser showers.

  15. Errors In Short Distance Photometry

    NASA Astrophysics Data System (ADS)

    Holmes, J. G.; Moermann, J. J. B.

    1982-02-01

    The errors involved in the short-distance photometry of projectors are evaluated and the same conclusions have been shown to apply to general purpose luminaires. The mathematical analysis from which the equations were derived has been published in Lighting Research and Technology (1981). The illuminance at a short distance from the projector does not follow the inverse square law; the errors depend on the angular subtense of the aperture of the projector relative to the divergence of the beam, and on the distribution of luminance across the aperture of the projector. At any particular distance, the errors are least in directions in which the curvature of the intensity distribution curve is least; the errors may therefore be greatest in the axial direction or in the direction of a shoulder on the curve, and they may change sign where the intensity distribution curve changes from convex to concave. In any particular direction, the error is greater if the outer zones of the projector have higher luminance or give a narrower relative spread; the worst case is a ring-shaped luminaire. If the relative error is less than 10 per cent, it is inversely proportional to the square of the distance of measurement. For general guidance, a nomogram relates the maximum likely percentage error to the beam divergence and to the relative distance of measurement; an empirical reference distance, to be known as the Beam Cross-over Distance, is suggested to replace the traditional 'cross-over distance' of a projector.

  16. Meteor44 Video Meteor Photometry

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  17. Calibration of the MACHO Photometry Database

    E-print Network

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

    1999-09-14

    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 photometry 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 photometry data: the construction of a color-magnitude diagram used to calculate our experimental sensitivity to detect microlensing in the LMC.

  18. Stellar photometry - Current techniques and future developments

    NASA Astrophysics Data System (ADS)

    Butler, C. J.; Elliott, I.

    1993-08-01

    Stellar photometry deals with the accurate measurement of light from stars and galaxies. It is one of the principal tools of the astronomer and is used in the determination of the brightness, radius and temperature of stars, and, increasingly, in the study of their atmospheres and interiors. The book contains the proceedings of a colloquium held in Dublin in August 1992 that reviewed the most recent developments in stellar photometry and the many technical problems that face photometrists in their quest for ever more accurate and meaningful data. This book covers the following topics: (1)Photometric systems; including the pros and cons of rival photometric systems and how they are affected by choice of detector and equipment design; (2)High precision photometry; the factors that limit the routine attainment of millimagnitude accuracy both in measurement and conversion to a standard system; (3)New techniques in photometry, using multichannel arrays in the optical and infrared regions; (4)Automatic photoelectric telescopes and the setting up of global networks to provide continuous photometric coverage; (5)Photometry with CCDs, and (6)Photometry from instruments in space or on the Moon.

  19. 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...

  20. 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...

  1. Linear Instabilities of Diffusion Flames.

    NASA Astrophysics Data System (ADS)

    Nguyen, Luan Nhan

    1992-09-01

    The role of hydrodynamics, thermal and species diffusion on the stability characteristics of a two-dimensional reacting mixing layer is studied. Effects of the body force (buoyancy) and nonunity Lewis number effects, i.e. differential diffusion, are not considered. Both flame sheet (infinite activation energy) and finite thickness (finite activation energy) heat-release models are considered. In a flame sheet model, the dispersion relation typical for nonreacting shear layers is modified by the temperature and density profiles associated with the diffusion flame. In a finite thickness flame model, where thermal and mass diffusion and variable reaction rate are considered, the possibility of new instability modes is investigated. A previous inviscid linear stability analysis of the flame sheet by Jackson and Grosch (1990a), based on the Howarth-transformed similarity solution of the velocity profile, indicated that a transition from convective instability to absolute instability could occur when the heat release parameter was increased. The transition is also observed in the present inviscid stability analyses of a flame sheet model based on the hyperbolic-tangent mean velocity profile. A sensitivity study shows that the absolute growth rate is closely related to the maximum slope of the mean temperature profile. The linear inviscid stability analysis is extended to the case of a finite thickness flame model based on asymptotic steady state solutions for large-activation -energy similar to those of Linan (1973). As expected, the stability results are found to asymptote to those of the flame sheet model. A linear stability analysis of the finite thickness flame model including the effects of viscosity, thermal and mass diffusion and variable reaction rate yields a new instability mode. The new mode, hereafter called the heat-release mode, becomes unstable when the unsteady heat release is sufficiently strong and in phase with the temperature disturbance over a significant portion of the flame zone. This phasing condition is met when the flame thickness becomes large, corresponding to a reduction of the Damkohler number or the activation energy. In the unstable region the growth rate increases with increasing heat release parameter. The heat-release mode is found to have a dispersion relation of the Klein-Gordon type where two values of the frequency exist for each value of the wavenumber and vice versa. The instability is convective for all problem parameters considered. The stability of the new mode is investigated as a function of the problem parameters, including the temperature ratio, the equivalence ratio, the nondimensional activation energy, the heat release parameter, the Reynolds number, and the Damkholer number.

  2. On the critical flame radius and minimum ignition energy for spherical flame initiation

    SciTech Connect

    Chen, Zheng; Burke, M. P.; Ju, Yiguang

    2011-01-01

    Spherical flame initiation from an ignition kernel is studied theoretically and numerically using different fuel/oxygen/helium/argon mixtures (fuel: hydrogen, methane, and propane). The emphasis is placed on investigating the critical flame radius controlling spherical flame initiation and its correlation with the minimum ignition energy. It is found that the critical flame radius is different from the flame thickness and the flame ball radius and that their relationship depends strongly on the Lewis number. Three different flame regimes in terms of the Lewis number are observed and a new criterion for the critical flame radius is introduced. For mixtures with Lewis number larger than a critical Lewis number above unity, the critical flame radius is smaller than the flame ball radius but larger than the flame thickness. As a result, the minimum ignition energy can be substantially over-predicted (under-predicted) based on the flame ball radius (the flame thickness). The results also show that the minimum ignition energy for successful spherical flame initiation is proportional to the cube of the critical flame radius. Furthermore, preferential diffusion of heat and mass (i.e. the Lewis number effect) is found to play an important role in both spherical flame initiation and flame kernel evolution after ignition. It is shown that the critical flame radius and the minimum ignition energy increase significantly with the Lewis number. Therefore, for transportation fuels with large Lewis numbers, blending of small molecule fuels or thermal and catalytic cracking will significantly reduce the minimum ignition energy.

  3. A Dramatic Flame Test Demonstration

    NASA Astrophysics Data System (ADS)

    Johnson, Kristin A.; Schreiner, Rodney

    2001-05-01

    A dramatic ball of colored fire appears when a salt/methanol mixture is sprayed into the flame of a Meker burner. The colored fireball is highly visible, even in large lecture halls. Although the fireball has a short duration, it can easily be recreated by repeated spraying of the salt/methanol mixture into the burner. The equipment for these striking flame tests is easy to prepare and store.

  4. FLAME reentry systems test vehicle

    Microsoft Academic Search

    R. B. Jenkins; J. R. Fryer; M. J. Rubenstein

    1976-01-01

    The Fighter Launched Advanced Material Experiment (FLAME) Program, wherein two-stage solid propellant sounding rockets were launched from an F-4J aircraft, is described. The aircraft-rocket system represents a new approach for the simulation of reentry conditions in the lower atmosphere. The FLAME Program consisted of 8 flights conducted with good vehicle success at the USN China Lake-Sandia Tonopah Ranges. A variety

  5. FLAME SPECTROPHOTOMETRIC STUDY OF BARIUM

    Microsoft Academic Search

    J. C. Burger; T. C. Rains; H. E. Zittel; J. A. Dean

    1961-01-01

    Flame emission characteristics of the barium ionic doublet at 455.4 and ; 4193.4 m mu , the atomic resonance line at 553.6 m mu , and the BaOH and BaO ; bands at 489 and 513 m mu were studied. A prism flame spectrophotometer ; (Beckman DU) and a grating type (Jarrell-Ash Ebert) were used. Barium ; concentrations ranged from

  6. Effects of buoyancy on premixed flame stabilization

    SciTech Connect

    Bedat, B.; Cheng, R.K.

    1995-10-01

    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.

  7. Gaia photometry for white dwarfs

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  8. Flame\\/stretch interactions of premixed hydrogen-fueled flames: measurements and predictions

    Microsoft Academic Search

    O. C. KWON; G. M. FAETH

    2001-01-01

    Fundamental unstretched laminar burning velocities, and flame response to stretch (represented by the Markstein number) were considered both experimentally and computationally for laminar premixed flames. Mixtures of hydrogen and oxygen with nitrogen, argon and helium as diluents were considered to modify flame transport properties for computationally tractable reactant mixtures. Freely (outwardly)-propagating spherical laminar premixed flames were considered for fuel-equivalence ratios

  9. Premixed Turbulent Flame Propagation in Microgravity

    NASA Technical Reports Server (NTRS)

    Menon, S.; Disseau, M.; Chakravarthy, V. K.; Jagoda, J.

    1997-01-01

    Papers included address the following topics: (1) Turbulent premixed flame propagation in microgravity; (2) The effect of gravity on turbulent premixed flame propagation - a preliminary cold flow study; and (3) Characteristics of a subgrid model for turbulent premixed combustion.

  10. Transient Supersonic Methane-Air Flames

    E-print Network

    Richards, John L.

    2012-07-16

    The purpose of this study was to investigate the thermochemical properties of a transient supersonic flame. Creation of the transient flame was controlled by pulsing air in 200 millisecond intervals into a combustor filled with flowing methane...

  11. Flame modifier to reduce NOx emissions

    Microsoft Academic Search

    T. S. Chao; J. E. Sheets; B. C. Vitchus; M. F. Zygowicz

    1981-01-01

    A method and apparatus for modifying the flow pattern of post ignition combustion products of a flame, preferably an oil fueled and air sustained flame, are disclosed which substantially reduces the concentration of NOx emissions.

  12. Detection of Terrestrial Planets Using Transit Photometry

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  13. Principles and scope of synthetic photometry

    NASA Technical Reports Server (NTRS)

    Buser, R.

    1986-01-01

    The synthetic photometry algorithm and various applications for the algorithm are described. The synthetic photometry algorithm provides magnitudes and colors computed from a spectral energy flux distribution and the response functions of a photometric system. The principles of synthetic photometry which include the observed and theoretical stellar energy distributions and passbands of the photometric systems are discussed. The equations utilized in the algorithm to compute the magnitudes and color indices are provided. There is a need for an evaluation of the passbands and a correlation between the observed photometric and spectrophotometric data of the stars. The algorithm is used as a universal translator providing the communication channels between different reseach areas; it is applicable to clusters, faint star counts, and deep multicolor surveys of galaxies.

  14. Photographic stellar photometry with the PDS microdensitometer

    NASA Technical Reports Server (NTRS)

    Stetson, P. B.

    1979-01-01

    A technique for photographic stellar photometry with the PDS microdensitometer is described. It employs a least-squares fit to a model density profile to derive an instrumental magnitude index, an image-abnormality index, and the local value of the background density for each image. The instrumental magnitude index is calibrated in terms of true magnitude by the same methods as for iris photometry. A preliminary test of the method using plates of the open cluster NGC 188 indicates that a precision comparable to or slightly better than that of conventional iris photometry or other methods of PDS reduction may easily be attained. Possibilities for the future elaboration of the technique are mentioned.

  15. Radiant Extinction Of Gaseous Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Berhan, S.; Chernovsky, M.; Atreya, A.; Baum, Howard R.; Sacksteder, Kurt R.

    2003-01-01

    The absence of buoyancy-induced flows in microgravity (mu:g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and :g flames have been reported in experiments on candle flames [1, 2], flame spread over solids [3, 4], droplet combustion [5,6], and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (i) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation, and (ii) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the Aweak@ (low burning rate per unit flame area) :g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in :g will burn indefinitely [1]. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the :g experiments and modeling because: (i) It reduces the complexity by making the problem one-dimensional. (ii) The spherical diffusion flame completely encloses the soot which is formed on the fuel rich side of the reaction zone. This increases the importance of flame radiation because now both soot and gaseous combustion products co-exist inside the high temperature spherical diffusion flame. (iii) For small fuel injection velocities, as is usually the case for a pyrolyzing solid, the diffusion flame in :g around the solid naturally develops spherical symmetry. Thus, spherical diffusion flames are of interest to fires in :g and identifying conditions that lead to radiation-induced extinction is important for spacecraft fire safety.

  16. Unsteady Spherical Diffusion Flames in Microgravity

    NASA Technical Reports Server (NTRS)

    Atreya, Arvind; Berhan, S.; Chernovsky, M.; Sacksteder, Kurt R.

    2001-01-01

    The absence of buoyancy-induced flows in microgravity (mu-g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and (mu-g) flames have been reported in experiments on candle flames, flame spread over solids, droplet combustion, and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (i) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation, and (ii) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the "weak" (low burning rate per unit flame area) mu-g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in mu-g will burn indefinitely. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the mu-g experiments and modeling because: (i) It reduces the complexity by making the problem one-dimensional; (ii) The spherical diffusion flame completely encloses the soot which is formed on the fuel rich side of the reaction zone. This increases the importance of flame radiation because now both soot and gaseous combustion products co-exist inside the high temperature spherical diffusion flame. (iii) For small fuel injection velocities, as is usually the case for a pyrolyzing solid, the diffusion flame in mu-g around the solid naturally develops spherical symmetry. Thus, spherical diffusion flames are of interest to fires in mu-g and identifying conditions that lead to radiation-induced extinction is important for spacecraft fire safety.

  17. Radiant Extinction of Gaseous Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Berhan, Sean; Atreya, Arvind; Everest, David; Sacksteder, Kurt R.

    1999-01-01

    The absence of buoyancy-induced flows in microgravity (mu-g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and mu-g flames have been reported in experiments on candle flames, flame spread over solids, droplet combustion, and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (1) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation; and (2) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the "weak" (low burning rate per unit flame area) mu-g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in mu-g will burn indefinitely. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the mu-g experiments and modeling because: (1) It reduces the complexity by making the problem one-dimensional; (2) The spherical diffusion flame completely encloses the soot which is formed on the fuel rich side of the reaction zone. This increases the importance of flame radiation because now both soot and gaseous combustion products co-exist inside the high temperature spherical diffusion flame; (3) For small fuel injection velocities, as is usually the case for a pyrolyzing solid, the diffusion flame in mu-g around the solid naturally develops spherical symmetry. Thus, spherical diffusion flames are of interest to fires in mu-g and identifying conditions that lead to radiation-induced extinction is important for spacecraft fire safety.

  18. Production Of Fullerenic Soot In Flames

    DOEpatents

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

    2000-12-19

    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.

  19. Production of fullerenic nanostructures in flames

    DOEpatents

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

    1999-01-01

    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.

  20. Displacement speeds in turbulent premixed flame simulations

    SciTech Connect

    Day, Marcus S.; Shepherd, Ian G.; Bell, J.; Grcar, Joseph F.; Lijewski, Michael J.

    2007-07-01

    The theory of turbulent premixed flames is based on acharacterization of the flame as a discontinuous surface propagatingthrough the fluid. The displacement speed, defined as the local speed ofthe flame front normal to itself, relative to the unburned fluid,provides one characterization of the burning velocity. In this paper, weintroduce a geometric approach to computing displacement speed anddiscuss the efficacy of the displacement speed for characterizing aturbulent flame.

  1. Oscillatory Extinction Of Spherical Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  2. Time-resolved photometry of cataclysmic variables

    E-print Network

    C. Papadaki; H. M. J. Boffin; J. Cuypers; V. Stanishev; Z. Kraicheva; V. Genkov

    2003-12-18

    We present time-resolved photometry of two cataclysmic variables whose CCD photometric observations were obtained with the 1m telescope at the South African Astronomical Observatory in October 2002 and August 2003 and with the 1m telescope at Hoher List in Germany. Concerning MCT 2347-3144 we detect for the first time a period of 6.65h. For V1193 Ori the 3.96 h periodicity has for the first time been confirmed through time-resolved photometry.

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

    NASA Technical Reports Server (NTRS)

    Buchanan, Thomas; Wang, Hai

    2005-01-01

    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.

  4. 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...

  5. Spark ignition of lifted turbulent jet flames

    Microsoft Academic Search

    S. F. Ahmed; E. Mastorakos

    2006-01-01

    This paper presents experiments on ignition and subsequent edge flame propagation in turbulent nonpremixed methane jets in air. The spark position, energy, duration, electrode diameter and gap, and the jet velocity and air premixing of the fuel stream are examined to study their effects on the ignition probability defined as successful flame establishment. The flame is visualized by a high-speed

  6. 30 CFR 14.20 - Flame resistance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS...Technical Requirements § 14.20 Flame resistance. Conveyor belts...underground coal mines must be flame-resistant and: (a) Tested...accordance with an alternate test determined by MSHA to be...

  7. 30 CFR 14.20 - Flame resistance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS...Technical Requirements § 14.20 Flame resistance. Conveyor belts...underground coal mines must be flame-resistant and: (a) Tested...accordance with an alternate test determined by MSHA to be...

  8. 30 CFR 14.20 - Flame resistance.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS...Technical Requirements § 14.20 Flame resistance. Conveyor belts...underground coal mines must be flame-resistant and: (a) Tested...accordance with an alternate test determined by MSHA to be...

  9. 30 CFR 14.20 - Flame resistance.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS...Technical Requirements § 14.20 Flame resistance. Conveyor belts...underground coal mines must be flame-resistant and: (a) Tested...accordance with an alternate test determined by MSHA to be...

  10. 30 CFR 14.20 - Flame resistance.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS...Technical Requirements § 14.20 Flame resistance. Conveyor belts...underground coal mines must be flame-resistant and: (a) Tested...accordance with an alternate test determined by MSHA to be...

  11. Mechanism of Soot Formation in Hydrocarbon Flames

    Microsoft Academic Search

    CLAUDE BERTRAND; JEAN-LOUIS DELFAU

    1985-01-01

    The analogy between a sooting hydrocarbon flame and a stoichiometric flame front seeded with alkaline metals is studied. It is found that under certain conditions they are very similar as far as their electrical behaviour is concerned. Theoretical and experimental demonstration is made that the presence of a thermal ionization zone in the post-flame region is the cause of a

  12. Electric-field-induced flame speed modification

    Microsoft Academic Search

    S. D. Marcum; B. N. Ganguly

    2005-01-01

    The effects of pulsed and continuous DC electric fields on the reaction zones of premixed propane–air flames have been investigated using several types of experimental measurements. All observed effects on the flame are dependent on the applied voltage polarity, indicating that negatively charged flame species do not play a role in the perturbation of the reaction zone. Experiments designed to

  13. Prediction of ionic structure in hydrocarbon flames

    Microsoft Academic Search

    Eraslan

    1987-01-01

    The objective of this research is to model the appearance and behavior of combustion-generated ions in hydrocarbon flames. An understanding of ionic phenomena is important to the development of advanced combustion technology including electrical control of flame structure and suppression of soot formation. Computer models were developed to evaluate the formation and behavior of ions in acetylene flames. The results

  14. IONIZATION IN A METHANOL+BXYGEN FLAME

    Microsoft Academic Search

    York Uniuersit

    The combustion of methanol was studied in a conical methanol-oxygen flame of fuel- lean composition (equivalence ratio $J = 0.25) burning at atmospheric pressure surrounded by a flowing argon shield. Oxygen bubbled through liquid methanol contained in two gas saturators provided a premixed flame of excellent stability and reproducibility. The flame gas was sampled into a mass spectrometer which was

  15. Flame temperature determination by dual laser ionization

    NASA Astrophysics Data System (ADS)

    Lin, K. C.; Hunt, P. M.; Crouch, S. R.

    1982-07-01

    A dual laser ionization (DLI) apparatus was used to determine ionic diffusion and mobility coefficients for sodium and lithium in a stoichiometric H 2/O 2/Ar flame. The flame temperature was calculated using the Einstein relation. The sodium and lithium DLI temperature estimates are in agreement with each other and with temperatures measured by the line-reversal technique in similar flames.

  16. Characteristics of microjet methane diffusion flames

    Microsoft Academic Search

    T. S. Cheng; C.-P. Chen; C.-S. Chen; Y.-H. Li; C.-Y. Wu; Y.-C. Chao

    2006-01-01

    Characteristics of microjet methane diffusion flames stabilized on top of the vertically oriented, stainless-steel tubes with an inner diameter ranging from 186 to 778 ? m are investigated experimentally, theoretically and numerically. Of particular interest are the flame shape, flame length and quenching limit, as they may be related to the minimum size and power of the devices in which

  17. Modelling of instabilities in turbulent swirling flames

    Microsoft Academic Search

    K. K. J. Ranga Dinesh; K. W. Jenkins; M. P. Kirkpatrick; W. Malalasekera

    2010-01-01

    A large eddy simulation-based data analysis procedure is used to explore the instabilities in turbulent non-premixed swirling flames. The selected flames known as SM flames are based on the Sydney swirl burner experimental database. The governing equations for continuity, momentum and mixture fraction are solved on a structured Cartesian grid and the Smagorinsky eddy viscosity model with dynamic procedure is

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  19. Flame Speed and Spark Intensity

    NASA Technical Reports Server (NTRS)

    Randolph, D W; Silsbee, F B

    1925-01-01

    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)

  20. Extrasolar planet transit photometry at Wallace Astrophysical Observatory

    E-print Network

    Fong, Wen-fai

    2008-01-01

    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 ...

  1. NIST Photometry Short Course September 27-30, 2011

    E-print Network

    Perkins, Richard A.

    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

  2. Flame Shapes of Luminous NonBuoyant Laminar Coflowing Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Lin, K.-C.; Faeth, G. M.

    1999-01-01

    Laminar diffusion flames are of interest as model flame systems that are more tractable for analysis and experiments than practical turbulent diffusion flames. Certainly understanding laminar flames must precede understanding more complex turbulent flames while man'y laminar diffusion flame properties are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar diffusion flame shapes have been of interest since the classical study of Burke and Schumann because they involve a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Motivated by these observations, the shapes of laminar flames were considered during the present investigation. The present study was limited to nonbuoyant flames because most practical flames are not buoyant. Effects of buoyancy were minimized by observing flames having large flow velocities at small pressures. Present methods were based on the study of the shapes of nonbu,3yant round laminar jet diffusion flames of Lin et al. where it was found that a simple analysis due to Spalding yielded good predictions of the flame shapes reported by Urban et al. and Sunderland et al.

  3. Electric-field-induced flame speed modification

    SciTech Connect

    Marcum, S.D. [Department of Physics, Miami University, Oxford, OH 45056 (United States); Ganguly, B.N. [Air Force Research Laboratory, Wright-Patterson AFB, OH 45433 (United States)

    2005-10-01

    The effects of pulsed and continuous DC electric fields on the reaction zones of premixed propane-air flames have been investigated using several types of experimental measurements. All observed effects on the flame are dependent on the applied voltage polarity, indicating that negatively charged flame species do not play a role in the perturbation of the reaction zone. Experiments designed to characterize the electric-field-induced modifications of the shape and size of the inner cone, and the concomitant changes in the temperature profiles of flames with equivalence ratios between 0.8 and 1.7, are also reported. High-speed two-dimensional imaging of the flame response to a pulsed DC voltage shows that the unperturbed conical flame front (laminar flow) is driven into a wrinkled laminar flamelet (cellular) geometry on a time scale of the order of 5 ms. Temperature distributions derived from thin filament pyrometry (TFP) measurements in flames perturbed by continuous DC fields show similar large changes in the reaction zone geometry, with no change in maximum flame temperature. All measurements are consistent with the observed flame perturbations being a fluid mechanical response to the applied field brought about by forcing positive flame ions counter to the flow. The resulting electric pressure decreases Lewis numbers of the ionic species and drives the effective flame Lewis number below unity. The observed increases in flame speed and the flame fronts trend toward turbulence can be described in terms of the flame front wrinkling and concomitant increase in reaction sheet area. This effect is a potentially attractive means of controlling flame fluid mechanical characteristics. The observed effects require minimal input electrical power (<1 W for a 1 kW burner) due to the much better electric field coupling achieved in the present experiments compared to the previous studies.

  4. Time Series Photometry Data: Standard Access, Standard Formats

    E-print Network

    Holl, András

    Time Series Photometry Data: Standard Access, Standard Formats Andr#19; as Holl Konkoly Observatory a discussion on data access and #12;le format aspects of photometry. Introduction Presently there is time series photometry data available in public databases, but the access to these varies from one collection

  5. Instrument Science Report ACS 2006-01 PSFs, Photometry,

    E-print Network

    Sirianni, Marco

    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

  6. Flame stabilizer for stagnation flow reactor

    DOEpatents

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

    1999-01-01

    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.

  7. Photometry of galaxies in compact groups

    SciTech Connect

    Tikhonov, N.A.

    1988-03-01

    The results are given of photographic photometry of galaxies in compact groups. The luminosity function of the galaxies in the investigated groups is similar to the luminosity function of field galaxies, open groups, and clusters. Of 54 groups, signs of merging of galaxies are observed in only one group.

