Sample records for flame photometry

  1. 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.

  2. 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.

  3. 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.

  4. Flame retardants

    NASA Technical Reports Server (NTRS)

    Troitzsch, J.

    1988-01-01

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

  5. Flames in vortices & tulip-flame inversion

    NASA Astrophysics Data System (ADS)

    Dold, J. W.

    This article summarises two areas of research regarding the propagation of flames in flows which involve significant fluid-dynamical motion [1]-[3]. The major difference between the two is that in the first study the fluid motion is present before the arrival of any flame and remains unaffected by the flame [1, 2] while, in the second study it is the flame that is responsible for all of the fluid dynamical effects [3]. It is currently very difficult to study flame-motion in which the medium is both highly disturbed before the arrival of a flame and is further influenced by the passage of the flame.

  6. 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.

  7. 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

  8. Photometry of asteroids

    Microsoft Academic Search

    D. F. Lupishko; Yu. N. Kruglyi; V. G. Shevchenko

    2007-01-01

    Photometry is one of the most efficient investigation techniques. It provided a large body of data on albedos, sizes, shapes,\\u000a rotation, optical properties, and structural characteristics of asteroids and other minor bodies of the solar system. The\\u000a contribution of photometry to the determination of asteroid parameters was most crucial. This review summarizes main results\\u000a of asteroid studies in three most

  9. Flame Imaging System

    NASA Technical Reports Server (NTRS)

    Barnes, Heidi L. (Inventor); Smith, Harvey S. (Inventor)

    1998-01-01

    A system for imaging a flame and the background scene is discussed. The flame imaging system consists of two charge-coupled-device (CCD) cameras. One camera uses a 800 nm long pass filter which during overcast conditions blocks sufficient background light so the hydrogen flame is brighter than the background light, and the second CCD camera uses a 1100 nm long pass filter, which blocks the solar background in full sunshine conditions such that the hydrogen flame is brighter than the solar background. Two electronic viewfinders convert the signal from the cameras into a visible image. The operator can select the appropriate filtered camera to use depending on the current light conditions. In addition, a narrow band pass filtered InGaAs sensor at 1360 nm triggers an audible alarm and a flashing LED if the sensor detects a flame, providing additional flame detection so the operator does not overlook a small flame.

  10. On the Flame Height Definition for Upward Flame Spread 

    E-print Network

    Consalvi, Jean L; Pizzo, Yannick; Porterie, Bernard; Torero, Jose L

    2007-01-01

    Flame height is defined by the experimentalists as the average position of the luminous flame and, consequently is not directly linked with a quantitative value of a physical parameter. To determine flame heights from ...

  11. Cool Flame Quenching

    NASA Technical Reports Server (NTRS)

    Pearlman, Howard; Chapek, Richard

    2001-01-01

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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Extremely weak hydrogen flames

    SciTech Connect

    Lecoustre, V.R.; Sunderland, P.B. [Department of Fire Protection Engineering, University of Maryland, College Park, MD 20742 (United States); Chao, B.H. [Department of Mechanical Engineering, University of Hawaii, Honolulu, HI 96822 (United States); Axelbaum, R.L. [Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 (United States)

    2010-11-15

    Hydrogen jet diffusion flames were observed near their quenching limits. These involved downward laminar flow of hydrogen from a stainless steel hypodermic tube with an inside diameter of 0.15 mm. Near their quenching limits these flames had hydrogen flow rates of 3.9 and 2.1 {mu}g/s in air and oxygen, respectively. Assuming complete combustion, the associated heat release rates are 0.46 and 0.25 W. To the authors' knowledge, these are the weakest self-sustaining steady flames ever observed. (author)

  18. Structure of hydrogen triple flames and premixed flames compared

    SciTech Connect

    Owston, Rebecca; Abraham, John [Purdue University, Chaffee Hall, 500 Allison Road, West Lafayette, IN 47907-2014 (United States)

    2010-08-15

    Triple flames consisting of lean, stoichiometric, and rich reaction zones may be produced in stratified mixtures undergoing combustion. Such flames have unique characteristics that differ from premixed flames. The present work offers a direct comparison of the structure and propagation behavior between hydrogen/air triple and premixed flames through a numerical study. Important similarities and differences are highlighted. Premixed flames are generated by spark-igniting initially quiescent homogeneous mixtures of hydrogen and air in a two-dimensional domain. Triple flame results are also generated in a two-dimensional domain by spark-igniting initially quiescent hydrogen/air stratified layers. Detailed flame structure and chemical reactivity information is collected along isocontours of equivalence ratio 0.5, 1.0, and 3.0 in the triple flame for comparison with premixed flames at the same equivalence ratios. Full chemistry and effective binary diffusion coefficients are employed for all computations. (author)

  19. 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

  20. Photometry from space

    NASA Technical Reports Server (NTRS)

    Nelson, M. J.; Bless, R. C.; Percival, J. W.; White, R. L.

    1992-01-01

    A brief description of the High Speed Photometer (HSP) of the Hubble Space Telescope is given, in particular the HSP light path, detectors, entrance apertures, and filters. The status of HSP testing to date is reported, and problems encountered with the bright earth and the telescope pointing system are described. The calibration effort for the HSP is well under way. Results of internal (instrument coordinate) aperture locations good to 0.05 arcsec and external (telescope coordinate) locations good to 0.02 arcsec are shown. The effects of spacecraft pointing and jitter on HSP photometry are detailed, and a preliminary measurement of spacecraft jitter with HSP is shown. The aperture calibration effort is verified by accurate pointing of a star to different HSP 1.0 arcsec entrance apertures, and photometric performance of the instrument is shown to be accurate to the 2 percent photon noise of the observations. Future science verification and guaranteed observing time programs are listed. Suggestions are made for future space-based photometers.

  1. 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)

  2. 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.

  3. Flame resistant elastic elastomeric fibers

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  4. Rubens Flame-Tube Demonstration.

    ERIC Educational Resources Information Center

    Ficken, George W.; Stephenson, Francis C.

    1979-01-01

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

  5. Flame propagation through periodic vortices

    SciTech Connect

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

    1995-02-01

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

  6. Flame resistant elastic elastomeric fiber

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  7. Experiments on Collapsing Cylindrical Flames

    Microsoft Academic Search

    D. Durox; S. Ducruix; S. Candel

    2001-01-01

    This article is concerned with the effect of curvature on laminar flame dynamics. This topic is of fundamental interest and it has practical implications in turbulent combustion. It is shown that highly curved premixed flames may be obtained by operating a standard axisymmetric burner in a specific pulsed mode. Collapsing cylindrical flames are observed by submitting the burner to suitably

  8. Influence of solution composition on the results of flame-photometric analysis as a function of solution introduction rate

    Microsoft Academic Search

    Yu. I. Korovin; S. A. Savostin

    1972-01-01

    In using flame photometry, the reliability of the analysis is governed to a considerable extent by the influence of sample composition on the analytic results. The relative role of various factors depends on the composition of the solution to be analyzed and the specific analytic conditions. However, the dominant role is often played by effects associated with the variation in

  9. Triaxial Burke-Schumann Flames with Applications to Flame Synthesis

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  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. Flame retardant polymeric materials

    SciTech Connect

    Lewin, M.; Atlas, S.M.; Pearce, E.M.

    1982-01-01

    The flame retardation of polyolefins is the focus of this volume. Methods for reduction of smoke and experimental evaluation of flammability parameters for polymeric materials are discussed. The flammability evaluation methods for textiles and the use of mass spectrometry for analysis of polymers and their degradation products are also presented.

  12. PHOTOM: Photometry of digitized images

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  13. Strip Photometry of Comet Halley

    NASA Astrophysics Data System (ADS)

    Ducati, J. R.; Bergmann, T. S.; Bevilacqua, C. M.; Bonatto, C.; Cavalcanti, R. L.; Costa, R. D. D.; Dottori, H. A.; Girardi, L.; Hadiimichef, D.; Kepler, S. O.; Livi, S. H. B.; Pastoriza, M. G.; Santos, J. F.; Schmidt, A.; Schroder, M. F. S.

    1987-05-01

    Post--perihelical observations of Comet Halley were performed on 25 nights at the 50-cm reflector of UFRGS by the technique of strip photometry. A slit of dimensions 8' x 8" scanned the comet image at a speed of 1.345" x cos (declination) /sec, in east-west direction or inversely. For photometry we used NASA interference filters C2, C3, CO+, H20+, ?4865 and ?6840. Calibration used IHW standard stars and scans of field stars. Significant signals are detected for H2O+, C2 and C3. Time evolution of coma is seen from profiles. No color effect was observed from the continuum filters.

  14. 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.

  15. Investigation of turbulent spherical flames

    NASA Astrophysics Data System (ADS)

    Swaminathan, N.

    2013-11-01

    The role of turbulence is generally taken to be the main cause for the growth of flame-brush thickness in turbulent spherical flames and Taylor's dispersion theory had been used in past studies to support this. Contrary to this view, this study shows that the differential propagation between the leading and trailing edges of the flame-brush is the predominant cause for the growth of the flame-brush thickness with time in the spherical flames. The leading edge accelerates continuously because of the cumulative effect of flow acceleration resulting from heat release. These insights are derived by analysing URANS computations of 7 spherical and 7 planar flames having combustion conditions in the corrugated flamelets and thin reaction zones regimes. The reaction rate closure is achieved using strained premixed flamelets with scalar dissipation rate as a parameter. Detailed analyses of the results showed that the mean reaction rate does not depend on the flame geometry, planar or spherical. However, the turbulent flame speed which is the leading edge displacement speed showed a flame geometry dependence due to the geometry dependence of turbulent scalar flux. The presentation will highlight these physical insights. The role of turbulence is generally taken to be the main cause for the growth of flame-brush thickness in turbulent spherical flames and Taylor's dispersion theory had been used in past studies to support this. Contrary to this view, this study shows that the differential propagation between the leading and trailing edges of the flame-brush is the predominant cause for the growth of the flame-brush thickness with time in the spherical flames. The leading edge accelerates continuously because of the cumulative effect of flow acceleration resulting from heat release. These insights are derived by analysing URANS computations of 7 spherical and 7 planar flames having combustion conditions in the corrugated flamelets and thin reaction zones regimes. The reaction rate closure is achieved using strained premixed flamelets with scalar dissipation rate as a parameter. Detailed analyses of the results showed that the mean reaction rate does not depend on the flame geometry, planar or spherical. However, the turbulent flame speed which is the leading edge displacement speed showed a flame geometry dependence due to the geometry dependence of turbulent scalar flux. The presentation will highlight these physical insights. In collaboration with I. Ahmed, Cambridge University Engineering Department.

  16. A two-dimensional flame table

    NASA Astrophysics Data System (ADS)

    Daw, Harold A.

    1987-08-01

    A two-dimensional flame table was constructed for visually demonstrating acoustical modes in a cavity. This flame table is an extension of the one-dimensional flame tube or Rubens flame tube apparatus. Photographs of some of the lower-order modes on rectangular box and cylindrical box flame table cavities are included.

  17. The development of photo-electric photometry

    Microsoft Academic Search

    C. M. Huffer

    1955-01-01

    Photo-electric photometry is to-day an important branch of astronomy and is used wherever accurate measures of light intensity are needed. The first electric photometry was with a selenium cell, which was first employed by Professor in England in 1891 for measuring the brightness of stars. It was little used until 1906 when and in America revived selenium photometry. In 1911

  18. 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.

  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. 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

  1. Photonic flame effect

    E-print Network

    Tcherniega, N V

    2006-01-01

    We observed new effect which we called photonic flame effect (PFE). Several 3-dimensional photonic crystals (artificial opals) were posed on Cu plate at the temperature of liquid nitrogen (77K). Typical distance between them was 1-5 centimeters. Long-continued optical luminescence was excited in one of them by the ruby laser pulse. Analogous visible luminescence manifesting time delay appeared in other samples of the crystals. Experiments were realized for opal crystals and for nanocomposites (opals filled with nonlinear liquids).

  2. 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.

  3. 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).

  4. Numerical simulation of dynamics of premixed flames: flame instability and vortex–flame interaction

    Microsoft Academic Search

    Satoshi Kadowaki; Tatsuya Hasegawa

    2005-01-01

    The characteristics of cellular flames generated by intrinsic instability has been studied using two-dimensional (2-D) and three-dimensional (3-D) unsteady calculations of reactive flows, based on the compressible Navier–Stokes equation. Three basic types of phenomena, responsible for the intrinsic instability of premixed flames, are examined here, i.e. hydrodynamic, body-force and diffusive-thermal effects. Cellular flames are generated by these effects, and their

  5. Atmospheric Scintillation in Astronomical Photometry

    E-print Network

    Osborn, J; Dhillon, V S; Wilson, R W

    2015-01-01

    Scintillation noise due to the Earth's turbulent atmosphere can be a dominant noise source in high-precision astronomical photometry when observing bright targets from the ground. Here we describe the phenomenon of scintillation from its physical origins to its effect on photometry. We show that Young's (1967) scintillation-noise approximation used by many astronomers tends to underestimate the median scintillation noise at several major observatories around the world. We show that using median atmospheric optical turbulence profiles, which are now available for most sites, provides a better estimate of the expected scintillation noise and that real-time turbulence profiles can be used to precisely characterise the scintillation noise component of contemporaneous photometric measurements. This will enable a better understanding and calibration of photometric noise sources and the effectiveness of scintillation correction techniques. We also provide new equations for calculating scintillation noise, including ...

  6. Strip Photometry of Halley's Comet

    NASA Astrophysics Data System (ADS)

    Ducati, J. R.; Bergmann, T.S.; Bonatto, C.; Cavalcanti, R.L.; Costa, R.D.D.; Dottori, H.A.; Girardi, L.A.; Hadjimichef, D.; Kepler, S.O.; Livi, S.H.B.; Pastoriza, M.G.; Santos, J.F.; Schmidt, A.; Schröder, M.F.S.

    1986-12-01

    Post-perihelical photometric observations of comet Halley were performed on 25 nights at the 50 cm reflector of UFRGS by the technique of strip photometry. A slit of dimensions 8arcmin×8arcsec scanned the comet image at a speed of 1arcsec.345 cos ? sec-1, in east-west direction or inversely. For photometry the authors used NASA interference filters C2, C3, CO+, H2O+, ?4845 and ?6840. Calibration used IHW standard stars and scans of field stars. Significant signals were detected for H2O+, C2 and C3. Time evolution of coma is seen from profiles. No color effect was observed from the continuum filters.

  7. Multipoint ignition by flame dispersion

    Microsoft Academic Search

    T RYCHTER

    1989-01-01

    In conventional piston engines exothermic chemical reactions occur in flames that are tightly localized in space. This is a cause of many problems encountered in engine combustion, such as knock and cycle-to-cycle variability. An alternative to the classical combustion process based on the propagation of the flame can be the initiation of exothermic reactions by a set of ignition centers

  8. Aromatic polysulfones for flame retardancy

    Microsoft Academic Search

    Doina Macocinschi; Aurelia Grigoriu; Daniela Filip

    2002-01-01

    A poly(ether sulfone) and a copoly(ester sulfone) were synthesized and characterized using elemental analyses, IR, 1H-NMR spectrometry, GPC, thermogravimetric analyses. These polysulfones which show good thermal stability and flame retardancy were applied on textile materials and measurements for the evaluation of the flame retardant effect were carried out.

  9. Flame Resistant Foam

    NASA Technical Reports Server (NTRS)

    1984-01-01

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

  10. 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).

  11. The nonlinear equation for curved flames applied to the problem of flames in cylindrical tubes

    Microsoft Academic Search

    Vitaliy Bychkov; Andrey Kleev

    1999-01-01

    The nonlinear equation for curved stationary flames of realistic expansion coefficients is solved numerically for the problem of flame propagation in cylindrical tubes. Two different configurations of a flame front corresponding to convex and concave flames are obtained. The convex and concave flames propagate with different velocities that depend on the tube radius and on the expansion coefficient of the

  12. Experimental analysis of nonlinear flame transfer functions for different flame geometries

    Microsoft Academic Search

    D. Durox; T. Schuller; N. Noiray; S. Candel

    2009-01-01

    Nonlinear features of flame dynamics are characterized by measuring the flame transfer functions for different input levels. This provides a family of gain and phase curves, which constitute the Flame Describing Functions (FDF) and can be used to analyze self-sustained combustion oscillations. Experiments correspond to four different flame geometries established for the same injection conditions: a single conical flame (CF),

  13. On the Physics of Jet Diffusion Flames

    Microsoft Academic Search

    EMMANUEL VILLERMAUX; DANIEL DUROX

    1992-01-01

    A physical model for the laminar jet diffusion flame including chemical kinetics effects is provided. We produce the appropriate set of dimensionless groups needed to discuss the role of buoyancy and jet outlet velocity Uo on such flames. We are particularly interested in flame lengths L\\\\ the behaviour of the flame is shown to split in two regimes. The regime

  14. Hysteresis and transition in swirling nonpremixed flames

    Microsoft Academic Search

    M. J. Tummers; A. W. Huebner; E. H. van Veen; K. Hanjalic; T. H. van der Meer

    2009-01-01

    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),

  15. Astronomical photometry from the Moon

    NASA Astrophysics Data System (ADS)

    Hudson, Hugh S.

    1994-06-01

    The Moon would be an excellent platform for photometric astronomical observations. This paper discusses such observations, emphasizing time-series photometry of oscillating stars (asteroseismology), of faint gravitating bodies (microlensing), and of the interplanetary medium. To prepare for the deployment of major new telescopes and instrumentation on the surface of the Moon, I suggest that smaller 'site survey' instruments be put in place as soon as possible. Each application suggested can derive great benefits from small site-survey instruments established relatively soon, and each would ultimately need extensive arrays of large instruments.

  16. Electrical Aspects of Impinging Flames

    NASA Astrophysics Data System (ADS)

    Chien, Yu-Chien

    This dissertation examines the use of electric fields as one mechanism for controlling combustion as flames are partially extinguished when impinging on nearby surfaces. Electrical aspects of flames, specifically, the production of chemi-ions in hydrocarbon flames and the use of convective flows driven by these ions, have been investigated in a wide range of applications in prior work but despite this fairly comprehensive effort to study electrical aspects of combustion, relatively little research has focused on electrical phenomena near flame extinguishment, nor for flames near impingement surfaces. Electrical impinging flames have complex properties under global influences of ion-driven winds and flow field disturbances from the impingement surface. Challenges of measurements when an electric field is applied in the system have limited an understanding of changes to the flame behavior and species concentrations caused by the field. This research initially characterizes the ability of high voltage power supplies to respond on sufficiently short time scales to permit real time electrical flame actuation. The study then characterizes the influence of an electric field on the impinging flame shape, ion current and flow field of the thermal plume associated with the flame. The more significant further examinations can be separated into two parts: 1) the potential for using electric fields to control the release of carbon monoxide (CO) from surface-impinging flames, and 2) an investigation of controlling electrically the heat transfer to a plate on which the flame impinges. Carbon monoxide (CO) results from the incomplete oxidation of hydrocarbon fuels and, while CO can be desirable in some syngas processes, it is usually a dangerous emission from forest fires, gas heaters, gas stoves, or furnaces where insufficient oxygen in the core reaction does not fully oxidize the fuel to carbon dioxide and water. Determining how carbon monoxide is released and how heat transfer from the flame to the plate can be controlled using the electric field are the two main goals of this research. Multiple diagnostic techniques are employed such as OH chemiluminescence to identify the reaction zone, OH PLIF to characterize the location of this radical species, CO released from the flame, IR imaging and OH PLIF thermometry to understand the surface and gas temperature distribution, respectively. The principal finding is that carbon monoxide release from an impinging diffusion flame results from the escape of carbon monoxide created on the fuel side of the flame along the boundary layer near the surface where it avoids oxidation by OH, which sits to the air side of the reaction sheet interface. In addition, the plate proximity to the flame has a stronger influence on the emission of toxic carbon monoxide than does the electric field strength. There is, however, a narrow region of burner to surface distance where the electric field is most effective. The results also show that heat transfer can be spatially concentrated effectively using an electric field driven ion wind, particularly at some burner to surface distances.

  17. Flame spraying of polymers

    SciTech Connect

    Varacalle, D.J. Jr.; Zeek, D.P. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Couch, K.W.; Benson, D.M. [Protech Laboratory Corp., Cincinnati, OH (United States); Kirk, S.M. [3M Co., St. Paul, MN (United States)

    1997-08-01

    Statistical design-of-experiment studies of the thermal spraying of polymer powders are presented. Studies of the subsonic combustion (i.e., Flame) process were conducted in order to determine the quality and economics of polyester and urethane coatings. Thermally sprayed polymer coatings are of interest to several industries for anticorrosion applications, including the chemical, automotive, and aircraft industries. In this study, the coating design has been optimized for a site-specific application using Taguchi-type fractional-factorial experiments. Optimized coating designs are presented for the two powder systems. A substantial range of thermal processing conditions and their effect on the resultant polymer coatings is presented. The coatings were characterized by optical metallography, hardness testing, tensile testing, and compositional analysis. Characterization of the coatings yielded the thickness, bond strength, Knoop microhardness, roughness, deposition efficiency, and porosity. Confirmation testing was accomplished to verify the coating designs.

  18. 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. %

  19. Making Thermoplastics Flame-Resistant

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  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. 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...

  2. Chemical limits to flame inhibition

    Microsoft Academic Search

    V. Babushok; W. Tsang; G. T. Linteris; D. Reinelt

    1998-01-01

    This paper deals with the ultimate limits of chemical contributions to flame inhibition. Particular attention is focussed on the inhibition cycles which regenerate the inhibitor. This leads to the definition of an idealized “perfect” inhibition cycle. It is demonstrated that for such an inhibitor in a stoichiometric methane\\/air flame, additive levels in the 0.001–0.01 mole percent range will lead to

  3. Coupling of wrinkled laminar flames with gravity

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    The overall objective of our research is to understand flame-gravity coupling processes in laminar and low turbulent Reynolds number, Re(sub l), premixed flames (i.e. wrinkled- laminar flames). The approach we have developed is to compare the flowfields and mean flame properties under different gravitational orientations. Key to our study is the investigation of microgravity (mu g) flames. These mu g experiments provide vital information to reconcile the differences between flames in normal gravity (+g, flame pointing upward) and reverse gravity (-g, flame pointing downwards). Traditionally, gravity effects are assumed to be insignificant or circumvented in the laboratory, therefore, not much is available in the literature on the behavior of -g flames.

  4. The 2060 Chiron: CCD photometry

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  5. 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.

  6. Modeling solid flame microstructure

    NASA Astrophysics Data System (ADS)

    Beck, Jeffrey M.

    A simple model of condensed phase combustion in a heterogeneous medium is introduced which allows for an investigation of the effects of spatially localized reaction sites on the propagation of macroscopically steady solid flames. The medium considered is an idealized model of a packed bed of chemically active particles. Heat transfer is assumed to be uniform but exothermic reactions occur only at specified locations. Thus, combustion wave propagation manifests itself as a process of sequential ignition and burning of discrete particles. Ignition temperature kinetics is justified under the assumption that burning within any given particle is diffusion limited. The system of non-linear partial differential equations is then reduced to a discrete dynamical system which relates the ignition times of the various particles in the packed bed, thereby formalizing the fundamentally discrete nature of combustion on this scale. Map iteration and linear stability analysis are then used to analyze periodic solutions. In one dimension, a period doubling cascade to chaos and subsequent extinction is observed and associated stability boundaries are generated. In two dimensions a similar bifurcation is observed and the stability boundaries associated with planar traveling waves are generated. Additionally, a technique is described which allows for the generation of a discrete "dispersion relationship" which relates linear growth rate to the length of the perturbation. Stochastic perturbations to both grid and particle parameters as well as ignition properties of this model are also discussed.

  7. Research Progress on Flame-Retardant of Silicone Rubber

    Microsoft Academic Search

    Jian Ding; Mingxia Shen

    2010-01-01

    The development of the flame-retardant of silicone rubber and flame-retardant mechanism of polymer has been reviewed. The studies on assorted flame retardant systems used in silicone rubber matrix are reviewed too. The influence of halogenated flame retardants, metal hydroxide, transition metal compounds, as well as flame retardant with nanoparticle on flame resistance properties of polymer are discussed in detail. Owing

  8. Illinois­—Where Astronomical Photometry Grew Up

    NASA Astrophysics Data System (ADS)

    Beaman, B. B.; Svec, M. T.

    2012-06-01

    In 1903 Dr. Joel Stebbins joined the University of Illinois faculty as an astronomy instructor and Director of the University of Illinois Observatory. In 1905 he and F. C. Brown began experimenting with selenium sell photometry and developed the equipment and many of the photometric practices used then. Those practices formed the foundation on which present day photometry processes are based. This paper will trace the history of Stebbins’ career and his development of photoelectric photometry from 1903 to 1922. This story explains how Stebbins’ wife, May, caused a change in astronomical observing that continues today.

  9. 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

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

    E-print Network

    Ju, Yiguang

    mixture. If the energy is smaller than the so-called minimum ignition energy (MIE), the resulting flameOn the critical flame radius and minimum ignition energy for spherical flame initiation Zheng Chen spherical flame initiation and its correlation with the min- imum ignition energy. It is found

  11. 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.

  12. 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Simulation of spherically expanding turbulent premixed flames

    E-print Network

    Ahmed, I.; Swaminathan, N.

    2013-09-16

    ; Lawes et al., 2012), bombs with decaying grid turbu- lence (Checkel and Thomas, 1994) and wind tunnels with grid turbulence (Hainsworth, 1985; Renou et al., 2002) to address the influence of turbulence on spherical flame propagation. Beretta et al. (1983... ) and Hainsworth (1985) have shown that the tur- bulent spherical flames initially expand as the laminar flame and then it is exposed gradually to a wide range of length and time scales of turbulence resulting in flame wrinkling thereby leading to an increase...

  18. 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.

  19. Direct comparison of turbulent burning velocity and flame surface properties in turbulent premixed flames

    Microsoft Academic Search

    T. W. Lee; S. J. Lee

    2003-01-01

    Direct comparison of the turbulent burning velocity (obtained from flame speeds) to the flame perimeter ratio has been made in turbulent premixed flames propagating freely downward for propane\\/air mixtures at various equivalence ratios, with u?\\/SL of ranging from 1.4 to 5.3. The turbulent flame speed ranged from 2.6 to about 7 times the laminar flame speed at high turbulence intensities,

  20. UBVRI photoelectric photometry of ten southern galaxies

    SciTech Connect

    Schroder, M.F.S.; Kepler, S.O. (Rio Grande do Sul, Universidade Federal, Porto Alegre (Brazil))

    1991-04-01

    This paper reports UBVRI photoelectric photometry of ten southern spiral galaxies with diaphragms ranging from 7 to 77 arc seconds. Total B and V magnitudes calculated through standard aperture-magnitude curve fittings are also reported. 13 refs.