  8. Photometry from online Digitized Sky Survey Plates

    E-print Network

    A. Bacher; S. Kimeswenger; P. Teutsch

    2005-07-22

    Online Digital Sky Survey (DSS) material is often used to obtain information on newly discovered variable stars for older epochs (e.g. Nova progenitors, flare stars, ...). We present here the results of an investigation of photometry on online digital sky survey material in small fields calibrated by CCD sequences. We compared different source extraction mechanisms and found, that even down near to the sensitivity limit, despite the H-compression used for the online material, photometry with an accuracy better than 0\\fm1 rms is possible on DSS-II. Our investigation shows that the accuracy depends strongly on the source extraction method. The SuperCOSMOS scans, although retrieved with an higher spatial resolution, do not give us better results. The methods and parameters presented here, allow the user to obtain good plate photometry in small fields down to the Schmidt plate survey limits with a few bright CCD calibrators, which may be calibrated with amateur size telescopes. Especially for the events mentioned above, new field photometry for calibration purposes mostly exists, but the progenitors were not measured photometrically before. Also the follow up whether stellar concentrations are newly detected clusters or similar work may be done without using mid size telescopes. The calibration presented here is a "local" one for small fields. We show that this method presented here gives higher accuracies than "global" calibrations of surveys (e.g. GSC-II, SuperCOSMOS and USNO-B)

  9. Diffraction Losses in Radiometry and Photometry

    Microsoft Academic Search

    W R Blevin

    1970-01-01

    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

  10. Near-Field Photometry: A New Approach

    Microsoft Academic Search

    Ian Ashdown

    1992-01-01

    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

  11. CCD photometry of asteroid 932 Hooveria

    NASA Astrophysics Data System (ADS)

    Sada, Pedro V.

    2004-03-01

    CCD photometry of asteroid 932 Hooveria taken during October 2001 and January 2002 at the Universidad de Monterrey Observatory is reported. A synodic rotation period of either 29.947 or 30.370 hours is determined from eight nights of observations.

  12. Wise Observatory System of Fast CCD Photometry

    NASA Astrophysics Data System (ADS)

    Leibowitz, E. M.; Ibbetson, P.; Ofek, E. O.

    We have developed a data acquisition and an online reduction system for fast (a few seconds integration time) photometry with the Wise Observatory CCD camera. The method is based on successively collecting frames, each one is a mere small fraction of the entire CCD array. If necessary, the observer is able to place the object star and the comparison star on one and the same row or column of the CCD chip by rotating the image plane, an option available with the Wise telescope. In so doing, the rectangular frame that has to be read out may have a small area of only some 30 columns or rows, even when the two stars are far away from each other. The readout time of the small frame is thus reduced to merely one or two seconds. Thus photometry with an integration time of 5 s and up becomes possible. The system is a network of 3 computers. One controls the telescope, second controls the camera whilst the third computer is used, during the exposure of each frame, for data reduction of the previous one in the observing sequence. The online photometry is performed using standard procedures of the IRAF CCD photometry package. It yields an instrumental magnitude of the object star relative to one or more reference stars that are present in the frame. The light curve of the object star is displayed with a delay of a single frame relative to the one currently under acquisition.

  13. Hysteresis and transition in swirling nonpremixed flames

    SciTech Connect

    Tummers, M.J.; Huebner, A.W.; van Veen, E.H.; Hanjalic, K. [Delft University of Technology, Faculty of Applied Sciences, P.O. Box 5046, 2600 GA Delft (Netherlands); van der Meer, T.H. [University of Twente, Faculty of Engineering Technology, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2009-02-15

    Strongly swirling nonpremixed flames are known to exhibit a hysteresis when transiting from an attached long, sooty, yellow flame to a short lifted blue flame, and vice versa. The upward transition (by increasing the air and fuel flow rates) corresponds to a vortex breakdown, i.e. an abrupt change from an attached swirling flame (unidirectional or with a weak bluff-body recirculation), to a lifted flame with a strong toroidal vortex occupying the bulk of the flame. Despite dramatic differences in their structures, mixing intensities and combustion performance, both flame types can be realised at identical flow rates, equivalence ratio and swirl intensity. We report here on comprehensive investigations of the two flame regimes at the same conditions in a well-controlled experiment in which the swirl was generated by the rotating outer pipe of the annular burner air passage. Fluid velocity measured with PIV (particle image velocimetry), the qualitative detection of reaction zones from OH PLIF (planar laser-induced fluorescence) and the temperature measured by CARS (coherent anti-Stokes Raman spectroscopy) revealed major differences in vortical structures, turbulence, mixing and reaction intensities in the two flames. We discuss the transition mechanism and arguments for the improved mixing, compact size and a broader stability range of the blue flame in comparison to the long yellow flame. (author)

  14. Imaging Invisible Flames Without Additives

    NASA Technical Reports Server (NTRS)

    Weiland, Karen J.

    1996-01-01

    Image intensifiers, video cameras, and image-data-processing computers used to study combustion. Possible to view and analyze methane, hydrogen, and other flames dim or invisible to human eye and difficult to image by use of conventional photographic and video cameras.

  15. Analysis of diffusion flame tests

    Microsoft Academic Search

    1987-01-01

    This report discusses the results and analysis of hydrogen diffusion flame tests conducted at the Nevada Test Site by EPRI and the US NRC. Those tests were designed to simulate the effects of hydrogen combustion inside a nuclear power plant containment following a degraded-core accident. Test initial conditions and sample data plots are given for 16 tests. Mixing and ignition

  16. An Improved Calcium Flame Test.

    ERIC Educational Resources Information Center

    Pearson, Robert S.

    1985-01-01

    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)

  17. Burning Laminar Jet Diffusion Flame

    NASA Technical Reports Server (NTRS)

    2003-01-01

    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.

  18. Pair dispersion of turbulent premixed flame elements

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Swetaprovo

    2015-02-01

    Flame particles are mathematical points comoving with a reacting isoscalar surface in a premixed flame. In this Rapid Communication, we investigate mean square pair separation of flame particles as a function of time from their positions tracked in two sets of direct numerical simulation solutions of H2-air turbulent premixed flames with detailed chemistry. We find that, despite flame particles and fluid particles being very different concepts, a modified Batchelor's scaling of the form <|?F(t ) -?F(0 ) | 2> =CF(0F?0F ) 2 /3t2 holds for flame particle pair dispersion. The proportionality constant, however, is not universal and depends on the isosurface temperature value on which the flame particles reside. Following this, we attempt to analytically investigate the rationale behind such an observation.

  19. Flex-flame burner and combustion method

    DOEpatents

    Soupos, Vasilios (Chicago, IL); Zelepouga, Serguei (Hoffman Estates, IL); Rue, David M. (Chicago, IL); Abbasi, Hamid A. (Naperville, IL)

    2010-08-24

    A combustion method and apparatus which produce a hybrid flame for heating metals and metal alloys, which hybrid flame has the characteristic of having an oxidant-lean portion proximate the metal or metal alloy and having an oxidant-rich portion disposed above the oxidant lean portion. This hybrid flame is produced by introducing fuel and primary combustion oxidant into the furnace chamber containing the metal or metal alloy in a substoichiometric ratio to produce a fuel-rich flame and by introducing a secondary combustion oxidant into the furnace chamber above the fuel-rich flame in a manner whereby mixing of the secondary combustion oxidant with the fuel-rich flame is delayed for a portion of the length of the flame.

  20. Large Lewis No. Edge-Flame Instabilities

    NASA Technical Reports Server (NTRS)

    Buckmaster, J.

    2001-01-01

    Edge-flames play an important role in a number of microgravity investigations, and in the general study of flames. Examples include the candle-flame experiments carried out on board both the Space Shuttle and the Mir Space Station; the flame-spread-over-liquid work carried out by H. Ross and W. Sirignano amongst others and lifted turbulent diffusion flames. In all of these configurations a local two-dimensional flame structure can be identified which looks like a flame-sheet with an edge, and these structures exhibit dynamical behavior which characterizes them and distinguishes them from ad hoc 2D flame structures. Edge-flames can exist in both a non-premixed context (edges of diffusion flames) and in a premixed context (edges of deflagrations), but the work reported here deals with the edges of diffusion flames. It is particularly relevant, we believe, to oscillations that have been seen in both the candle-flame context, and the flame-spread-over-liquid context. These oscillations are periodic edge-oscillations (in an appropriate reference frame), sans oscillation of the trailing diffusion flame. It is shown that if the Lewis number of the fuel is sufficiently large (the Lewis number of the oxidizer is taken to be 1), and the Damkohler number is sufficiently small, oscillating-edge solutions can be found. Oscillations are encouraged by an on-edge convective flow and the insertion of a cold probe, discouraged by an off-edge convective flow. In the present work, the nature of these oscillations is examined in more depth, using a variety of numerical strategies.

  1. Radiant extinction of gaseous diffusion flames

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

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

    SciTech Connect

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

    2004-03-01

    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.

  3. On flame holes and local extinction in lifted-jet diffusion flames

    SciTech Connect

    Lyons, K.M. [Department of Mechanical and Aerospace Engineering, North Carolina State University, Box 7910, Raleigh, NC 27695-7910 (United States); Watson, K.A. [Department of Mechanical Engineering, University of the Pacific, Stockton, CA 95211 (United States); Carter, C.D.; Donbar, J.M. [Air Force Research Laboratory, AFRL/PRA, Wright-Patterson Air Force Base, OH 45433 (United States)

    2005-08-01

    This paper reports observations of local extinction events characterized by flame holes in the CH profiles that have been gathered during a simultaneous sequential CH planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) investigation of a lifted methane-air diffusion flame. Flame bulges are also reported - that are thought to precede extinction events - as well as ''pinched'' regions upstream of the flame bulges. This information is of use to modelers regarding structures interacting with the reaction zone. It is also relevant to those analyzing and modeling breaks in the reaction zones in studies of flame holes and edge flames.

  4. Methane\\/Air-Lifted Flames in Magnetic Gradients

    Microsoft Academic Search

    P. Gillon; J. N. Blanchard; V. Gilard

    2010-01-01

    The authors analyzed the behavior of a laminar CH4\\/air flame with a central methane jet and surrounding air jet in a large range of fuel and air flow rates. Different regimes of flame stability are observed from an anchored flame to a stable lifted flame, which is destabilized before extinction. It is shown that the flame instabilities are coupled to

  5. Effects of Buoyancy on Lean Premixed V-Flames Part I: Laminar and Turblent Flame Structure

    NASA Technical Reports Server (NTRS)

    Cheng, Robert K.; Bedat, Benoit; Kostiuk, Larry W.

    1998-01-01

    Laser schlieren and planar laser-induced fluorescence techniques have been used to investigate laminar and turbulent v-flames in +g, -g, and micro g under flow conditions that span the regimes of momentum domination (Ri < 0. 1) and buoyancy domination (Ri > 0.1). Overall flame features shown by schlieren indicate that buoyancy dominates the entire flow field for conditions close to Ri = 1. With decreasing Ri, buoyancy effects are observed only in the far-field regions. Analyses of the mean flame angles demonstrate that laminar and turbulent flames do not have similar responses to buoyancy. Difference in the laminar +g and -g flame angles decrease with Ri (i.e., increasing Re) and converge to the microgravity flame angle at the momentum limit (Ri - 0). This is consistent with the notion that the effects of buoyancy diminish with increasing flow momentum. The +g and -g turbulent flame angles, however, do not converge at Ri = 0. As shown by OH-PLIF images, the inconsistency in +g and -g turbulent flame angles is associated with the differences in flame wrinkles. Turbulent flame wrinkles evolve more slowly in +g than in -g. The difference in flame wrinkle structures, however, cannot be explained in terms of buoyancy effects on flame instability mechanisms. It seems to be associated with the field effects of buoyancy that stretches the turbulent flame brushes in +g and compresses the flame brush in -g. Flame wrinkling offers a mechanism through which the flame responds to the field effects of buoyancy despite increasing flow momentum. These observations point to the need to include both upstream and downstream contributions in theoretical analysis of flame turbulence interactions.

  6. Effects of confinement on partially premixed flames

    NASA Technical Reports Server (NTRS)

    Ruetsch, G. R.; Broadwell, J. E.

    1995-01-01

    Partially premixed combustion is an intermediate regime between the limiting cases of premixed and nonpremixed combustion. Although combustion problems are generally approached from one of these two limiting cases, there are many practical situations where flames cannot be considered as purely premixed or nonpremixed, and thus the partially premixed approach must be used. In partially premixed combustion, mechanisms from the premixed and nonpremixed regimes can coexist, and as a result some interesting new phenomena can arise. One such phenomenon is the flame stabilization in laminar mixing layers by triple flames. One of the first observations of triple flames was made by Phillips (1965), who investigated a triple flame propagating in a methane mixing layer. Kioni et al. (1993) also examined triple flames both experimentally and numerically. There have also been numerous analytical studies on the shape and propagation of triple flames under various assumptions by Dold (1989), Dold et al. (1991), and Hartley and Dold (1991). In terms of modeling, Muller et al. (1994) have combined the flamelet formulations for premixed and nonpremixed combustion in order to treat lifted diffusion flames. One common feature in the analytical and numerical studies mentioned above is the assumption of zero heat release, which is necessary to make the problem tractable. The effect of heat release on triple flames was investigated by Ruetsch et al. (1995), where for the unconfined case, flame speeds larger than their premixed counterparts were found. One of the most important practical situations in which these conditions arise is in lifted turbulent jet diffusion flames. At a critical velocity the burning zone of a fuel jet lifts off from the nozzle, moves to increasing distances as the jet velocity increases, and finally blows off. The mechanisms that control these phenomena, i.e. that determine the stability of these flames, are still not understood. In addition to regions where diffusion flame stabilization takes place, partially premixed conditions also exist during the ignition process in nonpremixed systems. Numerical simulations by Reveillon et al. (1994) of the ignition process in a weakly stirred mixture of fuel and oxidizer show that triple flames propagate along lines of stoichiometric mixture fraction throughout the fluid. In addition, Peters (1994) notes that NO(x) emissions are likely to be large in such transient cases, and therefore an understanding of triple flames can provide information concerning pollutant formation. This study extends the work previously done and examines the effects of lateral confinement on partially premixed flames. Once again, we study both the flame structure and propagation.

  7. Recalibrating SFD Using SDSS Spectroscopy And Photometry

    NASA Astrophysics Data System (ADS)

    Schlafly, Eddie; Finkbeiner, D. P.

    2011-05-01

    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.

  8. Lightcurve Photometry Opportunities: 2015 April-June

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  9. Galileo photometry of Asteroid 951 Gaspra

    Microsoft Academic Search

    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

    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

  10. An investigation of multiple jet acetylene flames

    SciTech Connect

    Leite, A.O.P. [Faculdade de Engenharia de Guaratingueta, Sao Paulo (Brazil). Dept. de Quimica] [Faculdade de Engenharia de Guaratingueta, Sao Paulo (Brazil). Dept. de Quimica; Ferreira, M.A.; Carvalho, J.A. Jr. [Inst. Nacional de Pesquisas Espaciais, Cachoeira Paulista, Sao Paulo (Brazil). Lab. Associado de Combustao e Propulsao] [Inst. Nacional de Pesquisas Espaciais, Cachoeira Paulista, Sao Paulo (Brazil). Lab. Associado de Combustao e Propulsao

    1996-11-01

    The interaction between turbulent acetylene flames was investigated experimentally by the analysis of their visible lengths. The study involved 1, 2, 3 and 5 turbulent flames formed by parallel vertical jets whose relative distance was varied. The tube internal diameters were 1, 2, 3 and 4.4 mm. The results quantify the increase of flame length of multiple jets of equal injection tube radii and equal initial velocities as the flame separation distance decreases and as the number of jets increases. An empirical formula relating the length of multiple jet flames to that of the individual flame of same burner diameter was derived. Results of experiments performed with parallel burners inclined of 45{degree} in relation to the vertical direction are also presented.

  11. Transitional Gas Jet Diffusion Flames in Microgravity

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  12. Synergistic Effect of Montmorillonite and Intumescent Flame Retardant on Flame Retardance Enhancement of ABS

    Microsoft Academic Search

    Ying Xia; Xi-gao Jian; Jian-feng Li; Xin-hong Wang; Yan-yan Xu

    2007-01-01

    The synergistic effects of organic montmorillonite (OMMT) and intumescent flame retardant (IFR) based on the ammonium polyphosphate (APP) and pentaerythritol (PER) on flame retardant enhancement of acrylonitrile-butadiene-styrene copolymer (ABS) were investigated by using the limiting oxygen index (LOI), the UL-94 (vertical flame) test, thermogravimetric analysis (TGA), x-ray diffractometry (XRD) and scanning electron microscopy (SEM). The LOI data and vertical flame

  13. Investigation of lengthscales, scalar dissipation, and flame orientation in a piloted diffusion flame by LES

    Microsoft Academic Search

    A. Kempf; F. Flemming; J. Janicka

    2005-01-01

    This work investigates the structure of a diffusion flame in terms of lengthscales, scalar dissipation, and flame orientation by using large eddy simulation. This has been performed for a turbulent, non-premixed, piloted methane\\/air jet flame (Flame D) at a Reynolds-number of 22,400. A steady flamelet model, which was represented by artificial neural networks, yields species mass fractions, density, and viscosity

  14. Large-Eddy Simulation of a Premixed Turbulent Bunsen Flame using Flame Surface Density Model

    Microsoft Academic Search

    W. Lin; Clinton P. T. Groth

    The application of large-eddy simulation (LES) to premixed turbulent flame provides substantial advantages in mod- elling of reacting flows. Compared to Reynolds-average Navier-Stokes (RANS) approaches, LES techniques for premixed turbulent flames have the potential to greatly improve predictive capabilities of scalar mixing process and dissipation rates. However, in many premixed flames, the propagating flame front, which is governed by the

  15. Effects of buoyancy on lean premixed v-flames. Part 1: Laminar and turbulent flame structures

    SciTech Connect

    Cheng, R.K.; Bedat, B. [Lawrence Berkeley National Lab., CA (United States). Environmental Energy Technologies Div.] [Lawrence Berkeley National Lab., CA (United States). Environmental Energy Technologies Div.; Kostiuk, L.W. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Mechanical Engineering] [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Mechanical Engineering

    1999-02-01

    Laser schlieren and planar laser-induced fluorescence techniques have been used to investigate laminar and turbulent v-flames in normal, inverse, and microgravity conditions under flow conditions that span the regimes of momentum domination (Ri < 0.1) and buoyancy domination (Ri > 0.1). Overall flame features shown by schlieren indicate that buoyancy dominates the entire flow field for conditions close to Ri = 1. With decreasing Ri, buoyancy effects are observed only in the far-field regions. Analyses of the mean flame angles demonstrate that laminar and turbulent flames do not have similar responses to buoyancy. Difference in the laminar +g and {minus}g flame angles decrease with Ri (i.e., increasing Re) and converge to the {micro}g flame angle at the momentum limit (Ri = 0). This is consistent with the notion that the effects of buoyancy diminish with increasing flow momentum. The +g and {minus}g turbulent flame angles, however, do not converge at Ri = 0. As shown by OH-PLIF images, the inconsistency in +g and {minus}g turbulent flame angles is associated with the differences in flame wrinkles. Turbulent flame wrinkles evolve more slowly in +g than in {minus}g. The difference in flame wrinkle structures, however, cannot be explained in terms of buoyancy that stretches the turbulent flame brushes in +g and compresses the flame brush in {minus}g. Flame wrinkling offers a mechanism through which the flame responds to the field effects of buoyancy despite increasing flow momentum. These observations point to the need to include both upstream and downstream contributions in theoretical analysis of flame turbulence interactions.

  16. The role of shock-flame interactions on flame acceleration in an obstacle laden channel

    SciTech Connect

    Ciccarelli, Gaby; Johansen, Craig T.; Parravani, Michael [Mechanical and Materials Engineering, Queen's University, Kingston, Ontario (Canada)

    2010-11-15

    Flame acceleration was investigated in an obstructed, square-cross-section channel. Flame acceleration was promoted by an array of top and bottom surface mounted obstacles that were distributed along the entire channel length at an equal spacing corresponding to one channel height. This work is based on a previous investigation of the effects of blockage ratio on the early stage of flame acceleration. This study is focused on the later stage of flame acceleration when compression waves, and eventually a shock wave, form ahead of the flame. The objective of the study is to investigate the effect of obstacle blockage on the rate of flame acceleration and on the final quasi-steady flame-tip velocity. Schlieren photography was used to track the development of the shock-flame complex. It was determined that the interaction between the flame front and the reflected shock waves produced from contact of the lead shock wave with the channel top, channel bottom, and obstacle surfaces govern the late stage of flame acceleration process. The shock-flame interactions produce oscillations in the flame-tip velocity similar to that observed in the early stage of flame acceleration, but only much larger in magnitude. Eventually the flame achieves a globally quasi-steady velocity. For the lowest blockage obstacles, the velocity approaches the speed of sound of the combustion products. The final quasi-steady flame velocity was lower in tests with the higher obstacle blockage. In the quasi-steady propagation regime with the lowest blockage obstacles, burning pockets of gas extended only a few obstacles back from the flame-tip, whereas burning pockets were observed further back in tests with the higher obstacle blockage. (author)

  17. Laminar Jet Diffusion Flame Burning

    NASA Technical Reports Server (NTRS)

    2003-01-01

    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.

  18. Transient response of premixed methane flames

    SciTech Connect

    Vagelopoulos, Christina M.; Frank, Jonathan H. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States)

    2006-08-15

    The response of premixed methane-air flames to transient strain and local variations in equivalence ratio is studied during isolated interactions between a line-vortex pair and a V-flame. The temporal evolution of OH and CH is measured with planar laser-induced fluorescence for N{sub 2}-diluted flames with equivalence ratios ranging from 0.8 to 1.2. One-dimensional laminar flame calculations are used to simulate the flame response to unsteady strain and variations in reactant composition. When the reactant composition of the vortex pair and the V-flame are identical, the measurements and predictions show that the peak mole fractions of OH and CH decay monotonically in lean, stoichiometric, and rich flames. We also investigate the effects of a vortex pair with a leaner composition than the V-flame. In a stoichiometric flame, the leaner vortex enhances the decay of both OH and CH. In a rich flame, we observe an abrupt increase in OH-LIF signal and a disappearance of CH-LIF signal that are consistent with a previous experimental investigation. Our results indicate that the previously observed OH burst and CH breakage were caused by a difference in the equivalence ratios of the vortex pair and the main reactant flow. A numerical study shows that N{sub 2} dilution enhances the response of premixed flames to unsteady strain and variations in stoichiometry. Reaction-path and sensitivity analyses indicate that the peak OH and CH mole fractions exhibit significant sensitivity to the main branching reaction, H+O{sub 2} {r_reversible}OH+O. The sensitivity of OH and CH to this and other reactions is enhanced by N{sub 2} dilution. As a result, N{sub 2}-diluted flames provide a good test case for studying the reliability of chemical kinetic and transport models. (author)

  19. Flame Suppression Agent, System and Uses

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2013-01-01

    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.

  20. Computational and experimental study of laminar flames

    SciTech Connect

    Smooke, M.; Long, M.

    1991-01-01

    During fiscal year 1991 we have made substantial progress in both the computational and experimental portions of our research. In particular we have continued our study of non-premixed axisymmetric methane-air flames. Computer calculations of multidimensional elliptic flames with two carbon atom chemistry using a shared memory parallel computer are reported for the first time. Also laser spectroscopy of flames utilizing a neodymium laser are also reported. (GHH)

  1. Kinetics of Chemical Reactions in Flames

    NASA Technical Reports Server (NTRS)

    Zeldovich, Y.; Semenov, N.

    1946-01-01

    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.

  2. A review of flame retardant polypropylene fibres

    Microsoft Academic Search

    Sheng Zhang; A. Richard Horrocks

    2003-01-01

    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

  3. Gravitational effects on the extinction conditions for premixed flames

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  4. 30 CFR 7.26 - Flame test apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Flame test apparatus. 7.26 Section 7...Ventilation Tubing § 7.26 Flame test apparatus. The principal parts of the apparatus used to test for flame-resistance of brattice...

  5. 30 CFR 7.26 - Flame test apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 false Flame test apparatus. 7.26 Section 7...Ventilation Tubing § 7.26 Flame test apparatus. The principal parts of the apparatus used to test for flame-resistance of brattice...

  6. 30 CFR 7.26 - Flame test apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false Flame test apparatus. 7.26 Section 7...Ventilation Tubing § 7.26 Flame test apparatus. The principal parts of the apparatus used to test for flame-resistance of brattice...

  7. 30 CFR 7.26 - Flame test apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 false Flame test apparatus. 7.26 Section 7...Ventilation Tubing § 7.26 Flame test apparatus. The principal parts of the apparatus used to test for flame-resistance of brattice...

  8. 30 CFR 7.26 - Flame test apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false Flame test apparatus. 7.26 Section 7...Ventilation Tubing § 7.26 Flame test apparatus. The principal parts of the apparatus used to test for flame-resistance of brattice...

  9. 49 CFR 195.438 - Smoking or open flames.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...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...

  10. 49 CFR 195.438 - Smoking or open flames.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 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...

  11. 49 CFR 195.438 - Smoking or open flames.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 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...

  12. 49 CFR 195.438 - Smoking or open flames.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 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...

  13. 49 CFR 195.438 - Smoking or open flames.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...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...

  14. Phase-Resolved DPIV Investigation of Vortex-Flame Interactions in Hydrogen Jet Diffusion Flames

    NASA Astrophysics Data System (ADS)

    Gogineni, Sivaram; Hancock, Robert; Schauer, Frederick; Lucht, Robert

    1997-11-01

    Turbulent diffusion flames consist of countless vortex-flame interactions with length- and time-scales that vary over several orders of magnitude. These vortex-flame interactions are the fundamental building blocks of turbulent diffusion flames. In this experiment, a hydrogen jet diffusion flame is driven with a loud speaker located below a cylindrical fuel tube. The modulation of the fuel velocity in the tube produces a toroidal-shaped vortex at the exit of the fuel tube that pushes out on the flame surface, causing the flame to deform, and at times be locally extinguished. Preliminary observations and numerical modeling results have indicated regions of positive and negative stretch in the flame surface during the vortex-flame interaction. It is within these stretched regions that the local flame temperature and nitric oxide (NO) concentration can vary significantly. The two-dimensional, two-color, particle-image velocimetry (PIV) data presented herein are used to characterize the velocity field and quantify the local flame stretch. The vortex-flame interaction is phase-locked with the laser system and data acquisition hardware so that an individual vortex can be observed at various stages of its development. The resulting velocity information is used to help interpret phase-locked temperature and nitric oxide (NO) laser-induced fluorescence (LIF) measurements collected previously.

  15. 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

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

    Microsoft Academic Search

    Zhuang Shu; Suresh K. Aggarwal; Viswanath R. Katta; Ishwar K. Puri

    1997-01-01

    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 ? = 1. A numerical study is conducted in an inverse configuration in which a fuel-rich (CH4-air) annular jet is sandwiched between an axisymmetric air jet (on the inside) and

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

    Microsoft Academic Search

    J.-M. Samaniego; T. Mantel

    1999-01-01

    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

  18. Spark ignition of lifted turbulent jet flames

    SciTech Connect

    Ahmed, S.F.; Mastorakos, E. [Hopkinson Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

    2006-07-15

    This paper presents experiments on ignition and subsequent edge flame propagation in turbulent nonpremixed methane jets in air. The spark position, energy, duration, electrode diameter and gap, and the jet velocity and air premixing of the fuel stream are examined to study their effects on the ignition probability defined as successful flame establishment. The flame is visualized by a high-speed camera and planar laser-induced fluorescence of OH. It was found that after an initially spherical shape, the flame took a cylindrical shape with a propagating edge upstream. The probability of successful ignition increases with high spark energy, thin electrode diameter and wide gap, but decreases with increasing dilution of the jet with air. The flame kernel growth rate is high when the ignition probability is high for all parameters, except for jet velocity. Increasing the jet velocity decreases the ignition probability at all locations. The average flame position as a function of time from the spark was measured and the data were used to estimate a net propagation speed, which then resulted in an estimate of the average edge flame speed relative to the incoming flow. This was about 3 to 6 laminar burning velocities of a stoichiometric mixture. The measurements can assist theoretical models for the probability of ignition of nonpremixed flames and for edge flame propagation in turbulent inhomogeneous mixtures, both of which determine the success of ignition in practical combustion systems. (author)

  19. Conditions for a split diffusion flame

    SciTech Connect

    Hertzberg, J.R. [Univ. of Colorado, Boulder, CO (United States)] [Univ. of Colorado, Boulder, CO (United States)

    1997-05-01

    An unusual phenomenon has been observed in a methane jet diffusion flame subjected to axial acoustic forcing. At specific excitation frequencies and amplitudes, the driven flame splits into a central jet and one or two side jets. The splitting is accompanied by a partial detachment of the flame from the nozzle exit, a shortening of the flame by a factor of 2, and a change from the common yellow color of soot radiation to a clear blue flame. Such a phenomenon may be useful for the control of soot production or product species. The splitting is intermittent in time, bifurcating between the split flame and an ordinary single jet diffusion flame. The experiment consists of an unconfined axisymmetric methane jet formed by a short length of 0.4 cm diameter pipe. The pipe is connected to a large plenum surrounding a bass reflex loudspeaker enclosure that provides the excitation. Conditions producing split and bifurcated flames are presented. The drive frequencies required to cause bifurcation correspond to the first two peaks in the system`s frequency response curve. Bifurcating behavior was observed at a wide range of flow rates, ranging from very small flames of Reynolds number 240 up to turbulent lift-off, at Re = 1,000, based on the inner pipe diameter. It was not sensitive to nozzle length, but the details of the nozzle tip, such as orifice or pipe geometry, can affect the frequency range.

  20. Confined superadiabatic premixed flame-flow interaction

    SciTech Connect

    Najm, H.N.

    1995-12-31

    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.

  1. Transition and structure of jet diffusion flames

    SciTech Connect

    Takeno, Tadao [Nagoya Univ. (Japan). Dept. of Mechanical Engineering

    1994-12-31

    The transition behavior from laminar to turbulent flames of fuel jet diffusion flames, observed experimentally, is described and compared with the behavior of unignited cold jets. The transition is caused by Kelvin-Helmholtz instability of the jet flow, and the mechanisms is essentially the same as that which causes transition of cold jets. The effects of the flame on this mechanisms are discussed. Next, the successful application of a numerical experiment, combined with the flame surface model, to reveal the significant roles played by the density change and the increase in transport coefficients in the flame is described. The concept has been applied further to understand the flame structure in the transitional region from laminar to turbulent jet diffusion flames, where large-scale vortex motion dominates the mixing process and the laminar flamelet concept can be applied safely. Finally, numerical modeling of interactions between flow fields and chemical reactions in turbulent diffusion flames in the laminar flamelet regime is discussed. It is shown that the concept of local scalar dissipation rate, combined with a flame surface model, is very useful for numerical modeling of the interactions. 38 refs., 16 figs.

  2. Gravitational Effects on Cellular Flame Structure

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  3. Imaging of premixed flames in microgravity

    NASA Astrophysics Data System (ADS)

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

    1994-12-01

    A laser schlieren system which uses video recording and digital images analysis has been developed and applied successfully to microgravity combustion experiments performed in a drop-tower. The optical system and the experiment are installed within a small package which is subjected to free-fall. The images are recorded on video tape and are digitized and analyzed by a computer-controlled image processor. The experimental results include laminar and turbulent premixed conical flames in microgravity, normal positive gravity (upward), and reverse gravity (downward). The procedures to extract frequency information from the digitized images are described. Many gross features of the effects of gravity on premixed conical flames are found. Flames that ignite easily in normal gravity fail to ignite in microgravity. Buoyancy driven instabilities associated with an interface formed between the hot products and the cold surrounding air is the mechanism through which gravity influences premixed laminar and turbulent flames. In normal gravity, this causes the flame to flicker. In reverse gravity, - g, and microgravity, ?g, the interface is stable and flame flickering ceases. The flickering frequencies of + g flames vary with changing upstream boundary conditions. The absence of flame flickering in ?g suggest that ?g flames would be less sensitive to these changes.

  4. Surface photometry of WINGS galaxies with GASPHOT

    NASA Astrophysics Data System (ADS)

    D'Onofrio, M.; Bindoni, D.; Fasano, G.; Bettoni, D.; Cava, A.; Fritz, J.; Gullieuszik, M.; Kjærgaard, P.; Moretti, A.; Moles, M.; Omizzolo, A.; Poggianti, B. M.; Valentinuzzi, T.; Varela, J.

    2014-12-01

    Aims: We present the B, V, and K band surface photometry catalogs obtained by running the automatic software GASPHOT on galaxies from the WINGS cluster survey with isophotal areas larger than 200 pixels. The catalogs can be downloaded at the Centre de Données Astronomiques de Strasbourg. Methods: The luminosity growth curves of stars and galaxies in a given catalog relative to a given cluster image were obtained simultaneously by slicing the image with a fixed surface brightness step in several SExtractor runs. Then, using a single Sersic law convolved with a space-varying point spread function (PSF), GASPHOT performed a simultaneous ?2 best-fit of the major- and minor-axis luminosity growth curves of galaxies. We outline the GASPHOT performances and compare our surface photometry with that obtained by SExtractor, GALFIT, and GIM2D. This analysis is aimed at providing statistical information about the accuracy that is generally achieved by the softwares for automatic surface photometry of galaxies. Results: The GASPHOT catalogs provide the parameters of the Sersic law that fit the luminosity profiles for each galaxy and for each photometric band. They are the sky coordinates of the galaxy center (RA, Dec), the total magnitude (m), the semi-major axis of the effective isophote (Re), the Sersic index (n), the axis ratio (b/a), and a flag parameter (QFLAG) that generally indicates the fit quality. The WINGS-GASPHOT database includes 41 463 galaxies in the B band, 42 275 in the V band, and 71 687 in the K band. The bright early-type galaxies have higher Sersic indices and larger effective radii, as well as redder colors in their center. In general, the effective radii increase systematically from the K to the V and B band. Conclusions: The GASPHOT photometry agrees well with the surface photometry obtained by GALFIT and GIM2D, and with the aperture photometry provided by SExtractor. In particular, the direct comparison of structural parameters derived by different softwares for common galaxies indicates that the systematic differences are small in general. The only significant deviations are most likely due to the peculiar (and very accurate) image processing adopted by WINGS for large galaxies. The main advantages of GASPHOT with respect to other tools are (i) the automatic finding of the local PSF; (ii) the short CPU execution time; and (iii) the remarkable stability against the choice of the initial-guess parameters. All these characteristics make GASPHOT an ideal tool for blind surface photometry of large galaxy samples in wide-field CCD mosaics. Catalogs are only 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/572/A87

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

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  7. Photometry Of The Semi-regular Variable Tx Tau

    Microsoft Academic Search

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

    2009-01-01

    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

  8. Flame Interactions in Turbulent Premixed Twin V-flames

    E-print Network

    Dunstan, T. D.; Swaminathan, N.; Bray, K. N. C.; Kingsbury, N. G.

    2013-01-16

    ). In addition, novel low-emission modes of combustion such as MILD (Moderate or Intense Low-Oxygen Dilution), in which partially premixed reactants and pockets of exhaust gases are injected into the combustion chamber above the ignition temper- ature, show... and Law, 1998). Chen et al. (1999) provide a detailed description of a single turbulence-generated normal flame interaction and pocket burn-out (where a pocket of fresh gas is consumed) using two- dimensional DNS with complex methane-air chemistry. Given a...

  9. The influences of electric fields on soot formation and flame structure of diffusion flames

    Microsoft Academic Search

    Lin Xie; Takeyuki Kishi; Michikata Kono

    1993-01-01

    The influences of DC and AC electric fields, at frequencies up to 1.48 MHz and the maximum strength of about 6 kV\\/cm, on soot\\u000a formation and flame structure were investigated using a counterflow type acetylene diffusion flame. The distributions of flame\\u000a luminosity, soot volume fraction, flame temperature and OH concentration in flame were measured by non-invasive detection\\u000a methods.\\u000a \\u000a Under the

  10. Unsteady planar diffusion flames: Ignition, travel, burnout

    NASA Technical Reports Server (NTRS)

    Fendell, F.; Wu, F.

    1995-01-01

    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.

  11. Flame acceleration studies in the MINIFLAME facility

    SciTech Connect

    Tieszen, S.R.; Sherman, M.P.; Benedick, W.B.

    1989-07-01

    Flame acceleration and deflagration-to-detonation transition (DDT) studies have been conducted in a 19.4-cm high, 14.5-cm wide, and 2. 242-m long channel (MINIFLAME) that is a 1:12.6 scale model of the 136-m{sup 3} FLAME facility. Tests were conducted with two levels of hydrogen concentration -- 20% and 30%, with and without obstacles in the channel, and with three levels of transverse top venting -- 0%, 13%, and 50%. The flame acceleration results in MINIFLAME are qualitatively similar to those in FLAME; however, the small-scale results are more benign quantitatively. The results show that insufficient venting, 13% venting in this case, can promote flame acceleration due to turbulence produced by the flow through the vents in smooth channels. However, with obstacle-generated turbulence in the channel, 13% top venting was found to be beneficial. Flame acceleration resulting in DDT was shown to occur in as little as 35 liters of mixture. Comparison of the DDT data with obstacles in MINIFLAME and FLAME supports d/{lambda} scaling of DDT, where {lambda} is the detonation cell width of the mixture and d is the characteristic open diameter of the channel. In the MINIFLAME and FLAME tests, DDT occurred for d/{lambda} greater than approximately three. Comparison with other experiments shows that the value of d/{lambda} for DDT is not constant but depends on the obstacle type, spacing, and channel geometry. The comparison of MINIFLAME and FLAME experiments extends the use of d/{lambda} scaling to different geometries and larger scales than previous studies. Small-scale-model testing of flame acceleration and DDT with the same combustible mixture as the full-scale prototype underpredicts flame speeds, overpressures, and the possibility of DDT. 18 refs., 16 figs.

  12. Accurate photometry of extended spherically symmetric sources

    NASA Astrophysics Data System (ADS)

    Anders, P.; Gieles, M.; de Grijs, R.

    2006-05-01

    We present a new method to derive reliable photometry of extended spherically symmetric sources from HST images (WFPC2, ACS/WFC and NICMOS/NIC2 cameras), extending existing studies of point sources and marginally resolved sources. We develop a new approach to accurately determine intrinsic sizes of extended spherically symmetric sources, such as star clusters in galaxies beyond the Local Group (at distances ?20 Mpc), and provide a detailed cookbook to perform aperture photometry on such sources, by determining size-dependent aperture corrections (ACs) and taking sky oversubtraction as a function of source size into account. In an extensive Appendix, we provide the parameters of polynomial relations between the FWHM of various input profiles and those obtained by fitting a Gaussian profile (which we have used for reasons of computational robustness, although the exact model profile used is irrelevant), and between the intrinsic and measured FWHM of the cluster and the derived AC. Both relations are given for a number of physically relevant cluster light profiles, intrinsic and observational parameters. AC relations are provided for a wide range of apertures. Depending on the size of the source and the annuli used for the photometry, the absolute magnitude of such extended objects can be underestimated by up to 3 mag, corresponding to an error in mass of a factor of 15. We carefully compare our results to those from the more widely used DeltaMag method, and find an improvement of a factor of 3-40 in both the size determination and the AC.

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

    PubMed Central

    Pearce, E M; Liepins, R

    1975-01-01

    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

  14. Dynamic electrochemistry in flame plasma electrolyte.

    PubMed

    Elahi, Atif; Fowowe, Toks; Caruana, Daren J

    2012-06-25

    Chemistry in flames: Dynamic electrochemistry in the gas phase is described by considering the ionized medium of a flame as an electrolyte (see picture). This study opens up the possibility of accessing redox reactions that are outside the potential limits set by the solvent in conventional liquid-phase electrochemistry. PMID:22588787

  15. Flame aerosol synthesis of ceramic powders

    Microsoft Academic Search

    Sotiris E. Pratsinis

    1998-01-01

    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

  16. 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...

  17. Conductivity of Flames Containing Salt Vapors

    Microsoft Academic Search

    A. B. Bryan

    1921-01-01

    Conductivity of a Flame Sprayed with Salt Solutions, as a Function of the Concentration.-The method used is due to H. A. Wilson. The ratio of the potential gradients in the central parts of two flames, each about 7 cm. wide, through which the same current was passed, was determined by means of a quadrant electrometer connected alternately to each of

  18. Simple Flame Test Techniques Using Cotton Swabs

    ERIC Educational Resources Information Center

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

    2004-01-01

    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.

  19. Mechanism of soot formation in hydrocarbon flames

    SciTech Connect

    Bertrand, C.; Delfau, J.L.

    1985-01-01

    The analogy between a sooting hydrocarbon flame and a stoichiometric flame front seeded with alkaline metals is studied. It is found that under certain conditions they are very similar as far as their electrical behaviour is concerned. Theoretical and experimental demonstration is made that the presence of a thermal ionization zone in the post-flame region is the cause of a large decrease of the potential necessary to extract a given current from the flame front. However, the saturation current extracted from the flame is very close to the saturation current measured in the absence of any thermal ionization. The consequence of the similarity of behaviour is that an ionic mechanism of nucleation of soot initiated by the flame chemi-ions appears to be insignificant compared to a pure radical mechanism of nucleation. The presence of positively charged soot particles in the post flame region of sooting hydrocarbon flames must be explained by the thermal ionization of large hydrocarbon molecules with low ionization potentials (around 5 eV).

  20. Do flame retardants threaten ocean life?

    Microsoft Academic Search

    Jacob de Boer; Peter G. Wester; Hans J. C. Klamer; Wilma E. Lewis; Jan P. Boon

    1998-01-01

    Brominated flame retardants are important in modern life. They are used at relatively high concentrations in electronic equipment such as computers and television sets, in textiles, cars and in many other applications. Here we show that two groups of these flame retardants, polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs), are present in sperm whales, which normally stay and feed

  1. Flame propagation in partially premixed conditions

    Microsoft Academic Search

    G. Ruetsch; T. Poinsot; D. Veynante; A. Trouvé

    1996-01-01

    Turbulent flame propagation is studied under inhomogenously premixed conditions via data from direct numerical simulations. Departures from the premixed case are studied using four different configurations, ranging from one dimensional unsteady flames to turbulent three-dimensional simulations. Simulations are performed in these cases with various values of the mean equivalence ratio, fluctuations about the mean equivlalence ratio, correlation length scales, and

  2. Jet flames of a refuse derived fuel

    SciTech Connect

    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

    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)

  3. 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, ...

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

    Microsoft Academic Search

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

    1990-01-01

    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

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

    SciTech Connect

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

    1997-11-01

    In the flamelet approach of turbulent premixed combustion, the flames are modeled as a wrinkled surface whose propagation speed, termed the {open_quotes}displacement speed,{close_quotes} is prescribed in terms of the local flow field and flame geometry. Theoretical studies suggest a linear relation between the flame speed and stretch for small values of stretch, S{sub L}/S{sub L}{sup 0} = 1 - MaKa, where S{sub L}{sup 0} is the laminar flame speed, Ka = {kappa}{delta}{sub F}/S{sub L}{sup 0} is the nondimensional stretch or the Karlovitz number, and Ma = L/{delta}{sub F} is the Markstein number. The nominal flame thickness, {delta}{sub F}, is determined as the ratio of the mass diffusivity of the unburnt mixture to the laminar flame speed. Thus, the turbulent flame model relies on an accurate estimate of the Markstein number in specific flame configurations. Experimental measurement of flame speed and stretch in turbulent flames, however, is extremely difficult. As a result, measurement of flame speeds under strained flow fields has been made in simpler geometries, in which the effect of flame curvature is often omitted. In this study we present results of direct numerical simulations of unsteady turbulent flames with detailed methane/air chemistry, thereby providing an alternative method of obtaining flame structure and propagation statistics. The objective is to determine the correlation between the displacement speed and stretch over a broad range of Karlovitz numbers. The observed response of the displacement speed is then interpreted in terms of local tangential strain rate and curvature effects. 13 refs., 3 figs.

  6. Quick and Dirty WFPC2 Stellar Photometry

    NASA Technical Reports Server (NTRS)

    Mighell, Kenneth J.

    2001-01-01

    The latest release of the IRAF (Image Reduction and Analysis Facility) MXTOOLS package includes the new tasks QDWFPC2 (Quick and Dirty Wide Field and Planetary Camera, which does quick CCD (charge-coupled device) stellar photometry on two Hubble Space Telescope (HST) WFPC2 (Wide Field and Planetary Camera) observations: WFPC2COLOR, which converts HST WFPC2 instrumental magnitudes to standard colors using the Holtzman et al. color equations, and QDCMD (Quick and Dirty Color Magnitude Diagram), which reads the output of WFPC2COLOR and displays a color-magnitude diagram on a user-chosen graphics device.

  7. New BVR Photometry of BL Camelopardalis

    NASA Astrophysics Data System (ADS)

    Joner, Michael D.

    2015-01-01

    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.

  8. Simultaneous Filter Photometry of V1727 Cygni

    NASA Astrophysics Data System (ADS)

    Sundin, Emma; Mason, P. A.; Robinson, E. L.; Morales, J.; Gomez, S.; Gonzalez, R.; Lopez, I.; Bell, K.

    2014-01-01

    We present high speed optical photometry of the low mass X-ray binary V1727 Cygni. Simultaneous observations were obtained during five consecutive nights in 2013 using McDonald Observatory's 2.7-m and 2.1-m telescopes using u' and R filters respectively. There is very little variation in the u' intensity. The R data displays night to night and orbital period variations. We discuss constraints on system properties provided by these multi-filter data. This program is funded by NSF grant 0958783.

  9. Charles Nordmann and Multicolour Stellar Photometry

    NASA Astrophysics Data System (ADS)

    Lequeux, James

    2010-11-01

    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.

  10. Rayleigh-Taylor Unstable Flames -- Fast or Faster?

    NASA Astrophysics Data System (ADS)

    Hicks, E. P.

    2015-04-01

    Rayleigh–Taylor (RT) unstable flames play a key role in the explosions of supernovae Ia. However, the dynamics of these flames are still not well understood. RT unstable flames are affected by both the RT instability of the flame front and by RT-generated turbulence. The coexistence of these factors complicates the choice of flame speed subgrid models for full-star Type Ia simulations. Both processes can stretch and wrinkle the flame surface, increasing its area and, therefore, the burning rate. In past research, subgrid models have been based on either the RT instability or turbulence setting the flame speed. We evaluate both models, checking their assumptions and their ability to correctly predict the turbulent flame speed. Specifically, we analyze a large parameter study of 3D direct numerical simulations of RT unstable model flames. This study varies both the simulation domain width and the gravity in order to probe a wide range of flame behaviors. We show that RT unstable flames are different from traditional turbulent flames: they are thinner rather than thicker when turbulence is stronger. We also show that none of the several different types of turbulent flame speed models accurately predicts measured flame speeds. In addition, we find that the RT flame speed model only correctly predicts the measured flame speed in a certain parameter regime. Finally, we propose that the formation of cusps may be the factor causing the flame to propagate more quickly than predicted by the RT model.

  11. Particle Cloud Flames in Acoustic Fields

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  12. Interaction Between Flames and Electric Fields Studied

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    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.

  13. Edge Diffusion Flame Propagation and Stabilization Studied

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2004-01-01

    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.

  14. Flame Structure and Emissions of Strongly-Pulsed Turbulent Diffusion Flames with Swirl

    NASA Astrophysics Data System (ADS)

    Liao, Ying-Hao

    This work studies the turbulent flame structure, the reaction-zone structure and the exhaust emissions of strongly-pulsed, non-premixed flames with co-flow swirl. The fuel injection is controlled by strongly-pulsing the fuel flow by a fast-response solenoid valve such that the fuel flow is completely shut off between pulses. This control strategy allows the fuel injection to be controlled over a wide range of operating conditions, allowing the flame structure to range from isolated fully-modulated puffs to interacting puffs to steady flames. The swirl level is controlled by varying the ratio of the volumetric flow rate of the tangential air to that of the axial air. For strongly-pulsed flames, both with and without swirl, the flame geometry is strongly impacted by the injection time. Flames appear to exhibit compact, puff-like structures for short injection times, while elongated flames, similar in behaviors to steady flames, occur for long injection times. The flames with swirl are found to be shorter for the same fuel injection conditions. The separation/interaction level between flame puffs in these flames is essentially governed by the jet-off time. The separation between flame puffs decreases as swirl is imposed, consistent with the decrease in flame puff celerity due to swirl. The decreased flame length and flame puff celerity are consistent with an increased rate of air entrainment due to swirl. The highest levels of CO emissions are generally found for compact, isolated flame puffs, consistent with the rapid quenching due to rapid dilution with excess air. The imposition of swirl generally results in a decrease in CO levels, suggesting more rapid and complete fuel/air mixing by imposing swirl in the co-flow stream. The levels of NO emissions for most cases are generally below the steady-flame value. The NO levels become comparable to the steady-flame value for sufficiently short jet-off time. The swirled co-flow air can, in some cases, increase the NO emissions. The elevated NO emissions are due to a longer combustion residence time due to the flow recirculation within the swirl-induced recirculation zone. The reaction zone structure, based on OH planar laser-induced fluorescence (PLIF) is broadly consistent with the observation of luminous flame structure for these types of flames. In many cases, the reaction zone exhibits discontinuities at the instantaneous flame tip in the early period of fuel injection. These discontinuities in the reaction zone likely result from the non-ignition of injected fuel, due to a relatively slower reaction rate in comparison with the mixing rate. The discontinuity in the OH zone is generally seen to diminish with increased swirl level. Statistics generated from the OH PLIF signals show that the reaction zone area generally increases with increased swirl level, consistent with a broader and more convoluted OH-zone structure for flames with swirl. The reaction zone area for swirled flames generally exhibits a higher degree of fluctuation, suggesting a relatively stronger impact of flow turbulence on the flame structure for flames with swirl.

  15. Quasar Selection using Optical Photometry and Variability

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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

  16. Speckle Interferometry and Photometry of Binary Stars

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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.