  1. Firefighters and flame retardant activism.

    PubMed

    Cordner, Alissa; Rodgers, Kathryn M; Brown, Phil; Morello-Frosch, Rachel

    2015-02-01

    In the past decade, exposure to flame retardant chemicals has become a pressing health concern and widely discussed topic of public safety for firefighters in the United States. Working through local, state, and national unions and independent health and advocacy organizations, firefighters have made important contributions to efforts to restrict the use of certain flame retardants. Firefighters are key members in advocacy coalitions dedicated to developing new environmental health regulations and reforming flammability standards to reflect the best available fire science. Their involvement has been motivated by substantiated health concerns and critiques of deceptive lobbying practices by the chemical industry. Drawing on observations and interviews with firefighters, fire safety experts, and other involved stakeholders, this article describes why firefighters are increasingly concerned about their exposure to flame retardant chemicals in consumer products, and analyzes their involvement in state and national environmental health coalitions. PMID:25816168

  2. Nanoparticle synthesis in low pressure flames

    Microsoft Academic Search

    Andrei Colibaba-Evulet

    2000-01-01

    The results of an experimental and computational study of nanoparticle synthesis in low pressure flames are presented. In a stagnation point flow configuration, hydrogen\\/oxygen low pressure flat flames were supplied with metalorganic vapor precursors and the flame conditions were identified for nanoparticle formation and growth, followed by deposition on a cooled substrate. The effects of pressure, burner to substrate distance,

  3. Acoustically perturbed turbulent premixed swirling flames

    Microsoft Academic Search

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

    2011-01-01

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

  4. Premixed and diffusion flames in a centrifuge

    SciTech Connect

    Durox, D.; Yuan, T.; Baillot, F. [Laboratoire d`Aerothermique du CNRS, Meudon (France)] [Laboratoire d`Aerothermique du CNRS, Meudon (France); Most, J.M. [Universite de Poitiers, Mignaloux-Beauvoir (France)] [Universite de Poitiers, Mignaloux-Beauvoir (France)

    1995-09-01

    Combustion experiments conducted in a centrifuge are rare, and the authors present results obtained during different tests campaigns. For premixed flames or for diffusion flames, two cases are distinguished--in one, small flames are steady, and in the other, tall flames may be sensitive to a natural instability created by buoyancy in burned gases. The results show that for premixed stationary flames, the flame shape is almost insensitive to buoyancy, except for a very light modification of the streamlines in burned and fresh gases due to the hydrodynamic effects. The physicochemistry of the flame front is not modified in the range of gravity levels studied (between 1g{sub 0} and 10 g{sub 0}). On the other hand, the morphology of stationary diffusion flames is strongly changed. Both flame height and surface area are reduced as gravity increases. A correlation with a theoretical model gives good agreement. Both diffusion and premixed flames oscillate vertically, at low frequency (of the order of about 10 Hz), if the flame height is sufficiently tall. This mechanism is created in the burned gas layer surrounding the flame, where buoyancy exerts an influence. The results show that the frequency increases with gravity intensity. The last part of the paper is devoted to the evaluation of the flow deflection in the burnt gases under the action of Coriolis force.

  5. Modeling of premixed swirling flames transfer functions

    Microsoft Academic Search

    P. Palies; T. Schuller; D. Durox; S. Candel

    2011-01-01

    An analytical model is derived for the linear response of swirling flames submitted to velocity disturbances. The flame dynamics is represented by a linearized version of the G-equation. Turbulent fluctuations are first averaged in time to obtain a kinematic equation in which the flame is represented by a wrinkled sheet. The variables are then phase averaged to describe acoustic perturbations

  6. 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...

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. KSC Launch Pad Flame Trench Environment Assessment

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  12. 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.

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

    SciTech Connect

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

    2004-03-01

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

  14. An experimental investigation on flame interaction and the existence of negative flame speeds

    NASA Technical Reports Server (NTRS)

    Sohrab, S. H.; Ye, Z. Y.; Law, C. K.

    1985-01-01

    Downstream interaction between two counterflow premixed flames of different stoichiometries are investigated. Various flame configurations are observed and quantified; these include the binary system of two lean or rich flames, the triplet system of a lean and a rich flame separated by a diffusion flame, and single diffusion flames with some degree of premixedness. Extinction limits are determined for methane/air and butane/air mixtures over the entire range of mixture concentrations. Results show that these extinction limits can be significantly modified in the presence of interaction such that a mixture much beyond the flammability limit can still burn if it is supported by a stronger flame. The experiment also demonstrates the existence of negative flames whose propagation velocity is in the same general direction as that of the bulk convective flow. Implications of the present results on the flammability of stratified mixtures and on the modeling of turbulent flames are discussed.

  15. 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.

  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. Nonlinear effects in the extraction of laminar flame speeds from expanding spherical flames

    SciTech Connect

    Kelley, A.P.; Law, C.K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

    2009-09-15

    Various factors affecting the determination of laminar flames speeds from outwardly propagating spherical flames in a constant-pressure combustion chamber were considered, with emphasis on the nonlinear variation of the stretched flame speed to the flame stretch rate, and the associated need to nonlinearly extrapolate the stretched flame speed to yield an accurate determination of the laminar flame speed and Markstein length. Experiments were conducted for lean and rich n-butane/air flames at 1atm initial pressure, demonstrating the complex and nonlinear nature of the dynamics of flame evolution, and the strong influences of the ignition transient and chamber confinement during the initial and final periods of the flame propagation, respectively. These experimental data were analyzed using the nonlinear relation between the stretched flame speed and stretch rate, yielding laminar flame speeds that agree well with data determined from alternate flame configurations. It is further suggested that the fidelity in the extraction of the laminar flame speed from expanding spherical flames can be facilitated by using small ignition energy and a large combustion chamber. (author)

  18. 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 of Variable Stars and Properties of CCDs. Question 1: The light variation from a variable star is shown in the figure to the right. a) Identify the type of variable star and explain your criteria for classifying

  19. The discrete regime of flame propagation

    NASA Astrophysics Data System (ADS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew

    The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment available only on orbital platforms.

  20. Numerical simulation of tulip flame dynamics

    SciTech Connect

    Cloutman, L.D.

    1991-11-30

    A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a tulip flame'' in the literature, occurred. The tulip flame'' was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.

  1. Numerical simulation of tulip flame dynamics

    SciTech Connect

    Cloutman, L.D.

    1991-11-30

    A finite difference reactive flow hydrodynamics program based on the full Navier-Stokes equations was used to simulate the combustion process in a homogeneous-charge, constant-volume combustion bomb in which an oddly shaped flame, known as a ``tulip flame`` in the literature, occurred. The ``tulip flame`` was readily reproduced in the numerical simulations, producing good agreement with the experimental flame shapes and positions at various times. The calculations provide sufficient detail about the dynamics of the experiment to provide some insight into the physical mechanisms responsible for the peculiar flame shape. Several factors seem to contribute to the tulip formation. The most important process is the baroclinic production of vorticity by the flame front, and this rate of production appears to be dramatically increased by the nonaxial flow generated when the initial semicircular flame front burns out along the sides of the chamber. The vorticity produces a pair of vortices behind the flame that advects the flame into the tulip shape. Boundary layer effects contribute to the details of the flame shape next to the walls of the chamber, but are otherwise not important. 24 refs.

  2. A numerical study of thin flame representations

    SciTech Connect

    Rotman, D.A.; Pindera, M.Z.

    1989-08-11

    In studies of reacting flows, the flame may be viewed as a moving discontinuity endowed with certain properties; notably, it acts as a source of velocity and vorticity. Asymptotic analysis shows this to be justified provided that the flame curvature is small compared to the flame thickness. Such an approach is useful when one is interested in the hydrodynamic effects of the flame on the surrounding flowfield. In numerical models of this kind it is customary to treat the discontinuity as a collection of discrete velocity blobs. In this study, we show that the velocities associated with such a representation can be very non-smooth, particularly very near to the flame surface. As an alternative, we propose the use of a finite line source as the basic flame element. Comparisons of the two flame representations are made for several simple test cases as well as for a flame propagating through an enclosure forming the tulip shape. The results show that the use of line sources eliminates spurious fluctuations in nearfield velocities thus allowing for a more accurate calculation of flame propagation and flame-flowfield interactions. 7 refs., 15 figs.

  3. The initial development of a tulip flame

    SciTech Connect

    Matalon, M.; Mcgreevy, J.L. [Northwestern Univ., Evanston, IL (United States)

    1994-12-31

    The initial development of a ``tulip flame``, often observed during flame propagation in closed tubes, is attributed to a combustion instability. The roles of hydrodynamic and of the diffusional-thermal processes on the onset of instability are investigated through a linear stability analysis in which the growth or decay of small disturbances, superimposed on an otherwise smooth and planar flame front, are followed. A range of the Markstein parameter, related to the mixture composition through an appropriately defined Lewis number, has been identified where a tulip flame could be observed. For a given value of the Markstein parameter within this range, a critical wavelength is identified as the most unstable mode. This wavelength is directly related to the minimal aspect ratio of the tube where a tulip flame could be observed. The time of onset of instability is identified as the time when the most unstable disturbance, associated with the critical wavelength, grows at a faster rate than the flame front itself and exceeds a certain threshold. This occurs after the flame has propagated a certain distance down the tube: a value which has been explicitly determined in terms of the relevant parameters. Experimental records on the tulip flame phenomenon support the finding of the analysis. That is, the tulip flame forms after the flame has traveled half the tube`s length, it does not form in short tubes, and its formation depends on the mixture composition and on the initial pressure in the tube.

  4. 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.

  5. Simulation of a diffusion flame in turbulent mixing layer by the flame hole dynamics model with level-set method

    Microsoft Academic Search

    J. Kim; S. H. Chung; K. Y. Ahn; J. S. Kim

    2006-01-01

    The partial quenching structure of diffusion flames, arising from the phenomenon of turbulent flame lift off, is investigated in a turbulent mixing layer by the method of flame hole dynamics. Modification of the flame hole dynamics by including the level-set method is specifically aimed to properly take into account the effect of slow flame-edge response near the crossover scalar dissipation

  6. 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.

  7. Premixed flames in closed cylindrical tubes

    NASA Astrophysics Data System (ADS)

    Metzener, Philippe; Matalon, Moshe

    2001-09-01

    We consider the propagation of a premixed flame, as a two-dimensional sheet separating unburned gas from burned products, in a closed cylindrical tube. A nonlinear evolution equation, that describes the motion of the flame front as a function of its mean position, is derived. The equation contains a destabilizing term that results from the gas motion induced by thermal expansion and has a memory term associated with vorticity generation. Numerical solutions of this equation indicate that, when diffusion is stabilizing, the flame evolves into a non-planar form whose shape, and its associated symmetry properties, are determined by the Markstein parameter, and by the initial data. In particular, we observe the development of convex axisymmetric or non-axisymmetric flames, tulip flames and cellular flames.

  8. 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)

  9. The VLT FLAMES Tarantula Survey

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  10. 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.

  11. 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 ...

  12. Author's personal copy Combustion and Flame 151 (2007) 104119

    E-print Network

    Lieuwen, Timothy C.

    2007-01-01

    were employed: one using flame area images of a conical Bunsen flame and the other based on velocity fundamental information on reactivity, diffusivity, and exothermic- ity. The value of the flame speed has

  13. Flow/Soot-Formation Interactions in Nonbuoyant Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  14. Nonlinear combustion instability analysis based on the flame describing function applied to turbulent premixed swirling flames

    Microsoft Academic Search

    P. Palies; D. Durox; T. Schuller; S. Candel

    2011-01-01

    Instability analysis of swirling flames is of importance in the design of advanced combustor concepts for aircraft propulsion and powerplant for electricity production. Thermoacoustic instabilities are analyzed here by making use of a nonlinear representation of flame dynamics based on a describing function. In this framework, the flame response is determined as a function of frequency and amplitude of perturbations

  15. Experimental investigation of self-turbulent flames

    NASA Astrophysics Data System (ADS)

    Almarcha, Christophe; Quinard, Joel

    2012-11-01

    When propagating downwards, premixed flames undergo hydrodynamic instabilities. The resulting dynamics exhibits multiple corrugations of the light emitting reaction zone. By changing the reactive mixture composition or the shape of the propagation volume, the characteristic lengths of perturbation are changed. We present here the experimental study of propane-air and methane-air flames propagating in vertical circular tubes and in vertically oriented Hele-Shaw cells. This last configuration allows comparison with two dimensional numerical models. The thermo acoustic instability, usually acting when flames propagate in confined volume, is damped thanks to an acoustic absorber, allowing the study of wide flames at the meter scale.

  16. 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)

  17. Rich methane premixed laminar flames doped with light unsaturated hydrocarbons

    Microsoft Academic Search

    H. A. Gueniche; P. A. Glaude; G. Dayma; R. Fournet; F. Battin-Leclerc

    2006-01-01

    The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of CâHâ was

  18. Rich methane premixed laminar flames doped with light unsaturated hydrocarbons

    Microsoft Academic Search

    Hadj-Ali Gueniche; Pierre-Alexandre Glaude; Guillaume Dayma; René Fournet; F. Battin-Leclerc

    2006-01-01

    The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C3H4 was

  19. Detecting Problematic Observer Offsets in Sparse Photometry

    NASA Astrophysics Data System (ADS)

    Calderwood, T.

    2014-06-01

    A heuristic method, based upon histogram analysis, is presented for detecting offsets pervasive enough to be symptoms of problematic observing technique or calibration. This method is illustrated by a study of scatter in AAVSO photoelectric photometry (PEP) for five well-observed variable stars.

  20. BVRIc photometry of Stock 8 (Jose+, 2008)

    Microsoft Academic Search

    J. Jose; A. K. Pandey; D. K. Ojha; K. Ogura; W. P. Chen; B. C. Bhatt; S. K. Ghosh; H. Mito; G. Maheswar; S. Sharma

    2008-01-01

    We present UBVIc CCD photometry of the young open cluster Stock 8 with the aim of studying its basic properties such as the amount of interstellar extinction, distance, age, stellar contents and initial mass function (IMF). We also studied the star formation scenario in this region. From optical data, the radius of the cluster is found to be ~6arcmin (~3.6pc)

  1. Characterizing Atmospheric Absorption for Precision Photometry

    Microsoft Academic Search

    R. Chris Smith; David Burke; Christopher Stubbs; Tim Axelrod; Chuck Claver; William High; Stephan Blondin; Abi Saha; Patrick Kelly

    2008-01-01

    For the next generation of ground-based imaging surveys, many of which will be attempting to achieve better than 1% photometry, precise calibration of all aspects of the observations will be a necessity. This focus on calibration together with the detailed characterization and understanding of possible systematic effects crucial in order to reach the scientific goals of LSST, as well as

  2. TRIPP: Time Resolved Imaging Photometry Package

    NASA Astrophysics Data System (ADS)

    Geckeler, Ralf D.; Schuh, Sonja; Dreizler, Stefan; Deetjen, Jochen; Gleissner, Thomas; Risse, Patrick; Rauch, Thomas; Göhler, Eckart; Hügelmeyer, Simon; Husser, Tim-Oliver; Israel, Holger; Benlloch-Garcia, Sara; Pottschmidt, Katja; Wilms, Jörn

    2014-05-01

    Written in IDL, TRIPP performs CCD time series reduction and analysis. It provides an on-line check of the incoming frames, performs relative aperture photometry and provides a set of time series tools, such as calculation of periodograms including false alarm probability determination, epoc folding, sinus fitting, and light curve simulations.

  3. 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.

  4. Tulip flames: changes in shape of premixed flames propagating in closed tubes

    NASA Astrophysics Data System (ADS)

    Dunn-Rankin, D.; Sawyer, R. F.

    The experimental results that are the subject of this communication provide high-speed schlieren images of the closed-tube flame shape that has come to be known as the tulip flame. The schlieren images, along with in-chamber pressure records, help demonstrate the effects of chamber length, equivalence ratio, and igniter geometry on formation of the tulip flame. The pressure/time records show distinct features which correlate with flame shape changes during the transition to tulip. The measurements indicate that the basic tulip flame formation is a robust phenomenon that depends on little except the overall geometry of the combustion vessel.

  5. 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.

  6. 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

  7. 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.

  8. Combustion dynamics of inverted conical flames

    Microsoft Academic Search

    D. Durox; T. Schuller; S. Candel

    2005-01-01

    An inverted conical flame anchored on a central bluff-body in an unconfined burner configuration features a distinctive acoustic response. This configuration typifies more complex situations in which the thermo-acoustic instability is driven by the interaction of a flame with a convective vorticity mode. The axisymmetric geometry investigated in this article features a shear region between the reactive jet and the

  9. Dynamics of premixed confined swirling flames

    Microsoft Academic Search

    P. Palies; D. Durox; T. Schuller; P. Morenton; S. Candel

    2009-01-01

    Considerable effort is currently being extended to examine the fundamental mechanisms of combustion instabilities and develop methods allowing predictions of these phenomena. One central aspect of this problem is the dynamical response of the flame to incoming perturbations. This question is examined in the present article, which specifically considers the response of premixed swirling flames to perturbations imposed on the

  10. An analogue study for flame flickering

    Microsoft Academic Search

    T. Yuan; D. Durox; E. Villermaux

    1994-01-01

    An analogue experiment is proposed to simulate flame flickering comprising a free ascending column fed on its side with a light gas (helium) emerging from a vertical slot in ambient air. The convective motion of the helium jet is considered to represent the motion of burnt gases of buoyant jet flames. The helium jet is accelerated by buoyancy effects and

  11. 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)

  12. NON-PREMIXED TURBULENT JET FLAMES

    EPA Science Inventory

    The paper, part of a general investigation of mixing and chemical reaction in turbulent jets, concerns the length of non-premixed turbulent jet flames in a stationary environment. Experimental results for the turbulent flame length of chemically reacting jets in water show both i...

  13. Propagating edge-flame response to multiple stoichiometry gradients

    SciTech Connect

    Kostka, Stanislav Jr.; Carnell, William F. Jr.; Renfro, Michael W. [Department of Mechanical Engineering, 191 Auditorium Rd, U-3139, University of Connecticut, Storrs, CT 06269 (United States)

    2008-07-15

    A five-slot contoured nozzle burner was used to create multiple lifted partially premixed flames in close proximity. The burner permits the stoichiometry gradient below each edge flame and the separation distance between stabilization points of the flames to be separately controlled. In previous work, we showed that edge-flame interactions lead to a bifurcation in the flame stabilization, where the liftoff height of neighboring edge flames differs even in symmetric flow fields. As the composition gradient below each flame is decreased, the edge flames broaden. Flow around the edge flames leads to an aerodynamic interaction, where upstream conditions below one flame are modified by the neighboring flame. These interactions cause a liftoff height difference between the two flames. Further reduction of stoichiometry gradient causes the neighboring flames to merge and approach the structure of a single premixed flame. In this work, the equivalence ratio gradient and separation distance between stoichiometric points were varied by controlling the burner slot equivalence ratios, so that these interactions could be studied in greater detail. Rayleigh scattering was used to measure flame curvature and calculate local stoichiometry gradients below each flame stabilization point. Planar laser-induced fluorescence signals of hydroxyl and formaldehyde were measured to provide qualitative comparisons of relative reaction rates between flames. Neighboring edge flames were found to behave based solely on local conditions below each flame. Only aerodynamic interactions were observed and no chemical or thermal interactions, caused by heat or radical transport between flames, were observed. The bifurcated flame response can be described simply from the effects that flow around the flame structure has on local velocities and scalar dissipation rates. (author)

  14. 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.

  15. 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.

  16. 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.

  17. Television photometry - The Mariner 9 experience

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1974-01-01

    Television photometry is compared to conventional techniques. Reduced data from Mariner 9 cameras should, under optimum conditions, have been accurate to a few percent. However, a combination of unstable camera properties and various unfortunate circumstances produced serious nonlinearities and other systematic errors. The means of estimating these errors are described in detail; they lean heavily on the fortuitous presence of a few specks of dust on the faceplate of one vidicon. Crude corrections will probably improve the photometric quality for the two most-used filter positions of the A camera. It would be very difficult to improve the photometry further. In view of their low photometric accuracy and detective quantum efficiency vidicons do not seem likely to replace conventional photography, except for special applications.

  18. 2060 Chiron - CCD and electronographic photometry

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  19. Photometry of Variables from Dome A, Antarctica

    NASA Astrophysics Data System (ADS)

    Wang, Lingzhi; Macri, L. M.; Wang, L.; Ashley, M. C. B.; Cui, X.; Feng, L. L.; Gong, X.; Lawrence, J. S.; Liu, Q.; Luong-Van, D.; Pennypacker, C. R.; Shang, Z.; Storey, J. W. V.; Yang, H.; Yang, J.; Yuan, X.; York, D. G.; Zhou, X.; Zhu, Z.; Zhu, Z.

    2013-01-01

    Dome A on the Antarctic plateau is likely one of the best observing sites on Earth (Saunders et al. 2009). We used the CSTAR telescope (Yuan et al. 2008) to obtain time-series photometry of 104 stars with i>14.5 mag during 128 days of the 2008 Antarctic winter season (Wang et al. 2011). During the 2010 season we observed 2 × 104 stars with i>15 mag for 183 days (Wang et al. 2012). We detected a total of 262 variables, a 6 × increase relative to previous surveys of the same area and depth carried out from temperate sites (Pojmanski 2004). Our observations show that high-precision, long-term photometry is possible from Antarctica and that astronomically useful data can be obtained during 80% of the winter season.

  20. Lightcurve Photometry Opportunities: 2015 July-September

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  1. Lightcurve Photometry Opportunities: 2013 July-September

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    We present lists of asteroid photometry opportunities for objects reaching a favorable apparition and have no 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.

  2. Lightcurve Photometry Opportunities: 2013 October-December

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    We present lists of asteroid photometry opportunities for objects reaching a favorable apparition and have no 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.

  3. Lightcurve Photometry Opportunities: 2014 April-June

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  4. Lightcurve Photometry Opportunities: 2014 October-December

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  5. Lightcurve Photometry Opportunities: 2013 October-December

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    We present lists of asteroid photometry opportunities for objects reaching a favorable apparition and have no 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.

  6. Lightcurve Photometry Opportunities: 2015 January-March

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  7. Lightcurve Photometry Opportunities: 2014 July-September

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  8. Far UV Stellar Photometry (Schmidt+ 1995)

    Microsoft Academic Search

    E. G. Schmidt; G. R. Carruthers

    1995-01-01

    Far-ultraviolet photometry for 741 objects in a field in Sagittarius centered near M8 and 541 objects in a field centered near zeta Scorpii is presented. These data were extracted from electrographic images obtained with two cameras during a shuttle flight in 1991 April\\/May. The cameras provided band passes with lambda_eff = 1375 A and lambda_eff = 1781 A. Synthetic colors

  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. 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.

  11. The Effects of Flame Structure on Extinction of CH4-O2-N2 Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Du, J.; Axelbaum, R. L.; Gokoglu, S. (Technical Monitor)

    1996-01-01

    The effects of flame structure on the extinction limits of CH4-O2-N2 counterflow diffusion flames were investigated experimentally and numerically by varying the stoichiometric mixture fraction Z(sub st), Z(sub st) was varied by varying free-stream concentrations, while the adiabatic flame temperature T(sub ad) was held fixed by maintaining a fixed amount of nitrogen at the flame. Z(sub st) was varied between 0.055 (methane-air flame) and 0.78 (diluted- methane-oxygen flame). The experimental results yielded an extinction strain rate K(sub ext) of 375/s for the methane-air flame, increasing monotonically to 1042/s for the diluted-methane-oxygen flame. Numerical results with a 58-step Cl mechanism yielded 494/s and 1488/s, respectively. The increase in K(sub ext) with Z(sub st) for a fixed T(sub ad) is explained by the shift in the O2 profile toward the region of maximum temperature and the subsequent increase in rates for chain-branching reactions. The flame temperature at extinction reached a minimum at Z(sub st) = 0.65, where it was 200 C lower than that of the methane-air flame. This significant increase in resistance to extinction is seen to correspond to the condition in which the OH and O production zones are centered on the location of maximum temperature.

  12. 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.

  13. 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.

  14. On the "Tulip Flame" Phenomenon CHRISTOPHE CLANET and GEOFFREY SEARBY'

    E-print Network

    Clanet, Christophe

    On the "Tulip Flame" Phenomenon CHRISTOPHE CLANET and GEOFFREY SEARBY' Insitut de Recherche sur les, France We present an experimental study of the "tulip flame" phenomenon using high-speed photography and the gas dynamics. In particular, the tulip flame results from an inversion of the flame front curvature

  15. The Transition to Turbulence of Rayleigh-Taylor Unstable Flames

    Microsoft Academic Search

    Elizabeth P. Hicks; R. Rosner

    2011-01-01

    Part of the uncertainty surrounding the explosion mechanism of Type 1A supernovae is the extent to which the turbulence created by the flame front can speed the flame up. A premixed flame moving against a sufficiently strong gravitational field becomes deformed and creates vorticity. If gravity is strong enough, this vorticity is shed and deposited behind the flame front. We

  16. Stabilization of the hydrodynamic flame instability by a weak shock

    NASA Astrophysics Data System (ADS)

    Bychkov, Vitaliy V.

    1998-10-01

    The problem of stabilization of the hydrodynamic flame instability due to collision of a flame with a weak shock is revised. It is shown that correct treatment of this problem leads to results different from the Markstein solution [G. H. Markstein, Nonsteady Flame Propagation (Pergamon, Oxford, 1964)]. It is obtained that depending on the shock intensity a flame-shock collision may lead to temporary reduction of the perturbation amplitude at the flame front, to complete suppression of initial perturbations, or to inversion of the flame shape. Scalings for the shock intensity leading to stabilization or destabilization of a flame front are obtained.

  17. Role of compressibility in moderating flame acceleration in tubes

    NASA Astrophysics Data System (ADS)

    Bychkov, Vitaly; Akkerman, V.'Yacheslav; Valiev, Damir; Law, Chung K.

    2010-02-01

    The effect of gas compression on spontaneous flame acceleration leading to deflagration-to-detonation transition is studied theoretically for small Reynolds number flame propagation from the closed end of a tube. The theory assumes weak compressibility through expansion in small Mach number. Results show that the flame front accelerates exponentially during the initial stage of propagation when the Mach number is negligible. With continuous increase in the flame velocity with respect to the tube wall, the flame-generated compression waves subsequently moderate the acceleration process by affecting the flame shape and velocity, as well as the flow driven by the flame.