  17. The flaming gypsy skirt injury.

    PubMed

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

    2007-01-01

    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

  18. On the extraction of laminar flame speed and Markstein length from outwardly propagating spherical flames

    SciTech Connect

    Chen, Zheng [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China)

    2011-02-15

    Large discrepancies among the laminar flame speeds and Markstein lengths of methane/air mixtures measured by different researchers using the same constant-pressure spherical flame method are observed. As an effort to reduce these discrepancies, one linear model (LM, the stretched flame speed changes linearly with the stretch rate) and two non-linear models (NM I and NM II, the stretched flame speed changes non-linearly with the stretch rate) for extracting the laminar flame speed and Markstein length from propagating spherical flames are investigated. The accuracy and performance of the LM, NM I, and NM II are found to strongly depend on the Lewis number. It is demonstrated that NM I is the most accurate for mixtures with large Lewis number (positive Markstein length) while NM II is the most accurate for mixtures with small Lewis number (negative Markstein length). Therefore, in order to get accurate laminar flame speed and Markstein length from spherical flame experiments, different non-linear models should be used for different mixtures. The validity of the theoretical results is further demonstrated by numerical and experimental studies. The results of this study can be used directly in spherical flame experiments measuring the laminar flame speed and Markstein length. (author)

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

    PubMed

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

    2013-09-01

    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 Re_{T,f}^{0.5} 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 Re_{T,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 Re_{T,M}^{0.5} irrespective of the fuel, equivalence ratio, pressure, and turbulence intensity for positive Markstein number flames. PMID:24125342

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  1. Flame Design: A Novel Approach Developed to Produce Clean, Efficient Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Axelbaum, Richard L.; Urban, David L.; Sunderland, Peter B.; Chao, Beei-Huan

    2000-01-01

    Soot formation and flame extinction are vital concerns in the combustion of fossil fuels. In particular, soot is responsible for pollutant emissions, and extinction can cause inefficient or unstable burning. Normal-gravity experiments have demonstrated that flames can be designed to improve both characteristics by redirecting some or all of the nitrogen from the oxidizer into the fuel. Such nitrogen exchange can produce permanently blue flames, which are soot free under all possible flame conditions. Furthermore, this approach can lead to stronger, extinction-resistant flames. Past investigations of nitrogen exchange were unable to identify the physical mechanisms responsible for its benefits because these mechanisms cannot be isolated when normal-gravity flames are studied. In contrast, the Diffusion Flame Extinction and Soot Inception (DESI) experiment considers spherical flames, where nearly perfect spherical symmetry affords new levels of control. Because of buoyancy, spherical flames cannot be created in Earth s gravity. DESI was conceived by principal investigator Professor R.L. Axelbaum of Washington University in St. Louis. Tests to date have utilized the 2.2-Second Drop Tower at the NASA Glenn Research Center at Lewis Field. The experiment is slated for testing aboard the International Space Station in a few years. Two mechanisms have been proposed to explain the connection between nitrogen exchange and permanently blue flames. These are the structure (chemical effects) and hydrodynamics (flow direction and speed). In normal-gravity flames, the structure and hydrodynamics are coupled, since nitrogen exchange simultaneously modifies both. Spherical microgravity flames, on the other hand, allow independent control of these factors. Specifically, structure can be modified via nitrogen exchange, and flow direction can be reversed by swapping the ambient and burner-feed gases. In DESI, these variations can be accomplished without changing the theoretical flame temperature.

  2. Wide-field stellar photometry in Piwnice Observatory

    E-print Network

    Gracjan Maciejewski

    2007-12-17

    In this paper research projects based on the wide-field CCD photometry performed in Piwnice Observatory are discussed. The used telescopes, as well as dedicated software pipeline for data reduction are presented. The prospects for collaboration between Polish and Bulgarian institutes in the field of wide-field photometry are also discussed.

  3. DOPHOT, a CCD photometry program: Description and tests

    Microsoft Academic Search

    Paul L. Schechter; Mario Mateo; Abhijit Saha

    1993-01-01

    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

  4. Photometry of Mercury from SOHO\\/LASCO and Earth

    Microsoft Academic Search

    Anthony Mallama; Dennis Wang; Russell A. Howard

    2002-01-01

    CCD observations of Mercury were obtained with the large angle spectrometric coronograph (LASCO) on the solar and heliospheric observatory spacecraft, near superior and inferior solar conjunctions. Whole disk photometry was extracted from the orange and blue filter images and transformed to V magnitudes on the UBV system. The LASCO data were combined with ground-based, V-filter photometry acquired at larger elongation

  5. JHK photometry of selected Trojan and Hilda asteroids

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  6. Observations on the leading edge in lifted flame stabilization

    Microsoft Academic Search

    K. A. Watson; K. M. Lyons; J. M. Donbar; C. D. Carter

    1999-01-01

    The objective of this paper is to report some of the first experimental evidence for the “leading edge” flame as the stabilization mechanism in lifted jet diffusion flames [1–5]. CH fluorescence has been used to indicate the flame front location (i.e., region of chemical reaction) and thereby characterize features of the stabilization region [5, 6]. The “leading edge” flame phenomenon

  7. Flaming: More than a Necessary Evil for Academic Mailing Lists?

    ERIC Educational Resources Information Center

    Wang, Hongjie

    1996-01-01

    States that although Internet "gurus" advocate that users refrain from "flaming," in fact, flaming permeates the Internet. Explores the nature of flaming in its characteristics and forms as seen in academic discussion groups. Argues that flaming educates the ignorant, tames the uncouth, and promotes effective communication. (PA)

  8. Identification of low-dimensional manifolds in turbulent flames

    E-print Network

    Identification of low-dimensional manifolds in turbulent flames A. Parente a,*, J.C. Sutherland b Diotisalvi 2, Pisa I-56126, Italy b Department of Chemical Engineering, University of Utah, Salt Lake City for a simple CO/H2/N2 jet flame and for a CH4 piloted flame (TNF Flame F). Results of the global PCA analysis

  9. Introduction HYBRID FLAME: combustion of a combustible gas and

    E-print Network

    Barthelat, Francois

    Future Work Verify data obtained for methane and aluminum flame Run test with constant equivalence ratioIntroduction HYBRID FLAME: combustion of a combustible gas and dust particles Hybrid Flames: occur may propagate at given conditions Quenching distances: important parameter for flame ignition

  10. MIXING AND NOZZLE GEOMETRY EFFECTS ON FLAME STRUCTURE AND STABILITY

    Microsoft Academic Search

    FAWZY EL-MAHALLAWY; AHMED ABDELHAFEZ; MOHY S. MANSOUR

    2007-01-01

    Flame stability and mean structure of partially premixed flames have been investigated under the effect of the level of partial premixing and nozzle cone angle. The stability curves and maps of the mean flame structure based on temperature and CO and O2 concentrations measurements in some selected partially premixed flames in the thin reaction zones regime are presented and discussed.

  11. Laminar Soot Processes Experiment Shedding Light on Flame Radiation

    NASA Technical Reports Server (NTRS)

    Urban, David L.

    1998-01-01

    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.

  12. Study of a Diffusion Flame in a Stretched Vortex

    Microsoft Academic Search

    ANN R.. KARAGOZIAN; FRANK E. MARBLE

    1986-01-01

    The time dependent interaction of a laminar diffusion flame with a single plane vortex and with a stretched line vortex is examined with the aim of determining the flame configuration and the augmentation to the reactant consumption rate resulting from the interaction. Elements of the resulting curved flame sheets behave essentially as isolated flamesuntil the neighboring flame sheets become so

  13. Visible and infrared photometry of Kuiper Belt objects: searching for evidence of trends

    E-print Network

    Sheppard, Scott S.

    Visible and infrared photometry of Kuiper Belt objects: searching for evidence of trends Neil Mc. © 2003 Elsevier Science (USA). All rights reserved. Keywords: Kuiper Belt objects; Photometry; Infrared

  14. Progress and challenges in swirling flame dynamics

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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.

  15. Thermonuclear Quenching in Flame-Vortex Interactions

    NASA Astrophysics Data System (ADS)

    Zingale, M.; Niemeyer, J. C.; Timmes, F. X.; Dursi, L. J.; Calder, A. C.; Fryxell, B.; Olson, K.; Ricker, P.; Rosner, R.; Truran, J. W.; Tufo, H.; MacNeice, P.

    2000-12-01

    A Type Ia supernova begins as a flame, deep in the interior of a white dwarf. At some point, the burning may undergo a deflagration-detonation transition (DDT). Some mechanisms for this transition require a preconditioned region in the star. As the flame propagates down the temperature gradient, the speed increases, and the transition to a detonation may occur (see Khokhlov et al. 1997; Niemeyer & Woosley 1997). For this to happen, the region must be free of any temperature fluctuations -- any burning must be quenched. We show direct numerical simulations of flame-vortex interactions in order to understand quenching of thermonuclear flames. The key question is -- can a thermonuclear flame be quenched? If not, the DDT mechanisms that demand the finely tuned preconditioned region are unlikely to work. In these simulations, we pass a steady-state laminar flame through a vortex pair. The vortex pair represents the most severe strain the flame front will encounter inside the white dwarf. We perform a parameter study, varying the speed and size of the vortex pair, in order to understand the quenching process. These simulations were carried out with the FLASH Code. This work is supported by the Department of Energy under Grant No. B341495 to the Center for Astrophysical Thermonuclear Flashes at the University of Chicago. These calculations were performed on the Nirvana Cluster at Los Alamos National Laboratory

  16. Particle clustering in turbulent premixed flames

    NASA Astrophysics Data System (ADS)

    F, Battista; F, Picano; G, Troiani; M, Casciola C.

    2011-12-01

    Transport of inertial particles in turbulent reacting flows is frequent in a number of engineering and natural systems. Aim of this work is to illustrate the effect of the fluctuating instantaneous flame front on the particle spatial distribution. To this purpose a Direct Numerical Simulation of a Bunsen premixed flame seeded with small inertial particles is performed. The flamelet Stokes number Stfl, defined as the ratio between the particle relaxation time and the flame front time scale, is found to be the proper parameter to characterize the particle dynamics in a premixed flame. Clustering of inertial particles is apparent, especially beyond the flame front. The amount of particle segregation is here quantified by the clustering index and two distinct contributions are found to interplay. The first is independent of the particle inertia and affects also tracers. Actually it is associated to the abrupt variation of the particle concentration induced by the fluid expansion across the flame front. The second effect is mainly due to the time lag associated to the particle inertia that, in proximity of the front, affects both the mean and the fluctuation of the particle number in a fixed volume. The global effect results in an intense clustering of the inertial particles in the flame brush region with a maximum for particles with flamelet Stokes number: Stfl = Script O(1).

  17. Ten Recent Enhancements To Aperture Photometry Tool

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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.

  18. Flame speed and self-similar propagation of expanding turbulent premixed flames.

    PubMed

    Chaudhuri, Swetaprovo; Wu, Fujia; Zhu, Delin; Law, Chung K

    2012-01-27

    In this Letter we present turbulent flame speeds and their scaling from experimental measurements on constant-pressure, unity Lewis number expanding turbulent flames, propagating in nearly homogeneous isotropic turbulence in a dual-chamber, fan-stirred vessel. It is found that the normalized turbulent flame speed as a function of the average radius scales as a turbulent Reynolds number to the one-half power, where the average radius is the length scale and the thermal diffusivity is the transport property, thus showing self-similar propagation. Utilizing this dependence it is found that the turbulent flame speeds from the present expanding flames and those from the Bunsen geometry in the literature can be unified by a turbulent Reynolds number based on flame length scales using recent theoretical results obtained by spectral closure of the transformed G equation. PMID:22400849

  19. Studies of Premixed Laminar and Turbulent Flames at Microgravity

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  20. Premixed-flame shapes and polynomials

    NASA Astrophysics Data System (ADS)

    Denet, Bruno; Joulin, Guy

    2015-02-01

    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.

  1. Clothes That Care -- Flame Resistant Protection.

    E-print Network

    Kerbel, Claudia

    1980-01-01

    Resistant Protection Claudia Kerbel * Concern for a safer environment has led to changes in many of the everyday products we use , including clothing . In the' past dec ade, flame-resistant (FR) garments and fabrics have become more available than ever... before. Consumers can now choose from a growing variety of styles in children 's and adult's sizes . Home sew ers can buy fabrics, threads and trims that are flame resistant. Since many of the finishes and fibers are new, some flame-resistant clothing...

  2. Aromatics oxidation and soot formation in flames

    SciTech Connect

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

    1993-12-01

    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.

  3. Heat release and flame structure measurements of self-excited acoustically-driven premixed methane flames

    SciTech Connect

    Kopp-Vaughan, Kristin M.; Tuttle, Steven G.; Renfro, Michael W. [Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Rd, U-3139, Storrs, CT 06269 (United States); King, Galen B. [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2009-10-15

    An open-open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane-air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re = 1780-4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube combustor. This coupling creates sustainable self-excited oscillations in flame front area and shape. The period of the oscillations occur at the resonant frequency of the combustion chamber when the flame is placed {proportional_to}1/4 of the distance from the bottom of the tube. In this investigation, the shape of these acoustically-driven flames is measured by employing both OH planar laser-induced fluorescence (PLIF) and chemiluminescence imaging and the images are correlated to simultaneously measured pressure in the combustor. Past research on acoustically perturbed flames has focused on qualitative flame area and heat release relationships under imposed velocity perturbations at imposed frequencies. This study reports quantitative empirical fits with respect to pressure or phase angle in a self-generated pressure oscillation. The OH-PLIF images were single temporal shots and the chemiluminescence images were phase averaged on chip, such that 15 exposures were used to create one image. Thus, both measurements were time resolved during the flame oscillation. Phase-resolved area and heat release variations throughout the pressure oscillation were computed. A relation between flame area and the phase angle before the pressure maximum was derived for all flames in order to quantitatively show that the Rayleigh criterion was satisfied in the combustor. Qualitative trends in oscillating flame area were found with respect to feed tube flow rates. A logarithmic relation was found between the RMS pressure and both the normalized average area and heat release rate for all flames. (author)

  4. Flame resistant nontoxic polymer development

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    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.

  5. TERMS PHOTOMETRY OF KNOWN TRANSITING EXOPLANETS

    SciTech Connect

    Dragomir, Diana; Kane, Stephen R.; Ciardi, David R.; Gelino, Dawn M.; Payne, Alan; Ramirez, Solange V.; Von Braun, Kaspar; Wyatt, Pamela [NASA Exoplanet Science Institute, Caltech, MS 100-22, Pasadena, CA 91125 (United States); Pilyavsky, Genady; Mahadevan, Suvrath; Wright, Jason T. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Zachary Gazak, J. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Rabus, Markus, E-mail: diana@phas.ubc.ca [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)

    2011-10-15

    The Transit Ephemeris Refinement and Monitoring Survey 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 toward planets not known to transit, but a small sample of our targets consists of known transiting systems. Here we present precision photometry for six WASP (Wide Angle Search for Planets) planets acquired during their transit windows. We perform a Markov Chain Monte Carlo 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 six systems.

  6. Techniques for Automated Single-Star Photometry

    NASA Technical Reports Server (NTRS)

    Henry, Gregory W.

    2001-01-01

    Tennessee State University operates several automatic photoelectric telescopes (APTs) located at Fairborn Observatory in the Patagonia Mountains of southern Arizona. The APTs are dedicated to photometric monitoring programs that would be expensive and difficult to accomplish without the advantages of automation. I review the operation of two of the telescopes (a 0.75- and 0.80-meter (m) APT) and the quality-control techniques that result in the routine acquisition of single-star differential photometry with a precision of 0.001 mag for single observations and 0.0001 - 0.0002 mag for seasonal means. I also illustrate the capabilities of the APTS with sample results from a program to measure luminosity cycles in sun-like stars and a related program to search for the signatures of extrasolar planets around these stars.

  7. Photometry Analysis using Oukaimeden IRIS Data

    NASA Astrophysics Data System (ADS)

    Benkhaldoun, Z.; Siher, E.

    Since 1988, a Moroccan astronomers began a site evaluation of the Oukaimeden (2600m) in the mountain ATLAS chain. The site has been selected, in parallel, for installation of IRIS helioseismograph as one of the seven stations by the world. The Oukaimeden appeared to be a good site, when compared to other former observatories, in term of daytime sky transparency, photometry and extinction and ground climatology. We present here a results of one year (1997) clouds cover, extinction coefficient and transparency fluctuation's measurement, using a total solar intensity provided by IRIS helioseismograph. We also compared the results with the same works mad by Hill et al (1994) in the GONG site testing campaign and Benkhaldoun et al (1993) using a simple flux integration photometer.

  8. JHK photometry of WD 0950+139

    NASA Astrophysics Data System (ADS)

    Fulbright, Michael S.; Liebert, James

    1993-06-01

    We present results from several nights of JHK photometry of the hot DA white dwarf 0950+139. It has a significant infrared excess over the expected flux from the white dwarf alone, confirming a previous finding by Zuckerman et al. (1991). The infrared excess corresponds to an upper limit on the spectral type of a companion of M4 V. We consider two models for the infrared excess of 0950+139, involving either a mid-M dwarf or a substellar object as a close companion. If 0950+139 is a close binary with a period of days, we predict that we should detect variation in the infrared fluxes due to reprocessing by the companion. Such variation was not detected, which may mean the system has a different orbital period or an inclination near 0 deg.

  9. JHK photometry of WD 0950+139

    NASA Technical Reports Server (NTRS)

    Fulbright, Michael S.; Liebert, James

    1993-01-01

    We present results from several nights of JHK photometry of the hot DA white dwarf 0950+139. It has a significant infrared excess over the expected flux from the white dwarf alone, confirming a previous finding by Zuckerman et al. (1991). The infrared excess corresponds to an upper limit on the spectral type of a companion of M4 V. We consider two models for the infrared excess of 0950+139, involving either a mid-M dwarf or a substellar object as a close companion. If 0950+139 is a close binary with a period of days, we predict that we should detect variation in the infrared fluxes due to reprocessing by the companion. Such variation was not detected, which may mean the system has a different orbital period or an inclination near 0 deg.

  10. Photometry of small asteroids and cometary cores

    NASA Technical Reports Server (NTRS)

    Gehrels, T.; Wisniewski, W. Z.; Zellner, B. H.

    1986-01-01

    The first asteroid lightcurves have now been made with a new technique of CCD photometry. The apparent magnitude is fainter (V>17) than what can be done with the 1.52-m Catalina reflector with a photomultiplier photometer. With the CCD system, however, the lightcurve shows remarkably good repetition; finding the asteroid is, of course, no problem as the object is recognized later by its motion on the CCD. Asteroid 1985RV has a lightcurve amplitude of about 0.4 mag and its period of rotation P = 4.0 hours, on the assumption that the lightcurve has two maxima and two minima as is the case for nearly all other asteroids. The diameter is about 3 km. 1985RV is a first example of results that are being obtained on asteroids and comets with CCD in the Catalinas, Kitt Peak, and Cerro Tololo.

  11. Gaia photometry: methods, performances and problems

    NASA Astrophysics Data System (ADS)

    Jordi, C.

    2011-02-01

    We present the pipeline processing (for photometry and spectrophotometry) primarily based on the comparison of the observation with a prediction from the spectral energy distribution and total flux of the source and a set of parameters modelling the instrument properties observation-to-observation. Experiments on G white light calibration yield residuals well below one mmag for most of the cases, but for extreme colour stars. For blue and red spectra, tests up to now yield residuals significantly smaller than the observational noise, except for sources with very strong spectral features, which present flux residuals of 2-3% in the spectral lines (at G = 15). Work continues to account for all instrumental effects, to add complexity to the instrument model and to improve the processing pipeline.

  12. The influences of electric fields on soot formation and flame structure of diffusion flames

    NASA Astrophysics Data System (ADS)

    Xie, Lin; Kishi, Takeyuki; Kono, Michikata

    1993-12-01

    The influences of DC and AC electric fields, at frequencies up to 1.48 MHz and the maximum strength of about 6 kV/cm, on soot formation and flame structure were investigated using a counterflow type acetylene diffusion flame. The distributions of flame luminosity, soot volume fraction, flame temperature and OH concentration in flame were measured by non-invasive detection methods. Under the influence of electric fields, the changes in distribution of the soot volume fraction were confirmed. Electric fields of high frequency and high intensity reduced the soot volume fraction, whereas other electric fields increased it. The maximum values of flame temperature and OH concentration decreased. In the relationship between the maximum value of the soot volume fraction and the maximum temperature, the maximum soot volume fraction showed both increase and decrease with maximum temperatures depending on the frequencies and intensities of the electric fields, and both of them occurred at temperatures lower than 1900 K. The production of the incipient particles seemed to be the dominant process controlling the soot volume fraction due to the electric fields. The luminosity of a sooting diffusion flame was found to depend on the volume fraction and temperature of the soot particles in the flame. As for the behavior of the flame in the electric fields, the ionic wind effect was not found to be dominant in the present work, and the result of the previous simulation based on the ionic wind theory was not consistent with the present experimental results.

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

    SciTech Connect

    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

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  15. Partially premixed flames in stagnating turbulence: The merging of planar triple flames

    SciTech Connect

    Bray, Ken [Cambridge University, Cambridge CB2 1PZ (United Kingdom); Champion, Michel [Laboratoire de Combustion et de Detonique, UPR9028 CNRS, ENSMA, 86961 Futuroscope (France); Libby, Paul A. [University of California San Diego, La Jolla, CA 92093 (United States)

    2008-07-15

    The aim of this work, which takes a RANS perspective, is to consider the prospect of establishing a planar turbulent triple flame whose mean consists of two parallel premixed flame brushes separated by a nonpremixed flame brush. Experiments involving a counterflow between fuel-rich and fuel-lean turbulent streams are considered. A correlation of published experimental data is used to estimate premixed turbulent flame brush locations and brush thicknesses. Previously validated model calculations then allow an estimate to be made of the thickness of a central nonpremixed flame or mixing layer, a thickness which is shown to be strongly influenced by flame-turbulence interactions in the premixed flames. This thickness turns out to be orders-of-magnitude greater than the width of the hot burned gas region between the two premixed flames strongly suggesting that the three reacting flow regions will merge with each other. It is concluded that unlike the corresponding laminar counterflow planar turbulent triple flames will be difficult to establish in laboratory scale experiments. (author)

  16. Laser speckle photometry: contactless nondestructive testing technique

    NASA Astrophysics Data System (ADS)

    Cikalova, Ulana; Nicolai, Juergen; Bendjus, Beatrice; Schreiber, Juergen

    2012-10-01

    Laser Speckle Photometry (LSP) is a newly developed contactless, fast and completely optical nondestructive testing method based on the detection and analysis of thermally or mechanically activated characteristic speckle dynamics. The heat propagation or tension process causes locally different degrees of thermal/mechanical expansion, which generates local and time-dependent strain fields, resulting in a local displacement of material surface. During this process, the normal surface slope and absolute height of the microscopic and mesoscopic surface segments, especially at rough sample surfaces, is transformed. These spatiotemporal changes include information about the material structure and conditions. Therefore, the proposed measurement technique includes a pulsed heating source for sample activation, a temperature detection of the sample at the measurement location in a distance from the heading point, a continuous wave laser for sample irradiation and activation of speckle patterns at the measurement point, and in addition, a fast CCD camera for the detection of the speckle movement during heat propagation at the measurement location. Laser Speckle Photometry can be used for evaluating material properties, such as hardness and porosity. The approach is based on the estimation of the "Speckle Thermal Diffusivity" parameter K, that can be determined using the thermal diffusion equation and the modified correlation function from the pixel intensity of the speckle image variations during thermal activation. After testing, the correlation between parameter K and hardness, and porosity respectively, was found. Furthermore, mechanical material stress changes, also at elevated operating temperatures, can be estimated by the presented technique using the calculated parameter K. In this case, the thermal excitation will be partially replaced by mechanical activation, such as the tension process. The technique of LSP and the results of calibration experiments are presented in this paper.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  18. Measured lengths of supersonic hydrogen-air jet flames—Compared to subsonic flame lengths—and analysis

    Microsoft Academic Search

    James F. Driscoll; Hwanil Huh; Youngbin Yoon; Jeffrey Donbar

    1996-01-01

    Measurements of flame length are reported that help to quantify the overall fuel-air mixing process that occurs within a jet-like flame in the supersonic regime. A nonpremixed, turbulent, hydrogen-air jet flame is stabilized along the axis of a Mach 2.2 coflowing air stream. Supersonic flame lengths are compared to measured lengths of subsonic hydrogen-air flames with coflow that were stabilized

  19. Prediction of ionic structure in hydrocarbon flames

    SciTech Connect

    Eraslan, A.N.

    1987-01-01

    The objective of this research is to model the appearance and behavior of combustion-generated ions in hydrocarbon flames. An understanding of ionic phenomena is important to the development of advanced combustion technology including electrical control of flame structure and suppression of soot formation. Computer models were developed to evaluate the formation and behavior of ions in acetylene flames. The results of computations are compared to experimental data of other researchers. Several important qualitative features were successfully modeled. Peak ion concentrations of 10/sup 9/ to 10/sup 11/ cm/sup -3/ are consistent with experimental measurements. The ratio of large ions to small ions increases sharply as the flame is made richer. The build-up and decay rates of ions observed experimentally are predicted by the model.

  20. 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...

  1. Theory of DDT in unconfined flames

    E-print Network

    Khokhlov, A M; Wheeler, J C; Wheeler, J Craig

    1996-01-01

    This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames which is relevant both to problems of terrestrial combustion and to thermonuclear burning in Type Ia supernovae. Two basic assumuptions are made: 1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and 2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, the laminar flame speed, and the laminar flame thickness in the reactive gas. This approach gives a lower-bound criterion for DDT for conditions where shock preheating, wall effects, and interactions with obstacles are absent. Regions in parameter space where unconfined DDT can and cannot occur are determined. A subsequent paper will address these issues specifically in the astrophysical context.

  2. Theory of DDT in Unconfined Flames

    E-print Network

    A. M. Khokhlov; E. S. Oran; J. Craig Wheeler

    1996-05-15

    This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames which is relevant both to problems of terrestrial combustion and to thermonuclear burning in Type Ia supernovae. Two basic assumuptions are made: 1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and 2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, the laminar flame speed, and the laminar flame thickness in the reactive gas. This approach gives a lower-bound criterion for DDT for conditions where shock preheating, wall effects, and interactions with obstacles are absent. Regions in parameter space where unconfined DDT can and cannot occur are determined. A subsequent paper will address these issues specifically in the astrophysical context.

  3. Dynamics and structure of turbulent premixed flames

    NASA Technical Reports Server (NTRS)

    Bilger, R. W.; Swaminathan, N.; Ruetsch, G. R.; Smith, N. S. A.

    1995-01-01

    In earlier work (Mantel & Bilger, 1994) the structure of the turbulent premixed flame was investigated using statistics based on conditional averaging with the reaction progress variable as the conditioning variable. The DNS data base of Trouve and Poinsot (1994) was used in this investigation. Attention was focused on the conditional dissipation and conditional axial velocity in the flame with a view to modeling these quantities for use in the conditional moment closure (CMC) approach to analysis of kinetics in premixed flames (Bilger, 1993). Two remarkable findings were made: there was almost no acceleration of the axial velocity in the flame front itself; and the conditional scalar dissipation remained as high, or higher, than that found in laminar premixed flames. The first finding was surprising since in laminar flames all the fluid acceleration occurs through the flame front, and this could be expected also for turbulent premixed flames at the flamelet limit. The finding gave hope of inventing a new approach to the dynamics of turbulent premixed flames through use of rapid distortion theory or an unsteady Bernoulli equation. This could lead to a new second order closure for turbulent premixed flames. The second finding was contrary to our measurements with laser diagnostics in lean hydrocarbon flames where it is found that conditional scalar dissipation drops dramatically below that for laminar flamelets when the turbulence intensity becomes high. Such behavior was not explainable with a one-step kinetic model, even at non-unity Lewis number. It could be due to depletion of H2 from the reaction zone by preferential diffusion. The capacity of the flame to generate radicals is critically dependent on the levels of H2 present (Bilger, et al., 1991). It seemed that a DNS computation with a multistep reduced mechanism would be worthwhile if a way could be found to make this feasible. Truly innovative approaches to complex problems often come only when there is the opportunity to work close at hand with the (in this case numerical) experimental data. Not only can one spot patterns and relationships in the data which could be important, but one can also get to know the limitations of the technique being used, so that when the next experiment is being designed it will address resolvable questions. A three-year grant from the Australian Research Council has enabled us to develop a small capability at the University of Sydney to work on DNS of turbulent reacting flow, and to analyze data bases generated at CTR. Collaboration between the University of Sydney and CTR is essential to this project and finding a workable modus operandum for this collaboration, given the constraints involved, has been a major objective of the past year's effort. The overall objectives of the project are: (1) to obtain a quantitative understanding of the dynamics of turbulent premixed flames at high turbulence levels with a view to developing improved second order closure models; and (2) to carry out new DNS experiments on turbulent premixed flames using a carefully chosen multistep reduced mechanism for the chemical kinetics, with a view to elucidating the laser diagnostic findings that are contrary to the findings for DNS using one-step kinetics. In this first year the objectives have been to make the existing CTR data base more accessible to coworkers at the University of Sydney, to make progress on understanding the dynamics of the flame in this existing CTR data base, and to carefully construct a suitable multistep reduced mechanism for use in a new set of DNS experiments on turbulent premixed flames.

  4. 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...

  5. 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...

  6. Light collection device for flame emission detectors

    DOEpatents

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

    1990-01-01

    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.

  7. Prediction of propagating methane--air flames

    Microsoft Academic Search

    L. D. Smoot; W. C. Hecker; G. A. Williams

    1976-01-01

    The kinetics and propagation of laminar methane-air flames were studied using a one-dimensional, flame propagation model. The model is based on a numerical, unsteady-state solution of transformed species and energy conservation equations using explicit techniques for diffusion terms and linearized, implicit techniques for kinetic terms. A methane-oxygen kinetic mechanism consisting of 28 elementary reactions was postulated and used in the

  8. Aromatics oxidation and soot formation in flames

    SciTech Connect

    Howard, J.B.

    1989-01-01

    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.

  9. Effects of compositional fluctuations on premixed flames

    Microsoft Academic Search

    R. W. Grout; N. Swaminathan; R. S. Cant

    2009-01-01

    Fully compressible direct numerical simulation (DNS) is used to study the behaviour of a stratified turbulent premixed flame in the wrinkled flamelet regime (Re? = 38, u?\\/SL = 0.7, Da = 2.3) with reduced multi-step chemistry. A laminar premixed flame in an initially quiescent domain propagates into a turbulent flow so that the scalar and velocity fields are correctly coupled.

  10. Nonlinear evolution of hydrodynamically unstable premixed flames

    NASA Astrophysics Data System (ADS)

    Rastigejev, Y.; Matalon, M.

    2006-05-01

    The nonlinear evolution of hydrodynamically unstable flames is studied numerically within the context of a hydrodynamic model, where the flame is confined to a surface separating the fresh mixture from the hot combustion products. The numerical scheme uses a variable-density Navier Stokes solver in conjunction with a level-set front-capturing technique for the numerical treatment of the propagating front. Unlike most previous studies that were limited to the weakly nonlinear Michelson Sivashinsky equation valid for small density changes, the present work places no restriction on the density contrast and thus elucidates the effect of thermal expansion on flame dynamics. It is shown that the nonlinear development leads to corrugated flames with a transverse dimension that is significantly larger than the wavelength corresponding to the most amplified disturbance predicted by the linear theory, and which is determined by the overall size of the system. The flame structure consists of wide troughs and relatively narrow cusp-like crests, and propagates ‘steadily’ at a constant speed, larger than the speed of a planar flame. The propagation speed increases as the cells widen, but eventually reaches a constant value that remains independent of the mixture's composition and of the transverse length. The dependence of the incremental increase in speed on thermal expansion is found to be nearly linear; for realistic values of thermal expansion it may be as large as 15% to 20%. In sufficiently large domains the dynamics is found to be extremely sensitive to background noise that may result, for example, from weak turbulence. Small-scale wrinkles appear sporadically on the flame surface and travel along its surface, causing a significant increase in the overall speed of propagation, up to twice the laminar flame speed.

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

    NASA Astrophysics Data System (ADS)

    Rosenberg, David Ari

    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.

  12. Automated surface photometry for the Coma Cluster galaxies: The catalog

    NASA Technical Reports Server (NTRS)

    Doi, M.; Fukugita, M.; Okamura, S.; Tarusawa, K.

    1995-01-01

    A homogeneous photometry catalog is presented for 450 galaxies with B(sub 25.5) less than or equal to 16 mag located in the 9.8 deg x 9.8 deg region centered on the Coma Cluster. The catalog is based on photographic photometry using an automated surface photometry software for data reduction applied to B-band Schmidt plates. The catalog provides accurate positions, isophotal and total magnitudes, major and minor axes, and a few other photometric parameters including rudimentary morphology (early of late type).

  13. The structure of particle cloud premixed flames

    NASA Technical Reports Server (NTRS)

    Seshadri, K.; Berlad, A. L.

    1992-01-01

    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.

  14. Formation and properties of distributed flames

    NASA Astrophysics Data System (ADS)

    Poludnenko, Alexei; Gamezo, Vadim; Oran, Elaine

    2008-11-01

    Interaction of flames with turbulence is a ubiquitous process encountered in a wide variety of systems, ranging from terrestrial flames to thermonuclear burning fronts in supernovae. Burning can alter the turbulent field by injecting additional energy on multiple scales thereby modifying its spectral energy distribution. On the other hand, turbulence itself can have pronounced effect on the flame changing its morphology, properties, etc. In this work we present results of detailed numerical and theoretical modeling of the interaction of flames in stoichiometric methane-air and hydrogen-air mixtures with turbulence of varying intensity and spectrum. We demonstrate the transition with increasing turbulent intensity from the laminar flame to the corrugated flamelet and finally to the distributed reaction zone. The latter represents a quasi-steady-state propagating burning front in which thermal conduction and species diffusion are mediated by turbulent transport. We discuss properties of such flames and their potential implications for deflagration-to-detonation transition both in confined and unconfined systems.

  15. Premixed Turbulent Flame Propagation in Microgravity

    NASA Technical Reports Server (NTRS)

    Menon, Suresh

    1999-01-01

    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.

  16. An elementary discussion of propellant flame geometry

    SciTech Connect

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

    1999-05-01

    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.

  17. NO concentration imaging in turbulent nonpremixed flames

    SciTech Connect

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

    1993-12-01

    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.

  18. Characterisation of an oxy-coal flame through digital imaging

    SciTech Connect

    Smart, John; Riley, Gerry [RWE npower plc, Windmill Hill Business Park, Whitehill Way, Swindon SN5 6PB (United Kingdom); Lu, Gang; Yan, Yong [Instrumentation, Control and Embedded Systems Research Group, School of Engineering and Digital Arts, University of Kent, Canterbury, Kent CT2 7NT (United Kingdom)

    2010-06-15

    This paper presents investigations into the impact of oxy-fuel combustion on flame characteristics through the application of digital imaging and image processing techniques. The characteristic parameters of the flame are derived from flame images that are captured using a vision-based flame monitoring system. Experiments were carried out on a 0.5 MW{sub th} coal combustion test facility. Different flue gas recycle ratios and furnace oxygen levels were created for two different coals. The characteristics of the flame and the correlation between the measured flame parameters and corresponding combustion conditions are described and discussed. The results show that the flame temperature decreases with the recycle ratio for both test coals, suggesting that the flame temperature is effectively controlled by the flue gas recycle ratio. The presence of high levels of CO{sub 2} at high flue gas recycle ratios may result in delayed combustion and thus has a detrimental effect on the flame stability. (author)

  19. A Computational Investigation of Sooting Limits of Spherical Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  20. Blowoff dynamics of bluff body stabilized turbulent premixed flames

    SciTech Connect

    Chaudhuri, Swetaprovo; Kostka, Stanislav; Renfro, Michael W.; Cetegen, Baki M. [Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Road, U-3139, Storrs, CT 06269 (United States)

    2010-04-15

    This article concerns the flame dynamics of a bluff body stabilized turbulent premixed flame as it approaches lean blowoff. Time resolved chemiluminescence imaging along with simultaneous particle image velocimetry and OH planar laser-induced fluorescence were utilized in an axisymmetric bluff body stabilized, propane-air flame to determine the sequence of events leading to blowoff and provide a quantitative analysis of the experimental results. It was found that as lean blowoff is approached by reduction of equivalence ratio, flame speed decreases and the flame shape progressively changes from a conical to a columnar shape. For a stably burning conical flame away from blowoff, the flame front envelopes the shear layer vortices. Near blowoff, the columnar flame front and shear layer vortices overlap to induce high local stretch rates that exceed the extinction stretch rates instantaneously and in the mean, resulting in local flame extinction along the shear layers. Following shear layer extinction, fresh reactants can pass through the shear layers to react within the recirculation zone with all other parts of the flame extinguished. This flame kernel within the recirculation zone may survive for a few milliseconds and can reignite the shear layers such that the entire flame is reestablished for a short period. This extinction and reignition event can happen several times before final blowoff which occurs when the flame kernel fails to reignite the shear layers and ultimately leads to total flame extinguishment. (author)

  1. The Effects of Gravity on Wrinkled Laminar Flames

    NASA Technical Reports Server (NTRS)

    Kostiuk, Larry W.; Zhou, Liming; Cheng, Robert K.

    1993-01-01

    The effects of gravity are significant to the dynamics of idealized unconfined open premixed flames. Moderate to low turbulence Reynolds number flames, i.e., wrinkled laminar flames, of various unconfined geometries have been used extensively for investigating fundamental processes of turbulent flame propagation and to validate theoretical models. Without the wall constraints, the flames are free to expand and interact with surrounding ambient air. The flow field in which the flame exists is determined by a coupling of burner geometry, flame orientation and the gravity field. These complex interactions raise serious questions regarding the validity of comparing the experimental data of open flames with current theoretical and numerical models that do not include the effects of gravity nor effects of the larger aerodynamic flowfield. Therefore, studies of wrinkled laminar flame in microgravity are needed for a better understanding of the role of gravity on flame characteristics such as the orientation, mean aerodynamics stretch, flame wrinkle size and burning rate. Our approach to characterize and quantify turbulent flame structures under microgravity is to exploit qualitative and quantitative flow visualization techniques coupled with video recording and computer controlled image analysis technologies. The experiments will be carried out in the 2.2 second drop tower at the NASA Lewis Research Center. The longest time scales of typical wrinkled laminar flames in the geometries considered here are in the order of 10 msec. Hence, the duration of the drop is sufficient to obtain the amount of statistical data necessary for characterize turbulent flame structures.

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

    SciTech Connect

    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

    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)

  3. A filtered flame approach for simulation of unsteady laminar premixed flames

    Microsoft Academic Search

    C. Duwig

    2009-01-01

    The simulation of laminar flames consists of capturing the evolution of a very large number of species that may react within a broad range of time scales. It results in a highly non-linear stiff numerical problem that requires large computational resources. In the present paper, an alternative approach for the simulation of unsteady premixed flames is proposed. The approach focuses

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

    E-print Network

    Large eddy simulation of a turbulent nonpremixed piloted methane jet flame (Sandia Flame D) M.R.H. Sheikhia,*, T.G. Drozdaa , P. Givia , F.A. Jaberib , S.B. Popec a Department of Mechanical Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA b Department of Mechanical Engineering, Michigan State

  5. Modeling Candle Flame Behavior In Variable Gravity

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  6. L' AND M' Photometry Of Ultracool Dwarfs

    NASA Technical Reports Server (NTRS)

    Marley, M. S.; Tsvetanov, Z. I.; Vrba, F. J.; Henden, A. A.; Luginbuhl, C. B.

    2004-01-01

    We have compiled L' (3.4-4.1 microns) and M' (4.6- 4.8 microns) photometry of 63 single and binary M, L, and T dwarfs obtained at the United Kingdom Infrared Telescope using the Mauna Kea Observatory filter set. This compilation includes new L' measurements of eight L dwarfs and 13 T dwarfs and new M' measurements of seven L dwarfs, five T dwarfs, and the M1 dwarf Gl 229A. These new data increase by factors of 0. 6 and 1.6, respectively, the numbers of ultracool dwarfs T (sub eff) photometry, and trigonometric parallaxes are available, and we estimate these quantities for nine other dwarfs whose parallaxes and flux-calibrated spectra have been obtained. BC(SUB K) is a well-behaved function of near-infrared spectral type with a dispersion of approx. 0.1 mag for types M6-T5 it is significantly more scattered for types T5-T9. T (sub eff) declines steeply and monotonically for types M6-L7 and T4-T9, but it is nearly constant at approx. 1450 K for types L7-T4 with assumed ages of approx. 3 Gyr. This constant T(sub eff) is evidenced by nearly unchanging values of L'-M' between types L6 and T3. It also supports recent models that attribute the changing near-infrared luminosities and spectral features across the L-T transition to the rapid migration, disruption, and/or thinning of condensate clouds over a narrow range of T(sub eff). The L' and M' luminosities of early-T dwarfs do not exhibit the pronounced humps or inflections previously noted in l through K bands, but insufficient data exist for types L6-T5 to assert that M(Sub L') and M(sub M') are strictly monotonic within this range of typew. We compare the observed K, L', and M' luminosities of L and T dwarfs in our sample with those predicted by precipitation-cloud-free models for varying surface gravities and sedimentation efficiencies.

  7. Detection of Extrasolar Planets by Transit Photometry

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  8. Ignition, Liftoff, and Extinction of Gaseous Diffusion Flames

    NASA Astrophysics Data System (ADS)

    Liñán, Amable; Vera, Marcos; Sánchez, Antonio L.

    2015-01-01

    This review uses as a vehicular example the jet-flame configuration to examine some phenomena that emerge in nonpremixed gaseous combustion as a result of the interaction between the temperature-sensitive chemical reaction, typical of combustion, and the convective and diffusive transport. These include diffusion-controlled flames, edge flames and their role in flame attachment, triple flames and their role as ignition fronts, and strain-induced extinction, including flame-vortex interactions. The aim is to give an overall view of the fluid dynamics of nonpremixed combustion and to review the most relevant contributions.

  9. A catalogue of IJK photometry of Planetary Nebulae with DENIS

    E-print Network

    S. Schmeja; S. Kimeswenger

    2001-05-15

    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).

  10. CCD Photometry of Seven Asteroids at the Belgrade Astronomical Observatory

    NASA Astrophysics Data System (ADS)

    Benishek, Vladimir

    2008-03-01

    CCD photometry of seven asteroids was performed at the Belgrade Astronomical Observatory from July 2006 to August 2007: 78 Diana, 125 Liberatrix, 702 Alauda, 888 Parysatis, 1095 Tulipa, 1293 Sonja, and 2006 VV2.

  11. DISTRIBUTED FLAMES IN TYPE Ia SUPERNOVAE

    SciTech Connect

    Aspden, A. J.; Bell, J. B. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50A-1148, Berkeley, CA 94720 (United States); Woosley, S. E. [Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

    2010-02-20

    At a density near a few x10{sup 7} g cm{sup -3}, the subsonic burning in a Type Ia supernova (SN) enters the distributed regime (high Karlovitz number). In this regime, turbulence disrupts the internal structure of the flame, and so the idea of laminar burning propagated by conduction is no longer valid. The nature of the burning in this distributed regime depends on the turbulent Damkoehler number (Da{sub T}), which steadily declines from much greater than one to less than one as the density decreases to a few x10{sup 6} g cm{sup -3}. Classical scaling arguments predict that the turbulent flame speed s{sub T} , normalized by the turbulent intensity u-check, follows s{sub T}/u-check = Da{sub T}{sup 1/2} for Da{sub T} {approx}< 1. The flame in this regime is a single turbulently broadened structure that moves at a steady speed, and has a width larger than the {integral} scale of the turbulence. The scaling is predicted to break down at Da{sub T} {approx} 1, and the flame burns as a turbulently broadened effective unity Lewis number flame. This flame burns locally with speed s{sub l}ambda and width l{sub l}ambda, and we refer to this kind of flame as a lambda-flame. The burning becomes a collection of lambda-flames spread over a region approximately the size of the {integral} scale. While the total burning rate continues to have a well-defined average, s{sub T}{approx}u-check, the burning is unsteady. We present a theoretical framework, supported by both one-dimensional and three-dimensional numerical simulations, for the burning in these two regimes. Our results indicate that the average value of s{sub T} can actually be roughly twice u-check for Da{sub T} {approx}> 1, and that localized excursions to as much as 5 times u-check can occur. We also explore the properties of the individual flames, which could be sites for a transition to detonation when Da{sub T} {approx} 1. The lambda-flame speed and width can be predicted based on the turbulence in the star (specifically the energy dissipation rate epsilon*) and the turbulent nuclear burning timescale of the fuel tau {sup T}{sub nuc}. We propose a practical method for measuring s{sub l}ambda and l{sub l}ambda based on the scaling relations and small-scale computationally inexpensive simulations. This suggests that a simple turbulent flame model can be easily constructed suitable for large-scale distributed SNe flames. These results will be useful both for characterizing the deflagration speed in larger full-star simulations, where the flame cannot be resolved, and for predicting when detonation occurs.

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

    E-print Network

    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

    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 ...

  13. Binary Star Synthetic Photometry and Distance Determination Using BINSYN

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  14. BINARY STAR SYNTHETIC PHOTOMETRY AND DISTANCE DETERMINATION USING BINSYN

    SciTech Connect

    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

    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.

  15. Laminar Flame Speeds of Moist Syngas Mixtures

    SciTech Connect

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

    2011-01-01

    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.

  16. Engineering Flame Retardant Biodegradable Nanocomposites

    NASA Astrophysics Data System (ADS)

    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

    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.

  17. Microlensing for extrasolar planets : improving the photometry

    NASA Astrophysics Data System (ADS)

    Bajek, David J.

    Gravitational Microlensing, as a technique for detecting Extrasolar Planets, is recognised for its potential in discovering small-mass planets similar to Earth, at a distance of a few Astronomical Units from their host stars. However, analysing the data from microlensing events (which statistically rarely reveal planets) is complex and requires continued and intensive use of various networks of telescopes working together in order to observe the phenomenon. As such the techniques are constantly being developed and refined; this project outlines some steps of the careful analysis required to model an event and ensure the best quality data is used in the fitting. A quantitative investigation into increasing the quality of the original photometric data available from any microlensing event demonstrates that 'lucky imaging' can lead to a marked improvement in the signal to noise ratio of images over standard imaging techniques, which could result in more accurate models and thus the calculation of more accurate planetary parameters. In addition, a simulation illustrating the effects of atmospheric turbulence on exposures was created, and expanded upon to give an approximation of the lucky imaging technique. This further demonstrated the advantages of lucky images which are shown to potentially approach the quality of those expected from diffraction limited photometry. The simulation may be further developed for potential future use as a 'theoretical lucky imager' in our research group, capable of producing and analysing synthetic exposures through customisable conditions.

  18. Surface photometry of comet P/Encke

    NASA Astrophysics Data System (ADS)

    Djorgovski, S.; Spinrad, H.

    1985-05-01

    A scheme to clean cometary digital images from offending background-star trails, and this technique has been applied to a pair of deep Kitt Peak 4-m plates of comet P/Encke, taken in October 1980. Simultaneous and subsequent digital spectra have been obtained at Lick Observatory. The non-polluted coma images show a strong asymmetric sunward-oriented fan/jet, and an extended and rounder (mostly gaseous) main coma, out to approximately 100,000 km radius. The stellar-trail point-spread function has a narrow width (sigma approximately 0.6 arcsec), so that spatial resolution better than approximately 300 km is achieved at the comet. The photometric gradient near the nucleus is very steep, strongly suggesting an icy-grain component which evaporates quickly (at radii equal to or less than 500 km) in the sunlight. Further from the nucleus, the profile becomes shallower, bluer, and more gas dominated. The effect of solar radiation pressure on C2, CN, and other molecules is probably responsible for the rounding of the outer, fainter isophotes. The source of the molecules is likely to be larger than the nucleus itself, and a substantial fraction may originate in the jet. The technique described here may also be applicable in surface photometry of galaxies, in cases where the heavy image pollution by foreground stars is present.

  19. Photometry of resolved galaxies. V - NGC 6822

    NASA Technical Reports Server (NTRS)

    Hoessel, J. G.; Anderson, N.

    1986-01-01

    Three-color CCD frames of the local group irregular galaxy NGC 6822 have been reduced to GRI photometry for 3475 stars using RICHFLD point-spread function fitting techniques. The data are compared with earlier work on this galaxy, particularly with Kayser (1966) on a star-by-star basis. Color-magnitude diagrams are constructed from the data and compared with both theoretical stellar model tracks and the expected foreground star contamination. A luminosity function for the blue stars is derived; comparison of this luminosity function with those of 10 other irregular galaxies indicates that NGC 6822 has a typical young star population. The stellar birthrate and initial mass function are estimated for this galaxy. The slope at the bright end of the mass function looks similar to recent results for the Galaxy, the Magellanic Clouds, and the irregular galaxy Sextans A. NGC 6822 appears to be presently forming stars at a slower rate for its mass than Sextans A or the Magellanic Clouds.

  20. FR Cnc Revisited: Photometry, Polarimetry and Spectroscopy

    E-print Network

    Golovin, A; Hernan-Obispo, M; Andreev, M; Barnes, J R; Montes, D; Pavlenko, E; Pandey, J C; Martinez-Arnaiz, R; Medhi, B J; Parihar, P S; Henden, A; Sergeev, A; Zaitsev, S V; Karpov, N

    2011-01-01

    Here we present the study of FR Cnc, a young, active and spotted star. We performed analysis of ASAS-3 (The All Sky Automated Survey) data for the years 2002-2008 and amended the value of the rotational period to be 0.826518 d. The amplitude of photometric variations decreased abruptly in the year 2005, while the mean brightness remained the same, which was interpreted as a quick redistribution of spots. BVRc and Ic broad band photometric calibration was performed for 166 stars in FR Cnc vicinity. The photometry at Terskol Observatory shows two brightening episodes, one of which occurred at the same phase as the flare of 2006 November 23. Polarimetric BVR observations indicate the probable presence of a supplementary source of polarization. We monitored FR Cnc spectroscopically during the years 2004-2008. We concluded that the RV changes cannot be explained by the binary nature of FR Cnc. We determined the spectral type of FR Cnc as K7V. Calculated galactic space-velocity components (U, V, W) indicate that FR...

  1. Identification of pulsation modes from photometry

    NASA Astrophysics Data System (ADS)

    Breger, Michel

    2014-02-01

    The identification of the detected pulsation modes in terms of the spherical harmonic quantum numbers is crucial for asteroseismology. Light curves obtained in different passbands have become an important tool for mode identifications, which rely on wavelength-dependent amplitudes and phase shifts. We demonstrate this for different types of pulsators and review recent successes from earth-based measurements, especially in determining the important l values. The extensive amount of accurate data needed to determine small phase shifts and accurate amplitude ratios suggests multicolor measurements using space satellites. This motivated the multicolor BRITE satellite project, for which the first two satellites have already been launched successfully. We demonstrate the potential from models computed for the BRITE wavelengths. Most of the excellent presently available satellite photometry is not multicolor, although frequencies with amplitudes as small as a few parts-per-million have been detected and confirmed. We briefly discuss mode identifications from frequency patterns, including the use of correlations between phase and amplitude changes.