  18. Numerical study of turbulent flame velocity

    SciTech Connect

    Akkerman, V'yacheslav [Department of Physics, Umeaa University, S-901 87 Umeaa (Sweden); Nuclear Safety Institute (IBRAE) of Russian Academy of Sciences, B. Tulskaya 52, 115191 Moscow (Russian Federation); Bychkov, Vitaly [Department of Physics, Umeaa University, S-901 87 Umeaa (Sweden); Eriksson, Lars-Erik [Department of Applied Mechanics, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)

    2007-11-15

    A premixed flame propagating through a combination of vortices in a tube/channel is studied using direct numerical simulations of the complete set of combustion equations including thermal conduction, diffusion, viscosity, and chemical kinetics. Two cases are considered, a single-mode vortex array and a multimode combination of vortices obeying the Kolmogorov spectrum. It is shown that the velocity of flame propagation depends strongly on the vortex intensity and size. The dependence on the vortex intensity is almost linear in agreement with the general belief. The dependence on the vortex size may be imitated by a power law {proportional_to}D{sup 2/3}. This result is different from theoretical predictions, which creates a challenge for the theory. In the case of the Kolmogorov spectrum of vortices, the velocity of flame propagation is noticeably smaller than for a single-mode vortex array. The flame velocity depends weakly on the thermal expansion of burning matter within the domain of realistically large expansion factors. Comparison to the experimental data indicates that small-scale turbulence is not the only effect that influences the flame velocity in the experimental flows. Large-scale processes, such as the Darrieus-Landau instability and flame-wall interaction, contribute considerably to the velocity of flame propagation. Still, on small scales, the Darrieus-Landau instability becomes important only for a sufficiently low vortex intensity. (author)

  19. Structure of Propagating and Attached Hydrocarbon Flames

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath

    2004-01-01

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

  20. Premixed turbulent flame propagation in microgravity

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    Microsoft Academic Search

    Munki Kim; Youngil Choi; Jeongseog Oh; Youngbin Yoon

    2009-01-01

    This study examines the effect of acoustic excitation using forced coaxial air on the flame characteristics of turbulent hydrogen non-premixed flames. A resonance frequency was selected to acoustically excite the coaxial air jet due to its ability to effectively amplify the acoustic amplitude and reduce flame length and NO emissions. Acoustic excitation causes the flame length to decrease by 15%

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

    Microsoft Academic Search

    Munki Kim; Youngil Choi; Jeongseog Oh; Youngbin Yoon

    2009-01-01

    This study examines the effect of acoustic excitation using forced coaxial air on the flame characteristics of turbulent hydrogen non-premixed flames. A resonance frequency was selected to acoustically excite the coaxial air jet due to its ability to effectively amplify the acoustic amplitude and reduce flame length and NOx emissions. Acoustic excitation causes the flame length to decrease by 15%

  3. Propagation rates of nonpremixed edge flames

    SciTech Connect

    Cha, Min Suk [Environmental System Research Center, Korea Institute of Machinery & amp; Materials, Daejeon, 305-343 (Korea, Republic of); Ronney, Paul D. [Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453 (United States)

    2006-07-15

    The propagation rates (U{sub edge}) of nonpremixed ignition (advancing) fronts and extinction (retreating) edge flames were measured as a function of global strain rate ({sigma}), jet spacing (d), mixture strength, stoichiometric mixture fraction (Z{sub st}), and Lewis number (Le) using a counterflow slot-jet burner in which edge flames propagated along its long dimension. Electrical heaters at both ends of the slot 'anchored' the flames, allowing conditions resulting in negative values of U{sub edge} to be studied by triggering local extinction of anchored flames with an N{sub 2} jet. Results are presented in terms of the effects of a dimensionless flame thickness ({epsilon}) related to {sigma} and a dimensionless heat loss (k) on a scaled U{sub edge}. Propagation rates were markedly enhanced/retarded in mixtures with low/high Le. Propagation rates and extinction conditions were highly asymmetric with respect to Z{sub st}=0.5 despite the symmetry of flame location; mixtures with Z{sub st} greater/less than 0.5 behaved like stronger/weaker mixtures, apparently due to the relative locations of the radical production zone and maximum temperature zone for varying Z{sub st}. Two extinction limits were identified, corresponding to a high-{sigma} strain-induced limit that was strongly dependent on Le but nearly independent of k and a low-{sigma} heat-loss-induced limit that was strongly dependent on k but not Le. Most experimental findings were in good agreement with theoretical predictions; however, unlike predictions, 'tailless' triple flames were not observed; instead standard triple flames and 'short length' edge flames were found, and only for a very narrow range of experimental conditions. This is proposed to be due to the difference between the volumetric heat loss presumed in the models and the conductive transfer to the jet exits that dominates heat loss in the experiments. (author)

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

    NASA Technical Reports Server (NTRS)

    Matalon, Moshe

    2003-01-01

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

  5. 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)

  6. 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.

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

    SciTech Connect

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

    2009-04-15

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

  8. Flame Resistant Fibrous Materials Development

    NASA Technical Reports Server (NTRS)

    Coskren, R. J.

    1982-01-01

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

  9. 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.

  10. 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...

  11. Environmentally Benign Flame Retardant Nanocoatings for Fabric 

    E-print Network

    Li, Yu-Chin

    2012-07-16

    A variety of materials were used to fabricate nanocoatings using layer-by-layer (LbL) assembly to reduce the flammability of cotton fabric. The most effective brominated flame retardants have raised concerns related to ...

  12. 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.

  13. 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.

  14. 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.

  15. Statistical calculations of spherical turbulent flames

    SciTech Connect

    Pope, S.B.; Chen, W.K.

    1986-01-01

    Turbulent flame balls can be produced by the spark ignition of a fuel-air mixture in turbulent motion. Calculations of these statistically-spherical flames are reported and compared with the recent data of Hainsworth. The calculations are based on the Monte Carlo solution of a modelled equation for the joint probability density function (pdf) of the velocities and the reaction progress variable. In order to compare the statistical calculations with single experimental realizations, the joint pdf considered is conditioned on the turbulent velocity at the spark. This separates the flame ball's growth from its random convection by the turbulence. Excellent agreement is found between the calculated and measured evolution of the flame ball radius. 18 refs., 7 figs.

  16. 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...

  17. 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.

  18. Thermally Stable and Flame Retardant Elastomeric Nanocomposites

    Microsoft Academic Search

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

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

  19. 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.

  20. 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.

  1. Quantitative Species Measurements In Microgravity Combustion Flames

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  2. 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.

  3. 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

  4. Photometry Transforms Generation with PTGP (Abstract)

    NASA Astrophysics Data System (ADS)

    Myers, G.; Menzies, K.; Silvis, G.; Harris, B.

    2015-06-01

    (Abstract only) Historically the development of photometry transformation coefficients required extensive manual effort and the use of large spreadsheets. A new release—version 5.0—of the Photometry Transformations Generation Program (PTGP) achieves the goal of generating transformation coefficients without the use of spreadsheets—saving considerable time and ensuring data accuracy. PTGP version 5.0 works directly with VSP to retrieve the most recent standard star reference magnitudes (currently for M67 and NGC7790). It then processes instrument magnitude file(s) downloaded from vphot or exported from AIP4WIN or MAXIM. Either AUID or “Boulder” star identifications can be used for AIP4WIN and MAXIM. When using VPHOT data or “Boulder” star identifications, PTGP determines the AUID names for each of the reference standard stars. All standard transforms are calculated. Plots of each transform's data can be reviewed, and individual star observations added/deleted. Transform sets can be saved for further use. Transform sets can be compared and selected sets averaged. The averaged sets can be exported in a file format compatible with the AAVSO TA tool. The presentation will provide a brief overview and demonstration of the tool. It will also discuss the implications of using PYTHON for the development—both benefits and potential problems. The program runs on both PCs and Macs. A subsequent presentation will discuss the use of VPHOT and PTGP to generate transforms and the testing of the impacts of varying key VPHOT and PTGP parameters.

  5. Multicolour photometry of EO Ceti (PB 8783)

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  6. STUDY ON FLAME HEIGHT OF MERGED FLAME FROM MULTIPLE FIRE SOURCES

    Microsoft Academic Search

    W. G. WENG; D. KAMIKAWA; Y. FUKUDA; Y. HASEMI; K. KAGIYA

    2004-01-01

    A series of experiments to study merged flame from multiple fire sources was carried out. The porous 15-cm burner was used as a unit burner and propane was employed as a fuel. Many burners with various heat release rates were placed in a square configuration with various separation distances. Flame height was measured using video images and temperature distribution with

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

    Microsoft Academic Search

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

    2011-01-01

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

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

    Microsoft Academic Search

    Jianjun Wang; Li Wang; Anguo Xiao

    2009-01-01

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

  9. 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.

  10. 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 should be able to locate time series photometry data on a given object stored at di#11;erent locations: Data stored at CDS Strasbourg, plotted with a software tool Standard access Time series photometric

  11. 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.

  12. 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.

  13. 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.

  14. Laminar flame speeds of moist syngas mixtures

    SciTech Connect

    Das, Apurba K. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States); Kumar, Kamal; Sung, Chih-Jen [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)

    2011-02-15

    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. (author)

  15. Sooting turbulent jet flame: characterization and quantitative soot measurements

    NASA Astrophysics Data System (ADS)

    Köhler, M.; Geigle, K. P.; Meier, W.; Crosland, B. M.; Thomson, K. A.; Smallwood, G. J.

    2011-08-01

    Computational fluid dynamics (CFD) modelers require high-quality experimental data sets for validation of their numerical tools. Preferred features for numerical simulations of a sooting, turbulent test case flame are simplicity (no pilot flame), well-defined boundary conditions, and sufficient soot production. This paper proposes a non-premixed C2H4/air turbulent jet flame to fill this role and presents an extensive database for soot model validation. The sooting turbulent jet flame has a total visible flame length of approximately 400 mm and a fuel-jet Reynolds number of 10,000. The flame has a measured lift-off height of 26 mm which acts as a sensitive marker for CFD model validation, while this novel compiled experimental database of soot properties, temperature and velocity maps are useful for the validation of kinetic soot models and numerical flame simulations. Due to the relatively simple burner design which produces a flame with sufficient soot concentration while meeting modelers' needs with respect to boundary conditions and flame specifications as well as the present lack of a sooting "standard flame", this flame is suggested as a new reference turbulent sooting flame. The flame characterization presented here involved a variety of optical diagnostics including quantitative 2D laser-induced incandescence (2D-LII), shifted-vibrational coherent anti-Stokes Raman spectroscopy (SV-CARS), and particle image velocimetry (PIV). Producing an accurate and comprehensive characterization of a transient sooting flame was challenging and required optimization of these diagnostics. In this respect, we present the first simultaneous, instantaneous PIV, and LII measurements in a heavily sooting flame environment. Simultaneous soot and flow field measurements can provide new insights into the interaction between a turbulent vortex and flame chemistry, especially since soot structures in turbulent flames are known to be small and often treated in a statistical manner.

  16. 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.

  17. Flame Acceleration and DDT in Narrow Tubes

    NASA Astrophysics Data System (ADS)

    Gamezo, Vadim N.; Oran, Elaine S.

    2004-11-01

    A laminar flame propagating towards the open end of a narrow channel filled with a gaseous combustible mixture can accelerate or oscillate, depending on the wall temperature and the channel width. The accelerating flame is able to produce a high-speed flow that has the potential to provide significant thrust, and this can be used in micropropulsion devices. Depending on the energetics of the reactive system and the length of the channel, the compression waves may converge to a strong shock, and eventually trigger a detonation that develops in the shock-compressed material near the wall. We study these phenomena using multidimensional reactive Navier-Stokes numerical simulations, and show that for adibatic walls the maximum flame acceleration occurs when the channel is about 5 times larger than the reaction zone of a laminar flame. The flame and the unreacted material ahead of it can accelerate to the velocities close to the sound speed without creating strong shocks. This combustion regime is of particular interest for micropropulsion because it allows an efficiet use of fuel and a gradual development of the trust.

  18. 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.

  19. Pulsating instability and self-acceleration of fast turbulent flames

    E-print Network

    Poludnenko, A Y

    2015-01-01

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

  20. Flame acceleration in the early stages of burning in tubes

    SciTech Connect

    Bychkov, Vitaly; Fru, Gordon; Petchenko, Arkady [Institute of Physics, Umeaa University, S-901 87 Umeaa (Sweden); Akkerman, V'yacheslav [Institute of Physics, Umeaa University, S-901 87 Umeaa (Sweden); Nuclear Safety Institute (IBRAE) of Russian Academy of Sciences, B. Tulskaya 52, 115191 Moscow (Russian Federation); Eriksson, Lars-Erik [Department of Applied Mechanics, Chalmers University of Technology, 412 96 Goeteborg (Sweden)

    2007-09-15

    Acceleration of premixed laminar flames in the early stages of burning in long tubes is considered. The acceleration mechanism was suggested earlier by Clanet and Searby [Combust. Flame 105 (1996) 225]. Acceleration happens due to the initial ignition geometry at the tube axis when a flame develops to a finger-shaped front, with surface area growing exponentially in time. Flame surface area grows quite fast but only for a short time. The analytical theory of flame acceleration is developed, which determines the growth rate, the total acceleration time, and the maximal increase of the flame surface area. Direct numerical simulations of the process are performed for the complete set of combustion equations. The simulations results and the theory are in good agreement with the previous experiments. The numerical simulations also demonstrate flame deceleration, which follows acceleration, and the so-called ''tulip flames''. (author)

  1. Modeling of NOx formation in circular laminar jet flames 

    E-print Network

    Siwatch, Vivek

    2007-04-25

    Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames ...

  2. 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

  3. Spectral types from uvby-beta photometry

    NASA Astrophysics Data System (ADS)

    Moon, T.

    1986-05-01

    New diagrams are presented for the assimilation of MK spectral types with uvby-beta photometry. Recently published mean uvby colors and beta indices for a wide selection of spectral types (Moon, 1985; Kilkenny and Whittet, 1985) are used for the revised diagram uvby values and the construction of a (c1), beta diagram for stars earlier than about AO. The Crawford and Mandwewala (1976) theoretical reddening ratios of E(ml)/E(b-y) equal to -0.33 and E(cl)E/(b-y) equal to 0.19 are used, and the supergiants are not displaced from the Main-Sequence band. The data provide estimations of the spectral types of normal stars and chemically peculiar stars, and show the separation of the luminosity classes.

  4. Simplified Color Photometry Using APASS Data (Abstract)

    NASA Astrophysics Data System (ADS)

    Dunkel, N.

    2014-12-01

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

  5. Photometry and Spectroscopy of 47 Cassiopeiae

    NASA Astrophysics Data System (ADS)

    Garner, H. L.; Etzel, P. B.

    1998-05-01

    The HIPPARCOS catalog lists the young rapidly rotating F0 V star 47 Cassiopeiae as a close visual binary. The orbit of the photocenter yields a semi-major axis of 39.3 mas and a period of 1616 days. Gudel et al. (1998, Tenth Cambridge Conference on Cool Stars and the Sun) discuss the puzzle of this system as evidenced by its high X-Ray flux (ROSAT All-Sky Survey), its strong radio flux (6 cm), and indications of rotational modulation in these bands with a period of about one day. Such signatures of coronal activity are not normally associated with early F-type main-sequence stars. Photometry (1996-1997) and spectroscopy (1994-1997) from SDSU's Mount Laguna Observatory will be presented and discussed in connection with the anomalous behavior of the system. Our photometry shows no evidence of rotational modulation, which might be consistent with large star-spot groups, nor any evidence of flaring events. Our spectroscopy does not show any evidence of emission or other forms of line variability at H-alpha that are normally associated with chromospheric activity. However, we do find evidence of radial velocity variations that are consistent with those expected from the HIPPARCOS orbit. Our preliminary orbit is consistent with the interpretation by Gudel et al. that the source of the anomalous X-Ray and radio flux is a very close, chromospherically active solar-type companion. This work was supported by NASA/AURA grant GO-06691 for HST and NSF grant AST94-17035.

  6. Prediction of laminar flame properties of propane-air mixtures

    Microsoft Academic Search

    C. K. Westbrook; W. J. Pitz

    1983-01-01

    A numerical model including a detailed chemical kinetic reaction mechanism is used to study laminar flame propagation in propane-air mixtures. The effects of variations in pressure and fuel-oxidizer equivalence ratio are examined. Propane-air flames are compared with methane-air, methanol-air, and ethylene-air laminar flames. Quenching of propane-air flames in thermal boundary layers is examined, and the results are compared with previous

  7. Prediction of laminar flame properties of propane-air mixtures

    Microsoft Academic Search

    C. K. Westbrook; W. J. Pitz

    1985-01-01

    A numerical model including a detailed chemical kinetic reaction mechanism is used to study laminar flame propagation in propane-air mixtures. The effects of variations in pressure and fuel-oxidizer equivalence ratio are examined. Propane-air flames are compared with methane-air, methanol-air, and ethylene-air laminar flames. Quenching of propane-air flames in thermal boundary layers is examined, and the results are compared with previous

  8. The Transition to Turbulence of Rayleigh-Taylor Unstable Flames

    NASA Astrophysics Data System (ADS)

    Hicks, Elizabeth P.; Rosner, R.

    2011-01-01

    Part of the uncertainty surrounding the explosion mechanism of Type 1A supernovae is the extent to which the turbulence created by the flame front can speed the flame up. A premixed flame moving against a sufficiently strong gravitational field becomes deformed and creates vorticity. If gravity is strong enough, this vorticity is shed and deposited behind the flame front. We have completed some two-dimensional direct numerical simulations of this shedding process for various values of the gravitational force. If gravity is weak enough, the flame front remains flat and no vorticity is created. If gravity is slightly stronger, the flame front becomes cusped and creates vorticity; long vortices attach to the flame front and extend behind it. For even larger values of gravity, the far end of these vortices becomes unstable and sheds more vortices. For simulations with increased gravity, the position of the shedding instability moves closer to the flame front. Next, the vortex shedding disturbs the flame front, causing the flame to pulsate. These pulsations lose their left/right symmetry and the period of oscillation doubles. For even higher values of gravity, an additional frequency is introduced into the system as the Rayleigh-Taylor instability begins to dominate over burning. Eventually, the pulsations of the flame become quite complex and the interaction between the flame front and the vortices can't be simply described. We have measured the subsequent wrinkling of the flame front by computing its fractal dimension and the energy spectra behind the flame front. Measurements of the fractal dimension suggest that it saturates, implying that any additional speed up of the flame must be due to large-scale stretching or disruption of the flame front. Our simulations were performed at NERSC which is supported by the Department of Energy.

  9. Spatial resolution of temperature and chemical species in a flame 

    E-print Network

    Albahadily, Fakhrildeen Niema

    1984-01-01

    to monitor the spatial resolution oi' hydroxyl radical and atomic hydrogen in an air-acetylene flame. Although the flame's first reaction zone is rich with radicals and ions because the production rate is higher than the recombination rate, the usability... and atomic hydrogen, as well as the flame temperature were measured by laser-induced fluorescence. Copper and copper hydride have been used as indicator species to study the spatial distribution oi atomic hydrogen in an air-acetylene flame. The ratio...

  10. Studies of Premixed Laminar and Turbulent Flames at Microgravity

    NASA Technical Reports Server (NTRS)

    Ronney, Paul D.

    1993-01-01

    The work of the Principal Investigator (PI) has encompassed four topics related to the experimental and theoretical study of combustion limits in premixed flames at microgravity, as discussed in the following sections. These topics include: (1) radiation effects on premixed gas flames; (2) flame structure and stability at low Lewis number; (3) flame propagation and extinction is cylindrical tubes; and (4) experimental simulation of combustion processes using autocatalytic chemical reactions.

  11. Rich methane premixed laminar flames doped by light unsaturated hydrocarbons

    Microsoft Academic Search

    H. A. Gueniche; P. A. Glaude; R. Fournet; F. Battin-Leclerc

    2008-01-01

    In line with the studies presented in Parts I (methane flame seeded with allene and propyne) and II (methane flame seeded with 1,3-butadiene) of this paper, the structure of a laminar rich premixed methane flame doped with cyclopentene has been investigated. The gases of this flame contain 15.3% (molar) of methane, 26.7% of oxygen, and 2.4% cyclopentene, corresponding to an

  12. 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.

  13. Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

    NASA Astrophysics Data System (ADS)

    Marschner, Karel; Musil, Stanislav; D?dina, Ji?í

    2015-07-01

    A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH4 in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were compared. Under optimum conditions sensitivity obtained with flame-in-gas-shield atomizer was approximately twice higher than with miniature diffusion flame. The additional advantage of flame-in-gas-shield atomizer is significantly lower flame emission resulting in a better signal to noise ratio. The resulting arsenic limits of detection for miniature diffusion flame and flame-in-gas-shield atomizer were 3.8 ng l- 1 and 1.0 ng l- 1, respectively.

  14. 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.

  15. Aerothermodynamic properties of stretched flames in enclosures

    NASA Astrophysics Data System (ADS)

    Rotman, D. A.; Oppenheim, A. K.

    Flames are stretched by being pulled along their frontal surface by the flow field in which they reside. Their trajectories tend to approach particle paths, acquiring eventually the role of contact boundaries, -interfaces between the burnt and unburnt medium that may broaden solely as a consequence of diffusion. Fundamental properties of flow fields governing such flames are determined here on the basis of the zero Mach number model, providng a rational method of approach to the computational analysis of combustion fields in enclosures where, besides the aerodynamic properties flow, the thermodynamic process of compression must be taken into account. To illustrate its application, the method is used to reveal the mechanism of formation of a tulip-shape flame in a rectangular enclosure under nonturbulent flow conditions.

  16. Interaction of pulsating and spinning waves in nonadiabatic flame propagation

    Microsoft Academic Search

    Michael R. Booty; Stephen B. Margolis; Bernard J. Matkowsky

    1987-01-01

    The authors consider nonadiabatic premixed flame propagation in a long cylindrical channel. A steadily propagating planar flame exists for heat losses below a critical value. It is stable provided that the Lewis number and the volumetric heat loss coefficient are sufficiently small. At critical values of these parameters, bifurcated states, corresponding to time-periodic pulsating cellular flames, emanate from the steadily

  17. 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

  18. 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

  19. Investigations of swirl flames in a gas turbine model combustor

    SciTech Connect

    Meier, W.; Duan, X.R.; Weigand, P. [Institut fuer Verbrennungstechnik, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), Pfaffenwaldring 38, D-70569 Stuttgart (Germany)

    2006-01-01

    The thermochemical states of three swirling CH{sub 4}/air diffusion flames, stabilized in a gas turbine model combustor, were investigated using laser Raman scattering. The flames were operated at different thermal powers and air/fuel ratios and exhibited different flame behavior with respect to flame instabilities. They had previously been characterized with respect to their flame structures, velocity fields, and mean values of temperature, major species concentrations, and mixture fraction. The single-pulse multispecies measurements presented in this article revealed very rapid mixing of fuel and air, accompanied by strong effects of turbulence-chemistry interactions in the form of local flame extinction and ignition delay. Flame stabilization is accomplished mainly by hot and relatively fuel-rich combustion products, which are transported back to the flame root within an inner recirculation zone. The flames are not attached to the fuel nozzle, and are stabilized approximately 10 mm above the fuel nozzle, where fuel and air are partially premixed before ignition. The mixing and reaction progress in this area are discussed in detail. The flames are short (<50 mm), especially that exhibiting thermoacoustic oscillations, and reach a thermochemical state close to adiabatic equilibrium at the flame tip. The main goals of this article are to outline results that yield deeper insight into the combustion of gas turbine flames and to establish an experimental database for the validation of numerical models.

  20. Sensitivity analysis of transfer functions of laminar flames

    Microsoft Academic Search

    F. Duchaine; F. Boudy; D. Durox; T. Poinsot

    The sensitivity of laminar premixed methane\\/air flames responses to acoustic forcing is investigated using direct numerical simulation to determine which parameters control their flame transfer function. Five parameters are varied: (1) the flame speed sL, (2) the expansion angle of the burnt gases ?, (3) the inlet air temperature Ta, (4) the inlet duct temperature Td and (5) the combustor

  1. The response of swirling premixed flames to velocity perturbations

    Microsoft Academic Search

    P. Palies; D. Durox; T. Schuller; S. Candel

    This article is focused on the dynamics of swirling premixed confined flames. The swirl number measured experimentally is near 0.6. Combustion dynamics is represented by the flame describing function (FDF) which is used to characterize the response of the flame to velocity disturbances. The FDF is determined by deducing the unsteady heat release rate from the chemiluminescence intensity of OH*

  2. The visualization and mapping of turbulent premixed impinging flames

    Microsoft Academic Search

    T. FOAT; K. P. YAP; Y. ZHANG

    2001-01-01

    Studies of the patterns and structures of turbulent premixed impinging flames and the regime of different flame modes are resolved. Up to four alternative combustion modes have been established under identical nozzle flow conditions. The creation of each alternative mode is dependent on the initial ignition location. Turbulence generation plays a very important role in wall stabilised flames. A high-speed

  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. New optical observations of auroral flames

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-12-01

    Auroral arcs are a visible manifestation of space weather. A common dynamic observed during geomagnetically disturbed periods is the breakup of auroral arcs into a multitude of small-scale filaments less than 1 kilometer across. These filaments can move rapidly upward along the geomagnetic field lines. Dahlgren et al. observed such "auroral flames" during a breakup event on 1 March 2011 using an advanced high-speed optical system with sensitive low-light detectors. The data provide new insight into the energy and flux of electrons in individual auroral flames and could help scientists better understand the dynamic processes involved in auroral breakup.

  7. 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).

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

    Microsoft Academic Search

    Bin Li; Miaojun Xu

    2006-01-01

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

  9. On the mechanism of flame retardancy and characterization of halogen-free, flame-retardant materials for wires and cables

    Microsoft Academic Search

    H. Kato; T. Futagami; M. Ishida; K. Sengoku; M. Ueda

    1986-01-01

    During exploratory on mechanistic pathway of halogen-free, flame-retardant materials, containing metal hydroxide with other ingredients, there were revealed that the char formation at high temperatures should play an important role to enhance flame retardancy of resultant compositions, and some metallic compounds which were capable of increase catalytically the amount of char could further improve flame retardancy. It has also been

  10. Flame Structure and Scalar Properties in Microgravity Laminar Fires

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  11. Characteristics of transitional and turbulent jet diffusion flames in microgravity

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  12. Correlation of Flame Speed with Stretch in Turbulent Premixed Methane/Air Flames

    NASA Astrophysics Data System (ADS)

    Chen, Jacqueline H.; Im, Hong G.

    1997-11-01

    Flame speed correlation with stretch is obtained from direct numerical simulations of lean to stoichiometric methane/air flames over a broad range of Karlovitz numbers. The correlation is interpreted in terms of local tangential strain rate and curvature effects. DNS results show that there exist two distinct branches in the correlation curve depending on the sign of the displacement speed. For small Karlovitz numbers with positive displacement speed, the estimated Markstein length from the DNS results agrees well with that obtained from steady strained laminar flame calculations as well as with experimental studies. Larger values of Karlovitz numbers observed in the DNS results are found to be mainly due to the effect of strong curvatures; for those cases the correlation shows nonlinear behavior. The sensitivity of the correlation to the definition of the flame front and the statistical importance of particular branches in the correlation are also discussed.

  13. 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.

  14. 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.

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

    Microsoft Academic Search

    Kristin M. Kopp-Vaughan; Steven G. Tuttle; Michael W. Renfro; Galen B. King

    2009-01-01

    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

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

    Microsoft Academic Search

    Kristin M. Kopp-Vaughan; Steven G. Tuttle; Michael W. Renfro; Galen B. King

    2009-01-01

    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

  17. Laser-saturated fluorescence measurements in laminar sooting diffusion flames

    NASA Technical Reports Server (NTRS)

    Wey, Changlie

    1993-01-01

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

  18. Dynamic response of a pulsed Burke-Schumann diffusion flame

    NASA Technical Reports Server (NTRS)

    Sheu, Jyh-Cherng; Stocker, Dennis P.; Chen, Lea-Der

    1995-01-01

    Turbulent flames are often envisioned as an ensemble of random vortices interacting with the combustion process. A better understanding of the vortex-flame interactions therefore would be useful in improving the modeling of turbulent diffusion flames. Substantial simplification may be made by investigating controlled interactions in a laminar flame, as opposed to random interactions in a turbulent flame. The general goals of the research project are to improve our understanding of (1) the influence of buoyancy on co-flow diffusion flames and (2) the effects of buoyancy on vortex-flame interactions in co-flow diffusion flames. As a first step toward objective (2), we conducted a joint experimental and numerical investigation of the vortex-flame interaction. Vortices were produced by mechanically pulsing the fuel flow at a low frequency, e.g., 10 Hz. Experiments were conducted using a nonflickering Burke-Schumann flame in both microgravity (mu-g) and normal gravity (1g) as a means of varying the buoyant force without modification of the pressure (i.e., density). The effects of buoyant convection may then be determined by a comparison of the mu-g and 1g results. The mu-g results may also reveal the important mechanisms which are masked or overwhelmed by buoyant convection in 1g. A numerical investigation was conducted using a validated, time-accurate numerical code to study the underlying physics during the flame interaction and to assist the interpretation of the experimental results.

  19. Kerosene wick lamp flame deformation in gradient magnetic fields

    NASA Astrophysics Data System (ADS)

    Saeedi, A.; Moghiman, M.

    2014-03-01

    The behavior of a kerosene wick lamp flame in the presence of non-uniform DC magnetic fields has been investigated and the results of this experimental study are presented. It has long been recognized that magnetic fields can influence the behavior of diffusion flames as a result of the paramagnetic and diamagnetic properties of the constituent gases. Using an electromagnet consisting of two coils and cores to generate a horizontal magnetic field, a non-uniform upward increasing and decreasing magnetic field was applied to a kerosene wick lamp flame. The experimental results show that the influence of DC gradient magnetic field on diffusion flame structure deformation depends on the flame position in the increasing or decreasing magnetic field, the flame situation relative to the maximum of the absolute value of the gradient and the quantity of the gradient magnetic field. It was also observed that both flame front area and flame height decrease in the positive and negative gradient field below the maximum of the absolute value of the gradient. Also, increasing the absolute of the gradient of the square magnetic induction in the positive and negative gradient field above the maximum of the absolute value of the gradient cause to elongate the flame and increase in the flame front area and then the flame height and front area decrease.

  20. 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.

  1. 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.

  2. Effects of Swirl on Strongly-Pulsed Turbulent Diffusion Flames

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  3. Excitation of thermoacoustic oscillations by small premixed flames

    SciTech Connect

    Coats, C.M.; Chang, Z.; Williams, P.D. [Department of Engineering, University of Leicester, Leicester LE1 7RH (United Kingdom)

    2010-06-15

    Experiments have been carried out in which very small lean premixed flames closely representative of those formed by modern multiport domestic gas burners have been subjected to controlled acoustic perturbation. PLIF from CH has been used to visualise the flame response and the heat-release-rate fluctuations have been evaluated directly from the flame images. It is shown that small laminar flames can amplify the effects of acoustic velocity fluctuations by mechanisms that do not involve resonant heat loss to the burner and that the fluctuations in flame-front area are not adequately characterised by a Strouhal number alone. The measured transfer function is compared with the predictions of various analytical formulations and a new model of the flame oscillation is proposed which applies specifically to situations in which the design of the burner renders the flame base immobile. (author)

  4. Flame quenching process in cavity based on model scramjet combustor

    NASA Astrophysics Data System (ADS)

    Pan, Yu; Lei, Jing; Liang, Jian-Han; Liu, Wei-Dong; Wang, Zhen-Guo

    2012-02-01

    The flame quenching process in combustors was observed by high speed camera and Schlieren system, at the inflow conditions of Ma = 2.64, T 0 = 1 483 K, P 0 = 1.65MPa, T = 724K and P = 76.3 kPa. Changing process of the flame and shock structure in the combustor was clearly observed. The results revealed that the precombustion shock disappeared accompanied with the process in which the flame was blown out and withdrawed from the mainflow into the cavity and vanished after a short while. The time of quenching process was extended by the cavity flame holder, and the ability of flame holding was enhanced by arranging more cavities in the downstream as well. The flame was blown from the upstream to the downstream, so the flame in the downstream of the cavity was quenched out later than that in the upstream.

  5. 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.

  6. 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.

  7. UBVRI aperture photometry of southern Seyfert galaxies and related objects.

    NASA Astrophysics Data System (ADS)

    Winkler, H.; Payne, P.

    UBV(RI)c photometry for 36 southern galaxies (mostly Seyferts) is presented. The majority of these galaxies have never been observed photometrically. Their absolute magnitudes are calculated after correcting the measured magnitudes for interstellar extinction in our Galaxy.

  8. Spectra and Latent Energy in Flame Gases

    Microsoft Academic Search

    Sydney Steele

    1935-01-01

    IN a recent letter on the above subject, Prof. W. T. David1 points out that after flame has travelled through an inflammable gaseous mixture, the gases remaining emit luminous (visible and ultra-violet) radiation for a considerable period of time if their temperature is kept up. In an investigation carried out at the United States Bureau of Standards, accounts of which

  9. Environmentally Benign Flame Retardant Nanocoatings for Fabric

    E-print Network

    Li, Yu-Chin

    2012-07-16

    nanocomposites in an effort to produce more flame-retardant coatings. Laponite and montmorillonite (MMT) clay were paired with branched poly(ethylenimine) to create thin film assemblies that can be tailored by changing pH and concentration of aqueous deposition...

  10. CFD for Flames Jack King (Selwyn College)

    E-print Network

    CFD for Flames by Jack King (Selwyn College) Fourth-year undergraduate project in Group A, 2009 to real ames. For a detailed investigation into ame structure, a numerical simulation is more appropriate the structure of ames near the lean ammability limit. In this work, a numerical simulation of a one

  11. The Flame Challenge What is Time?

    E-print Network

    ." ­ Saint Augustine It's a deep question, and it has no simple answer. But science is more aboutThe Flame Challenge What is Time? Alan Alda, the Center for Communicating Science -- and 11- year-olds around the country ­ are seeking answers from scientists to a timeless question: What is time

  12. Zinc recovery via the flame reactor process

    Microsoft Academic Search

    J. F. Pusateri; C. O. Bounds; L. W. Lherbier

    1988-01-01

    A major objective of the zinc industry for the 1990s will be to maintain high zinc recovery while eliminating the disposal of copious quantities of hazardous iron residues. The flame reactor process has demonstrated the potential of meeting this objective by either treating the residues or smelting zinc directly. The process has been proven commercially viable for treating flue dusts

  13. 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

  14. Gas phase radiative effects in diffusion flames

    Microsoft Academic Search

    Hasan Bedir

    1998-01-01

    Several radiation models are evaluated for a stagnation point diffusion flame of a solid fuel in terms of accuracy and computational time. Narrowband, wideband, spectral line weighted sum of gray gases (SLWSGG), and gray gas models are included in the comparison. Radiative heat flux predictions by the nongray narrowband, wideband, and SLWSGG models are found to be in good agreement

  15. Flame Retardancy Behavior of Zinc Borate

    Microsoft Academic Search

    Youming Yang; Xichang Shi; Ruirong Zhao

    1999-01-01

    The effect of boron chloride formation from zinc borate in burn ing PVC was elucidated. By thermodynamic calculation, experiment, and infra red spectrum analysis, the conditions for boron halide formation when PVC was burned were addressed. It is found that when boron halide is produced, the B2O3 glass layer is destroyed and boron is volatilized, which is unfavorable to flame

  16. Flame in methane jet after spark ignition

    E-print Network

    Ahmed, Samer F; Mastorakos, Epaminondas

    2009-05-21

    The video shows the flame motion following spark ignition in a turbulent methane jet. The flow conditions were: 30% air, 70% CH4, jet velocity 12.5m/s & 25m/s, framing rate 4200 fps, spark at r=0, z=40d (40 jet diameters; d=5mm). For details, see: S...

  17. 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...

  18. 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...

  19. TFIT: Mixed-resolution data set photometry package

    NASA Astrophysics Data System (ADS)

    Laidler, Victoria G.; Papovich, Casey; Grogin, Norman A.; Idzi, Rafal; Dickinson, Mark; Ferguson, Henry C.; Hilbert, Bryan; Clubb, Kelsey; Ravindranath, Swara

    2015-05-01

    TFIT measures galaxy photometry using prior knowledge of sources in a deep, high-resolution image (HRI) to improve photometric measurements of objects in a corresponding low-resolution image (LRI) of the same field, usually at a different wavelength. For background-limited data, this technique produces optimally weighted photometry that maximizes signal-to-noise ratio (S/N). For objects not significantly detected in the low-resolution image, it provides useful and quantitative information for setting upper limits.

  20. EMCCD Technology in High Precision Photometry on Short Timescales

    Microsoft Academic Search

    Niall Smith; Alan Giltinan; Aidan O’Connor; Stephen O’Driscoll; Adrian Collins; Dylan Loughnan; Andreas Papageorgiou

    2008-01-01

    We discuss the advantages and limitations of Electron Multiplying CCD technology in high precision photometry on short timescales,\\u000a with special emphasis on probing the smallest structures in active galactic jets. Factors external to the EMCCD, rather than\\u000a the architecture of the EMCCD itself, most often limit the precision of photometry that can be reached with groundbased observations.\\u000a Although EMCCDs can

  1. 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.

  2. 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...

  3. 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.

  4. 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

  5. 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.

  6. Flame behaviors of propane/air premixed flame propagation in a closed rectangular duct with a 90-deg bend

    NASA Astrophysics Data System (ADS)

    He, Xuechao; Sun, Jinhua; Yuen, K. K.; Ding, Yibin; Chen, Sining

    2008-11-01

    Experiments of flame propagation in a small, closed rectangular duct with a 90° bend were performed for a propane-air mixture. The high speed camera and Schlieren techniques were used to record images of flame propagation process in the combustion pipe. Meanwhile, the fine thermocouples and ion current probes were applied to measure the temperature distribution and reaction intensity of combustion. The characteristics of propane-air flame and its microstructure were analyzed in detail by the experimental results. In the test, the special tulip flame formation was observed. Around the bend, the flame tip proceeded more quickly at the lower side with the flame front elongated toward the axial direction. And transition to turbulent flame occurred. It was suggested that fluctuations of velocity, ion current and temperature were mainly due to the comprehensive effects of multi-wave and the intense of turbulent combustion.

  7. 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

  8. Mechanisms of Microgravity Flame Spread Over a Thin Solid Fuel: Oxygen and Opposed Flow Effects

    Microsoft Academic Search

    S. L. OLSON

    1991-01-01

    Microgravity tests varying oxygen concentration and forced flow velocity have examined the importance of transport processes on flame spread over very thin solid fuels. Flame spread rates, solid phase temperature profiles and flame appearance for these tests are measured. A flame spread map is presented which indicates three distinct regions where different mechanisms control the flame spread process. In the

  9. 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.

  10. Suppression and Structure of Low Strain Rate Nonpremixed Flames

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  11. 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.

  12. 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.

  13. The propagation of premixed flames in closed tubes

    NASA Astrophysics Data System (ADS)

    Matalon, Moshe; Metzener, Philippe

    1997-04-01

    A nonlinear evolution equation that describes the propagation of a premixed flame in a closed tube has been derived from the general conservation equations. What distinguishes it from other similar equations is a memory term whose origin is in the vorticity production at the flame front. The two important parameters in this equation are the tube's aspect ratio and the Markstein parameter. A linear stability analysis indicates that when the Markstein parameter [alpha] is above a critical value [alpha]c the planar flame is the stable equilibrium solution. For [alpha] below [alpha]c the planar flame is no longer stable and there is a band of growing modes. Numerical solutions of the full nonlinear equation confirm this conclusion. Starting with random initial conditions the results indicate that, after a short transient, a at flame develops when [alpha]>[alpha]c and it remains flat until it reaches the end of the tube. When [alpha]<[alpha]c, on the other hand, stable curved flames may develop down the tube. Depending on the initial conditions the flame assumes either a cellular structure, characterized by a finite number of cells convex towards the unburned gas, or a tulip shape characterized by a sharp indentation at the centre of the tube pointing toward the burned gases. In particular, if the initial conditions are chosen so as to simulate the elongated finger-like flame that evolves from an ignition source, a tulip flame evolves downstream. In accord with experimental observations the tulip shape forms only after the flame has travelled a certain distance down the tube, it does not form in short tubes and its formation depends on the mixture composition. While the initial deformation of the flame front is a direct result of the hydrodynamic instability, the actual formation of the tulip flame results from the vortical motion created in the burned gas which is a consequence of the vorticity produced at the flame front.

  14. Analytical study in the mechanism of flame movement in horizontal tubes. II. Flame acceleration in smooth open tubes

    NASA Astrophysics Data System (ADS)

    Kazakov, Kirill A.

    2013-08-01

    The problem of spontaneous acceleration of premixed flames propagating in open horizontal tubes with smooth walls is revisited. It is proved that in long tubes, this process can be considered quasi-steady, and an equation for the flame front position is derived using the on-shell description. Numerical solutions of this equation are found which show that as in the case of uniform flame movement, there are two essentially different regimes of flame propagation. In the type I regime, the flame speed and its acceleration are comparatively low, whereas the type II regime is characterized by significant flame acceleration that rapidly increases as the flame travels along the tube. A detailed comparison of the obtained results with the experimental data on flame acceleration in methane-air mixtures is given. In particular, it is confirmed that flames propagating in near-stoichiometric mixtures and mixtures near the limits of inflammability belong to the types II and I, respectively, whereas flames in transient mixtures undergo transitions between the two regimes during their travel.

  15. Approaches to flame resistant polymeric materials

    NASA Technical Reports Server (NTRS)

    Liepins, R.

    1975-01-01

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

  16. Numerical simulations of flows around flame holders

    NASA Astrophysics Data System (ADS)

    Bai, X. S.; Fuchs, L.; Li, Y.

    1992-01-01

    The numerical simulations of turbulent flow around a flame holder model placed in a wind tunnel is presented. The calculations include both isothermal and reacting flows. The (cold) isothermal flow is modeled by Reynolds averaged Navier-Stokes N-S equations equipped with standard two-equation k-epsilon model and Large Eddy Simulations (LES). The (hot) reacting flow is calculated by a premixed flame model based on Magnussen's eddy dissipation concept, in addition to the N-S equations and k-epsilon equations. The system of equations is solved numerically on a system of global and locally refined grids, using a multigrid method. The results show that the numerical calculations compare well with the experimental results.

  17. A thermal equation for flame quenching

    NASA Technical Reports Server (NTRS)

    Potter, A E , Jr; Berlad, A I

    1956-01-01

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

  18. Two-dimensional stability of laminar flames

    NASA Technical Reports Server (NTRS)

    Mukunda, H. S.; Drummond, J. Philip

    1992-01-01

    The stability of laminar flames was studied numerically and the dependence of stability on finite rate chemistry with low activation energy and variable thermodynamic and transport properties was addressed. The calculations show that activation energy and details of chemistry play a minor role in altering the linear neutral stability results from asymptotic analysis. Variable specific heat makes a marginal change to the stability; variable transport properties, on the other hand, tend to substantially enhance the stability from a critical wave number of about 0.50 to 0.20. Also, the effects of variable properties tend to nullify the effects of nonunity Lewis number. When the Lewis number of a single species is different from unity, as is true in a hydrogen-air premixed flame, the stability results remain close to that of unity Lewis number.

  19. Interaction of pulsating and spinning waves in nonadiabatic flame propagation

    SciTech Connect

    Booty, M.R.; Margolis, S.B.; Matkowsky, B.J.

    1987-12-01

    The authors consider nonadiabatic premixed flame propagation in a long cylindrical channel. A steadily propagating planar flame exists for heat losses below a critical value. It is stable provided that the Lewis number and the volumetric heat loss coefficient are sufficiently small. At critical values of these parameters, bifurcated states, corresponding to time-periodic pulsating cellular flames, emanate from the steadily propagating solution. The authors analyze the problem in a neighborhood of a multiple primary bifurcation point. By varying the radius of the channel, they split the multiple bifurcation point and show that various types of stable periodic and quasi-periodic pulsating flames can arise as secondary, tertiary, and quaternary bifurcations. Their analysis describes several types of spinning and pulsating flame propagation which have been experimentally observed in nonadiabatic flames, and also describes additional quasi-periodic modes of burning which have yet to be documented experimentally.

  20. Stretch-induced quenching in flame-vortex interactions

    NASA Technical Reports Server (NTRS)

    Samaniego, J.-M.

    1993-01-01

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

  1. Turbulent Nonpremixed Flames (TNF): Experimental Data Archives and Computational Submodels

    DOE Data Explorer

    In the 1990s an international collaboration formed around a series of workshops that became known collectively as the International Workshop on Measurement and Computation of Turbulent Non-Premixed Flames (TNF). An online library, hosted by Sandia National Laboratory (California) was established that provides data sets and submodels or "mechanisms" for the study of turbulence-chemistry interactions in turbulent nonpremixed and partially premixed combustion. Data are organized by flame types: simple jet flames, piloted jet flames, bluff body flames, and swirl flames. These data sets provide a means for collaborative comparisons of both measured and simulated/modeled research results and also assist scientists in determining priorities for further research. More than 20 data sets or databases are available from this website, along with various downloadable files of chemical mechanisms. The website also provides an extensive bibliography and the proceedings of the workshops themselves from 1996 through 2012. Information continues to be added to this collection.

  2. Flame and acid resistant polymide fibers

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  3. Soot Deposit Properties in Practical Flames

    SciTech Connect

    Preciado, Ignacio [University of Utah; Eddings, Eric G. [University of Utah; Sarofim, Adel F. [University of Utah; Dinwiddie, Ralph Barton [ORNL; Porter, Wallace D [ORNL; Lance, Michael J [ORNL

    2009-01-01

    Soot deposition from hydrocarbon flames was investigated in order to evaluate the evolution of the deposits during the transient process of heating an object that starts with a cold metal surface that is exposed to a flame. The study focused on the fire/metal surface interface and the critical issues associated with the specification of the thermal boundaries at this interface, which include the deposition of soot on the metal surface, the chemical and physical properties of the soot deposits and their subsequent effect on heat transfer to the metal surface. A laboratory-scale device (metallic plates attached to a water-cooled sampling probe) was designed for studying soot deposition in a laminar ethylene-air premixed flame. The metallic plates facilitate the evaluation of the deposition rates and deposit characteristics such as deposit thickness, bulk density, PAH content, deposit morphology, and thermal properties, under both water-cooled and uncooled conditions. Additionally, a non-intrusive Laser Flash Technique (in which the morphology of the deposit is not modified) was used to estimate experimental thermal conductivity values for soot deposits as a function of deposition temperature (water-cooled and uncooled experiments), location within the flame and chemical characteristics of the deposits. Important differences between water-cooled and uncooled surfaces were observed. Thermophoresis dominated the soot deposition process and enhanced higher deposition rates for the water-cooled experiments. Cooler surface temperatures resulted in the inclusion of increased amounts of condensable hydrocarbons in the soot deposit. The greater presence of condensable material promoted decreased deposit thicknesses, larger deposit densities, different deposit morphologies, and higher thermal conductivities.

  4. The Characteristics Method and Cusped Flame Fronts

    Microsoft Academic Search

    F. BAILLOT; A. BOUREHLA; D. DUROX

    1996-01-01

    The kinematic effects of a space-time forced velocity field upon a thin premixed flame, stabilized above a circular cross-section burner, are studied in order to point out the non-linearities due to a sufficiently high velocity perturbation level whose RMS amplitudes remain nonetheless inferior to the normal burning velocity. The present calculation proposes to seek a solution using the characteristics method,

  5. Photovoltaic module spread-of-flame testing

    NASA Astrophysics Data System (ADS)

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

    1984-10-01

    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 brand standard. The most promising is stainless steel foil.

  6. Fluid mechanical properties of flames in enclosures

    SciTech Connect

    Rotman, D.A.; Pindera, M.Z.; Oppenheim, A.K.

    1988-07-01

    In an enclosure where the reacting medium is initially at rest, the flame first generates a flowfield that then gets stretched, i.e., its front is pulled along the surface by the flowfield in which it then finds itself residing. A methodology developed for numerical modeling of such fields is described. Of key significance in this respect is the zero Mach number model/endash/a reasonable idealization in view of the relatively high temperature, and hence sound speed, that exists, concomitantly with a comparatively low particle velocity, in the confinement of a combustion chamber. According to this model, the density gradient in the field is nullified, while across the flame front it approaches infinity. One has thus two regimes: one of the unburned medium and the other of the burned gas, each of spatially uniform density, separated by a flame front interface. The latter is endowed with four properties, of which the first two are purely kinematic and the others dynamic in nature, namely: 1) it is advected at the local velocity of flow; 2) it self-advances at the normal burning speed, the eigenvalue of the system; 3) it acts as the velocity source due to the exothermicity of the combustion process; and 4) it acts as the vorticity source due to the baroclinic effect generated by the pressure gradient along its surface and the density gradient across it. A solution obtained for a flame propagating in an oblong rectangular enclosure demonstrates that the latter has a significant influence upon the formation of the well known tulip shape. 12 refs., 4 figs.

  7. On Flame-Wall Thermal-Coupling in Micro Combustors Yong Fan, Yuji Suzuki, and Nobuhide Kasagi

    E-print Network

    Kasagi, Nobuhide

    -resolved chemiluminescence images of the flame taken by the high-speed ICCD camera, flame oscillation is interpreted in the sideway to capture the streamwise motion of the flame. OH* chemiluminescence images are taken for flame

  8. 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.

  9. A Series of Laminar Jet 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, using propane fuel, was taken STS-94, July 4 1997, MET:2/05:30 (approximate). LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel-like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (249KB JPEG, 1350 x 1524 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300185.html.

  10. Establishment of deacon equilibrium in a flame

    SciTech Connect

    Mal'tseva, A.S.; Frolov, Y.E.; Rozlovskii, A.I.

    1984-03-01

    The authors study in detail the chemistry of the transformation of combustible and noncombustible chlorohydrocarbons in a flame and obtain results that contradict the assertions made. They discover that a significant amount of bound chlorine (up to 9-18% of the total amount), depending on the nature of the auxiliary fuel, remains in the absorbed gases in an elemental state, and up to 6% of the total amount of chlorine transforms into phosgene. The results obtained were virtually independent of the oxidizer ratio and of the combustion temperature; the water content in all investigated systems was significant. The work results in the conclusion that the Deacon equilibrium is not established in the products of high-temperature and even flame reprocessing of mixtures containing chlorine derivatives and oxygen. The possibility of the formation of appreciable amounts of elemental chlorine and phosgene, aside from the large dilution of the absorbed products in the absorbed gases, treated by water flushing, makes the process of flame decontamination of chlorine derivatives undesirable.

  11. On burner-stabilized cylindrical premixed flames in microgravity

    NASA Technical Reports Server (NTRS)

    Eng, James A.; Zhu, Delin; Law, Chung K.

    1995-01-01

    An experimental and theoretical program on cylindrical and spherical premixed flames in microgravity has been initiated. We are especially interested in: (1) assessing heat loss versus flow divergence as the dominant stabilization mechanism; (2) understanding the effects of flame curvature on the burning intensity; and (3) determining the laminar burning velocity by using this configuration. In the present study we have performed analytical, computational, and mu g-experimental investigations of the cylindrical flame. The results are presented.

  12. Noise Reduction in Non-Premixed Lifted-Jet Flames

    Microsoft Academic Search

    K. Ramamurthi; R. K. Patnaik

    2004-01-01

    The characteristic changes in non-premixed lifted flames when excited by hole tones from a cavity, placed in the flow path\\u000a of the fuel gas, were studied. A significant reduction of the sound pressure level was observed in the low-frequency noise\\u000a at the flame base of the lifted flame when the hole tones were induced in the jet. The liftoff height

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  14. Effect of Intense Sound Waves on a Stationary Gas Flame

    NASA Technical Reports Server (NTRS)

    Hahnemann, H; Ehret, L

    1950-01-01

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

  15. Modelling of turbulent diffusion flames stabilized on a bluff body

    Microsoft Academic Search

    Chang E. Lee; Ok Y. Yang; Yoshiaki Onuma

    1992-01-01

    The present authors previously proposed a modification of the k-epsilon turbulence model in the modeling of jet diffusion flames to represent the so-called laminarization phenomenon, caused by combustion in the low-turbulence region, and recently found, in experiments on diffusion flames stabilized on a bluff body, that this phenomenon also exerts an important influence on the structure of these flames with

  16. Rich premixed laminar methane flames doped by light unsaturated hydrocarbons

    Microsoft Academic Search

    H. A. Gueniche; P. A. Glaude; R. Fournet; F. Battin-Leclerc

    2007-01-01

    In line with the study presented in Part I of this paper, the structure of a rich premixed laminar methane flame doped with 1,3-butadiene has been investigated. The flame contains 20.7% (molar) of methane, 31.4% of oxygen, and 3.3% of 1,3-butadiene, corresponding to an equivalence ratio of 1.8, and a C4H6\\/CH4 ratio of 16%. The flame has been stabilized on

  17. 45 (2008-5) Thermal Effect of Wall on Micro Premixed Flame in Quartz Channels

    E-print Network

    Kasagi, Nobuhide

    -resolved chemiluminescence images of the flame taken by the high-speed ICCD camera. Flammability limits are obtained in the sideway, and CH*/OH* chemiluminescence images of the flame are taken for flame visualization up to 2000

  18. Combustion and Flame 149 (2007) 340352 www.elsevier.com/locate/combustflame

    E-print Network

    Aggarwal, Suresh K.

    2007-01-01

    in lifted methane­air coflow flames, while both counterflow and coflow flames were simulated using a time, because they may correspond to the corre- sponding requirements for axisymmetric cup burner flames [4

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  20. BVRI Surface Photometry of Isolated Galaxy Triplets

    NASA Astrophysics Data System (ADS)

    Hernández-Toledo, H. M.; Méndez-Hernández, H.; Aceves, H.; Olguín, L.

    2011-03-01

    Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets of Galaxies in the Northern Hemisphere have been carried out at San Pedro Mártir National Observatory to evaluate their photometric and morphological properties. We complement our analysis with Two-Micron All Sky Survey (2MASS) and Sloan Digital Sky Survey (SDSS) images and look for signatures likely related to interactions/mergers. We report apparent/absolute BVRI magnitudes and colors for the 54 galaxies. The membership of these galaxies is re-evaluated by imposing a reasonable condition of concordant redshifts upon the original selection criteria, rendering a final sample of 34 galaxies in 13 triplets, 12 galaxies in close pairs, and 8 galaxy outliers. The triplets are spiral-dominated systems in different dynamical stages from loosely interacting to almost merged objects. The incidence fraction of features likely associated with interactions is ~56%, similar to those found in northern and southern compact groups. The average fraction of bars is 35% with a mean value of maximum bar ellipticity epsilonmax ? 0.4. Bars are hosted in the late-type triplet spirals, almost twice more than in early-type spirals. The global fraction of rings is 20%, all in the late-type components. The overdensity of triplets with respect to the background and their current dynamical status, as devised from our estimate of their dynamical parameters, namely the harmonic radius RH , velocity dispersion ?, dimensionless crossing time H 0? c , and virial mass MV , appear to be sufficient to favor galaxy transformations similar to those seen in dense groups and clusters. By contrast, the lower fraction of bonafide ellipticals and the relatively higher fraction of late-type spirals make these triplets essentially different from the Hickson Compact Groups and more representative of the field. A modest 1.6 enhancement factor in the optical luminosity of the late-type triplet components relative to an isolated galaxy control sample is also interpreted as consistent with interactions in physically bounded aggregates. Our results lead us to suggest that non-negligible populations of physical triplets might be found in complete and well-observed samples. We provide individual mosaics for the 54 galaxies containing (1) logarithmic-scaled R-band images, (2) R-band sharp/filtered images, (3) (B - I) color index maps, (4) RGB images from the SDSS database, (5) co-added J + H + K images generated from the 2MASS archives that were also sharp/filtered, and (6) epsilon, position angle radial profiles from a surface photometry analysis of (a) the R band and (b) the co-added near-infrared images, all used for the present analysis.