  2. The HST Milky Way Stellar Photometry Archive

    NASA Astrophysics Data System (ADS)

    Radburn-Smith, David

    2012-10-01

    The Hubble Legacy Archive has invested a significant effort into automatically generating photometry for point sources in all HST observations regardless of the target. We estimate that this archive contains up to 800,000 Milky Way {MW} stars, distributed across the whole sky, complete to some three magnitudes fainter than SDSS. Approximately half of these stars have color information, which is required for stellar population analysis. This considerable archive is thus in need of collation, analysis, and publication.Here we propose to compile such a catalog for public access and to use it for two science goals: 1} A test of existing MW stellar models, where we will in particular constrain the fainter and more distant stellar populations; and 2} Probe the shape and structure of the MW stellar halo with a deeper star catalog than is currently available. These science cases will be used to fully define the catalog, in particular by assessing the different populations present in the observations, and by assessing the level of noise from contaminants and the completeness of the survey

  3. BVI CCD photometry of 47 Tucanae

    SciTech Connect

    Alcaino, G.; Liller, W.

    1987-08-01

    CCD BVI main-sequence photometry of 47 Tuc is presented, matched to the recent BVI isochrones of VandenBerg and Bell (1985). The main-sequence turnoffs are found to be at V = 17.60 + or - 0.1, B-V = 0.56 + or - 0.02; V-I = 0.68 + or - 0.02, and B-I = 1.24 + or - 0.02. The magnitude difference between the main-sequence turnoff and the horizontal branch is 3.55 + or - 0.15 for all three color indices. A consistent age for 47 Tuc of 17 Gyr and a consistent distance modulus of (m-M)v = 13.2 are obtained for all three indices, and an absolute magnitude of Mv = 0.85 is determined for the horizontal branch stars. The results also favor the adoption of (Fe/H) near -0.5 as the best abundance value for 47 Tuc. 38 references.

  4. Recent Advances in Video Meteor Photometry

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  5. BVRI PHOTOMETRY OF 53 UNUSUAL ASTEROIDS

    SciTech Connect

    Ye, Q.-Z., E-mail: tom6740@gmail.com [Department of Atmospheric Sciences, School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou (China)

    2011-02-15

    We present the results of BVRI photometry and classification of 53 unusual asteroids, including 35 near-Earth asteroids (NEAs), 6 high eccentricity/inclination asteroids, and 12 recently identified asteroid-pair candidates. Most of these asteroids were not classified prior to this work. For the few asteroids that have been previously studied, the results are generally in agreement. In addition to observing and classifying these objects, we merge the results from severalphotometric/spectroscopic surveys to create the largest-ever sample with 449 spectrally classified NEAs for statistical analysis. We identify a 'transition point' of the relative number of C/X-like and S-like NEAs at H {approx} 18 {r_reversible} D {approx} 1 km with confidence level at {approx}95% or higher. We find that the C/X-like:S-like ratio for 18 {<=} H < 22 is about twice as high as that of H < 18 (0.33 {+-} 0.04 versus 0.17 {+-} 0.02), virtually supporting the hypothesis that smaller NEAs generally have less weathered surfaces (therefore less reddish appearance) due to younger collision ages.

  6. NEW UBVRI PHOTOMETRY OF 234 M33 STAR CLUSTERS

    SciTech Connect

    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

    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.

  7. FIXING THE U-BAND PHOTOMETRY OF TYPE Ia SUPERNOVAE

    SciTech Connect

    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

    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.

  8. Cars temperature measurements in sooting, laminar diffusion flames

    NASA Astrophysics Data System (ADS)

    Boedeker, L. R.; Dobbs, G. M.

    1984-07-01

    Temperature distributions have been measured in axisymmetric ethylene-air diffusion flames using high spatial resolution coherent anti-Stokes Raman spectroscopy. As ethylene flow increased and the flame approached a smoke-point condition, the temperatures attained in the upper part of the flame were reduced by about 300K below the maximum radial temperatures low in the flame. Addition of diluent N2 to ethylene caused a reduction in temperature low in the flame but increased temperature higher in the flame. Maximum temperatures attained in all ethylene flames were between 0.84 and 0.89 of respective adiabatic flame temperatures (AFT). The upper temperature of the near-smoke-point flame was only 0.76 of AFT. Results are compared with the generalized flame front model of Mitchell. MIE scattering measurements are also discussed. Brief studies with propane and a nonsooting, CO flame are reported; maximum axial and radial temperatures were between 0.84 and 0.87 of AFT. Results indicate the importance of thermal loss from soot radiation, radial transport processes and fuel pyrolysis. Nonluminous radiation and finite reaction rates are other possible factors. The upper luminous part of the highly sooting ethylene flame is likely above the primary flame front and is a soot burnout zone.

  9. Influence of edge velocity on flame front position and displacement speed in turbulent premixed combustion

    E-print Network

    Gülder, Ömer L.

    Influence of edge velocity on flame front position and displacement speed in turbulent premixed velocity Flame front position Flame displacement speed a b s t r a c t Using a novel concept, the present of the flame front velocity normal to the flame front and the flame displace- ment speed. Several studies have

  10. A laminar vortex interacting with a premixed flame - Regimes of interaction

    NASA Astrophysics Data System (ADS)

    Roberts, Wm. L.; Driscoll, J. F.; Drake, M. C.

    1992-01-01

    A single toroidal, laminar vortex interacts with a counterpropagating laminar premixed flame to examine the fundamentals of the flame-vortex interaction. This interaction represents a fundamental 'building block' of premixed turbulent combustion. Experimental results quantify the degree of flame rollup, the boundary of the pocket formation (corrugated flame) regime, the flame perimeter increase due to wrinkling, and local quenching of the premixed flame.

  11. On Soot Inception in Nonpremixed Flames and the Effects of Flame Structure

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    A simplified three-step model of soot inception has been employed with high activation energy asymptotics to study soot inception in nonpremixed counterflow systems with emphasis on understanding the effects of hydrodynamics and transport. The resulting scheme yields three zones: (1) a fuel oxidation zone wherein the fuel and oxidizer react to form product as well as a radical R, (e.g., H), (2) a soot/precursor formation zone where the radical R reacts with fuel to form "soot/precursor" S, and (3) a soot/precursor consumption zone where S reacts with the oxidizer to form product. The kinetic scheme, although greatly simplified, allows the coupling between soot inception and flame structure to be assessed. The results yield flame temperature, flame location, and a soot/precursor index S(sub I) as functions of Damkohler number for S formation. The soot/precursor index indicates the amount of S at the boundary of the formation region. The flame temperature indirectly indicates the total amount of S integrated over the formation region because as S is formed less heat release is available. The results show that unlike oxidation reactions, an extinction turning-point behavior does not exist for soot. Instead, the total amount of S slowly decreases with decreasing Damkohler number (increasing strain rate), which is consistent with counterflow flame experiments. When the Lewis number of the radical is decreased from unity, the total S reduces due to reduced residence time for the radical in the soot formation region. Similarly, when the Lewis number of the soot/precursor is increased from unity the amount of S increases for all Damkohler numbers. In addition to studying fuel-air (low stoichiometric mixture fraction) flames, the air-side nitrogen was substituted into the fuel, yielding diluted fuel-oxygen (high stoichiometric mixture fraction) flames with the same flame temperature as the fuel - air flames. The relative flame locations were different however, and, consistent with counterflow flame experiments, this difference was found to dramatically reduce the total amount of S generated because the change in stoichiometric mixture fraction affects residence times, temperatures and concentrations in the soot/precursor formation and consumption zones. Furthermore, while the soot/precursor consumption reaction had a negligible effect on the soot process for fuel-air flames it was very important to diluted fuel - oxygen flames.

  12. Launch Pad Flame Trench Refractory Materials

    NASA Technical Reports Server (NTRS)

    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

    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.

  13. A Theory of Oscillating Edge Flames

    NASA Technical Reports Server (NTRS)

    Buckmaster, J.; Zhang, Yi

    1999-01-01

    It has been known for some years that when a near-limit flame spreads over a liquid pool of fuel, the edge of the flame can oscillate relative to a frame moving with the mean speed. Each period of oscillation is characterized by long intervals of modest motion during which the edge gases radiate like those of a diffusion flame, punctuated by bursts of rapid advance during which the edge gases radiate like those in a deflagration. Substantial resources have been brought to bear on this issue within the microgravity program, both experimental and numerical. It is also known that when a near-asphyxiated candle-flame burns at zero gravity, the edge of the (hemispherical) flame can oscillate violently prior to extinction. Thus a web-surfer, turning to the NASA web-site at http://microgravity.msfc.nasa.gov, and following the trail combustion science/experiments/experimental results/candle flame, will find photographs and a description of candle burning experiments carried out on board both the Space-shuttle and the Russian space station Mir. A brief report can also be found in the proceedings of the Fourth Workshop. And recently, in a third microgravity program, the leading edge of the flame supported by injection of ethane through the porous surface of a plate over which air is blown has been found to oscillate when conditions are close to blow-off. A number of important points can be made with respect to these observations: It is the edge itself which oscillates, advancing and retreating, not the diffusion flame that trails behind the edge; oscillations only occur under near limit conditions; in each case the Lewis number of the fuel is significantly larger than 1; and because of the edge curvature, the heat losses from the reacting edge structure are larger than those from the trailing diffusion flame. We propose a general theory for these oscillations, invoking Occam's 'Law of Parsimony' in an expanded form, to wit: The same mechanism is responsible for the oscillations in all three experiments; and no new mechanism is invoked (Occam's original 'Razor'). Such a strategy eliminates Marangoni effects as the source, for these are absent in the second and third experiments. And it eliminates arguments that point to numerically predicted gas eddies as the source, a new mechanism, unelucidated. Indeed, we hypothesize that the essential driving mechanism for the instability is a combination of large Lewis number and heat losses from the reacting structure near the flame edge. Instabilities driven by these mechanisms are commonplace in 1D configurations. Chemical reactor theory, for example, leads to system responses which mimic the response of the candle flame - steady flame, oscillations, extinction. In a combustion context, oscillating instabilities were first reported for diffusion flames in a theoretical study by Kirkby and Schmitz, and here also the instabilities are associated with near-extinction conditions, large Lewis numbers, and heat losses. And deflagrations will oscillate if the Lewis number is large enough, oscillations that are exacerbated when heat losses are present, whether global or to a surface.

  14. 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)

    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

    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

  15. FLAME: a program to flexibly align molecules.

    PubMed

    Cho, Sung Jin; Sun, Yaxiong

    2006-01-01

    Herein, we describe a method to flexibly align molecules (FLAME = FLexibly Align MolEcules). FLAME aligns two molecules by first finding maximum common pharmacophores between them using a genetic algorithm. The resulting alignments are then subjected to simultaneous optimizations of their internal energies and an alignment score. The utility of the method in pairwise alignment, multiple molecule flexible alignment, and database searching was examined. For pairwise alignment, two carboxypeptidase ligands (Protein Data Bank codes and ), two estrogen receptor ligands ( and ), and two thrombin ligands ( and ) were used as test sets. Alignments generated by FLAME starting from CONCORD structures compared very well to the X-ray structures (average root-mean-square deviation = 0.36 A) even without further minimization in the presence of the protein. For multiple flexible alignments, five structurally diverse D3 receptor ligands were used as a test set. The FLAME alignment automatically identified three common pharmacophores: a base, a hydrogen-bond acceptor, and a hydrophobe/aromatic ring. The best alignment was then used to search the MDDR database. The search results were compared to the results using atom pair and Daylight fingerprint similarity. A similar database search comparison was also performed using estrogen receptor modulators. In both cases, hits identified by FLAME were structurally more diverse compared to those from the atom pair and Daylight fingerprint methods. PMID:16426065

  16. Aromatics oxidation and soot formation in flames

    SciTech Connect

    Howard, J.B.; Pope, C.J.; Shandross, R.A.; Yadav, T.

    1993-04-01

    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 confirm or determine rate constants for, the main benzene oxidation reactions in flames, and to characterize soot and fullerenes and their formation mechanisms and kinetics. Stable and radical species profiles in the aromatics oxidation study are measured using molecular beam sampling with on-line mass spectrometry. The rate of soot formation measured by conventional optical techniques is found to support the hypotheses that particle inception occurs through reactive coagulation of high molecular weight PAH in competition with destruction by OHattack, and that the subsequent growth of the soot mass occurs through addition reactions of PAH and C[sub 2]H[sub 2] with the soot particles. During the first year of this reporting period, fullerenes C[sub 60] and C[sub 70] in substantial quantities were found in the flames being studied. The fullerenes were recovered, purified and spectroscopically identified. The yields of C[sub 60] and C[sub 70] were then determined over ranges of conditions in low-pressure premixed flames of benzene and oxygen.

  17. An Improved Method for Students' Flame Tests in Qualitative Analysis

    Microsoft Academic Search

    William D. Bare; Tom Bradley; Elizabeth Pulliam

    1998-01-01

    A new method for flame tests to be performed by students is presented. The method involves the use of a hot wire to vaporize the sample,which is subsequently drawn into the flame via the burner air vent.

  18. 41. HISTORIC VIEW LOOKING SOUTH FROM THE FLAME TRENCH AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. HISTORIC VIEW LOOKING SOUTH FROM THE FLAME TRENCH AT THE TEST STAND AND LOOKING INTO THE FLAME DEFLECTOR. - Marshall Space Flight Center, Redstone Rocket (Missile) Test Stand, Dodd Road, Huntsville, Madison County, AL

  19. Flashback flame arrester devices for fuel cargo tank vapor vents

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  20. 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...

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

    NASA Technical Reports Server (NTRS)

    Driscoll, James F.; Feikema, Douglas A.

    2003-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Mantel, Thierry

    1994-01-01

    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.

  3. Flame photometric detector for thin-layer chromatography

    Microsoft Academic Search

    Minoru Ogasawara; Kyoko Tsuruta; Shinsuke Arao

    2002-01-01

    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

  4. The Conductivity of Flames for Rapidly Alternating Currents

    Microsoft Academic Search

    H. A. Wilson; A. B. Bryan

    1924-01-01

    Conductivity of salted flames for high frequency currents.-Theory. Expressions are developed for the capacity and series resistance of a parallel plate condenser in a flame, which enable certain constants to be computed from the measurements of Bryan given in the preceding paper. Calculated density of positive ions increases from.03 e.s.u. in the unsalted flame to 1.5 e.s.u. for the flame

  5. Structure and dynamics of diffusion flames in microgravity

    NASA Technical Reports Server (NTRS)

    Matalon, Moshe

    1995-01-01

    The objectives of this project are to gain insight into diffusion flames by modeling various configurations related to ongoing experimental investigations in the microgravity combustion science program. The emphasis of the work is to understand the structure and dynamics of diffusion flames. Improving our fundamental understanding of diffusion flames is most relevant to issues related to fire safety and fire prevention because most fires consist of diffusion flames.

  6. Dithering Strategies and Point-Source Photometry

    SciTech Connect

    Samsing, Johan; Kim, Alex G

    2011-02-22

    The accuracy in the photometry of a point source depends on the point-spread function (PSF), detector pixelization, and observing strategy. The PSF and pixel response describe the spatial blurring of the source, the pixel scale describes the spatial sampling of a single exposure, and the observing strategy determines the set of dithered exposures with pointing offsets from which the source flux is inferred. In a wide-field imaging survey, sources of interest are randomly distributed within the field of view and hence are centered randomly within a pixel. A given hardware configuration and observing strategy therefore have a distribution of photometric uncertainty for sources of fixed flux that fall in the field. In this article we explore the ensemble behavior of photometric and position accuracies for different PSFs, pixel scales, and dithering patterns. We find that the average uncertainty in the flux determination depends slightly on dither strategy, whereas the position determination can be strongly dependent on the dithering. For cases with pixels much larger than the PSF, the uncertainty distributions can be non-Gaussian, with rms values that are particularly sensitive to the dither strategy. We also find that for these configurations with large pixels, pointings dithered by a fractional pixel amount do not always give minimal average uncertainties; this is in contrast to image reconstruction for which fractional dithers are optimal. When fractional pixel dithering is favored, a pointing accuracy of better than {approx}0.15 {approx}0.15 pixel width is required to maintain half the advantage over random dithers.

  7. Flame Tests Using Improvised Alcohol Burners

    NASA Astrophysics Data System (ADS)

    Dragojlovic, Veljko

    1999-07-01

    In this demonstration, an improvised alcohol burner, with a methanol solution of a salt as fuel, produces a long-lasting brightly colored flame. A disadvantage when using a regular alcohol burner is that the burner has to be cleaned and a wick replaced, before a solution of a different salt can be used. For our demonstration, alcohol burners are made from small (5-mL) glass vials. The vials are filled with a methanol solution of the desired salt and a paper wick is added. Thus, a small amount of solvent (5 mL or less) provides a colored flame, which lasts for several minutes. Vials and paper wicks can be reused. Use of the described alcohol burner in a flame test demonstration has several advantages. It is inexpensive, a number of tests can be run simultaneously, and stock solutions of metal salts can be prepared in advance and stored for future demonstrations.

  8. Pentan isomers compound flame front structure

    SciTech Connect

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

    1995-08-13

    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.

  9. Flame synthesis of molybdenum oxide whiskers

    NASA Astrophysics Data System (ADS)

    Merchan-Merchan, Wilson; Saveliev, Alexei V.; Kennedy, Lawrence A.

    2006-04-01

    The spectacular growth of molybdenum oxide hollow and solid whiskers with rectangular and circular cross-section is reported. The synthesis is performed using molybdenum probes inserted in an opposed-flow methane oxy-flame. The solid rectangular and circular whiskers with characteristic cross-sectional dimensions from 100 nm to 4 ?m and hollow rectangular channels with wall thickness from 50 to 100 nm are grown on 1-mm diameter probes inserted at the high temperature zone on the oxidizer side of the flame front. The shape and structural parameters of grown whisker materials strongly depend on the flame position (temperature) and probe diameter. Well-defined elongated crystal structures with a large number of facets and complex symmetry were grown on the probes with a diameter of 0.25 mm.

  10. Recyclable flame retardant nonwoven for sound absorption; RUBA®

    Microsoft Academic Search

    Kazuhiko Kosuge; Akira Takayasu; Teruo Hori

    2005-01-01

    A flame retardant nonwoven fabric for sound absorption, using para-aramid fibre and polyester fibre as a substitute for conventional materials (such as glass wool, flame retardant foam and flame retardant polyester fibre) was investigated. A combination of nonwoven fabric and paper was studied, and the resulting sound absorption qualities and sound permeation loss were compared. By attaching para-aramid paper with

  11. Characteristics of hydrogen–hydrocarbon composite fuel turbulent jet flames

    Microsoft Academic Search

    Ahsan R. Choudhuri; S. R. Gollahalli

    2003-01-01

    The characteristics (flame length, pollutant emission, radiative heat loss fraction, and volumetric soot concentration) of hydrogen–hydrocarbon composite fuel turbulent jet diffusion flames are presented. A correlation of flame length with hydrogen concentration in the fuel mixture is shown. The reactivity of fuel mixture increases with the increase of hydrogen concentration, which ultimately shortens the combustion time, and thereby reduces the

  12. 63. VIEW OF FLAME BUCKET AND LAUNCHER FROM SOUTHEAST. TRICHLOROETHENE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    63. VIEW OF FLAME BUCKET AND LAUNCHER FROM SOUTHEAST. TRICHLOROETHENE RECOVERY TANK LEFT OF FLAME BUCKET; LIQUID OXYGEN CATCH TANK RIGHT OF FLAME BUCKET. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  13. 30 CFR 18.65 - Flame test of hose.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 false Flame test of hose. 18.65 Section 18...Inspections and Tests § 18.65 Flame test of hose. (a) Size of test specimen...by thickness of the hose. (b) Flame-test apparatus. The principal...

  14. 30 CFR 18.65 - Flame test of hose.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Flame test of hose. 18.65 Section 18...Inspections and Tests § 18.65 Flame test of hose. (a) Size of test specimen...by thickness of the hose. (b) Flame-test apparatus. The principal...

  15. Watch out for those variables in flame testing!

    Microsoft Academic Search

    C. N. Keeney

    1978-01-01

    The flammability of plastics systems became a significant consideration for industrial formulators as legislation and fire regulations began coming into prominence in the mid- and late 1960s. As the mass of legislation grew, the number and variety of flame tests increased. Along with the increasing number and complexity of the flame tests, the science of flame testing began to develop.

  16. 30 CFR 18.65 - Flame test of hose.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 false Flame test of hose. 18.65 Section 18...Inspections and Tests § 18.65 Flame test of hose. (a) Size of test specimen...by thickness of the hose. (b) Flame-test apparatus. The principal...

  17. Preconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda

    E-print Network

    Zhang, Jun

    that their solution constitutes a challenging test for nonlinear elliptic solvers. The flame sheet model adds only onePreconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda Samir Karaa of an elliptic flame sheet problem. By selecting the generalized minimum residual method as the linear smoother

  18. Laminar premixed flame response to equivalence ratio oscillations

    Microsoft Academic Search

    Ju Hyeong Cho; Tim Lieuwen

    2005-01-01

    Self-excited oscillations in low emission, premixed combustion systems are often caused by feedback between unsteady heat release rates and reactive mixture equivalence ratio perturbations. This paper presents an analysis of the flame response to equivalence ratio perturbations, showing that the heat release response is controlled by the superposition of three disturbances: heat of reaction, flame speed, and flame area. The

  19. Terahertz transmission spectroscopy of high-pressure flames

    Microsoft Academic Search

    M. Naftaly; M. R. Stringer; R. E. Miles; J. Bassi; Y. Zhang

    2005-01-01

    Laser spectroscopy in the visible and NIR is widely used to study flame behaviour in internal combustion engines and turbines, but is inapplicable at high pressures because high soot concentration renders flames opaque; however they remain transparent to THz radiation. We use THz time-domain transmission spectroscopy to characterise gaseous species in flames. A specially designed high-pressure burner vessel has been

  20. Characterisation of the dispersion in polymer flame retarded nanocomposites

    Microsoft Academic Search

    Fabienne Samyn; Serge Bourbigot; Charafeddine Jama; Séverine Bellayer; Shonali Nazare; Richard Hull; Alberto Fina; Andrea Castrovinci; Giovanni Camino

    2008-01-01

    Flame retardant nanocomposites have attracted many research efforts because they combine the advantages of a conventional flame retardant polymer with that of polymer nanocomposite. However the properties obtained depend on the dispersion of the nanoparticles. In this study, three types of polymer flame retarded nanocomposites based on different matrices (polypropylene (PP), polybutadiene terephtalate (PBT) and polyamide 6 (PA6)) have been

  1. 30 CFR 57.7805 - Smoking and open flames.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 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...

  2. 30 CFR 57.6904 - Smoking and open flames.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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...

  3. 30 CFR 56.7805 - Smoking and open flames.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...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...

  4. 30 CFR 56.6904 - Smoking and open flames.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 1 2012-07-01 2012-07-01 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...

  5. 30 CFR 57.7805 - Smoking and open flames.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...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...

  6. 30 CFR 56.6904 - Smoking and open flames.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 1 2014-07-01 2014-07-01 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...

  7. 30 CFR 56.7805 - Smoking and open flames.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 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...

  8. 30 CFR 57.7805 - Smoking and open flames.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 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...

  9. 30 CFR 57.6904 - Smoking and open flames.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 1 2014-07-01 2014-07-01 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...

  10. 30 CFR 57.6904 - Smoking and open flames.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 1 2012-07-01 2012-07-01 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...

  11. 30 CFR 56.7805 - Smoking and open flames.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 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...

  12. 30 CFR 57.6904 - Smoking and open flames.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 1 2013-07-01 2013-07-01 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...

  13. 30 CFR 57.7805 - Smoking and open flames.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 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...

  14. 30 CFR 56.6904 - Smoking and open flames.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 1 2013-07-01 2013-07-01 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...

  15. 30 CFR 56.6904 - Smoking and open flames.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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...

  16. 30 CFR 56.7805 - Smoking and open flames.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 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...

  17. LES of Recirculation and Vortex Breakdown in Swirling Flames

    Microsoft Academic Search

    W. Malalasekera; K. K. J. Ranga-Dinesh; S. S. Ibrahim; A. R. Masri

    2008-01-01

    In this study large eddy simulation (LES) technique has been applied to predict a selected swirling flame from the Sydney swirl burner experiments. The selected flame is known as the SM1 flame operated with fuel CH 4 at a swirl number of 0.5. In the numerical method used, the governing equations for continuity, momentum and mixture fraction are solved on

  18. 30 CFR 56.7805 - Smoking and open flames.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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...

  19. 30 CFR 57.6904 - Smoking and open flames.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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...

  20. 30 CFR 57.7805 - Smoking and open flames.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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...

  1. 30 CFR 56.6904 - Smoking and open flames.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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...

  2. Simulation of turbulent lifted methane jet flames: effects of air-dilution and transient flame propagation

    E-print Network

    Chen, Z.; Ruan, S.; Swaminathan, N.

    2014-10-03

    the centreline at different distances from the jet exit for this numerical work. The above two axial locations, 30 and 40dj, are considered to study the process of flame kernel growth, propagation, and its final stabilisation height. Both high-speed movies and OH... PLIF (planar laser-induced fluorescence) imaging were used to visualise the flame propagation stages. The 14 temporal variation of flame lift-off height and its final steady state value were analysed using direct high speed digital movies and OH...

  3. The dynamics of turbulent premixed flames: Mechanisms and models for turbulence-flame interaction

    NASA Astrophysics Data System (ADS)

    Steinberg, Adam M.