  1. Particle-Image Velocimetry in Microgravity Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, P. B.; Greenberg, P. S.; Urban, D. L.; Wernet, M. P.; Yanis, W.

    1999-01-01

    This paper discusses planned velocity measurements in microgravity laminar jet diffusion flames. These measurements will be conducted using Particle-Image Velocimetry (PIV) in the NASA Glenn 2.2-second drop tower. The observations are of fundamental interest and may ultimately lead to improved efficiency and decreased emissions from practical combustors. The velocity measurements will support the evaluation of analytical and numerical combustion models. There is strong motivation for the proposed microgravity flame configuration. Laminar jet flames are fundamental to combustion and their study has contributed to myriad advances in combustion science, including the development of theoretical, computational and diagnostic combustion tools. Nonbuoyant laminar jet flames are pertinent to the turbulent flames of more practical interest via the laminar flamelet concept. The influence of gravity on these flames is deleterious: it complicates theoretical and numerical modeling, introduces hydrodynamic instabilities, decreases length scales and spatial resolution, and limits the variability of residence time. Whereas many normal-gravity laminar jet diffusion flames have been thoroughly examined (including measurements of velocities, temperatures, compositions, sooting behavior and emissive and absorptive properties), measurements in microgravity gas-jet flames have been less complete and, notably, have included only cursory velocity measurements. It is envisioned that our velocity measurements will fill an important gap in the understanding of nonbuoyant laminar jet flames.

  2. Active Control for Statistically Stationary Turbulent PremixedFlame Simulations

    SciTech Connect

    Bell, J.B.; Day, M.S.; Grcar, J.F.; Lijewski, M.J.

    2005-08-30

    The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.

  3. Flame Chemiluminescence Rate Constants for Quantitative Microgravity Combustion Diagnostics

    NASA Technical Reports Server (NTRS)

    Luque, Jorge; Smith, Gregory P.; Jeffries, Jay B.; Crosley, David R.; Weiland, Karen (Technical Monitor)

    2001-01-01

    Absolute excited state concentrations of OH(A), CH(A), and C2(d) were determined in three low pressure premixed methane-air flames. Two dimensional images of chemiluminescence from these states were recorded by a filtered CCD camera, processed by Abel inversion, and calibrated against Rayleigh scattering, Using a previously validated 1-D flame model with known chemistry and excited state quenching rate constants, rate constants are extracted for the reactions CH + O2 (goes to) OH(A) + CO and C2H + O (goes to) CH(A) + CO at flame temperatures. Variations of flame emission intensities with stoichiometry agree well with model predictions.

  4. Flame-sound interaction in tubes with nonslip walls

    SciTech Connect

    Petchenko, Arkady; Bychkov, Vitaly [Institute of Physics, Umeaa University, SE-90187 Umeaa (Sweden); Akkerman, V'yacheslav [Institute of Physics, Umeaa University, SE-90187 Umeaa (Sweden); Nuclear Safety Institute (IBRAE) of Russian Academy of Sciences, B. Tulskaya 52, 115191 Moscow (Russian Federation); Eriksson, Lars-Erik [Department of Applied Mechanics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)

    2007-06-15

    Flame interaction with sound is studied for a premixed flame propagating to the closed end of a tube with nonslip walls. The flow geometry is similar to that in the classical Searby experiments on flame-acoustic interaction [Combust. Sci. Technol. 81 (1992) 221]. The problem is solved by direct numerical simulations of the combustion equations. The flame-sound interaction strongly influences oscillations of the flame front. Particularly, sound noticeably increases the oscillation amplitude in comparison with that in an open tube with nonreflecting boundary conditions at the ends studied previously. Oscillations become especially strong in the second part of the tube, where flame pulsations are in resonance with the acoustic wave. Parameters of the flame oscillations are investigated for different values of the tube width and length. It is demonstrated that the oscillations are stronger in wider tubes, though the investigated tube width is limited by the computational facilities. In sufficiently wide tubes, violent folding of a flame front is observed because of the flame-acoustic resonance. By increasing the Lewis number, one also increases the oscillation amplitude. (author)

  5. Effects of Lewis Number on Temperatures of Spherical Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    Spherical diffusion flames supported on a porous sphere were studied numerically and experimentally. Experiments were performed in 2.2 s and 5.2 s microgravity facilities. Numerical results were obtained from a Chemkin-based program. The program simulates flow from a porous sphere into a quiescent environment, yields both steady-state and transient results, and accounts for optically thick gas-phase radiation. The low flow velocities and long residence times in these diffusion flames lead to enhanced radiative and diffusive effects. Despite similar adiabatic flame temperatures, the measured and predicted temperatures varied by as much as 700 K. The temperature reduction correlates with flame size but characteristic flow times and, importantly, Lewis number also influence temperature. The numerical results show that the ambient gas Lewis number would have a strong effect on flame temperature if the flames were steady and nonradiating. For example, a 10% decrease in Lewis number would increase the steady-state flame temperature by 200 K. However, for these transient, radiating flames the effect of Lewis number is small. Transient predictions of flame sizes are larger than those observed in microgravity experiments. Close agreement could not be obtained without either increasing the model s thermal and mass diffusion properties by 30% or reducing mass flow rate by 25%.

  6. Flame dynamics in a micro-channeled combustor

    NASA Astrophysics Data System (ADS)

    Hussain, Taaha; Markides, Christos N.; Balachandran, Ramanarayanan

    2015-01-01

    The increasing use of Micro-Electro-Mechanical Systems (MEMS) has generated a significant interest in combustion-based power generation technologies, as a replacement of traditional electrochemical batteries which are plagued by low energy densities, short operational lives and low power-to-size and power-to-weight ratios. Moreover, the versatility of integrated combustion-based systems provides added scope for combined heat and power generation. This paper describes a study into the dynamics of premixed flames in a micro-channeled combustor. The details of the design and the geometry of the combustor are presented in the work by Kariuki and Balachandran [1]. This work showed that there were different modes of operation (periodic, a-periodic and stable), and that in the periodic mode the flame accelerated towards the injection manifold after entering the channels. The current study investigates these flames further. We will show that the flame enters the channel and propagates towards the injection manifold as a planar flame for a short distance, after which the flame shape and propagation is found to be chaotic in the middle section of the channel. Finally, the flame quenches when it reaches the injector slots. The glow plug position in the exhaust side ignites another flame, and the process repeats. It is found that an increase in air flow rate results in a considerable increase in the length (and associated time) over which the planar flame travels once it has entered a micro-channel, and a significant decrease in the time between its conversion into a chaotic flame and its extinction. It is well known from the literature that inside small channels the flame propagation is strongly influenced by the flow conditions and thermal management. An increase of the combustor block temperature at high flow rates has little effect on the flame lengths and times, whereas at low flow rates the time over which the planar flame front can be observed decreases and the time of existence of the chaotic flame increases. The frequency of re-ignition of successive flames decreases at higher flow rates and increases at higher temperatures. The data and results from this study will not only help the development of new micro-power generation devices, but they will also serve as a validation case for combustion models capable of predicting flame behavior in the presence of strong thermal and flow boundary layers, a situation common to many industrial applications.

  7. Scope on Safety: Flame Tests--A Burning Safety Issue

    NSDL National Science Digital Library

    Ken Roy

    2008-11-01

    Flame-test demonstrations are conducted annually in middle and high school science labs across the country. The purpose of the flame test is to help identify an unknown metal or metalloid ion based on a characteristic color the salt produces in a flame. The emission spectra help the observer distinguish certain elements. Although they can be an effective and exciting learning tool for science teachers to use, they can also present safety hazards. This month's column describes some safer alternatives science teachers can use to conduct flame tests.

  8. Flame propagation in heterogeneous mixtures of fuel drops and air

    NASA Technical Reports Server (NTRS)

    Myers, G. D.; Lefebvre, A. H.

    1984-01-01

    Photographic methods are used to measure flame speeds in flowing mixtures of fuel props and air at atmospheric pressure. The fuels employed include a conventional fuel oil plus various blends JP 7 with stocks containing single-ring and mullti-ring aromatics. The results for stoichiometric mixtures show that flame propagation cannot occur in mixtures containing mean drop sizes larger than 300 to 400 microns, depending on the fuel type. For smaller drop sizes, down to around 60 microns, flame speed is inversely proportional to drop size, indicating that evaporation rates are limiting to flame speed. Below around 60 microns, the curves of flame speed versus mean drop size flatten out, thereby demonstrating that for finely atomized sprays flame speeds are much less dependent on evaporation rates, and are governed primarily by mixing and/or chemical reaction rates. The fuels exhibiting the highest flame speeds are those containing multi-ring aromatics. This is attributed to the higher radiative heat flux emanating from their soot-bearing flames which enhances the rate of evaporation of the fuel drops approaching the flame front.

  9. An experimental investigation of flame behavior during cylindrical vessel explosions

    SciTech Connect

    Starke, R.; Roth, P.

    1986-12-01

    The propagation of premixed flames centrally ignited at one of the end flanges of a closed cylindrical vessel and the flame-induced fluid flow have been investigated in the present study. Photographic records show that under specific geometrical conditions the flame exhibits a cone form with a backward directed top, called ''tulip'' -shaped. This appears after the flame has lost a main part of its area by side wall quenching. With a laser-Doppler anemometer the instantaneous flow velocity during the short explosion process was measured together with pressure records.

  10. An experimental investigation of flame behavior during cylindrical vessel explosions

    NASA Astrophysics Data System (ADS)

    Starke, R.; Roth, P.

    1986-12-01

    The propagation of premixed flames centrally ignited at one of the end flanges of a closed cylindrical vessel and the flame-induced flow have been investigated. Photographic records show that under specific geometrical conditions the flame exhibits a cone form with a backward directed top, called tulip-shaped. This appears after the flame has lost a main part of its area by side wall quenching. The instantaneous flow velocity during the short explosion process was measured, together with pressure records, with an LDV. An analogy to the experiments of Markstein (1964), is shown, and the explanations of several authors for the 'tulip' formation are given.

  11. Rich methane premixed laminar flames doped by light unsaturated hydrocarbons - Part I : allene and propyne

    Microsoft Academic Search

    Hadj-Ali Gueniche; Pierre-Alexandre Glaude; Guillaume Dayma; René Fournet; Frédérique Battin-Leclerc

    2007-01-01

    The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C3H4 was

  12. FIELD TEST OF THE FLAME QUALITY INDICATOR

    SciTech Connect

    Andrew M. Rudin; Thomas Butcher; Henry Troost

    2003-02-04

    The flame quality indicator concept was developed at BNL specifically to monitor the brightness of the flame in a small oil burner and to provide a ''call for service'' notification when the brightness has changed from its setpoint, either high or low. In prior development work BNL has explored the response of this system to operational upsets such as excess air changes, fouled atomizer nozzles, poor fuel quality, etc. Insight Technologies, Inc. and Honeywell, Inc. have licensed this technology from the U.S. Department of Energy and have been cooperating to develop product offerings which meet industry needs with an optimal combination of function and price. Honeywell has recently completed the development of the Flame Quality Monitor (FQM or Honeywell QS7100F). This is a small module which connects via a serial cable to the burners primary operating control. Primary advantages of this approach are simplicity, cost, and ease of installation. Call-for-service conditions are output in the form of front panel indicator lights and contact closure which can trigger a range of external communication options. Under this project a field test was conducted of the FQM in cooperation with service organizations in Virginia, Pennsylvania, New Jersey, New York, and Connecticut. At total of 83 field sites were included. At each site the FQM was installed in parallel with another embodiment of this concept--the Insight AFQI. The AFQI incorporates a modem and provides the ability to provide detailed information on the trends in the flame quality over the course of the two year test period. The test site population was comprised of 79.5% boilers, 13.7% warm air furnaces, and 6.8% water heaters. Nearly all were of residential size--with firing rates ranging from 0.6 gallons of oil per hour to 1.25. During the course of the test program the monitoring equipment successfully identified problems including: plugged fuel lines, fouled nozzles, collapsed combustion chambers, and poor fuel pump cut-off. Service organizations can use these early indications to reduce problems and service costs. There were also some ''call-for-service'' indications for which problems were not identified. The test program also showed that monitoring of the flame can provide information on burner run times and this can be used to estimate current oversize factors and to determine actual fuel usage, enabling more efficient fuel delivery procedures.

  13. DAOPHOT - A computer program for crowded-field stellar photometry

    NASA Astrophysics Data System (ADS)

    Stetson, Peter B.

    1987-03-01

    The tasks of the DAOPHOT program, developed to exploit the capability of photometrically linear image detectors to perform stellar photometry in crowded fields, are discussed. Raw CCD images are prepared prior to analysis, and following the obtaining of an initial star list with the FIND program, synthetic aperture photometry is performed on the detected objects with the PHOT routine. A local sky brightness and a magnitude are computed for each star in each of the specified stellar apertures, and for crowded fields, the empirical point-spread function must then be obtained for each data frame. The GROUP routine divides the star list for a given frame into optimum subgroups, and then the NSTAR routine is used to obtain photometry for all the stars in the frame by means of least- squares profile fits. The process is illustrated with images of stars in a crowded field, and shortcomings and possible improvements of the program are considered.

  14. 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.

  15. Photometry Of The Semi-regular Variable Tx Tau

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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 Sky optical transient search system at Las Campanas Observatory developed by a consortium of institutions in Poland. Modern periods are determined, the V-band and I-band light curves are compared, and V-I colors are derived. It is possible that the classification for this variable should be reconsidered.

  16. CCD Photometry of bright stars using objective wire mesh

    SciTech Connect

    Kami?ski, Krzysztof; Zgórz, Marika [Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, S?oneczna 36, 60-286 Pozna? (Poland); Schwarzenberg-Czerny, Aleksander, E-mail: chrisk@amu.edu.pl [Copernicus Astronomical Centre, ul. Bartycka 18, PL 00-716 Warsaw (Poland)

    2014-06-01

    Obtaining accurate photometry of bright stars from the ground remains problematic due to the danger of overexposing the target and/or the lack of suitable nearby comparison stars. The century-old method of using objective wire mesh to produce multiple stellar images seems promising for the precise CCD photometry of such stars. Furthermore, our tests on ? Cep and its comparison star, differing by 5 mag, are very encouraging. Using a CCD camera and a 20 cm telescope with the objective covered by a plastic wire mesh, in poor weather conditions, we obtained differential photometry with a precision of 4.5 mmag per two minute exposure. Our technique is flexible and may be tuned to cover a range as big as 6-8 mag. We discuss the possibility of installing a wire mesh directly in the filter wheel.

  17. Time-resolved blowoff transition measurements for two-dimensional bluff body-stabilized flames in vitiated flow

    Microsoft Academic Search

    Steven G. Tuttle; Swetaprovo Chaudhuri; Stanislav Kostka; Kristin M. Kopp-Vaughan; Trevor R. Jensen; Baki M. Cetegen; Michael W. Renfro

    Flame holding and blowoff characteristics of bluff-body stabilized, turbulent flames were measured in an enclosed rectangular duct with a triangular flame holder in vitiated, premixed flows. Blowoff stability margins were characterized with chemiluminescence measurements performed by high-speed imaging to capture flame dynamics during the approach to flame blow off. As the equivalence ratio was decreased, local extinctions along the flames

  18. The Structure of Galaxies I: Surface Photometry Techniques

    NASA Astrophysics Data System (ADS)

    Schombert, J.; Smith, A. K.

    2012-04-01

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

  19. Photometry of Peculiar Type 1A Supernova SN2005HK

    NASA Astrophysics Data System (ADS)

    Carter, Jessica C.; Leising, Mark

    2010-07-01

    BV RI photometry of the peculiar Type Ia supernova SN2005hk is presented, with emphasis on late-time observations. Results are derived by performing aperture photometry on images taken with the Bok and Mayall telescopes. Instrumental magnitudes are calibrated with published magnitudes of stars in the frames. The light curve presented demonstrates that this particular supernova is classified as "peculiar" due to its deviation from the standard light curve of Type Ia Supernovae. The late light curves appear quite flat, though some questions about our analysis, subtraction of the underlying galaxy in particular, remain.

  20. The Open Cluster NGC 2516. I. Optical Photometry

    Microsoft Academic Search

    Hwankyung Sung; Michael S. Bessell; Bo-Won Lee; Sang-Gak Lee

    2002-01-01

    We present UBVI CCD photometry of the intermediate-age open cluster NGC 2516. From this new photometry we derive the cluster parameters [V0-MV=7.77+\\/-0.11 mag, E(B-V)=0.112+\\/-0.024 mag], age [log(age)=8.2+\\/-0.1], and a photometric abundance ([Fe\\/H]=-0.10+\\/-0.04) from a comparison with theoretical isochrones of the Padua group. We find that the X-ray bright stars [logLX(ergs s-1)>~29.0] are systematically bluer in B-V and U-B. It was

  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. 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.

  3. Similarity solutions in buoyancy-controlled turbulent diffusion flame modeling; Turbulent buoyant diffusion flame modeling

    Microsoft Academic Search

    M. A. Pivovarov; H. Zhang; D. E. Ramakev; P. A. Tatem; F. W. Williams

    1993-01-01

    This paper considers the applicability of different versions of the k-[epsilon] hypothesis of turbulence for flame modeling. Utilizing similarity solutions, the authors find that the k-[epsilon] hypothesis gives a finite radius for a weak axisymmetric plume above the heat source. The radius of this plume is defined as an eigenvalue of the boundary value problem with unknown boundary. Solving this

  4. Experimental study on the flame behaviors of premixed methane/air mixture in horizontal rectangular ducts

    NASA Astrophysics Data System (ADS)

    Chen, Dongliang; Sun, Jinhua; Chen, Sining; Liu, Yi; Chu, Guanquan

    2007-01-01

    In order to explore the flame propagation characteristics and tulip flame formation mechanism of premixed methane/air mixture in horizontal rectangular ducts, the techniques of Schlieren and high-speed video camera are used to study the flame behaviors of the premixed gases in a closed duct and opened one respectively, and the propagation characteristics in both cases and the formation mechanism of the tulip flame are analyzed. The results show that, the propagation flame in a closed duct is prior to form a tulip flame structure than that in an opened duct, and the tulip flame structure formation in a closed duct is related to the flame propagation velocity decrease. The sharp decrease of the flame propagation velocity is one of the reasons to the tulip flame formation, and the decrease of the flame propagation velocity is due to the decrease of the burned product flow velocity mainly.

  5. Premixed laminar flame propagation in a rotating vessel

    NASA Astrophysics Data System (ADS)

    Parra, Teresa; Gorczakowski, Andrzej; Chomiak, Jerzy; Jarosinski, Jozef

    2008-11-01

    Combustion in a swirling flow is devoted to burn lean mixture in spark ignition engines since it provides fuel economy and exhaust emission reduction. Therefore it is important to know the flame behavior under centrifugal forces. The flame in a rotating gas is modified by an aerodynamic mechanism due to action of centrifugal forces instead the laminar burning velocity due to chemical kinetics. The paper deals with important characteristics of eddy combustion mechanism such as: flame shape and propagation as a function of the rotation rate. Therefore pictures captured by a video camera are treated with the image processing toolbox from Matlab in order to establish the main characteristics of the flame kernel of a mixture propane -- air at different rotation rates ranging from 500 to 4000 rpm. It is observed that the flame propagates along the rotation axis and that the extinguishing of the flame is involved with the heat losses as soon the flame reaches the wall of the chamber. In addition, the flame shape is quite similar to the intrusion head of a light fluid penetrating into a stagnated heavy fluid.

  6. Flame retardant properties of triazine phosphonates derivative with cotton fabric

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The flame retardant behavior of a cotton fabric treated with phosphorus-nitrogen containing triazine compound was evaluated. It was found that cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) is an excellent starting material for the preparation of phosphonates flame retardants that interacts wel...

  7. Environmentally-benign Flame Retardant Nanocoating for Foam and Fabric

    E-print Network

    Cain, Amanda Ashley

    2014-12-09

    for the purpose of inhibiting or suppressing the combustion cycle. Inspiration for first applying polymer/clay thin films (i.e., nanobrick walls) as flame retardant (FR) coatings to polyurethane foam via LbL came from the final stage of a proposed flame...

  8. Flame/Wall interactions : laminar study of unburnt HC formation

    E-print Network

    Paris-Sud XI, Université de

    Flame/Wall interactions : laminar study of unburnt HC formation M. Chauvy 1,2 , B. Delhom1 , J (HOQ) on a planar wall and in crevices, are considered. It is well known that they contribute is to use laminar flame simulations (LFS) to understand how the unburnt HC are produced near walls

  9. Coherent acoustic wave amplification\\/damping by wrinkled flames

    Microsoft Academic Search

    T. Lieuwen; Ju Hyeong Cho

    2005-01-01

    The objective of this paper is to determine the conditions under which a monochromatic acoustic wave incident upon a wrinkled flame is amplified or damped. Recent experiments and analysis have demonstrated that the wrinkled characteristics of the flame act as a source of damping of coherent acoustic energy. This coherent energy is fed into spectrally broadened, incoherent acoustic oscillations. It

  10. Simulation of a turbulent flame in a channel

    NASA Technical Reports Server (NTRS)

    Bruneaux, G.; Akselvoll, K.; Poinsot, T.; Ferziger, J. H.

    1994-01-01

    The interaction between turbulent premixed flames and channel walls is studied. Combustion is represented by a simple irreversible reaction with a large activation temperature. Feedback to the flowfield is suppressed by invoking a constant density assumption. The effect of wall distance on local and global flame structure is investigated. Quenching distances and maximum wall heat fluxes computed in laminar cases are compared to DNS results. It is found that quenching distances decrease and maximum heat fluxes increase relative to laminar flame values. It is shown that these effects are due to large coherent structures which push flame elements towards to wall. The effect of wall strain is studied in flame-wall interaction in a stagnation line flow; this is used to explain the DNS results. It is also shown that 'remarkable' flame events are produced by interaction with a horseshoe vortex: burnt gases are pushed towards the wall at high speed and induce quenching and high wall heat fluxes while fresh gases are expelled from the wall region and form finger-like structures. Effects of the wall on flame surface density are investigated, and a simple model for flame-wall interaction is proposed; its predictions compare well with the DNS results.

  11. Limits for hydrogen leaks that can support stable flames

    Microsoft Academic Search

    M. S. Butler; C. W. Moran; P. B. Sunderland; R. L. Axelbaum

    2009-01-01

    Quenching and blowoff limits of hydrogen diffusion flames on small burners were observed. Four burner types, with diameters as small as 8?m, were considered: pinhole burners, curved-wall burners, tube burners, and leaky fittings. In terms of mass flow rate, hydrogen had a lower quenching limit and a higher blowoff limit than either methane or propane. Hydrogen flames at their quenching

  12. Modulated hydrogen-ion flame detector: A concept

    NASA Technical Reports Server (NTRS)

    Dimeff, J.

    1974-01-01

    To improve sensitivity of flame ionization detectors chop flow of sample into flame so resulting ionization will be modulated and therefore readily amplified independently of steady-state background ionization, thermoelectric effects, contact potentials, etc. Detector should discriminate sharply between desired signal and undesired signals.

  13. PROTOTYPE CORRELATION MASK FLAME PHOTOMETRIC DETECTOR FOR MEASURING SULFUR DIOXIDE

    EPA Science Inventory

    A prototype flame photometric detector system (FPD) to measure gaseous sulfur compounds was fabricated using a previously developed correlation mask optical system and a new flame housing. Also, a new burner for the FPD system was optimized to view the excited molecular sulfur em...

  14. Stationary premixed flames in spherical and cylindrical geometries

    NASA Technical Reports Server (NTRS)

    Ronney, P. D.; Whaling, K. N.; Abbud-Madrid, A.; Gatto, J. L.; Pisowiscz, V. L.

    1994-01-01

    Stationary source-free spherical flames ('flame balls') in premixed combustible gases were studied by employing low-gravity (micro-g) environments in a drop tower and an aircraft flying parabolic trajectories to diminish the impact of buoyancy-induced convective flow. Flame balls were found in all mixture families tested when: (1) the Lewis number Le of the deficient reactant was sufficiently low; and (2) the compositions were sufficiently close to the flammability limits. Probably as a consequence of the reduction in buoyant convection, the flammability limits at micro-g were significantly more dilute than those at Earth gravity; for example, 3.35% H2 vs 4.0% H2 in lean H2-air mixtures. By comparison with analytical and computational models, it is inferred that the phenomenon is probably related to diffusive-thermal effects in low-Le mixtures in conjunction with flame-front curvature and radiative heat losses from the combustion products. The chemical reaction mechanism appears to play no qualitative role. In the aircraft experiments, the gravity levels (approximately equal 10(exp -2)g(sub 0)) were found to cause noticeable motion of flame balls due to buoyancy, which in turn influenced the behavior of flame balls. At these g levels, a new type of transient, nearly cylindrical flame structure, termed 'flame strings,' was observed.

  15. MODELING OF PARTICLE FORMATION AND DYNAMICS IN A FLAME INCINERATOR

    EPA Science Inventory

    A model has been developed to predict the formation and growth of metallic particles in a flame incinerator system. Flow fields and temperature profiles in a cylindrical laminar jet flame have been used to determine the position and physical conditions of the species along the fl...

  16. PDF Calculations of Turbulent Nonpremixed Flames with Local Extinction

    E-print Network

    PDF Calculations of Turbulent Nonpremixed Flames with Local Extinction JUN XU and STEPHEN B. POPE. These flames exhibit an increasing amount of local extinction with increasing jet velocity, and are good cases to test the capabilities of turbulent combustion models to account for local extinction in turbulent

  17. Durability and Antimicrobial Properties for Flame Resistant Cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this presentation we will discuss the design, synthesis, and characterization of new epoxy phosphonate monomers that impart flame resistance to cotton regardless of fabric construction. Furthermore, we will discuss formulations, textile treatments, and the extent of flame protection the new comp...

  18. Field Effects of Buoyancy on Lean Premixed Turbulent Flames

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    Buoyancy affects the entire flowfield of steady turbulent flames and this aspect of flame buoyancy coupling is largely unexplored by experiments or by theory. Open flames and flames within large confinements are free to expand and interact with the surrounding environment. In addition to fluid and combustion conditions, their aerodynamic flowfields are determined by the flame brush orientation and geometry, wake of the stabilizer, enclosure size, and of course, the gravitational field. Because the flowfield consists mainly of cold reactants (mostly in the nearfield) and hot products (mostly in the farfield), buoyancy effects are manifested in the farfield region. In upward pointing flames, an obvious effect is a favorable axial pressure gradient that accelerates the products thereby increasing the axial aerodynamic stretch rate. Intrinsic to turbulent flows, changes in mean aerodynamic stretch also couple to the fluctuating pressure field. Consequently, buoyancy can influence the turbulence intensities upstream and downstream of the flame. Flame wrinkling process, and heat release rate are also directly affected. This backward coupling mechanism is the so-called elliptic problem. To resolve the field effects of buoyancy would require the solution of three-dimensional non-linear Navier Stokes equations with full specification of the upstream, wall and downstream boundary conditions.

  19. Experimental and Numerical Study of Ammonium Perchlorate Counterflow Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Smooke, M. D.; Yetter, R. A.; Parr, T. P.; Hanson-Parr, D. M.; Tanoff, M. A.

    1999-01-01

    Many solid rocket propellants are based on a composite mixture of ammonium perchlorate (AP) oxidizer and polymeric binder fuels. In these propellants, complex three-dimensional diffusion flame structures between the AP and binder decomposition products, dependent upon the length scales of the heterogeneous mixture, drive the combustion via heat transfer back to the surface. Changing the AP crystal size changes the burn rate of such propellants. Large AP crystals are governed by the cooler AP self-deflagration flame and burn slowly, while small AP crystals are governed more by the hot diffusion flame with the binder and burn faster. This allows control of composite propellant ballistic properties via particle size variation. Previous measurements on these diffusion flames in the planar two-dimensional sandwich configuration yielded insight into controlling flame structure, but there are several drawbacks that make comparison with modeling difficult. First, the flames are two-dimensional and this makes modeling much more complex computationally than with one-dimensional problems, such as RDX self- and laser-supported deflagration. In addition, little is known about the nature, concentration, and evolution rates of the gaseous chemical species produced by the various binders as they decompose. This makes comparison with models quite difficult. Alternatively, counterflow flames provide an excellent geometric configuration within which AP/binder diffusion flames can be studied both experimentally and computationally.

  20. 40 CFR 1065.260 - Flame-ionization detector.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...not allow the FID fuel and burner air to mix before entering the FID analyzer to ensure that the FID analyzer operates with a diffusion flame and not a premixed flame. (e) Methane. FID analyzers measure total hydrocarbons (THC). To determine...

  1. 40 CFR 1065.260 - Flame-ionization detector.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...not allow the FID fuel and burner air to mix before entering the FID analyzer to ensure that the FID analyzer operates with a diffusion flame and not a premixed flame. (e) NMHC. For demonstrating compliance with NMHC standards, you may either...

  2. Open Packet Monitoring on FLAME: Safety, Performance and Applications

    E-print Network

    Plotkin, Joshua B.

    Open Packet Monitoring on FLAME: Safety, Performance and Applications K. G. Anagnostakis, M. B, Philadelphia PA 19104, USA fanagnost,mbgreen,sotiris,miltchevg@dsl.cis.upenn.edu Abstract. Packet monitoring of applications built on top of FLAME. We use measurement data and analysis to predict the workload at which our

  3. IN VITRO DERMAL ABSORPTION OF FLAME RETARDANT CHEMICALS

    EPA Science Inventory

    IN VITRO DERMAL ABSORPTION OF FLAME RETARDANT CHEMICALS. M F Hughes1, B C Edwards1, C T Mitchell1, and B Bhooshan2. 1US EPA, ORD, NHEERL, RTP, NC; 2US CPSC, LSC, Rockville, MD. Two flame retardant chemicals that are candidates for treating furniture fabrics were evaluated for ...

  4. The combined dynamics of swirler and turbulent premixed swirling flames

    Microsoft Academic Search

    P. Palies; D. Durox; T. Schuller; S. Candel

    2010-01-01

    The dynamics of premixed confined swirling flames is investigated by examining their response to incident velocity perturbations. A generalized transfer function designated as the flame describing function (FDF) is determined by sweeping a frequency range extending from 0 to 400 Hz and by changing the root mean square fluctuation level between 0% and 72% of the bulk velocity. The unsteady

  5. The Effect of Buoyancy on Flickering in Diffusion Flames

    Microsoft Academic Search

    D. DUROX; T. YUAN; E. VILLERMAUX

    1997-01-01

    Flame flickering of jet diffusion flames reflects the instability of the hot gases ascending column, This phenomenon, which is related to buoyancy, has been characterized in terms of pressure and gravitational force by experiments conducted on the ground and on board of an aircraft. The measurements show that the relationship between the frequency F and the gravity g is very

  6. Nonlinear mode triggering in a multiple flame combustor

    Microsoft Academic Search

    F. Boudy; D. Durox; T. Schuller; S. Candel

    2011-01-01

    A nonlinear analysis of combustion instability is carried out by making use of the Flame Describing Function (FDF) framework. Predictions are compared with data obtained from experiments on a multipoint injection combustor. The burner comprises a premixer manifold of variable length, an injection system and a flame tube. This device features several types of self-sustained oscillation and its dynamics is

  7. Experimental and theoretical study of a premixed vibrating flame

    Microsoft Academic Search

    F. Baillot; D. Durox; R. PrudHomme

    1992-01-01

    This paper reports on an experimental study of vibrating flames above a cylindrical burner which has been conducted in order to examine some of the fundamental characteristics of the flow perturbations-combustion interaction. Here the perturbation chosen is a space-time sinusoidal flow velocity. The vibrational nature of the flow has been studied with the without the flame, using a LDV setup

  8. The combined dynamics of swirler and turbulent premixed swirling flames

    Microsoft Academic Search

    P. Palies; D. Durox; T. Schuller; S. Candel

    2010-01-01

    The dynamics of premixed confined swirling flames is investigated by examining their response to incident velocity perturbations. A generalized transfer function designated as the flame describing function (FDF) is determined by sweeping a frequency range extending from 0 to 400Hz and by changing the root mean square fluctuation level between 0% and 72% of the bulk velocity. The unsteady heat

  9. 23. VIEW DOWN INTO LAUNCHER AND FLAME BUCKET FROM STATION ...

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

    23. VIEW DOWN INTO LAUNCHER AND FLAME BUCKET FROM STATION 48 IN SLC-3W MST. NOTE REMOVABLE METAL PLANKS BELOW LAUNCHER AND ROPE NET OVER FLAME BUCKET. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  10. Interaction of Heat Release and Vortex Breakdown in Swirling Flames

    Microsoft Academic Search

    Marco Konle; Thomas Sattelmayer

    The interaction of heat release by chemical reaction and the flow dominates flame transition in swirling flows caused by Combustion Induced Vortex Breakdown (CIVB). The simultaneous application of 1 kHz high speed Particle Imaging Velocimetry (PIV) for the analysis of the flow field and OH Planar Laser Induced Fluorescence (PLIF) for the detection of the flame front is particularly useful

  11. Large eddy simulation of vortex breakdown/flame interaction

    NASA Astrophysics Data System (ADS)

    Duwig, Christophe; Fuchs, Laszlo

    2007-07-01

    The dynamics of a swirl-stabilized premixed flame is studied using large eddy simulation (LES). A filtered flamelet model is used to account for the subgrid combustion. The model provides a consistent and robust reaction-diffusion expression for simulating the propagation of turbulent premixed flames correctly. The numerical results were found to be relatively insensitive to small changes in the inflow boundary conditions and to the numerical mesh employed. Furthermore, the results were found to agree well with the available experimental data both for velocity and scalar fields. In addition, unsteady flame features [i.e., precessing vortex core (PVC)] were identified and compared with experimental data. The agreement between LES results and experimental data, in terms of flame dynamics, was also good. Increasing swirl did not affect the flame strongly but a decrease of swirl number was shown to change the flame shape and suppress the PVC. The PVC and flame dynamics were studied using proper orthogonal decomposition (POD) allowing us to identify and isolate the PVC from smaller-scale turbulence. The POD results indicate that the PVC corresponds to a helical wave consisting of two counter-rotating helices. A dynamical reduced model was also derived do describe the flame response to the PVC.

  12. 62. VIEW OF FLAME BUCKET BELOW LAUNCHER ON SOUTH END ...

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

    62. VIEW OF FLAME BUCKET BELOW LAUNCHER ON SOUTH END OF LAUNCH PAD. FIRE SUPPRESSION EQUIPMENT RIGHT OF FLAME BUCKET. SOUTH FACE OF MST IS IN BACKGROUND. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  13. Flow Field of a Flame in a Channel

    Microsoft Academic Search

    Mahinder S. Uberoi

    1959-01-01

    A stationary flame is stabilized in a two-dimensional channel in such a way that it closely corresponds to the case of a flame propagating in a channel. The entire flow field of unburned and burned gases is mapped by taking stroboscopic photographs of small particles suspended in the combustible gases. The asymptotic flow field of the burned gases is analyzed

  14. Control of flame configuration and combustion performance in industrial furnaces

    Microsoft Academic Search

    C. Presser; Y. Goldman; J. B. Greenberg; Y. M. Timnat

    1980-01-01

    The influence of geometric and kinematic factors on combustion performance is studied in a liquid fuelled furnace, experimentally and theoretically. By varying the spray axial location, it is possible to produce a more uniform air\\/fuel distribution with an apparent shortening and widening of the flame shape. Increasing the swirl number enhances turbulent mixing, creating a shorter flame in the combustion

  15. 5. Credit GE. Photographic copy of photograph, completed flame pit ...

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

    5. Credit GE. Photographic copy of photograph, completed flame pit in Test Stand 'A' with steel plate flame deflector over refractory brick. (JPL negative no. 383-1033, 17 January 1946) - Jet Propulsion Laboratory Edwards Facility, Test Stand A, Edwards Air Force Base, Boron, Kern County, CA

  16. Novel phosphonates triazine derivative as economic flame retardant for cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphorous-containing flame retardants are widely used in standard and engineering plastics, polyurethane foams, thermosets, coatings, and textiles. Organophosphorous flame retardants have been known to be more effective when used in conjunction with nitrogen-containing systems. Their mixture produ...

  17. Camping Burner-Based Flame Emission Spectrometer for Classroom Demonstrations

    ERIC Educational Resources Information Center

    Ne´el, Bastien; Crespo, Gasto´n A.; Perret, Didier; Cherubini, Thomas; Bakker, Eric

    2014-01-01

    A flame emission spectrometer was built in-house for the purpose of introducing this analytical technique to students at the high school level. The aqueous sample is sprayed through a homemade nebulizer into the air inlet of a consumer-grade propane camping burner. The resulting flame is analyzed by a commercial array spectrometer for the visible…

  18. Field Effects of Buoyancy on a Premixed Turbulent Flame Studied by Particle Image Velocimetry

    NASA Technical Reports Server (NTRS)

    Cheng, Robert K.

    2003-01-01

    Typical laboratory flames for the scientific investigation of flame/turbulence interactions are prone to buoyancy effects. Buoyancy acts on these open flame systems and provides upstream feedbacks that control the global flame properties as well as local turbulence/flame interactions. Consequently the flame structures, stabilization limits, and turbulent reaction rates are directly or indirectly coupled with buoyancy. The objective of this study is to characterize the differences between premixed turbulent flames pointing upwards (1g), pointing downwards (-1g), and in microgravity (mg). The configuration is an inverted conical flame stabilized by a small cone-shaped bluff body that we call CLEAN Flames (Cone-Stabilized Lean Flames). We use two laser diagnostics to capture the velocity and scalar fields. Particle image velocimetry (PIV) measures the mean and root mean square velocities and planar imaging by the flame fronts method outlines the flame wrinkle topology. The results were obtained under typical conditions of small domestic heating systems such as water heaters, ovens, and furnaces. Significant differences between the 1g and -1g flames point to the need for including buoyancy contributions in theoretical and numerical calculations. In Earth gravity, there is a complex coupling of buoyancy with the turbulent flow and heat release in the flame. An investigation of buoyancy-free flames in microgravity will provide the key to discern gravity contributions. Data obtained in microgravity flames will provide the benchmark for interpreting and analyzing 1g and -1g flame results.

  19. Nanotechnology finding its way into flame retardancy

    NASA Astrophysics Data System (ADS)

    Schartel, Bernhard

    2014-05-01

    Nanotechnology is one of the key technologies of the 21st century. The exploitation of "new" effects that arise from materials structured on the nano-scale has also been proposed successfully for flame retardancy of polymers since the end of the 90s. Of all of the approaches these include, at this time the use of nanocomposites offers the best potential for industrial application, also some other ideas are sketched, such as using electrospun nanofibers mats or layer-by-layer deposits as protection coatings, as well as sub-micrometer multilayer coatings as effective IR-mirrors. The general phenomena, inducing a flow limit in the pyrolysing melt and changing the fire residue, are identified in nanocomposites. Key experiments are performed such as quasi online investigation of the protection layer formation to understand what is going on in detail. The flame retardancy mechanisms are discussed and their impact on fire behaviour quantified. With the latter, the presentation pushes forward the state of the art. For instance, the heat shielding is experimentally quantified for a layered silicate epoxy resin nanocomposite proving that it is the only import mechanism controlling the reduction in peak heat release rate in the investigated system for different irradiations. The flame retardancy performance is assessed comprehensively illuminating not only the strengths but also the weak points of the concepts. Guidelines for materials development are deduced and discussed. Apart from inorganic fillers (layered silicate, boehmite, etc.) not only carbon nanoobjects such as multiwall carbon nanotubes, multilayer graphene and graphene are investigated, but also nanoparticles that are more reactive and harbor the potential for more beneficial interactions with the polymer matrix.

  20. Nanotechnology finding its way into flame retardancy

    SciTech Connect

    Schartel, Bernhard, E-mail: bernhard.schartel@bam.de [BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin (Germany)

    2014-05-15

    Nanotechnology is one of the key technologies of the 21{sup st} century. The exploitation of 'new' effects that arise from materials structured on the nano-scale has also been proposed successfully for flame retardancy of polymers since the end of the 90s. Of all of the approaches these include, at this time the use of nanocomposites offers the best potential for industrial application, also some other ideas are sketched, such as using electrospun nanofibers mats or layer-by-layer deposits as protection coatings, as well as sub-micrometer multilayer coatings as effective IR-mirrors. The general phenomena, inducing a flow limit in the pyrolysing melt and changing the fire residue, are identified in nanocomposites. Key experiments are performed such as quasi online investigation of the protection layer formation to understand what is going on in detail. The flame retardancy mechanisms are discussed and their impact on fire behaviour quantified. With the latter, the presentation pushes forward the state of the art. For instance, the heat shielding is experimentally quantified for a layered silicate epoxy resin nanocomposite proving that it is the only import mechanism controlling the reduction in peak heat release rate in the investigated system for different irradiations. The flame retardancy performance is assessed comprehensively illuminating not only the strengths but also the weak points of the concepts. Guidelines for materials development are deduced and discussed. Apart from inorganic fillers (layered silicate, boehmite, etc.) not only carbon nanoobjects such as multiwall carbon nanotubes, multilayer graphene and graphene are investigated, but also nanoparticles that are more reactive and harbor the potential for more beneficial interactions with the polymer matrix.

  1. Transition from cool flame to thermal flame in compression ignition process

    SciTech Connect

    Yamada, Hiroyuki; Suzaki, Kotaro; Goto, Yuichi [National Traffic Safety and Environment Laboratory, 7-42-27 Jindaiji-Higashimachi, Chofu, Tokyo 182-0012 (Japan); Tezaki, Atsumu [Department of Mechanical and Intellectual Systems Engineering, University of Toyama, Gofuku 3190, Toyama-shi, Toyama 930-8555 (Japan)

    2008-07-15

    The mechanism that initiates thermal flames in compression ignition has been studied. Experimentally, a homogeneous charge compression ignition (HCCI) engine was used with DME, n-heptane, and n-decane. Arrhenius plots of the heat release rate in the HCCI experiments showed that rates of heat release with DME, n-heptane, and n-decane exhibited a certain activation energy that is identical to that of the H{sub 2}O{sub 2} decomposition reaction. The same feature was observed in diesel engine operation using ordinary diesel fuel with advanced ignition timing to make ignition occur after the end of fuel injection. These experimental results were reproduced in nondimensional simulations using kinetic mechanisms for DME, n-heptane, and n-decane, the last being developed by extending the n-heptane mechanism. Methanol addition, which suppresses low-temperature oxidation (LTO) and delays the ignition timing, had no effect on the activation energy obtained from the Arrhenius plot of heat release rate. Nevertheless, methanol addition lowered the heat release rates during the prethermal flame process. This is because H{sub 2}O{sub 2} formation during cool flame was reduced by adding methanol. The mechanism during the transition process from cool flame to thermal flame can be explained quantitatively using thermal explosion theory, in which the rate-determining reaction is H{sub 2}O{sub 2} decomposition, assuming that heat release in this period is caused by partial oxidation of DME and HCHO initiated with the reaction with OH produced though H{sub 2}O{sub 2} decomposition. (author)

  2. Investigations of swirl flames in a gas turbine model combustor

    SciTech Connect

    Weigand, P.; Meier, W.; Duan, X.R.; Stricker, W.; Aigner, M. [Institut fuer Verbrennungstechnik, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), Pfaffenwaldring 38, D-70569 Stuttgart (Germany)

    2006-01-01

    A gas turbine model combustor for swirling CH{sub 4}/air diffusion flames at atmospheric pressure with good optical access for detailed laser measurements is discussed. Three flames with thermal powers between 7.6 and 34.9 kW and overall equivalence ratios between 0.55 and 0.75 were investigated. These behave differently with respect to combustion instabilities: Flame A burned stably, flame B exhibited pronounced thermoacoustic oscillations, and flame C, operated near the lean extinction limit, was subject to sudden liftoff with partial extinction and reanchoring. One aim of the studies was a detailed experimental characterization of flame behavior to better understand the underlying physical and chemical processes leading to instabilities. The second goal of the work was the establishment of a comprehensive database that can be used for validation and improvement of numerical combustion models. The flow field was measured by laser Doppler velocimetry, the flame structures were visualized by planar laser-induced fluorescence (PLIF) of OH and CH radicals, and the major species concentrations, temperature, and mixture fraction were determined by laser Raman scattering. The flow fields of the three flames were quite similar, with high velocities in the region of the injected gases, a pronounced inner recirculation zone, and an outer recirculation zone with low velocities. The flames were not attached to the fuel nozzle and thus were partially premixed before ignition. The near field of the flames was characterized by fast mixing and considerable finite-rate chemistry effects. CH PLIF images revealed that the reaction zones were thin (=<0.5 mm) and strongly corrugated and that the flame zones were short (h=<50 mm). Despite the similar flow fields of the three flames, the oscillating flame B was flatter and opened more widely than the others. In the current article, the flow field, structures, and mean and rms values of the temperature, mixture fraction, and species concentrations are discussed. Turbulence intensities, mixing, heat release, and reaction progress are addressed. In a second article, the turbulence-chemistry interactions in the three flames are treated.

  3. Pulsating Instability of Turbulent Thermonuclear Flames in Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Poludnenko, Alexei Y.

    2014-01-01

    Presently, one of the main explosion scenarios of type Ia supernovae (SNIa), aimed at explaining both "normal" and subluminous events, is the thermonuclear incineration of a white-dwarf in a single-degenerate system. The underlying engine of such explosions is the turbulent thermonuclear flame. Modern, large-scale, multidimensional simulations of SNIa cannot resolve the internal flame structure, and instead must include a subgrid-scale prescription for the turbulent-flame properties. As a result, development of robust, parameter-free, large-scale models of SNIa crucially relies on the detailed understanding of the turbulent flame properties during each stage of the flame evolution. Due to the complexity of the flame dynamics, such understanding must be validated by the first-principles direct numerical simulations (DNS). In our previous work, we showed that sufficiently fast turbulent flames are inherently susceptible to the development of detonations, which may provide the mechanism for the deflagration-to-detonation transition (DDT) in the delayed-detonation model of SNIa. Here we extend this study by performing detailed analysis of the turbulent flame properties at turbulent intensities below the critical threshold for DDT. We carried out a suite of 3D DNS of turbulent flames for a broad range of turbulent intensities and system sizes using a simplified, single-step, Arrhenius-type reaction kinetics. Our results show that at the later stages of the explosion, as the turbulence intensity increases prior to the possible onset of DDT, the flame front will become violently unstable. We find that the burning rate exhibits periodic pulsations with the energy release rate varying by almost an order of magnitude. Furthermore, such flame pulsations can produce pressure waves and shocks as the flame speed approaches the critical Chapman-Jouguet deflagration speed. Finally, in contrast with the current theoretical understanding, such fast turbulent flames can propagate at speeds, which are much higher than the characteristic speeds of turbulent fluctuations. These effects can qualitatively change the dynamics of the explosion and, therefore, must be properly accounted for in the turbulent-flame subgrid-scale models.

  4. 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

  5. Blue band photometry of Cygnus X-1. [and Fourier analysis

    NASA Technical Reports Server (NTRS)

    Walker, E. N.

    1976-01-01

    Results of blue band photometry of HDE 226868 in the years 1972-3-4 and provisional results for 1975 are presented. A mean light curve is obtained from the first three years observations which is based on 192 nights observations. Intercomparison of the results from the different years shows that the light curve is not constant.

  6. Far-ultraviolet stellar photometry: Fields in Sagittarius and Scorpius

    Microsoft Academic Search

    Edward G. Schmidt; George R. Carruthers

    1995-01-01

    Far-ultraviolet photometry for 741 objects in a field in Sagittarius centered near M8 and 541 objects in a field centered near sigma Scorpii is presented. These data were extracted from electographic images obtained with two cameras during a shuttle flight in 1991 April\\/May. The cameras provided band passes with lambdaeff = 1375 A and lambdaeff = 1781 A. Synthetic colors

  7. BVR Photometry of Northern Galactic Plane Luminous Stars

    Microsoft Academic Search

    B. Cameron Reed; Patrick M. Carmody; David H. Landy

    1998-01-01

    CCD-based BVR photometry of 90 stars listed in Volumes II, III, and IV of the Case-Hamburg Catalog of Luminous Stars in the Northern Milky Way is reported. This research was performed at the Lowell Observatory 31 inch telescope, which, under an agreement with Northern Arizona University and the NURO Consortium, is operated 60% of the time as the National Undergraduate

  8. Photometry of Delta Serpentis: results of three campaigns

    NASA Astrophysics Data System (ADS)

    Hobart, M. A.; De La Cruz, C.; Rolland, A.; Olivares, I.; Costa, V.; Rodríguez, E.; López de Coca, P.; García-Pelayo, J.M.; Parrao, L.; Peña, J. H.

    2002-02-01

    We present preliminary results derived from the data obtained during the three observing campaigns in 1984, 1996 (coordinated multisite campaigns in Mexico and Spain), and 1999 of the delta Sct type star delta Ser. In all cases, we have carried out simultaneous uvbybeta photometry. Data analysis in the v band, using the Fourier Transform method, shows five significant frequencies.

  9. Cousins BVRI photometry of high-proper-motion stars

    Microsoft Academic Search

    P. C. Dawson; Douglas Forbes

    1992-01-01

    Broadband BVRI photometry on the Cousins system is presented for 127 stars with annual proper motions greater than 1\\/2 arcsec. The sample includes three spectroscopically confirmed degenerate stars, and a considerable number of cool subdwarfs, several of which are discussed. Two stars with peculiar colors are identified, and the significance of certain of the Luyten color classes is briefly considered.

  10. New hybrid halogen-free flame retardants

    NASA Astrophysics Data System (ADS)

    Kijowska, Dorota; Jankowski, Piotr

    2014-05-01

    The main objective of this work were researches concerning the methods of the in-situ modification of silicate layer-tubular mineral (SL-TM) halloysite, using the salts of melamine, i.e. melamine cyanurate. The modified mineral was used as flame retardant to thermoplastic polymers. In the case of the application of halloysite modified by melamine cyanurate to polyamide 6 (PA6) the highest parameters of vertical and horizontal flammability were achieved. The mechanical properties of filled polyamide 6 have been improved.

  11. CARS system for turbulent flame measurements

    NASA Technical Reports Server (NTRS)

    Antcliff, R. R.; Jarrett, O., Jr.; Rogers, R. C.

    1984-01-01

    Simultaneous nitrogen number density and rotational-vibrational temperatures were measured in a turbulent diffusion flame with a Coherent Anti-Stokes Raman Scattering (CARS) instrument. The fuel jet was diluted with nitrogen (20 percent by volume) to allow temperature measurements across the entire jet mixing region. These measurements were compared with fluid dynamics computations. The CARS system incorporated a neodymium YAG laser, an intensified silicon photodiode array detector, and unique dynamic range enhancement methods. Theoretical calculations were based on a parabolic Navier-Stokes computer code. The comparison of these techniques will aid their development in the study of complex flowfields.

  12. Flame soot stably deposited on silicone coatings possess superhydrophobic surface

    NASA Astrophysics Data System (ADS)

    Shen, Lie; Wang, Wen; Ding, Hongliang; Guo, Qipeng

    2013-11-01

    A flame soot deposited silicone coating was successfully prepared by butane flame along with a deposition process of flame soot. Field emission scanning electron microscopy equipped with an energy-dispersive X-ray analyzer and X-ray photoelectron spectroscopy were used to analyze the chemical compositions and structure of flame soot, showing that the surface is mainly composed of carbon nanoparticles being closely packed and forming tree branch-like network with micro- and nanoscale roughness. Meanwhile, the flame soot can stably deposit on the silicone coatings during the water-flow impact test. When the deposition time is 20 s, the silicone coating possesses a water contact angle of 168 ± 2° combining with a sliding angle less than 1°, and a transmittance reduced less than 28% for wavelengths above 500 nm compared to glass substrate. The superhydrophobicity has a little increase with the extension of deposition time, but at the expense of transmittance.

  13. Behaviour of a premixed flame subjected to acoustic oscillations.

    PubMed

    Qureshi, Shafiq R; Khan, Waqar A; Prosser, Robert

    2013-01-01

    In this paper, a one dimensional premixed laminar methane flame is subjected to acoustic oscillations and studied. The purpose of this analysis is to investigate the effects of acoustic perturbations on the reaction rates of different species, with a view to their respective contribution to thermoacoustic instabilities. Acoustically transparent non reflecting boundary conditions are employed. The flame response has been studied with acoustic waves of different frequencies and amplitudes. The integral values of the reaction rates, the burning velocities and the heat release of the acoustically perturbed flame are compared with the unperturbed case. We found that the flame's sensitivity to acoustic perturbations is greatest when the wavelength is comparable to the flame thickness. Even in this case, the perturbations are stable with time. We conclude that acoustic fields acting on the chemistry do not contribute significantly to the emergence of large amplitude pressure oscillations. PMID:24376501

  14. Behaviour of a Premixed Flame Subjected to Acoustic Oscillations

    PubMed Central

    Qureshi, Shafiq R.; Khan, Waqar A.; Prosser, Robert

    2013-01-01

    In this paper, a one dimensional premixed laminar methane flame is subjected to acoustic oscillations and studied. The purpose of this analysis is to investigate the effects of acoustic perturbations on the reaction rates of different species, with a view to their respective contribution to thermoacoustic instabilities. Acoustically transparent non reflecting boundary conditions are employed. The flame response has been studied with acoustic waves of different frequencies and amplitudes. The integral values of the reaction rates, the burning velocities and the heat release of the acoustically perturbed flame are compared with the unperturbed case. We found that the flame's sensitivity to acoustic perturbations is greatest when the wavelength is comparable to the flame thickness. Even in this case, the perturbations are stable with time. We conclude that acoustic fields acting on the chemistry do not contribute significantly to the emergence of large amplitude pressure oscillations. PMID:24376501

  15. Premixing quality and flame stability: A theoretical and experimental study

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, K.; Heywood, J. B.; Tabaczynski, R. J.