    The use of turbulent premixed combustion in engines has been garnering renewed interest due to its potential to reduce NOx emissions. However there are many aspects of turbulence-flame interaction that must be better understood before such flames can be accurately modeled. The focus of this dissertation is to develop an improved understanding for the manner in which turbulence interacts with a premixed flame in the 'thin flamelet regime'. To do so, two new diagnostics were developed and employed in a turbulent slot Bunsen flame. These diagnostics, Cinema-Stereoscopic Particle Image Velocimetry and Orthogonal-Plane Cinema-Stereoscopic Particle Image Velocimetry, provided temporally resolved velocity and flame surface measurements in two- and three-dimensions with rates of up to 3 kHz and spatial resolutions as low as 280 mum. Using these measurements, the mechanisms with which turbulence generates flame surface area were studied. It was found that the previous concept that flame stretch is characterized by counter-rotating vortex pairs does not accurately describe real turbulence-flame interactions. Analysis of the experimental data showed that the straining of the flame surface is determined by coherent structures of fluid dynamic strain rate, while the wrinkling is caused by vortical structures. Furthermore, it was shown that the canonical vortex pair configuration is not an accurate reflection of the real interaction geometry. Hence, models developed based on this geometry are unlikely to be accurate. Previous models for the strain rate, curvature stretch rate, and turbulent burning velocity were evaluated. It was found that the previous models did not accurately predict the measured data for a variety of reasons: the assumed interaction geometries did not encompass enough possibilities to describe the possible effects of real turbulence, the turbulence was not properly characterized, and the transport of flame surface area was not always considered. New models therefore were developed that accurately reflect real turbulence-flame interactions and agree with the measured data. These can be implemented in Large Eddy Simulations to provide improved modeling of turbulence-flame interaction.

  4. Large Scale Flame Spread Environmental Characterization Testing

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    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.

  5. Flame-Vortex Interactions Imaged in Microgravity - To Assess the Theory Flame Stretch

    NASA Technical Reports Server (NTRS)

    Driscoll, James F.

    2001-01-01

    The goals of this research are to: 1) Assess the Theory of Flame Stretch by operating a unique flame-vortex experiment under microgravity conditions in the NASA Glenn 2.2 Second Drop Tower (drops to identify operating conditions have been completed); 2) Obtain high speed shadowgraph images (500-1000 frames/s) using the drop rig (images were obtained at one-g, and the NASA Kodak RO camera is being mounted on the drop rig); 3) Obtain shadowgraph and PIV images at 1-g while varying the effects of buoyancy by controlling the Froude number (completed); 4) Numerically model the inwardly-propagating spherical flame that is observed in the experiment using full chemistry and the RUN 1DL code (completed); 5) Send images of the flame shape to Dr. G. Patniak at NRL who is numerically simulating the entire flame-vortex interaction of the present experiment (data transfer completed); and 6) Assess the feasibility of obtaining PIV velocity field images in the drop rig, which would be useful (but not required) for our assessment of the Theory of Flame Stretch (PIV images were obtained at one-g using same low laser power that is available from fiber optic cable in drop tower). The motivation for the work is to obtain novel measurement needed to develop a physically accurate model of turbulent combustion that can help in the control of engine pollutants. The unique experiment allows, for the first time, the detailed study of a negatively-curved (negatively stretched) flame, which is one of the five fundamental types of premixed flames. While there have been studies of flat flames, positively-curved (outwardly-propagating) cases and positively-strained (counterflow) cases, this is the first detailed study of a negatively-curved (inwardly-propagating) flame. The first set of drops in the 2.2 Second Drop Tower showed that microgravity provides more favorable conditions for achieving inwardly-propagating flames (IPFs) than 1-g. A vortex interacts with a flame and creates a spherical pocket, which burns inwardly. Shadowgraphs at 1000 frames/sec quantify the Markstein number and flame speed. A Low-Laser Power PIV System was developed and is being added to the drop package. Numerical computations were required to explain why the Markstein numbers measured for the inwardly-propagating flames differ from those of outward propagating flames; this is an important research issue in the assessment of the Theory of Flame Stretch. The RUN-1DL code (developed by Prof. B. Rogg) was run for IPF and OPFs with complex methane and propane chemistry. Results confirmed that Ma for the IPFs are larger than for OPFs as was observed experimentally. Physical reasons for these new findings about the Theory of Flame Stretch are being determined from the experiments and the computations. Several journal papers have been published; the drop package is described in the AIAA Journal, while the one-g results appear in three other journal papers.

  6. Equivalence ratio gradient effects on flame front topology in a stratified iso-octane\\/air turbulent V-flame

    Microsoft Academic Search

    P. C. Vena; B. Deschamps; G. J. Smallwood; M. R. Johnson

    2011-01-01

    The effect of partial premixing on the local topology of globally stoichiometric flames was considered using a novel burner that permits controlled transverse variation of equivalence ratio along a continuous stratified flame front. Five iso-octane\\/air V-flames with different levels of stratification were studied in experiments designed to quantify differences in flame surface density and curvature between a reference homogeneous case

  7. Flame synthesis of high Tc superconductors

    NASA Astrophysics Data System (ADS)

    Zachariah, Michael R.; Huzarewicz, Serge

    1991-10-01

    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.

  8. Pdf prediction of supersonic hydrogen flames

    NASA Technical Reports Server (NTRS)

    Eifler, P.; Kollmann, W.

    1993-01-01

    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.

  9. Velocity profiles in laminar diffusion flames

    NASA Technical Reports Server (NTRS)

    Lyons, Valerie J.; Margle, Janice M.

    1986-01-01

    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.

  10. Computatonal and experimental study of laminar flames

    SciTech Connect

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

    1993-12-01

    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.

  11. Liftoff of turbulent jet flames—assessment of edge flame and other concepts using cinema-PIV

    Microsoft Academic Search

    Ansis Upatnieks; James F. Driscoll; Chadwick C. Rasmussen; Steven L. Ceccio

    2004-01-01

    Three theories of the liftoff of a turbulent jet flame were assessed using cinema-particle imaging velocimetry movies recorded at 8000 images\\/s. The images visualize the time histories of the eddies, the flame motion, the turbulence intensity, and streamline divergence. The first theory assumes that the flame base has a propagation speed that is controlled by the turbulence intensity. Results conflict

  12. The effect of flame structure on soot formation and transport in turbulent nonpremixed flames using direct numerical simulation

    SciTech Connect

    Lignell, David O. [Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84098 (United States); Reacting Flow Research Department, Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States); Chen, Jacqueline H. [Reacting Flow Research Department, Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States); Smith, Philip J. [Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84098 (United States); Lu, Tianfeng; Law, Chung K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08540 (United States)

    2007-10-15

    Direct numerical simulations of a two-dimensional, nonpremixed, sooting ethylene flame are performed to examine the effects of soot-flame interactions and transport in an unsteady configuration. A 15-step, 19-species (with 10 quasi-steady species) chemical mechanism was used for gas chemistry, with a two-moment, four-step, semiempirical soot model. Flame curvature is shown to result in flames that move, relative to the fluid, either toward or away from rich soot formation regions, resulting in soot being essentially convected into or away from the flame. This relative motion of flame and soot results in a wide spread of soot in the mixture fraction coordinate. In regions where the center of curvature of the flame is in the fuel stream, the flame motion is toward the fuel and soot is located near the flame at high temperature and hence has higher reaction rates and radiative heat fluxes. Soot-flame breakthrough is also observed in these regions. Fluid convection and flame displacement velocity relative to fluid convection are of similar magnitudes while thermophoretic diffusion is 5-10 times lower. These results emphasize the importance of both unsteady and multidimensional effects on soot formation and transport in turbulent flames. (author)

  13. Comparison of different reactive organophosphorus flame retardant agents for cotton. Part II: Fabric flame resistant performance and physical properties

    Microsoft Academic Search

    Weidong Wu; Charles Q. Yang

    2007-01-01

    N-Methylol dimethylphosphonopropionamide (MDPA) is one of the most commonly used durable flame retardant agents for cotton. In our previous research, we developed a new flame retardant finishing system based on a hydroxy-functional organophosphorus oligomer (HFPO) and bonding agents, such as dimethyloldihydroxyethyleneurea (DMDHEU) and trimethylolmelamine (TMM). In this research, we compared the flame resistant performance as well as physical properties of

  14. COMBUSTION AND FLAME 24, 27-34 (1975) 27 Flame Emission Studies of Ozone with Metal Alkyls

    E-print Network

    Zare, Richard N.

    COMBUSTION AND FLAME 24, 27-34 (1975) 27 Flame Emission Studies of Ozone with Metal Alkyls: Zn (CH3 of combustion. Premixed [2, 3] anddiffusion [4] flames of metal alkyl compounds have been carried out to deter- tageous to study the combustion of polyatomic molecules under single-collision conditions, i

  15. Flame Structure and Flame Reaction Kinetics. VI. Structure, Mechanism and Properties of Rich Hydrogen+Nitrogen+Oxygen Flames

    Microsoft Academic Search

    M. J. Day; G. Dixon-Lewis; K. Thompson

    1972-01-01

    Burning velocities of a number of slow-burning, fuel-rich hydrogen + nitrogen + oxygen flames have been measured and compared with values computed on the basis of the chemical mechanism proposed by Dixon-Lewis (1970 a). This mechanism is shown to be incomplete, and in order to obtain agreement between theory and experiment over the composition range studied, it is necessary to

  16. Suppression of Low Strain Rate Nonpremixed Flames by an Agent

    NASA Technical Reports Server (NTRS)

    Hamins, A.; Bundy, M.; Puri, I. K.; McGrattan, K.; Park, W. C.

    2001-01-01

    The agent concentration required to achieve the suppression of low strain rate nonpremixed flames is an important consideration for fire protection in a microgravity environment such as a space platform. Currently, there is a lack of understanding of the structure and extinction of low strain rate (<20 s(exp -1)) nonpremixed flames. The exception to this statement is the study by Maruta et al., who reported measurements of low strain rate suppression of methane-air diffusion flames with N2 added to the fuel stream under microgravity conditions. They found that the nitrogen concentration required to achieve extinction increased as the strain rate decreased until a critical value was obtained. As the strain rate was further decreased, the required N2 concentration decreased. This phenomenon was termed "turning point" behavior and was attributed to radiation-induced nonpremixed flame extinction. In terms of fire safety, a critical agent concentration assuring suppression under all flow conditions represents a fundamental limit for nonpremixed flames. Counterflow flames are a convenient configuration for control of the flame strain rate. In high and moderately strained near-extinction nonpremixed flames, analysis of flame structure typically neglects radiant energy loss because the flames are nonluminous and the hot gas species are confined to a thin reaction zone. In counterflowing CH4-air flames, for example, radiative heat loss fractions ranging from 1 to 6 percent have been predicted and measured. 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 number of suppressants (N2, CO2, or CF3Br) was considered as they were added to either the fuel or oxidizer streams of low strain rate methane-air diffusion flames.

  17. CP2 stars in clusters: deep Delta a-photometry

    E-print Network

    H. M. Maitzen; M. Rode; E. Paunzen

    1998-05-05

    The search for chemically peculiar (CP) stars in open clusters using photoelectric photometry sampling the presence of the characteristic flux depression feature at 5200A via the Delta a-system (Maitzen 1976) has so far delivered data for objects usually no more distant than 1000 pc from the Sun. If one intends to study the presence of CP stars at larger distances from the Sun, classical photometry has to be replaced by CCD photometry. For the first time, our investigation presents the results of CCD-photometry in the Delta a-system for a rich open cluster which is at a distance clearly beyond hitherto studied objects, Melotte 105 (2 kpc, log age = 8.5). Comparison with published uvby-photometry yields the calibration of the colour index g_1-y of our system, which is necessary for deriving the peculiarity index Delta a. For this we achieve an average accuracy of 0.007 mag. Six objects with only marginally peculiar Delta a-values were found, but spectroscopic and additional photometric evidence is needed to substantiate their peculiarity.

  18. Revised Filter Profiles and Zero Points for Broadband Photometry

    NASA Astrophysics Data System (ADS)

    Mann, Andrew W.; von Braun, Kaspar

    2015-02-01

    Estimating accurate bolometric fluxes for stars requires reliable photometry to absolutely flux calibrate the spectra. This is a significant problem for studies of very bright stars, which are generally saturated in modern photometric surveys. Instead we must rely on photometry with less precise calibration. We utilize precisely flux-calibrated spectra to derive improved filter bandpasses and zero points for the most common sources of photometry for bright stars. In total, we test 39 different filters in the General Catalog of Photometric Data as well as those from Tycho-2 and Hipparcos. We show that utilizing inaccurate filter profiles from the literature can create significant color terms resulting in fluxes that deviate by ?10% from actual values. To remedy this we employ an empirical approach; we iteratively adjust the literature filter profile and zero point, convolve it with catalog spectra, and compare to the corresponding flux from the photometry. We adopt the passband values that produce the best agreement between photometry and spectroscopy and are independent of stellar color. We find that while most zero points change by < 5%, a few systems change by 10-15%. Our final profiles and zero points are similar to recent estimates from the literature. Based on determinations of systematic errors in our selected spectroscopic libraries, we estimate that most of our improved zero points are accurate to 0.5-1%.

  19. Radiative Structures of Lycopodium-Air Flames in Low Gravity

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  20. Analytical Study of Gravity Effects on Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  1. Thermal degradation and flame retardancy of epoxy resins containing intumescent flame retardant

    Microsoft Academic Search

    M. Gao; W. Wu; Y. Yan

    2009-01-01

    Pentaerythritol diphosphonate melamine-urea-formaldehyde resin salt, a novel cheap macromolecular intumescent flame retardants\\u000a (IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Epoxy\\u000a resins (EP) were modified with IFR to get the flame retardant EP, whose flammability and burning behavior were characterized\\u000a by UL 94 and limiting oxygen index (LOI). 25 mass% of IFR

  2. Measurements of lead vapor and particulate in flames and post-flame gases

    Microsoft Academic Search

    Steven G. Buckley; Robert F. Sawyer; Catherine P. Koshland; Donald Lucas

    2002-01-01

    We describe several laser fluorescence methods used to measure lead in flames and in post-flame gases. Each relies on excitation of the 7s 3P1 ? 6p2 3P0 transition from the ground state of lead and detection of fluorescence on the 7s 3P1 ? 6p2 3P1 and 7s 3P1 ? 6p23P2 transitions. Aqueous solutions of lead salts are atomized and injected

  3. Freely propagating open premixed turbulent flames stabilized by swirl

    SciTech Connect

    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

    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.

  4. The effects of gravity on wrinkled laminar flames

    SciTech Connect

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

    1992-09-01

    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.

  5. The effects of gravity on wrinkled laminar flames

    SciTech Connect

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

    1992-09-01

    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.

  6. Flame propagation with a sequential reaction mechanism

    Microsoft Academic Search

    Stephen B. Margolis; Bernard J. Matkowsky

    1982-01-01

    The steady propagation of a flame characterized by the production and depletion of a significant intermediate species through a premixed combustible mixture is studied. The method of matched asymptotic expansions is employed to derive a solution for the large activation energies, which confine the two chemical reactions involved to a thin layer. The small separation distance between the points where

  7. Carbonaceous Deposits from Hydrocarbon Diffusion Flames

    Microsoft Academic Search

    J. R. Arthur; P. K. Kapur; D. H. Napier

    1952-01-01

    As a prelude to more general studies on the formation of smoke and soot during the combustion of coals and their distillation products, some observations have been made of the effects of fuel type and mode of combustion on the amount and character of the carbonaceous matter deposited from flames of simple gaseous and liquid fuels. Examination of solvent extracts

  8. 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...

  9. Flame Tests Using Improvised Alcohol Burners

    Microsoft Academic Search

    Veljko Dragojlovic; Richard F. Jones

    1999-01-01

    In this demonstration, an improvised alcohol burner, with a methanol solution of a salt as fuel, produces a long-lasting brightly colored flame. A disadvantage when using a regular alcohol burner is that the burner has to be cleaned and a wick replaced, before a solution of a different salt can be used. For our demonstration, alcohol burners are made from

  10. Photovoltaic module spread-of-flame testing

    Microsoft Academic Search

    R. S. Sugimura; D. H. Otth; J. C. Arnett

    1984-01-01

    Photovoltaic modules used in solar energy conversion are tested for flammability. Class B burning brand tests were conducted with the following results: module glass shattered and hydrocarbon encapsulants ignited. Penetration of back surface material was the prime cause of failure. Materials with greater flame and heat resistance are under consideration to increase back surface integrity up to Class A burning

  11. Simple Flame Test Techniques Using Cotton Swabs

    Microsoft Academic Search

    Michael J. Sanger; Amy J. Phelps

    2004-01-01

    This article describes three new methods for performing simple flame tests using cotton swabs. The first method uses a Bunsen burner and solid metal salts; the second method uses a Bunsen burner and 1 M aqueous solutions of metal salts; and the third method uses candles, rubbing alcohol, and solid metal salts. These methods have the advantage of being easy

  12. Soret and Dilution Effects on Premixed Flames

    Microsoft Academic Search

    PEDRO GARCÍA-YBARRA; COLETTE NICOLI; PAUL CLAVIN

    1984-01-01

    The structure of a wrinkled premixed flame is analysed theoretically. By assuming the reactive mixture diluted in an inert gas and a weak cross-diffusion coupling between the heat and mass fluxes, the effect of the change by the reaction of the physical gas properties (thermal conductivity, specific heat, number of molecules) and Soret and Dufour diffusions have been investigated in

  13. Chemistry of Molecular Growth Processes in Flames

    Microsoft Academic Search

    Kermit C. Smyth; J. Houston Miller

    1987-01-01

    Chemical mechanisms of pyrolysis, growth, and oxidation processes in flames have traditionally been inferred from spatial profile measurements of species concentrations. Experimental investigations now include the detection of numerous minor species such as reactive radicals and intermediate hydrocarbons. In assessing a proposed mechanism important new constraints can be established when the detailed species profile data are combined with velocity and

  14. Chemistry of molecular growth processes in flames

    Microsoft Academic Search

    K. C. Smyth; J. H. Miller

    1987-01-01

    Chemical mechanisms of pyrolysis, growth, and oxidation processes in flames have traditionally been inferred from spatial profile measurements of species concentrations. Experimental investigations now include the detection of numerous minor species such as reactive radicals and intermediate hydrocarbons. In assessing a proposed mechanism important new constraints can be established when the detailed species profile data are combined with velocity and

  15. Analytic modeling of a spray diffusion flame

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  16. Are brominated flame retardants endocrine disruptors?

    Microsoft Academic Search

    Juliette Legler; Abraham Brouwer

    2003-01-01

    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

  17. Premixed-gas flames Paul D. Ronney

    E-print Network

    . tcond can be estimated as the ratio of the flame temperature to the rate of temperature decay due and oxidant must mix in stoichiometric proportions before chemical reaction can occur. The propagation speed. #12;2 2. COMPARISON OF TIME SCALES To estimate under what conditions gravity can affect premixed

  18. 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...

  19. 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...

  20. 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...

  1. Polybrominated diphenyl ether (PBDE) flame retardants

    Microsoft Academic Search

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

    2001-01-01

    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

  2. Flame retardant effects of magnesium hydroxide

    Microsoft Academic Search

    R. N. Rothon; P. R. Hornsby

    1996-01-01

    Magnesium hydroxide has all the characteristics required for use as a flame retardant filler. It can be made synthetically with high purity and in a range of useful morphologies, responds well to surface modifiers and decomposes endothermically with release of water at temperatures close to those of polymer degradation and high enough to allow incorporation into most polymer types. Crystal

  3. Song and the Zimbabwean film, Flame (1996)

    Microsoft Academic Search

    Urther Rwafa

    2011-01-01

    The Zimbabwean film Flame (1996) encountered its public life in a controversial way. Its producer Ingrid Sinclair aimed to produce a film that would reveal the seamy side of Zimbabwe's liberation war, the rape of women being the central motive to the narrative plot of the film that sought to symbolically ‘overthrow’ the regimes of heroic images that the armed

  4. Control of Reaction Rate in Dust Flames

    Microsoft Academic Search

    J. M. Beér; R. H. Essenhigh

    1960-01-01

    EVER since Nusselt1 introduced the boundary layer concept, about forty years ago, for calculating rates of heat and mass transfer to a spherical particle, it has been universally accepted (without proof) by subsequent theoretical work (see ref. 2) that the reaction-rate of particles in a dust flame is determined by the rate of supply of oxygen through a diffusional boundary

  5. Power-law Wrinkling Turbulence-Flame Interaction Model for Astrophysical Flames

    NASA Astrophysics Data System (ADS)

    Jackson, Aaron P.; Townsley, Dean M.; Calder, Alan C.

    2014-04-01

    We extend a model for turbulence-flame interactions (TFI) to consider astrophysical flames with a particular focus on combustion in Type Ia supernovae. The inertial range of the turbulent cascade is nearly always under-resolved in simulations of astrophysical flows, requiring the use of a model in order to quantify the effects of subgrid-scale wrinkling of the flame surface. We provide implementation details to extend a well-tested TFI model to low-Prandtl number flames for use in the compressible hydrodynamics code FLASH. A local, instantaneous measure of the turbulent velocity is calibrated for FLASH and verification tests are performed. Particular care is taken to consider the relation between the subgrid rms turbulent velocity and the turbulent flame speed, especially for high-intensity turbulence where the turbulent flame speed is not expected to scale with the turbulent velocity. Finally, we explore the impact of different TFI models in full-star, three-dimensional simulations of Type Ia supernovae.

  6. Effect of turbulence characteristics on local flame structure of H2 air premixed flames

    NASA Astrophysics Data System (ADS)

    Nada, Y.; Tanahashi, M.; Miyauchi, T.

    2004-04-01

    Direct numerical simulations (DNS) of turbulent premixed flames are conducted to investigate effects of turbulence characteristics on the local flame structure. A detailed kinetic mechanism including 12 reactive species and 27 elementary reactions is used to represent the H2-air reaction in turbulence. Numerical conditions of DNS can be classified into a wrinkled-flamelets regime, a corrugated-flamelets regime and thin reaction zones near the boundary of Karlovitz number Ka=1.0 of the turbulent-combustion diagram. For all cases, the distribution of heat-release rate shows a three-dimensionally connected sheet-like feature, even though the heat-release rate highly fluctuates along the flamefront. The heat-release rate tends to increase at the flamefronts that are convex towards the burnt side. For the turbulent premixed flames in the corrugated-flamelets regime, the handgrip structure is produced by the intrusion of the coherent fine-scale eddy into the flame and the heat-release rate in this structure increases up to 1.2 times of that of a laminar flame. In the wrinkled-flamelets regime, the spire-like structure of the flamefront is created due to the coherent fine-scale eddies in turbulence. By identifying flame elements in turbulence, their statistical characteristics are also discussed. This article was chosen from Selected Proceedings of the Third International Symposium on Turbulence and Shear Flow Phenomena (Sendai, Japan, 24-27 June 2003) ed N Kasagi et al.

  7. Properties of Young Massive Cluster Derived from Photometry

    E-print Network

    U. Fritze-v. Alvensleben

    2004-08-25

    I will show that photometry -- if extending over a reasonable choice of passbands -- can give fairly precise information about young star clusters and their evolutionary state. Optical colors alone are known to leave severe ambiguities due to degeneracies between age, metallicity and extinction. High quality photometry including $U, B, V$ or $I$, and a NIR band, however, in combination with an extensive grid of evolutionary synthesis models for star clusters and a dedicated tool to analyse spectral energy distributions allows to assess and largely disentangle star cluster ages, metallicities, extinction values and, hence, to derive their masses. Gaseous emission contributions sensibly affect broad band colors during the youngest stages, depending on metallicity. Mass functions of young star cluster systems may considerably differ in shape from luminosity functions. An ESO ASTROVIRTEL project provides multi-color photometry for a large number of young, intermediate age and old star cluster systems. As a first example I show results obtained for NGC 1569.

  8. First time-series optical photometry from Antarctica

    E-print Network

    K. G. Strassmeier; R. Briguglio; T. Granzer; G. Tosti; I. DiVarano; I. Savanov; M. Bagaglia; S. Castellini; A. Mancini; G. Nucciarelli; O. Straniero; E. Distefano; S. Messina; G. Cutispoto

    2008-07-18

    Beating the Earth's day-night cycle is mandatory for long and continuous time-series photometry and had been achieved with either large ground-based networks of observatories at different geographic longitudes or when conducted from space. A third possibility is offered by a polar location with astronomically-qualified site characteristics. Aims. In this paper, we present the first scientific stellar time-series optical photometry from Dome C in Antarctica and analyze approximately 13,000 CCD frames taken in July 2007. We conclude that high-precision CCD photometry with exceptional time coverage and cadence can be obtained at Dome C in Antarctica and be successfully used for time-series astrophysics.

  9. A new flame monitor with triple photovoltaic cells

    SciTech Connect

    Xu, L.J.; Yan, Y. [Beijing University for Aeronaut & Astronaut, Beijing (China)

    2006-08-15

    In this paper, we present a new flame monitor that uses three photovoltaic cells covering the ultraviolet (UV), visible, and infrared (IR) spectral bands. A gain-adjustable amplifier is incorporated into the monitor so that it is applicable to the coal-, oil-, or gas-fired flames. Self-checking of the monitor is implemented through cross correlation of the signals from the three cells, and hence, no additional self-checking hardware is required. Both the oscillation frequency and the brightness of the flame are used to monitor flame stability and to detect flame presence as well as sighting-tube blockage. Unlike conventional single-cell flame detectors, the new multicell devices can still be in operation before being repaired, after a cell-failure alarm has gone off. Experiments were carried out on an industrial-scale combustion test facility in order to demonstrate the operability and efficacy of the new flame monitor.