    1979-01-01

    Models for predicting flame ignition and blowout in a combustor primary zone are presented. A correlation for the blowoff velocity of premixed turbulent flames is developed using the basic quantities of turbulent flow, and the laminar flame speed. A statistical model employing a Monte Carlo calculation procedure is developed to account for nonuniformities in a combustor primary zone. An overall kinetic rate equation is used to describe the fuel oxidation process. The model is used to predict the lean ignition and blow out limits of premixed turbulent flames; the effects of mixture nonuniformity on the lean ignition limit are explored using an assumed distribution of fuel-air ratios. Data on the effects of variations in inlet temperature, reference velocity and mixture uniformity on the lean ignition and blowout limits of gaseous propane-air flames are presented.

  16. An experimental investigation of an acoustically excited laminar premixed flame

    SciTech Connect

    Kartheekeyan, S.; Chakravarthy, S.R. [Department of Aerospace Engineering, Indian Institute of Technology - Madras, Chennai 600036 (India)

    2006-08-15

    A two-dimensional laminar premixed flame is stabilized over a burner in a confined duct and is subjected to external acoustic forcing from the downstream end. The equivalence ratio of the flame is 0.7. The flame is stabilized in the central slot of a three-slotted burner. The strength of the shear layer of the cold reactive mixture through the central slot is controlled by the flow rate of cold nitrogen gas through the side slots. The frequency range of acoustic excitation is 400-1200 Hz, and the amplitude levels are such that the acoustic velocity is less than the mean flow velocity of the reactants. Time-averaged chemiluminescence images of the perturbed flame front display time-mean changes as compared to the unperturbed flame shape at certain excitation frequencies. Prominent changes to the flame front are in the form of stretching or shrinkage, asymmetric development of its shape, increased/preferential lift-off of one or both of the stabilization points of the flame, and nearly random three-dimensional fluctuations over large time scales under some conditions. The oscillations of the shear layer and the response of the confined jet of the hot products to the acoustic forcing, such as asymmetric flow development and jet spreading, are found to be responsible for the observed mean changes in the flame shape. A distinct low-frequency component ({approx}60-90 Hz) relative to the excitation frequency is observed in the fluctuations of the chemiluminescent intensity in the flame under most conditions. It is observed that fluctuations in the flame area predominantly contribute to the origin of the low-frequency component. This is primarily due to the rollup of vortices and the generation of enthalpy waves at the burner lip. Both of these processes are excited at the externally imposed acoustic time scale, but convect/propagate downstream at the flow time scale, which is much larger. (author)

  17. Effects of pressure gradients on turbulent premixed flames

    NASA Technical Reports Server (NTRS)

    Veynante, D.; Poinsot, T.

    1995-01-01

    The influence of a constant acceleration on a turbulent premixed flame is studied by direct numerical simulation. This acceleration induces a mean pressure gradient across the flame brush, leading to a modification of the turbulent flame structure due to differential buoyancy mechanisms between heavy cold fresh and light hot burnt gases. Such a pressure gradient may be encountered in practical applications in ducted flames. A favorable pressure gradient, i.e. the pressure decreases from unburnt to burnt gases, is found to decrease the flame wrinkling, the flame brush thickness, and the turbulent flame speed. A favorable pressure gradient also promotes counter-gradient turbulent transport. On the other hand, adverse pressure gradients tend to increase the flame brush thickness and turbulent flame speed, and promote classical gradient turbulent transport. The balance equation for the turbulent flux of the Favre averaged progress variable is also analyzed. The first results show that the fluctuating pressure term, cannot be neglected as generally assumed in models. Simple models assuming that a high mean pressure gradient may only be balanced by the cross-dissipation term seem too approximate. This analysis has to be continued to compare simulation data and closure schemes proposed for the transport equation. The analysis developed by Veynante et al.(1995) has been extended to imposed acceleration and mean pressure gradients. A simple model for the turbulent flux is proposed and validated from simulation data. Then, a modified criterion is derived to delineate between counter-gradient and gradient turbulent diffusion. In fact, counter-gradient diffusion may occur in most practical applications, especially for ducted flames.

  18. Pulsating instability and self-acceleration of fast turbulent flames

    NASA Astrophysics Data System (ADS)

    Poludnenko, Alexei Y.

    2015-01-01

    A series of three-dimensional numerical simulations is used to study the intrinsic stability of high-speed turbulent flames. Calculations model the interaction of a fully resolved premixed flame with a highly subsonic, statistically steady, homogeneous, isotropic turbulence. The computational domain is unconfined to prevent the onset of thermoacoustic instabilities. We consider a wide range of turbulent intensities and system sizes, corresponding to the Damköhler numbers Da = 0.1 - 6.0. These calculations show that turbulent flames in the regimes considered are intrinsically unstable. In particular, we find three effects. (1) Turbulent flame speed, ST, develops pulsations with the observed peak-to-peak amplitude ST max / ST min > 10 and a characteristic time scale close to a large-scale eddy turnover time. Such variability is caused by the interplay between turbulence, which continuously creates the flame surface, and highly intermittent flame collisions, which consume the flame surface. (2) Unstable burning results in the periodic pressure build-up and the formation of pressure waves or shocks, when ST approaches or exceeds the speed of a Chapman-Jouguet deflagration. (3) Coupling of pressure gradients formed during pulsations with density gradients across the flame leads to the anisotropic amplification of turbulence inside the flame volume and flame acceleration. Such process, which is driven by the baroclinic term in the vorticity transport equation, is a reacting-flow analog of the mechanism underlying the Richtmyer-Meshkov instability. With the increase in turbulent intensity, the limit-cycle instability discussed here transitions to the regime described in our previous work, in which the growth of ST becomes unbounded and produces a detonation.

  19. Flame Velocities over a Wide Composition Range for Pentane-air, Ethylene-air, and Propyne-air Flames

    NASA Technical Reports Server (NTRS)

    Simon, Dorothy M; Wong, Edgar, L

    1951-01-01

    Fundamental flame velocities are reported for pentane air, ethylene-air, and propylene-air mixtures for the concentration range 60 to 130 percent of stoichiometric. A form of the Tanford and Pease equation, which includes a small constant velocity term independent of diffusion, will predict the observed changes in flame velocity.

  20. Development of fiber reactive, non-halogenated flame retardant on cotton fabrics and the enhanced flame retardancy by covalent bonding

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The US law requires flame resistant properties on apparel or house hold items to prevent or minimize the fire damage. The objective of this research was to develop a non-halogenated flame retardant for application onto cotton fabrics. These treated fabrics can then be used in clothes or beddings to ...

  1. Effect of Blending on High-Pressure Laminar Flame Speed Measurements, Markstein Lengths, and Flame Stability of Hydrocarbons

    E-print Network

    Lowry, William Baugh

    2012-02-14

    uncertainty analysis has been performed, showing a range of 0.3 cm/s to 3.5 cm/s depending on equivalence ratio and initial pressure. v ACKNOWLEDGMENTS I would first like to acknowledge my advisor, Dr... ......................................................................................................................... 5 2.1 Premixed Laminar Flame Theory ............................................................................... 5 2.2 Measurement Techniques ......................................................................................... 11 2.3 Flame...

  2. Effect of Blending on High-Pressure Laminar Flame Speed Measurements, Markstein Lengths, and Flame Stability of Hydrocarbons 

    E-print Network

    Lowry, William Baugh

    2012-02-14

    ......................................................................................................... 47 Figure 34 Results for methane/DME laminar flame speeds. (a) Flame speed for 1-atm CH3OCH3, 60/40 CH4/CH3OCH3, 80/20 CH4/CH3OCH3 and CH4, (b) Flame speed for 5-atm CH3OCH3, 60/40 CH4/CH3OCH3, 80/20 CH4/CH3OCH3 and CH4, (c) Flame speed for 10... .......................................................................... 25 Figure 16 Flame images for 1 (left), 5 (middle), and 10-atm (right) stoichiometric 60/40 CH4/C2H6 at initial pressures of 1, 5, and 10 atm ............................................................ 25 Figure 17 Experimental pressure trace...

  3. Flame front tracking in turbulent lean premixed flames using stereo PIV and time-sequenced planar LIF of OH

    NASA Astrophysics Data System (ADS)

    Hartung, G.; Hult, J.; Balachandran, R.; Mackley, M. R.; Kaminski, C. F.

    2009-09-01

    This paper describes the simultaneous application of time-sequenced laser-induced fluorescence imaging of OH radicals and stereoscopic particle image velocimetry for measurements of the flame front dynamics in lean and premixed LP turbulent flames. The studied flames could be acoustically driven, to simulate phenomena important in LP combustion technologies. In combination with novel image post processing techniques we show how the data obtained can be used to track the flame front contour in a plane defined by the illuminating laser sheets. We consider effects of chemistry and convective fluid motion on the dynamics of the observed displacements and analyse the influence of turbulence and acoustic forcing on the observed contour velocity, a quantity we term as s {/d 2D}. We show that this quantity is a valuable and sensitive indicator of flame turbulence interactions, as (a) it is measurable with existing experimental methodologies, and (b) because computational data, e.g. from large eddy simulations, can be post processed in an identical fashion. s {/d 2D} is related (to a two-dimensional projection) of the three-dimensional flame displacement speed s d , but artifacts due to out of plane convective motion of the flame surface and the uncertainty in the angle of the flame surface normal have to be carefully considered. Monte Carlo simulations were performed to estimate such effects for several distributions of flame front angle distributions, and it is shown conclusively that s {/d 2D} is a sensitive indicator of a quantity related to s d in the flames we study. s {/d 2D} was shown to increase linearly both with turbulent intensity and with the amplitude of acousting forcing for the range of conditions studied.

  4. Detailed characterization of the dynamics of thermoacoustic pulsations in a lean premixed swirl flame

    Microsoft Academic Search

    W. Meier; P. Weigand; X. R. Duan; R. Giezendanner-Thoben

    2007-01-01

    A nozzle configuration for technically premixed gas turbine flames was operated with CH4 and air at atmospheric pressure. The flames were confined by a combustion chamber with large quartz windows, allowing the application of optical and laser diagnostics. In a distinct range of operating conditions the flames exhibited strong self-excited thermoacoustic pulsations at a frequency around 290 Hz. A flame

  5. Opposed Jet Flames of Very Lean or Rich Premixed Propane-Air Reactants vs. Hot Products

    Microsoft Academic Search

    Zhongxian Cheng; Joseph A. Wehrmeyer; Robert W. Pitz

    Several opposed jet flames of very lean and rich premixed propane-air versus hot products generated by lean hydrogen flames are investigated in order to study stratified charge combustion processes in a DISI engine. A high spatial resolution visible Raman system is used to measure major species concentration and flame temperature simultaneously. The flames are numerically simulated with the Oppdif\\/CHEMKIN software

  6. Effect of electric fields on the liftoff of nonpremixed turbulent jet flames

    Microsoft Academic Search

    Sang Min Lee; Cheol Soo Park; Min Suk Cha; Suk Ho Chung

    2005-01-01

    The effect of electric fields on the liftoff of nonpremixed turbulent jet flames has been investigated by applying high-voltage alternate current (ac) to the nozzle of propane fuel. Flame liftoff velocities and liftoff heights were measured as functions of applied voltage and frequency. The fuel jet velocity at flame liftoff increased and flame liftoff height decreased with increasing voltage, implying

  7. Blowoff behavior of bluff body stabilized flames in vitiated and partially premixed flows

    Microsoft Academic Search

    Steven G. Tuttle

    2010-01-01

    Turbulent flame holding and blowoff characteristics of bluff body stabilized flames were measured in an enclosed rectangular duct with a triangular flame holder in vitiated, premixed and unvitiated, asymmetrically stratified flows. Blowoff stability margins were characterized, with chemiluminescence measurements performed by high-speed imaging to capture flame dynamics during blow off. As the equivalence ratio was decreased, local extinction along the

  8. A unified model for the prediction of laminar flame transfer functions

    Microsoft Academic Search

    T. Schuller; D. Durox; S. Candel

    2003-01-01

    Transfer functions of premixed laminar flames submitted to incident flow perturbations are envisaged and a unified model is derived analytically. This model, based on a linearization of the G-equation for an inclined flame, includes convective effects of the flow modulations propagating upstream of the flame. It is shown that the flame dynamics is governed by two relevant parameters, a reduced

  9. Flow Fields of Flame Propagating in Channels Based on the Source Sheet Approximation

    Microsoft Academic Search

    Mahinder S. Uberoi

    1963-01-01

    A volume source sheet plus a uniform flow is used to represent the flow field of a flame propagating in a channel. The unknown flame shape is determined by the requirement that the velocity normal and relative to it, i. e., the local flame speed is constant. The ratio of the propagation speed of the flame as a whole to

  10. PIV Measurements in Weakly Buoyant Gas Jet Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, Peter B.; Greenbberg, Paul S.; Urban, David L.; Wernet, Mark P.; Yanis, William

    2001-01-01

    Despite numerous experimental investigations, the characterization of microgravity laminar jet diffusion flames remains incomplete. Measurements to date have included shapes, temperatures, soot properties, radiative emissions and compositions, but full-field quantitative measurements of velocity are lacking. Since the differences between normal-gravity and microgravity diffusion flames are fundamentally influenced by changes in velocities, it is imperative that the associated velocity fields be measured in microgravity flames. Velocity measurements in nonbuoyant flames will be helpful both in validating numerical models and in interpreting past microgravity combustion experiments. Pointwise velocity techniques are inadequate for full-field velocity measurements in microgravity facilities. In contrast, Particle Image Velocimetry (PIV) can capture the entire flow field in less than 1% of the time required with Laser Doppler Velocimetry (LDV). Although PIV is a mature diagnostic for normal-gravity flames , restrictions on size, power and data storage complicate these measurements in microgravity. Results from the application of PIV to gas jet flames in normal gravity are presented here. Ethane flames burning at 13, 25 and 50 kPa are considered. These results are presented in more detail in Wernet et al. (2000). The PIV system developed for these measurements recently has been adapted for on-rig use in the NASA Glenn 2.2-second drop tower.

  11. Reduced Order Modeling of Premixed Flame Dynamics in Bluffbody Combustors

    NASA Astrophysics Data System (ADS)

    Mehta, Prashant G.; Soteriou, Marios C.

    2003-11-01

    Thermoacoustic instabilities arise in power generation devices such as gas turbines and rockets when acoustic modes couple with unsteady heat released due to combustion in a positive feedback loop. This work focuses on the development of a reduced order model for understanding flame dynamics in the case of flameholder stabilized premixed combustion in a duct - a situation typical in many of these applications. Similar to earlier studies in reduced order modeling of this flow, we employ a G-equation formulation to obtain kinematical representation of the premixed flame and ignore the impact of the unsteady (vortical) fluid dynamics downstream of the flameholder. Unlike those studies, however, we retain the impact of combustion exothermicity in the form of a density jump and associated volume generation at the flame front. The reduced order model yields analytical solutions for the flame location and for linear transfer functions between imposed (acoustic) perturbation and combustion heat release. We validate these solutions against detailed numerical simulations. Results show that for realistic density ratios across the flame, the flow is accelerated in the streamwise direction on account of combustion exothermicity and the effects of confinement. This alters the flame location in a significant way as compared to the non-exothermic case. It also changes the linearised dynamics of the flame in a fundamental way and brings into question conclusions drawn from similar analyses in which exothermicity effects were neglected. This is discussed in the context of modeling and controlling thermoacoustic instabilities.

  12. Radiation from Gas-Jet Diffusion Flames in Microgravity Environments

    NASA Technical Reports Server (NTRS)

    Bahadori, M. Yousef; Edelman, Raymond B.; Sotos, Raymond G.; Stocker, Dennis P.

    1991-01-01

    This paper presents the first demonstration of quantitative flame-radiation measurement in microgravity environments, with the objective of studying the influences and characteristics of radiative transfer on the behavior of gas-jet diffusion flames with possible application to spacecraft fire detection. Laminar diffusion flames of propane, burning in quiescent air at atmospheric pressure, are studied in the 5.18-Second Zero-Gravity Facility of NASA Lewis Research Center. Radiation from these flames is measured using a wide-view angle, thermopile-detector radiometer, and comparisons are made with normal-gravity flames. The results show that the radiation level is significantly higher in microgravity compared to normal-gravity environments due to larger flame size, enhanced soot formation, and entrapment of combustion products in the vicinity of the flame. These effects are the consequences of the removal of buoyancy which makes diffusion the dominant mechanism of transport. The results show that longer test times may be needed to reach steady state in microgravity environments.

  13. Experimental investigation of boundary-layer flashback in swirl flames

    NASA Astrophysics Data System (ADS)

    Ebi, Dominik; Clemens, Noel

    2013-11-01

    Swirling flows are widely employed for flame stabilization purposes in gas turbine combustors. However, flames in swirling flows are more prone to flashback, a potentially catastrophic phenomenon leading to thermal damage of the burner. The physical mechanism driving flashback in a swirling flow is not yet fully understood. The mechanism is particularly complex if the upstream flame propagation interacts with a boundary layer. In a previous study we showed that the flame/boundary-layer interaction is important for burners, which include an axial swirler and a central body attached to the swirler hub. We are investigating the mechanism of flashback in atmospheric pressure lean-premixed methane/hydrogen-air flames inside the mixing tube of our confined model swirl combustor. Flashback occurs at an equivalence ratio of approximately 0.7. The effect of hydrogen is investigated by testing different methane-to-hydrogen ratios. The duration of a single flashback event is on the order of 100 ms, requiring high-speed diagnostic techniques. We are applying simultaneous stereoscopic PIV, flame front detection based on Mie scattering, and chemiluminescence imaging to investigate the flame/flow interaction during flashback events.

  14. Buoyancy Effects in Fully-Modulated, Turbulent Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Hermanson, J. C.; Johari, H.; Ghaem-Maghami, E.; Stocker, D. P.; Hegde, U. G.; Page, K. L.

    2003-01-01

    Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The objective of this experiment (PuFF, for Pulsed-Fully Flames) is to increase the fundamental understanding of the fuel/air mixing and combustion behavior of pulsed, turbulent diffusion flames by conducting experiments in microgravity. In this research the fuel jet is fully-modulated (i.e., completely shut off between pulses) by an externally controlled valve system. This gives rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing compared to acoustically excited or partially-modulated jets. Normal-gravity experiments suggest that the fully-modulated technique also has the potential for producing turbulent jet flames significantly more compact than steady flames with no increase in exhaust emissions. The technique also simplifies the combustion process by avoiding the acoustic forcing generally present in pulsed combustors. Fundamental issues addressed in this experiment include the impact of buoyancy on the structure and flame length, temperatures, radiation, and emissions of fully-modulated flames.

  15. GRAVITATIONALLY UNSTABLE FLAMES: RAYLEIGH-TAYLOR STRETCHING VERSUS TURBULENT WRINKLING

    SciTech Connect

    Hicks, E. P. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Rosner, R., E-mail: eph2001@columbia.edu [Computation Institute, University of Chicago, 5735 S. Ellis Ave., Chicago, IL 60637 (United States)

    2013-07-10

    In this paper, we provide support for the Rayleigh-Taylor-(RT)-based subgrid model used in full-star simulations of deflagrations in Type Ia supernovae explosions. We use the results of a parameter study of two-dimensional direct numerical simulations of an RT unstable model flame to distinguish between the two main types of subgrid models (RT or turbulence dominated) in the flamelet regime. First, we give scalings for the turbulent flame speed, the Reynolds number, the viscous scale, and the size of the burning region as the non-dimensional gravity (G) is varied. The flame speed is well predicted by an RT-based flame speed model. Next, the above scalings are used to calculate the Karlovitz number (Ka) and to discuss appropriate combustion regimes. No transition to thin reaction zones is seen at Ka = 1, although such a transition is expected by turbulence-dominated subgrid models. Finally, we confirm a basic physical premise of the RT subgrid model, namely, that the flame is fractal, and thus self-similar. By modeling the turbulent flame speed, we demonstrate that it is affected more by large-scale RT stretching than by small-scale turbulent wrinkling. In this way, the RT instability controls the flame directly from the large scales. Overall, these results support the RT subgrid model.

  16. Joint scalar transported PDF modeling of nonpiloted turbulent diffusion flames

    SciTech Connect

    Lindstedt, R.P.; Ozarovsky, H.C. [Thermofluids Division, Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AZ (United Kingdom)

    2005-12-01

    A transported joint probability density function (JPDF) approach closed at the joint scalar level has been applied to investigate two nonpiloted CH{sub 4}/H{sub 2}/N{sub 2} turbulent (Re 15200 and 22800) jet diffusion flames. The flames have been studied experimentally at the Deutsches Zentrum fur Luft- und Raumfahrt (DLR) and at Sandia National Laboratories and are well characterized experimentally through extensive velocity and scalar measurements. The flames offer the opportunity of computational investigations of turbulence-chemistry interactions in CH{sub 4}/H{sub 2} flames in the absence of both partial premixing with air and with a smaller stoichiometric mixture fraction (Z{sub st}=0.167) than in the corresponding piloted Sandia flames. The two flames also offer different levels of local extinction. Comparatively few theoretical studies have been performed of these flames and the present work provides an assessment of the ability of the transported PDF approach to reproduce their detailed thermochemical structure. The chemical closure is obtained through a systematically reduced C/H/O/N mechanism featuring 16 independent, 4 dependent, and 28 steady-state scalars. The velocity field is computed using the second moment closure of Speziale et al. and molecular mixing is modeled using the modified Curl's model. It is shown that velocity and scalar fields are generally well reproduced for 10=

  17. Buoyant Low Stretch Diffusion Flames Beneath Cylindrical PMMA Samples

    NASA Technical Reports Server (NTRS)

    Olson, S. L.; Tien, J. S.

    1999-01-01

    A unique new way to study low gravity flames in normal gravity has been developed. To study flame structure and extinction characteristics in low stretch environments, a normal gravity low-stretch diffusion flame is generated using a cylindrical PMMA sample of varying large radii. Burning rates, visible flame thickness, visible flame standoff distance, temperature profiles in the solid and gas, and radiative loss from the system were measured. A transition from the blowoff side of the flammability map to the quenching side of the flammability map is observed at approximately 6-7/ sec, as determined by curvefits to the non-monotonic trends in peak temperatures, solid and gas-phase temperature gradients, and non-dimensional standoff distances. A surface energy balance reveals that the fraction of heat transfer from the flame that is lost to in-depth conduction and surface radiation increases with decreasing stretch until quenching extinction is observed. This is primarily due to decreased heat transfer from the flame, while the magnitude of the losses remains the same. A unique local extinction flamelet phenomena and associated pre-extinction oscillations are observed at very low stretch. An ultimate quenching extinction limit is found at low stretch with sufficiently high induced heat losses.

  18. Flame Retardant Applications in Camping Tents and Potential Exposure.

    PubMed

    Keller, Alexander S; Raju, Nikhilesh P; Webster, Thomas F; Stapleton, Heather M

    2014-02-11

    Concern has mounted over health effects caused by exposure to flame retardant additives used in consumer products. Significant research efforts have focused particularly on exposure to polybrominated diphenyl ethers (PBDEs) used in furniture and electronic applications. However, little attention has focused on applications in textiles, particularly textiles meeting a flammability standard known as CPAI-84. In this study, we investigated flame retardant applications in camping tents that met CPAI-84 standards by analyzing 11 samples of tent fabrics for chemical flame retardant additives. Furthermore, we investigated potential exposure by collecting paired samples of tent wipes and hand wipes from 27 individuals after tent setup. Of the 11 fabric samples analyzed, 10 contained flame retardant additives, which included tris(1,3-dichloroisopropyl) phosphate (TDCPP), decabromodiphenyl ether (BDE-209), triphenyl phosphate, and tetrabromobisphenol-A. Flame retardant concentrations were discovered to be as high as 37.5 mg/g (3.8% by weight) in the tent fabric samples, and TDCPP and BDE-209 were the most frequently detected in these samples. We also observed a significant association between TDCPP levels in tent wipes and those in paired hand wipes, suggesting that human contact with the tent fabric material leads to the transfer of the flame retardant to the skin surface and human exposure. These results suggest that direct contact with flame retardant-treated textiles may be a source of exposure. Future studies will be needed to better characterize exposure, including via inhalation and dermal sorption from air. PMID:24804279

  19. Great (Flame) Balls of Fire! Structure of Flame Balls at Low Lewis-number-2 (SOFBALL-2)

    NASA Technical Reports Server (NTRS)

    Ronney, Paul; Weiland, Karen J.; Over, Ann (Technical Monitor)

    2002-01-01

    Everyone knows that an automobile engine wastes fuel and energy when it runs with a fuel-rich mixture. 'Lean' burning, mixing in more air and less fuel, is better for the environment. But lean mixtures also lead to engine misfiring and rough operation. No one knows the ultimate limits for lean operation, for 'weak' combustion that is friendly to the environment while still moving us around. This is where the accidental verification of a decades-old prediction may have strong implications for designing and running low-emissions engines in the 21st century. In 1944, Soviet physicist Yakov Zeldovich predicted that stationary, spherical flames are possible under limited conditions in lean fuel-air mixtures. Dr. Paul Ronney of the University of Southern California accidentally discovered such 'flame balls' in experiments with lean hydrogen-air mixtures in 1984 during drop-tower experiments that provided just 2.2 seconds of near weightlessness. Experiments aboard NASA's low-g aircraft confirmed the results, but a thorough investigation was hampered by the aircraft's bumpy ride. And stable flame balls can only exist in microgravity. The potential for investigating combustion at the limits of flammability, and the implications for spacecraft fire safety, led to the Structure of Flame Balls at Low Lewis-number (SOFBALL) experiment flown twice aboard the Space Shuttle on the Microgravity Sciences Laboratory-1 (MSL-1) in 1997. Success there led to the planned reflight on STS-107. Flame balls are the weakest fires yet produced in space or on Earth. Typically each flame ball produced only 1 watt of thermal power. By comparison, a birthday candle produces 50 watts. The Lewis-number measures the rate of diffusion of fuel into the flame ball relative to the rate of diffusion of heat away from the flame ball. Lewis-number mixtures conduct heat poorly. Hydrogen and methane are the only fuels that provide low enough Lewis-numbers to produce stable flame balls, and even then only for very weak, barely flammable mixtures. Nevertheless, under these conditions flame balls give scientists the opportunity to test models in one of the simplest combustion experiments possible. SOFBALL-2 science objectives include: Improving our understanding of the flame ball phenomenon; Determining the conditions under which flame balls exist; Testing predictions of flame ball lifetimes; Acquiring more precise data for critical model comparison.