  10. Computational predictions of flame spread over alcohol pools

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  11. Numerical study on lateral movements of cellular flames

    NASA Astrophysics Data System (ADS)

    Kadowaki, Satoshi

    1997-09-01

    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.

  12. Theory and modeling of accelerating flames in tubes

    NASA Astrophysics Data System (ADS)

    Bychkov, Vitaly; Petchenko, Arkady; Akkerman, V.'Yacheslav; Eriksson, Lars-Erik

    2005-10-01

    The analytical theory of premixed laminar flames accelerating in tubes is developed, which is an important part of the fundamental problem of flame transition to detonation. According to the theory, flames with realistically large density drop at the front accelerate exponentially from a closed end of a tube with nonslip at the walls. The acceleration is unlimited in time; it may go on until flame triggers detonation. The analytical formulas for the acceleration rate, for the flame shape and the velocity profile in the flow pushed by the flame are obtained. The theory is validated by extensive numerical simulations. The numerical simulations are performed for the complete set of hydrodynamic combustion equations including thermal conduction, viscosity, diffusion, and chemical kinetics. The theoretical predictions are in a good agreement with the numerical results. It is also shown how the developed theory can be used to understand acceleration of turbulent flames.

  13. Chemistry and toxicity of flame retardants for plastics.

    PubMed Central

    Liepins, R; Pearce, E M

    1976-01-01

    An overview of commercially used flame retardants is give. The most used flame retardants are illustrated and the seven major markets, which use 96% of all flame-retarded polymers, are described. Annual flame retardant growth rate for each major market is also projected. Toxicity data are reviewed on only those compositions that are considered commercially significant today. This includes 18 compounds or families of compounds and four inherently flame-retarded polymers. Toxicological studies of flame retardants for most synthetic materials are of recent origin and only a few of the compounds have been evaluated in any great detail. Considerable toxicological problems may exist in the manufacturing of some flame retardants, their by-products, and possible decomposition products. PMID:1026419

  14. Experimental studies of inhibited counterflow flames

    NASA Astrophysics Data System (ADS)

    Truett, Leonard Franklin, III

    An experimental and numerical study was performed to investigate the fundamental mechanisms of chemical inhibition. The first part of this work examined the structure of non-premixed counterflow methane-air flames. Gas samples were taken with a quartz microprobe and analyzed using a gas chromatograph with a thermal conductivity detector. Experimental and detailed numerical results were obtained for an uninhibited flame and flames inhibited by 1.5% CF3Br and 1.5% CF3I added to the oxidizer, all with a strain rate of 150s-1. The experimental data showed a slight shift toward the oxidizer duct above the flame, but showed excellent agreement with the numerical results below the flame in all cases. The inhibiting effect of CF3Br on a non-premixed diluted hydrogen-air flame was also investigated in the counterflowing configuration. Extinction results were obtained for 15%H2/85%N2 and 16%H 2/84%N2 in the fuel stream. The experimental results supported the theory that carbon chemistry does not play a significant role in inhibition by CF3Br. These results were compared with two different numerical models with different inhibition mechanisms. The effect of partially premixing a methane-air counterflow flame on the extinction strain rate was also examined. Premixing the oxidizer flow had a stabilizing effect, premixing the fuel flow had a weak inhibiting effect, and premixing in both flows had a very weak stabilizing effect that was basically the average of the two individual cases. These results were compared with detailed calculations, asymptotic and one-step analysis. The detailed numerical calculations had excellent agreement with the experiments but the asymptotic and one-step analysis predicted incorrect trends for all cases. Tests were also performed to examine the inhibiting effectiveness of alkali metal salts. Experiments were performed with NaHCO3 and KHCO3 with particle sizes of <30 microns and <20 microns, NaBr and KBr with a particle size of 5--25 microns, and silica (SiO 2) with a particle size of 1--3 microns. Inhibiting effectiveness increased as the particle sized decreased for all powders. The KHCO3 was approximately twice as effective as the NaHCO3, NaBr and KBr for similar particle sizes. These powders were approximately 10 times more efficient than silica and CF3Br on a mass basis.

  15. Fixing the U-band Photometry of Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Krisciunas, Kevin; Bastola, Deepak; Espinoza, Juan; Gonzalez, David; Gonzalez, Luis; Gonzalez, Sergio; Hamuy, Mario; Hsiao, Eric Y.; Morrell, Nidia; Phillips, Mark M.; Suntzeff, Nicholas B.

    2013-01-01

    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 ~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. Based in part on observations taken at the Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

  16. Field Effects of Buoyancy on Lean Premixed Turbulent Flames

    NASA Technical Reports Server (NTRS)

    Cheng, R. K.; Johnson, M. R.; Greenberg, P. S.; Wernet, M. P.

    2003-01-01

    The study of field effects of buoyancy on premixed turbulent flames is directed towards the advancement of turbulent combustion theory and the development of cleaner combustion technologies. Turbulent combustion is considered the most important unsolved problem in combustion science and laboratory studies of turbulence flame processes are vital to theoretical development. Although buoyancy is dominant in laboratory flames, most combustion models are not yet capable to consider buoyancy effects. This inconsistency has impeded the validation of theories and numerical simulations with experiments. Conversely, the understanding of buoyancy effects is far too limited to help develop buoyant flame models. Our research is also relevant to combustion technology because lean premixed combustion is a proven method to reduce the formation of oxides of nitrogen (NOx). In industrial lean premixed combustion systems, their operating conditions make them susceptible to buoyancy thus affecting heat distribution, emissions, stability, flashback and blowoff. But little knowledge is available to guide combustion engineers as to how to avoid or overcome these problems. Our hypothesis is that through its influence on the mean pressure field, buoyancy has direct and indirect effects on local flame/turbulence interactions. Although buoyancy acts on the hot products in the farfield the effect is also felt in the nearfield region upstream of the flame. These changes also influence the generation and dissipation of turbulent kinetic energy inside the flame brush and throughout the flowfield. Moreover, the plume of an open flame is unstable and the periodic fluctuations make additional contributions to flame front dynamics in the farfield. Therefore, processes such as flame wrinkling, flow acceleration due to heat release and flame- generated vorticity are all affected. Other global flame properties (e.g. flame stabilization limits and flame speed) may all be coupled to buoyancy. This problem poses major challenges to combustion modeling due to its need for a computation domain extending into the farfield and full specifications of upstream, wall and downstream boundary conditions.

  17. Premixed Flame-Vortex Interactions Imaged in Microgravity

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  18. Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, Peter B.; Yuan, Zeng-Guang; Urban, David L.

    1997-01-01

    Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient pressures. Soot concentrations were minimized by selecting conditions at low flowrates and low ambient pressures; this allows identification of actual flame sheets associated with blue emissions of CH and CO2. The present modeling effort follows that of Roper and is useful in explaining many of the trends observed.

  19. Plasma electrochemistry: electroreduction in a flame.

    PubMed

    Hadzifejzovic, Emina; Stankovic, Jovan; Firth, Steven; McMillan, Paul F; Caruana, Daren J

    2007-10-21

    The manipulation of electron transfer reactions at surfaces forms the cornerstone of electrodeposition and processing of materials on substrates with precise control of stoichiometry and oxidation state. However, the utility of this technique, which is mainly carried out in liquid electrolytes, is ultimately limited by the electrolysis of the solvent which limits a potential window to at best 4.8 V in nonaqueous solutions (A. J. Bard and L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, Wiley, New York, NY, 2nd edn, 2001; ref. 1) and can be up to 6 V in ionic liquids (A. P. Abbott, K. J. McKenzie, Phys. Chem. Chem. Phys., 2006, 8, 4265-4279; ref. 2). A long-sought-after goal has been to develop a corresponding technique at the solid/gas interface in the absence of a solvent which will allow in principle a potential window in excess of 100 V (J. M. Goodings, J. Guo, A. N. Hayhurst and S. G. Taylor, Int. J. Mass Spectrom., 2001, 206, 137-151; ref. 3). This extended potential window will enable chemistry at the solid/gas interface that is not possible at the solid/liquid interface. Here we describe a new approach to gas-phase electrochemistry using a flame plasma as the electrolyte medium. We demonstrate the controlled electrochemical reduction of Cu(+) to Cu(0) at an electrode surface in a flame environment with resulting deposition of either Cu(2)O or Cu species on conducting diamond electrodes. This approach is novel in that it involves the application of an electrochemical potential difference to change the redox state of surface confined species, not the measurement of flame bore ions (as in flame ionisation detectors). This new technique will permit deposition of films and particles on surfaces with control over the oxidation state of the species. This will provide a valuable enhancement to the capabilities of materials preparation methods such as flame spray deposition. PMID:17914469

  20. HUBBLE SPACE TELESCOPE Photometry of the Globular Cluster M4

    NASA Astrophysics Data System (ADS)

    Ibata, Rodrigo A.; Richer, Harvey B.; Fahlman, Gregory G.; Bolte, Michael; Bond, Howard E.; Hesser, James E.; Pryor, Carlton; Stetson, Peter B.

    1999-02-01

    This paper presents a detailed description of the acquisition and processing of a large body of imaging data for three fields in the globular cluster M4 taken with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. Analysis with the ALLFRAME package yielded the deepest photometry yet obtained for this cluster. The resulting data set for 4708 stars (positions and calibrated photometry in V, I, and, in two fields, U) spanning approximately six cluster core radii is presented. The scientific analysis is deferred to three companion papers, which investigate the significant white dwarf population discovered and the main-sequence population.

  1. Transit and secondary eclipse photometry in the near-infrared

    E-print Network

    Ignas Snellen

    2007-05-02

    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.

  2. Characterization of transiting exoplanets by way of differential photometry

    NASA Astrophysics Data System (ADS)

    Cowley, Michael; Hughes, Stephen

    2014-05-01

    This paper describes a simple activity for plotting and characterizing the light curve from an exoplanet transit event by way of differential photometry analysis. Using free digital imaging software, participants analyse a series of telescope images with the goal of calculating various exoplanet parameters, including size, orbital radius and habitability. The activity has been designed for a high-school or undergraduate university level and introduces fundamental concepts in astrophysics and an understanding of the basis for exoplanetary science, the transit method and digital photometry.

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

    E-print Network

    Baum, Bryan A.

    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

  4. Galileo Photometry of Asteroid 951 Gaspra

    USGS Publications Warehouse

    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

    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.

  5. Numerical Study of Buoyancy and Differential Diffusion Effects on the Structure and Dynamics of Triple Flames

    NASA Technical Reports Server (NTRS)

    Chen, J. -Y.; Echekki, T.

    1999-01-01

    Triple flames arise in a number of practical configurations where fuel and oxidizer are partially premixed, such as in the base of a lifted jet flame. Past experimental studies, theoretical analyses, and numerical modeling of triple flames suggested the potential role of triple flames in stabilizing turbulent flames and in promoting flame propagation. From recent numerical simulations of laminar triple flames, a strong influence of differential diffusion among species and heat on the triple flame structure has been gradually appreciated. This paper reports preliminary numerical results on the influence of gravity and differential diffusion effects on the structure and dynamics of triple flames with a one-step global irreversible chemistry model.

  6. Infrared space observatory photometry of circumstellar dust in Vega-type systems

    NASA Technical Reports Server (NTRS)

    Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.; Thakur, N.

    1998-01-01

    The ISOPHOT (Infrared Space Observatory Photometry) instrument onboard the Infrared Space Observatory (ISO) was used to obtain 3.6-90 micron photometry of Vega-type systems. Photometric data were calibrated with the ISOPHOT fine calibration source 1 (FCS1). Linear regression was used to derive transformations to make comparisons to ground-based and IRAS photometry systems possible. These transformations were applied to the photometry of 14 main-sequence stars. Details of these results are reported on.

  7. Phase-resolved characterization of vortex-flame interaction in a turbulent swirl flame

    NASA Astrophysics Data System (ADS)

    Stöhr, M.; Sadanandan, R.; Meier, W.

    2011-10-01

    The relation between flow field and flame structure of a turbulent swirl flame is investigated using simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence of OH (OH-PLIF). The measurements are performed in one axial and three transverse sections through the combustion chamber of a gas turbine model combustor, which is operated with methane and air under atmospheric pressure. Analysis of the velocity fields using proper orthogonal decomposition (POD) shows that the dominant unsteady flow structure is a so-called precessing vortex core (PVC). In each of the four sections, the PVC is represented by a characteristic pair of POD eigenmodes, and the phase angle of the precession can be determined for each instantaneous velocity field from its projection on this pair. Phase-conditioned averages of velocity field and OH distribution are thereby obtained and reveal a pronounced effect of the PVC in the form of convection-enhanced mixing. The increased mixing causes a rapid ignition of the fresh gas, and the swirling motion of the PVC leads to an enlarged flame surface due to flame roll-up. A three-dimensional representation shows that the PVC is accompanied by a co-precessing vortex in the outer shear layer, which, however, has no direct impact on the flame. As an alternative to phase averaging, a low-order representation of the phase-resolved dynamics is calculated based on the first pair of POD modes. It is found that small-scale structures are represented more accurately in the phase averages, whereas the low-order model has a considerable smoothing effect and therefore provides less detailed information. The findings demonstrate that the combined application of POD, PIV, and PLIF can provide detailed insights into flow-flame interaction in turbulent flames.

  8. Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  9. Flame quality monitor system for fixed firing rate oil burners

    DOEpatents

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

    1992-01-01

    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.

  10. Upward Flame Spread Over Thin Solids in Partial Gravity

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  11. Fractal characterisation of high-pressure and hydrogen-enriched CH4air turbulent premixed flames

    E-print Network

    Gülder, �mer L.

    Fractal characterisation of high-pressure and hydrogen-enriched CH4­air turbulent premixed flames. Keywords: Premixed turbulent combustion; High-pressure premixed turbulent flames; Hydrogen-enriched methane flames; Fractal characteristics of premixed flames; Surface density of high-pressure flames 1

  12. Damköhler Number Similarity for Static Flame Stability in Gaseous-Fueled Augmentor Flows

    Microsoft Academic Search

    Hossam A. El-Asrag; Heinz Pitsch; Wookyung Kim; M. Godfrey Mungal

    2011-01-01

    Afterburners (or augmentors) are used to increase thrust in aircraft engines. Static flame stability, or the robustness to flame blowoff, is an important metric in the performance assessment of combustion in aircraft engine afterburners, where bluff-body-type flame holders are typically used to stabilize the flame. The design of such flame holders is complicated by the operating conditions, which involve flows

  13. Turbulence-Flame Interactions in Type Ia Supernovae A. J. Aspden1

    E-print Network

    Turbulence-Flame Interactions in Type Ia Supernovae A. J. Aspden1 , J. B. Bell1 , M. S. Day1 , S. E supernovae (SN Ia) requires the use of flame models. As a prelude to exploring various options for flame-scale dynamics of nuclear flames in the supernova envi- ronment in which the details of the flame structure

  14. Effect of Wind Velocity on Flame Spread in Microgravity

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  15. The coupling of conical wrinkled laminar flames with gravity

    SciTech Connect

    Kostiuk, L.W.; Cheng, R.K. [Lawrence Berkeley Lab., CA (United States)] [Lawrence Berkeley Lab., CA (United States)

    1995-10-01

    This work explores the influences that gravity has on conical premixed laminar and mildly turbulent flames (i.e., wrinkled laminar flames). The approach is to compare overall flame characteristics in normal (+g) reverse ({minus}g), and micro-gravity ({micro}g). Laser schlieren is the principal diagnostic for the {micro}g experiments. Laboratory investigation of +g and {minus}g flames also include two components laser doppler anemometry. The results obtained in a wide range of flow, mixture and turbulence conditions show that gravity has a profound effect on the lean stabilization limits, features of the flowfield, and mean flame heights. in +g and {micro}g do not flicker. analysis of the flame flickering frequencies produces in an empirical relationship St*{sup 2}/Ri = 0.0018 Re{sup 2/3} (where St*, Ri, and Re are, respectively, the Strouhal number normalized by the heat release ratio, the Richardson number, and the Reynolds number). This correlation would be useful for theoretical prediction of buoyancy induced flame instabilities. Comparison of mean flame heights shows that +g, {minus}g, {micro}g flame properties do not converge with increased flow momentum. Velocity measurements in laminar flames show that in +g, the flow generated by the rising products plum is almost non-divergent, slightly turbulent and unstable. In {minus}g, the flow becomes divergent but is stable and non-turbulent in the region surrounding the flame cone. The change from a nondivergent to divergent flow field seems to account for the differences in the observed mean flame heights. The schlieren images and the velocity measurements in +g and {minus}g also provide some insight into the overall flowfield features of {micro}g flames.

  16. Optical properties of boreal forest fire smoke derived from Sun photometry

    E-print Network

    Li, Zhanqing

    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

  17. 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

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

    E-print Network

    Ovaldsen, Jan-Erik

    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

  19. An Improved Technique for the Photometry and Astrometry of Faint Companions

    E-print Network

    Dainty, Chris

    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

  20. 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

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

    E-print Network

    Lowenthal, James D.

    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

  2. Notes for KINGFISH on SPIRE Photometry DRAFT: v8 2013.3.16.759

    E-print Network

    Draine, Bruce T.

    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

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

    E-print Network

    Lee, Hyun-chul

    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

  4. Comet Kohoutek. [proceedings - astronomical photometry/astronomical spectroscopy

    NASA Technical Reports Server (NTRS)

    Gary, G. A. (editor)

    1975-01-01

    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.

  5. Photometry of Standard Stars and Open Star Clusters

    NASA Astrophysics Data System (ADS)

    Jefferies, Amanda; Frinchaboy, Peter

    2010-10-01

    Photometric CCD observations of open star clusters and standard stars were carried out at the McDonald Observatory in Fort Davis, Texas. This data was analyzed using aperture photometry algorithms (DAOPHOT II and ALLSTAR) and the IRAF software package. Color-magnitude diagrams of these clusters were produced, showing the evolution of each cluster along the main sequence.

  6. Characterization of Transiting Exoplanets by Way of Differential Photometry

    ERIC Educational Resources Information Center

    Cowley, Michael; Hughes, Stephen

    2014-01-01

    This paper describes a simple activity for plotting and characterizing the light curve from an exoplanet transit event by way of differential photometry analysis. Using free digital imaging software, participants analyse a series of telescope images with the goal of calculating various exoplanet parameters, including size, orbital radius and…

  7. Characterizing New Eclipsing Binaries Identified from STEREO Photometry

    NASA Astrophysics Data System (ADS)

    Markov, Harry; Tsvetanov, Zlatan; Iliev, Ilian; Stateva, Ivanka; Markova, Nevena

    2012-04-01

    Since 2010, a program to explore new eclipsing binary systems identified from STEREO photometry has been in progress. Our first results are presented here: light curves and high resolution spectra taken with Coudé spectrograph (National Astronomical Observatory Rozhen) and ARC Échelle spectrometer (ARCES, Apache Point Observatory).

  8. Crab Pulsar Photometry and the Signature of Free Precession

    E-print Network

    Andrej Cadez; Simon Vidrih; Mirjam Galicic; Alberto Carraminana

    2003-03-17

    Optical photometry for the pulsar PSR0531+21 has been extended with new observations that strengthen evidence for a previously observed 60 seconds periodicity. This period is found to be increasing with time at approximately the same rate as the rotational period of the pulsar. The observed period and its time dependence fit a simple free precession model.

  9. Error analysis of multi-wavelength sun photometry

    Microsoft Academic Search

    Glenn E. Shaw

    1976-01-01

    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

  10. uvby--beta photoelectric photometry of NGC 7063

    E-print Network

    J. H. Pena; L. Fox Machado; R. Garrido

    2007-07-15

    From uvby photometry of 75 stars in the direction of NGC 7063 we were able to determine membership of some stars and fix the distance (722 +- 105 pc), log age (of 8.146) and reddening (E(b-y) = 0.091 +- 0.039 mag) for the cluster.

  11. CCD Photometry of Nova V1500 Cygni Twenty Years After

    E-print Network

    I. Semeniuk; A. Olech; M. Nalezyty

    1995-12-14

    We report on CCD photometry of Nova V1500 Cygni obtained in July 1995 to show that twenty years after outburst, being of about 18~mag, the star can still be observed with small telescopes. The 0.1396 day period continues to be stable.

  12. JCMT COADD: UKT14 continuum and photometry data reduction

    NASA Astrophysics Data System (ADS)

    Hughes, David; Oliveira, Firmin J.; Tilanus, Remo P. J.; Jenness, T.

    2014-11-01

    COADD was used to reduce photometry and continuum data from the UKT14 instrument on the James Clerk Maxwell Telescope in the 1990s. The software can co-add multiple observations and perform sigma clipping and Kolmogorov-Smirnov statistical analysis. Additional information on the software is available in the JCMT Spring 1993 newsletter (large PDF).

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

    Microsoft Academic Search

    P. Cinzano

    2003-01-01

    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

  14. Empirical color transformations between SDSS photometry and other photometric systems

    Microsoft Academic Search

    Katrin Jordi; E. K. Grebel; Karin Ammon

    2006-01-01

    Aims.We present empirical color transformations between the Sloan Digital Sky Survey (SDSS) ugriz photometry and the Johnson-Cousins UBVRI system and Becker's RGU system, respectively. Owing to the magnitude of data that is becoming available in the SDSS photometric system it is particularly important to be able to convert between this new system and traditional photometric systems. Unlike earlier published transformations

  15. Photometry and Coravel observations of IC 2488 (Claria+, 2003)

    Microsoft Academic Search

    J. J. Claria; A. E. Piatti; E. Lapasset; J.-C. Mermilliod

    2002-01-01

    We present new UBV photoelectric observations of 119 stars in the field of the southern open cluster IC 2488, supplemented by DDO and Washington photometry and Coravel radial velocities for a sample of red giant candidates. Nearly 50% of the stars sampled - including three red giants and one blue straggler - are found to be probable cluster members. Photometric

  16. Astrometry and Photometry of Asteroids and Comets Detected by WISE

    Microsoft Academic Search

    Robert S. McMillan; Amy Mainzer; Jeff Larsen; Jim Scotti; Joe Masiero; James Bauer; Tommy Grav; Chet Maleszewski

    2011-01-01

    Telescope time is requested to recover and do astrometry and photometry of carefully selected asteroids, comets, and suspected comets previously detected by WISE. The WISE all-sky thermal infrared survey uncovered more solar system objects with dark albedos and more objects with comet-like orbital elements than expected. These outliers may represent hitherto unexplored populations and may reveal characteristics of the evolution

  17. High Speed Photometry of the Transiting Planet HD 209458b

    NASA Astrophysics Data System (ADS)

    Schultz, Alfred

    2001-07-01

    HD 209458b is the only extrasolar giant planet {EGP} detected that has an orbit inclined enough toward the Sun for the transits to be detected. Differential photometry of HD 209458 with respect to comparison stars showed a transit depth of 1.5 a transit time of 3.2 hours. Transit ingress and egress are 25 minutes in duration suggesting the planet transits along a short chord instead of the full stellar disk. We propose to observe the transit ingress {1-orbit} and egress {1-orbit} with a Fine Guidance Sensor {FGS} used as a high- speed photometer {40 Hz}. An FGS can be used to obtain relative photometry with better than milli-mag accuracy and one-minute time resolution. FGS photometry of the ingress and egress will allow an independent determination of the planet radius and the inclination of the orbit. We also propose to observe the ingress and egress at least five times during Cycle 10 {10 orbits requested} to determine any variability of transit times that would indicate precession of the orbit caused by secondary bodies in the HD 209458 system. As a secondary goal, we will search for structure in the photometry that would indicate the presence of planetary satellites.

  18. Readmefirst_planetary_photometry_data Purpose of this archive

    E-print Network

    Lockwood, Wes

    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

  19. Application Note (A14) A guide to photometry and

    E-print Network

    Johnsen, Sönke

    .3.4. Stray Light 1.3.5. Blocking Filters 1.3.6. Grating Optimization 1.3.7. Detectors 1.3.8. Signal Detection, Systematic and Periodic errors 1.7.2. Error Sources Photometry and Spectroradiometry #12;#12;1 1 radiant energy emitted by the radiating source over the entire optical spectrum (1 nm to 1000 µm

  20. Strained flamelets for turbulent premixed flames, I: Formulation and planar flame results

    SciTech Connect

    Kolla, H.; Swaminathan, N. [Department of Engineering, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2010-05-15

    A strained flamelet model is proposed for turbulent premixed flames using scalar dissipation rate as a parameter. The scalar dissipation rate of reaction progress variable is a suitable quantity to describe the flamelet structure since it is governed by convection-diffusion-reaction balance and it is defined at every location in the flamelets, which are represented by laminar flames in reactant-to-product opposed flow configuration. The mean reaction rate is obtained by using the flamelets reaction rate and the joint pdf of the progress variable and its dissipation rate. The marginal pdf of the progress variable is presumed to be {beta}-pdf and the pdf of the conditional dissipation rate is taken to be log-normal. The conditional mean dissipation rate is obtained from modelled mean dissipation rate. This reaction rate closure is assessed using RANS calculations of statistically planar flames in the corrugated flamelets and thin reaction zones regimes. The flame speeds calculated using this closure are close to the experimental data of Abdel-Gayed et al. (1987) for flames in both the regimes. Comparisons with other reaction rate closures showed the benefits of the strained flamelets approach. (author)