  20. Ionization and chemiluminescence during the progressive aeration of methane flames

    SciTech Connect

    Weinberg, Felix; Carleton, Fred [Imperial College London, London SW7 2AZ (United Kingdom)

    2009-12-15

    Saturation currents and chemiluminescence, especially at the CH{sup *} and C{sub 2}{sup *} wavelengths, are measured for a range of small, laminar methane flames during progressive addition of air, with the principal objective of distinguishing between pure diffusion flames, premixed flames of compositions falling between the upper and lower flammability limits, and the broad range of aerated flames lying in between these regimes. Flame areas defined by the loci of maximum luminosity and by schlieren contours were recorded, so that saturation current densities, CH{sup *} and C{sub 2}{sup *} emission per unit flame area, as well as burning velocities could be deduced. For admixtures of less than 70 vol.%, air appears to act, surprisingly, as an inert diluent as regards saturation currents, so that saturation currents are essentially proportional to fuel flow alone. Much the same applies to chemiluminescence. However, schlieren contours, which were recorded both to provide a basis for burning velocity measurements and to explore density changes in the reactants, indicated the presence of a burner - stabilised propagating reaction zone ahead of the luminous flame surface starting at around 50 vol.% and possibly even at lower air admixtures. This evidence of a steep change in refractive index is indicative of a premixed reaction zone involving the added oxygen, which however generates no chemi-ionization and emits no light. Even photographing the flame by radiation emitted at the CH{sup *} and C{sub 2}{sup *} wavelengths shows no sign of its existence. Its burning velocity is about 10 cm/s, when stabilized by the surrounding diffusion flame. The most plausible rationale for these observations is the formation of syngas by the partial oxidation of methane. The subsequent burning of CO and H{sub 2} is known to occur without chemi-ionization or appreciable light emission. (author)

  1. Non-flammable elastomeric fiber from a fluorinated elastomer and containing an halogenated flame retardant

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    Flame retardant elastomeric compositions are described comprised of either spandex type polyurethane having incorporated into the polymer chain halogen containing polyols, conventional spandex type polyurethanes in physical admixture with flame retardant additives, or fluoroelastomeric resins in physical admixture with flame retardant additives. Methods are described for preparing fibers of the flame retardant elastomeric materials and articles of manufacture comprised of the flame retardant clastomeric materials and non elastic materials such as polybenzimidazoles, fiberglass, nylons, etc.

  2. Synergistic effect between polyhedral oligomeric silsesquioxane and flame retardants

    NASA Astrophysics Data System (ADS)

    Safarikova, B.; Kalendova, A.; Habrova, V.; Zatloukalova, S.; Machovsky, M.

    2014-05-01

    Synergistic effect was observed between two types of flame retardant and two types of polyhedral oligomeric silsesquioxanes (POSS). The polymer matrix was represented by low density polyethylene Bralen RB 2-62 (Slovnaft). The polyethylene was mixed with nanofillers OctaIsobutyl POSS and TriSilanolIsobutyl POSS. The flame retardants was represented by ADK STAB® FP 2200 and Exolite® APP 722. The flammability was investigated by UL-94 test. The results showed that the APP/POSS system had important flame retardant and anti-dripping abilities for LDPE.

  3. A nonlinear wave equation in nonadiabatic flame propagation

    SciTech Connect

    Booty, M.R.; Matalon, M.; Matkowsky, B.J.

    1988-06-01

    The authors derive a nonlinear wave equation from the diffusional thermal model of gaseous combustion to describe the evolution of a flame front. The equation arises as a long wave theory, for values of the volumeric heat loss in a neighborhood of the extinction point (beyond which planar uniformly propagating flames cease to exist), and for Lewis numbers near the critical value beyond which uniformly propagating planar flames lose stability via a degenerate Hopf bifurcation. Analysis of the equation suggests the possibility of a singularity developing in finite time.

  4. REAL TIME FLAME MONITORING OF GASIFIER BURNER AND INJECTORS

    SciTech Connect

    James Servaites; Serguei Zelepouga; David Rue

    2003-10-01

    This report is submitted to the United States Department of Energy in partial fulfillment of the contractual requirements for Phase I of the project titled, ''Real Time Flame Monitoring of Gasifier Burner and Injectors'', under co-operative agreement number DE-FS26-02NT41585. The project is composed of three one-year budget periods. The work in each year is divided into separate Tasks to facilitate project management, orderly completion of all project objectives, budget control, and critical path application of personnel and equipment. This Topical Report presents results of the Task 1 and 2 work. The 2 D optical sensor was developed to monitor selected UV and visible wavelengths to collect accurate flame characterization information regarding mixing, flame shape, and flame rich/lean characteristic. Flame richness, for example, was determined using OH and CH intensity peaks in the 300 to 500 nanometer range of the UV and visible spectrum. The laboratory burner was operated over a wide range of air to fuel ratio conditions from fuel rich to fuel lean. The sooty oxygen enriched air flames were established to test the sensor ability to characterize flame structures with substantial presence of hot solid particles emitting strong ''black body radiation''. The knowledge gained in these experiments will be very important when the sensor is used for gasifier flame analyses. It is expected that the sensor when installed on the Global Energy gasifier will be exposed to complex radiation patterns. The measured energy will be a combination of spectra emitted by the combusting gases, hot solid particulates, and hot walls of the gasifier chamber. The ability to separate flame emissions from the ''black body emissions'' will allow the sensor to accurately determine flame location relative to the gasifier walls and the injectors, as well as to analyze the flame's structure and condition. Ultimately, this information should enable the gasification processes to be monitored and controlled and as a result increase durability and efficiency of the gasifier. To accomplish goals set for Task 2 GTI will utilize the CANMET Coal Gasification Research facility. The Entrained Coal Gasifier Burner Test Stand has been designed and is currently under construction in the CANMET Energy Technology Center (CETC), the research and technology arm of Natural Resources Canada (NRCan). This Gasifier Burner Stand (GBS) is a scaled-down mock-up of a working gasifier combustion system that can provide the flexible platform needed in the second year of the project to test the flame sensor. The GBS will be capable of simulating combustion and gasification processes occurring in commercial gasifiers, such as Texaco, Shell, and Wabash River.

  5. Theoretical and Numerical Investigation of Radiative Extinction of Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Ray, Anjan

    1996-01-01

    The influence of soot radiation on diffusion flames was investigated using both analytical and numerical techniques. Soot generated in diffusion flames dominate the flame radiation over gaseous combustion products and can significantly lower the temperature of the flame. In low gravity situations there can be significant accumulation of soot and combustion products in the vicinity of the primary reaction zone owing to the absence of any convective buoyant flow. Such situations may result in substantial suppression of chemical activities in a flame, and the possibility of a radiative extinction may also be anticipated. The purpose of this work was to not only investigate the possibility of radiative extinction of a diffusion flame but also to qualitatively and quantitatively analyze the influence of soot radiation on a diffusion flame. In this study, first a hypothetical radiative loss profile of the form of a sech(sup 2) was assumed to influence a pure diffusion flame. It was observed that the reaction zone can, under certain circumstances, move through the radiative loss zone and locate itself on the fuel side of the loss zone contrary to our initial postulate. On increasing the intensity and/or width of the loss zone it was possible to extinguish the flame, and extinction plots were generated. In the presence of a convective flow, however, the movement of the temperature and reaction rate peaks indicated that the flame behavior is more complicated compared to a pure diffusional flame. A comprehensive model of soot formation, oxidation and radiation was used in a more involved analysis. The soot model of Syed, Stewart and Moss was used for soot nucleation and growth and the model of Nagle and Strickland-Constable was used for soot oxidation. The soot radiation was considered in the optically thin limit. An analysis of the flame structure revealed that the radiative loss term is countered both by the reaction term and the diffusion term. The essential balance for the soot volume fraction was found to be between the processes of soot convection and soot growth. Such a balance yielded to analytical treatment and the soot volume fraction could be expressed in the form of an integral. The integral was evaluated using two approximate methods and the results agreed very well with the numerical solutions for all cases examined.

  6. System and method for optical monitoring of a combustion flame

    DOEpatents

    Brown, Dale M; Sandvik, Peter M; Fedison, Jeffrey B; Matocha, Kevin S; Johnson, Thomas E

    2006-09-26

    An optical spectrometer for combustion flame temperature determination includes at least two photodetectors positioned for receiving light from a combustion flame, each of the at least two photodetectors having a different, overlapping bandwidth for detecting a respective output signal in an ultraviolet emission band; and a computer for subtracting a respective output signal of a first one of the at least two photodetectors from a respective output signal of a second one of the at least two photodetectors to obtain a segment signal, and using the segment signal to determine the combustion flame temperature.

  7. On the opening of premixed Bunsen flame tips

    NASA Technical Reports Server (NTRS)

    Law, C. K.; Ishizuka, S.; Cho, P.

    1982-01-01

    The local extinction of Bunsen flame tip and edges of hydrocarbon/air premixtures has been experimentally investigated using a variety of burners. Results show that, while for both rich propane/air and butane/air mixtures tip opening occurs at a constant fuel equivalence ratio of 1.44 and is therefore independent of the intensity, uniformity, and configuration of the approach flow, for rich methane/air flames burning is intensified at the tip and therefore opening is not possible. These results substantiate the concept and dominance of the diffusional stratification mechanism in causing extinction, and clarify the theoretical predictions on the possible opening of two-dimensional flame wedges.

  8. Halogenated Flame Retardants in the Great Lakes Environment.

    PubMed

    Venier, Marta; Salamova, Amina; Hites, Ronald A

    2015-07-21

    Flame retardants are widely used industrial chemicals that are added to polymers, such as polyurethane foam, to prevent them from rapidly burning if exposed to a small flame or a smoldering cigarette. Flame retardants, especially brominated flame retardants, are added to many polymeric products at percent levels and are present in most upholstered furniture and mattresses. Most of these chemicals are so-called "additive" flame retardants and are not chemically bound to the polymer; thus, they migrate from the polymeric materials into the environment and into people. As a result, some of these chemicals have become widespread pollutants, which is a concern given their possible adverse health effects. Perhaps because of their environmental ubiquity, the most heavily used group of brominated flame retardants, the polybrominated diphenyl ethers (PBDEs), was withdrawn from production and use during the 2004-2013 period. This led to an increasing demand for other flame retardants, including other brominated aromatics and organophosphate esters. Although little is known about the use or production volumes of these newer flame retardants, it is evident that some of these chemicals are also becoming pervasive in the environment and in humans. In this Account, we describe our research on the occurrence of halogenated and organophosphate flame retardants in the environment, with a specific focus on the Great Lakes region. This Account starts with a short introduction to the first generation of brominated flame retardants, the polybrominated biphenyls, and then presents our measurements of their replacement, the PBDEs. We summarize our data on PBDE levels in babies, bald eagles, and in air. Once these compounds came off the market, we began to measure several of the newer flame retardants in air collected on the shores of the Great Lakes once every 12 days. These new measurements focus on a tetrabrominated benzoate, a tetrabrominated phthalate, a hexabrominated diphenoxyethane, several brominated benzenes, and a highly chlorinated norbornene compound called Dechlorane Plus. Most recently, we have begun measuring the atmospheric concentrations of several organophosphate esters, which are an increasing part of the flame retardant market. The interesting feature of this story is how one compound or set of compounds has followed another out of and into the marketplace even though none of them have been officially regulated. This replacement of one commercial product by another with similar functions shows that the chemical industry does respond to scientific environmental measurements and to the resulting bad publicity. This is a good thing. The problem is that often the replacement chemicals also become environmentally ubiquitous. PMID:26050713

  9. Modeling and experimental validation of unsteady impinging flames

    SciTech Connect

    Fernandes, E.C.; Leandro, R.E. [Center for Innovation, Technology and Policy Research, Mechanical Engineering Department, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa Codex (Portugal)

    2006-09-15

    This study reports on a joint experimental and analytical study of premixed laminar flames impinging onto a plate at controlled temperature, with special emphasis on the study of periodically oscillating flames. Six types of flame structures were found, based on parametric variations of nozzle-to-plate distance (H), jet velocity (U), and equivalence ratio (f). They were classified as conical, envelope, disc, cool central core, ring, and side-lifted flames. Of these, the disc, cool central core, and envelope flames were found to oscillate periodically, with frequency and sound pressure levels increasing with Re and decreasing with nozzle-to-plate distance. The unsteady behavior of these flames was modeled using the formulation derived by Durox et al. [D. Durox, T. Schuller, S. Candel, Proc. Combust. Inst. 29 (2002) 69-75] for the cool central core flames where the convergent burner acts as a Helmholtz resonator, driven by an external pressure fluctuation dependent on a velocity fluctuation at the burner mouth after a convective time delay {tau}. Based on this model, the present work shows that {tau} = [Re[2jtanh{sup -1}((2{delta}{omega}+(1+N)j{omega}{sup 2}-j{omega}{sub 0}{sup 2})/ (2{delta}{omega}+(1-N)j{omega}{sup 2}-j{omega}{sub 0}{sup 2}))]+2{pi}K]/{omega}, i.e., there is a relation between oscillation frequency ({omega}), burner acoustic characteristics ({omega}{sub 0},{delta}), and time delay {tau}, not explicitly dependent on N, the flame-flow normalized interaction coefficient [D. Durox, T. Schuller, S. Candel, Proc. Combust. Inst. 29 (2002) 69-75], because {partial_derivative}t/{partial_derivative}N = 0. Based on flame motion and noise analysis, K was found to physically represent the integer number of perturbations on flame surface or number of coherent structures on impinging jet. Additionally, assuming that {tau}={beta}H/U, where H is the nozzle-to-plate distance and U is the mean jet velocity, it is shown that {beta}{sub Disc}=1.8, {beta}{sub CCC}=1.03, and {beta}{sub Env}=1.0. A physical analysis of the proportionality constant {beta} showed that for the disc flames, {tau} corresponds to the ratio between H and the velocity of the coherent structures. In the case of envelope and cool central core flames, {tau} corresponds to the ratio between H and the mean jet velocity. The predicted frequency fits the experimental data, supporting the validity of the mathematical modeling, empirical formulation, and assumptions made. (author)

  10. Development of flame resistant treatment for nomex fibrous structures

    NASA Technical Reports Server (NTRS)

    Toy, M. S.

    1978-01-01

    Technology which renders aramid fibrous structures flame resistant through chemical modification was developed. The project scaled up flame resistant treatment from laboratory fabric swatches of a few inches to efficiently producing ten yards of commercial width (41 inches) aromatic polyamide. The radiation intensity problem of the processor was resolved. Further improvement of the processor cooling system was recommended for two reasons: (1) To advance current technology of flame proofing Nomex fabric to higher oxygen enriched atmospheres; and (2) To adapt the processor for direct applicability to low cost commercial fabrics.

  11. HST Photometry of the Globular Cluster M4

    E-print Network

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

    1998-05-14

    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 available on the AAS CD-ROM (or email a request to RAI). The scientific analysis is deferred to three companion papers, which investigate the significant white dwarf population discovered and the main sequence population.

  12. ESSENCE Photometry and SN Light-Curve Fitting

    NASA Astrophysics Data System (ADS)

    Wood-Vasey, W. M.; Clocchiatti, A.; Jha, S.; Miknaitis, G.; Pignata, G.; Rest, A.; Stubbs, C. W.; ESSENCE Collaboration

    2005-12-01

    We present and discuss the photometric measurements and analysis of SN Ia light curves from the first 3 years of the ESSENCE project. We have used and verified multiple photometric packages to thoroughly understand and cross-check our photometry. Using both deep-template and NN2-based frame-subtraction methods to achieve high signal-to-noise ratio lightcurves, we detail the complementarity of both approaches in minimizing systematics in the ESSENCE photometry. To understand our calibration of the relative luminosity distances to our SNe Ia, we compare the results of 3 different SN Ia lightcurve luminosity width-brightness packages: MLCS2k2, Dm15, and BATM. This work is partially supported by grant AST-0443378 from the US National Science Foundation.

  13. Optical Photometry of V404 Cyg (=GS2023+338)

    NASA Astrophysics Data System (ADS)

    Wagner, R. M.; Shrader, C. R.; Starrfield, S. G.

    2000-03-01

    In response to the request by Hjellming et al. in ATEL #54, Rose Finn (Steward Observatory/U. Arizona) obtained for us two R-band CCD images of V404 Cyg (=GS2023+338) on 2000 Mar 3.52 UT with the Steward Observatory Bok 2.3-m telescope and direct CCD (scale = 0.3 arcsec/pixel, airmass = 1.8, seeing = 1.7 arcsec FWHM). Photometry of V404 Cyg was obtained with respect to the comparison stars C1, C4, and C5 of Udalski and Kaluzny (1991, PASP, 103, 198), Casares et al. (1993, MNRAS, 265, 834), and our own photometry of C1 (R = 12.39).

  14. Stellar Mass Function From SIM Astrometry/Photometry

    E-print Network

    Andrew Gould; Samir Salim

    1999-07-07

    By combining SIM observations with ground-based photometry, one can completely solve microlensing events seen toward the Galactic bulge. One could measure the mass, distance, and transverse velocity of ~100 lenses to ~5% precision in only ~500 hours of SIM time. Among the numerous applications are 1) measurement of the mass functions (MFs) of the bulge and disk 2) measurement of the relative normalizations of the bulge and disk MFs (and so their relative contribution to the Galactic potential), 3) measurement of the number of bulge white dwarfs and neutron stars (and so the initial MF well above the present turnoff). SIM astrometric measurements are simultaneously photometric measurements. SIM astrometry determines the angular size of the Einstein ring on the sky, and comparison of SIM and ground-based photometry determines the size of the Einstein ring projected onto the observer plane. Only by combining both of these measurements is it possible to completely solve the microlensing events.

  15. Properties of plasma flames sustained by microwaves and burning hydrocarbon fuels

    NASA Astrophysics Data System (ADS)

    Hong, Yong Cheol; Uhm, Han Sup

    2006-11-01

    Plasma flames made of atmospheric microwave plasma and a fuel-burning flame were presented and their properties were investigated experimentally. The plasma flame generator consists of a fuel injector and a plasma flame exit connected in series to a microwave plasma torch. The plasma flames are sustained by injecting hydrocarbon fuels into a microwave plasma torch in air discharge. The microwave plasma torch in the plasma flame system can burn a hydrocarbon fuel by high-temperature plasma and high atomic oxygen density, decomposing the hydrogen and carbon containing fuel. We present the visual observations of the sustained plasma flames and measure the gas temperature using a thermocouple device in terms of the gas-fuel mixture and flow rate. The plasma flame volume of the hydrocarbon fuel burners was more than approximately 30-50 times that of the torch plasma. While the temperature of the torch plasma flame was only 868K at a measurement point, that of the diesel microwave plasma flame with the addition of 0.019lpm diesel and 30lpm oxygen increased drastically to about 2280K. Preliminary experiments for methane plasma flame were also carried out, measuring the temperature profiles of flames along the radial and axial directions. Finally, we investigated the influence of the microwave plasma on combustion flame by observing and comparing OH molecular spectra for the methane plasma flame and methane flame only.

  16. Precise Photometry Mission -- Measuring Stellar Microvariability from Space

    Microsoft Academic Search

    T. M. Brown; W. Borucki; S. Frandsen; R. L. Gilliland; A. Jones; R. W. Noyes; T. Tarbell; R. K. Ulrich

    1995-01-01

    Atmospheric scintillation limits the precision attainable by ground-based photometry; this limitation is a major obstacle to progress in several fields, notably asteroseismology of Sun-like stars. A space-borne photometric telescope could operate near the shot noise limit, removing this obstacle and providing new opportunities for inquiry. As part of the program for New Mission Concepts in Astrophysics, we are studying the

  17. Astronomical Photometry and the Legacy of Arne Henden (Abstract)

    NASA Astrophysics Data System (ADS)

    Joner, M.

    2015-06-01

    (Abstract only) Arne Henden has helped provide a valuable resource to the photometric community with the publication of the 1982 book Astronomical Photometry. I will present a brief review of the topics covered in this handbook and recount some of the many times that it has been useful to myself and my students for answering a wide variety of questions dealing with the acquisition and reduction of photometric observations.

  18. An interactive modular design for computerized photometry in spectrochemical analysis

    NASA Technical Reports Server (NTRS)

    Bair, V. L.

    1980-01-01

    An interactive, top-down structured program design is described which produces a general flexible description of totally automatic photometry of emission spectra in an operating environment in which sample compositions and analysis procedures are low-volume and nonroutine. The use of this type of programming is illustrated by a project to computerize trace elemental determinations including the automated reading of spectrographic plates produced by a 3.4-m Ebert mount spectrograph using a dc-arc in an argon atmosphere.

  19. Blue-light imagery and photometry of sprites

    Microsoft Academic Search

    David M. Suszcynsky; Robert Roussel-Dupré; Walter A. Lyons; Russell A. Armstrong

    1998-01-01

    We have obtained blue (350–475 nm) video images and simultaneous high-time resolution narrow-band blue (415–435 nm) photometry records of four sprite events. The brightest blue images show a sustained tendril geometry and a nearly constant intensity of emission over the entire vertical extent of the sprite (from 35–90 km altitude). Photometer light curves display an exponential decay with a 0.3

  20. Luminosities and temperatures of M dwarf stars from infrared photometry

    NASA Technical Reports Server (NTRS)

    Veeder, G. J.

    1974-01-01

    Bolometric magnitudes for a large number of M type dwarf stars, obtained by broadband infrared photometry at 1.65, 2.2, and 3.5 microns, are reviewed. The data obtained indicate that one parameter is sufficient to describe the blanketing in all of the UBVRI bands for all types of M dwarfs. In general, late M dwarfs seem to have lower effective temperatures than are predicted by theoretical models.

  1. Astrometry and Photometry for Two Dwarf Carbon Stars

    Microsoft Academic Search

    Hugh C. Harris; Conard C. Dahn; Richard L. Walker; Christian B. Luginbuhl; Alice K. B. Monet; Harry H. Guetter; Ronald C. Stone; Frederick J. Vrba; David G. Monet; Jeffrey R. Pier

    1998-01-01

    Preliminary trigonometric parallaxes and BVI photometry are presented for two dwarf carbon stars, LP 765-18 (=LHS 1075) and LP 328-57 (=CLS 96). The data are combined with the literature values for a third dwarf carbon star, G77-61 (=LHS 1555). All three stars have very similar luminosities (9.6 < MV < 10.0) and very similar broadband colors across the entire visual-to-near-IR

  2. Zinc recovery via the flame reactor process

    SciTech Connect

    Pusateri, J.F.; Bounds, C.O.; Lherbier, L.W.

    1988-08-01

    A major objective of the zinc industry for the 1990s will be to maintain high zinc recovery while eliminating the disposal of copious quantities of hazardous iron residues. The flame reactor process has demonstrated the potential of meeting this objective by either treating the residues or smelting zinc directly. The process has been proven commercially viable for treating flue dusts generated during electric arc furnace steelmaking. Zinc, lead and cadmium are recovered from the dust as a crude oxide for recycle while a nonhazardous slag is produced for sale. Similar products are efficiently produced from electrolytic zinc plant neutral leach and iron precipitation residues. In addition, the reactor shows promise of fulfilling its original objective of being a low-energy primary zinc smelter by fuming and condensing zinc from roasted concentrates.

  3. Graphite oxide flame-retardant polymer nanocomposites.

    PubMed

    Higginbotham, Amanda L; Lomeda, Jay R; Morgan, Alexander B; Tour, James M

    2009-10-01

    Graphite oxide (GO) polymer nanocomposites were developed at 1, 5, and 10 wt % GO with polycarbonate (PC), acrylonitrile butadiene styrene, and high-impact polystyrene for the purpose of evaluating the flammability reduction and material properties of the resulting systems. The overall morphology and dispersion of GO within the polymer nanocomposites were studied by scanning electron microscopy and optical microscopy; GO was found to be well-dispersed throughout the matrix without the formation of large aggregates. Mechanical testing was performed using dynamic mechanical analysis to measure the storage modulus, which increased for all polymer systems with increased GO loading. Microscale oxygen consumption calorimetry revealed that the addition of GO reduced the total heat release and peak heat release rates in all systems, and GO-PC composites demonstrated very fast self-extinguishing times in vertical open flame tests, which are important to some regulatory fire safety applications. PMID:20355860

  4. Splitting of Forced Elliptic Jets and Flames

    NASA Technical Reports Server (NTRS)

    Hertzberg, J.; Carlton, J.; Schwieterman, M.; Davis, E.; Bradley, E.; Linne, M.

    1997-01-01

    The objective of this work is to understand the fluid dynamics in the interaction of large scale, three-dimensional vortex structures and transitional diffusion flames in a microgravity environment. The vortex structures are used to provide a known perturbation of the type used in passive and active shear layer control techniques. 'Passive techniques' refers to manipulation of the system geometry to influence the three dimensional dynamics of vortex structures, and 'active' refers to any technique which adds energy (acoustic or kinetic) to the flow to influence the shear layer vortex dynamics. In this work the passive forcing is provided by an elliptic jet cross-section, and the active forcing is incorporated by perturbing the jet velocity using a loudspeaker in the plenum section.

  5. Panchromatic Hubble Andromeda Treasury Survey: Resolved Stellar Photometry

    NASA Astrophysics Data System (ADS)

    Williams, Benjamin F.; Dalcanton, J. J.; Dolphin, A. E.; Lang, D.; Weisz, D.; Seth, A. C.; Kalirai, J.; Lauer, T.; Rosema, K.

    2012-01-01

    The PHAT survey is collecting photometric data with 3 cameras aboard the Hubble Space Telescope covering about one quarter of the M31 inner disk and bulge. The observing strategy allows coverage of the full survey area in 6 broad bands from the Near-UV to the Near-IR. Initial survey photometry has been performed on the data from each camera separately, then the resulting catalogs have been matched to improve astrometry and provide our first 6-band catalogs. We provide a summary of our crowding-optimized point spread function measuring technique. We present color-magnitude diagrams showing our data quality in each camera for areas of varying surface brightness in M31, and we present color-color diagrams to show the quality of our current ability to match stars across all 6 bands. These data are samples of the survey's first public data release to the Hubble data archive. Finally we present preliminary results from simultaneous photometry across all 6 bands where matching is done at the pixel level, eliminating the need for catalog matching. This new ability provides optimal depth in overlapping fields and more reliable matching of all 6 bands. Future survey data releases will include such optimized 6-band photometry. PHAT is supported by HST GO-12055 administered by NASA.

  6. Transformed photometry of young stars in Cha requested

    NASA Astrophysics Data System (ADS)

    Waagen, Elizabeth O.

    2013-01-01

    Dr. Peter Abraham (Konkoly Observatory, Budapest, Hungary) requested the assistance of AAVSO observers in monitoring eight young stars in Chamaeleon in support of photometry he and his colleagues will be obtaining with the VLT/ISAAC (infrared) and Herschel Space Observatory (far-infrared) during January-February 2013. The targets are CR Cha, CT Cha, HP Cha (Glass I), VW Cha, VZ Cha, WW CHa, WX Cha, XX Cha. Calibrated, transformed VRI photometry is requested to precisely monitor changes in the optical brightness and colors of these objects. Calibration and transformation of the photometry is crucial - if all of the data are not on the same system and particularly if the colors are not transformed, it will be extremely difficult to correlate the data usefully. Previous observations indicate that the stars are highly variable. Brightness changes can be expected from a few tenths of a magnitude to up to 1-2 magnitudes on a timescale of a few days to a few weeks. Observers are asked to try to obtain one to two sets of VRI images per night. Finder charts with sequences may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp). Observations should be submitted to the AAVSO International Database. See full Alert Notice for more details.

  7. Aperture Photometry of Saturated Star Images from Digitised Photographic Plates

    E-print Network

    J. L. Innis; D. W. Coates; A. P. Borisova; M. K. Tsvetkov

    2005-02-21

    Saturated stellar images on digitised photographic plates are many times greater in area than the `seeing disk' seen in unsaturated CCD images. Indeed the flux profile of a bright star can be traced out for several degrees from the star's centre. The radius of the saturated stellar image can often be directly related to the magnitude of the star, a fact well known and exploited in iris photometry. In this work we compare the radial flux profile of stars in the approximate range B ~9 to ~13 mag, obtained from scans of plates from the Bamberg Sky Patrol archive, with a profile of the form measured by King. We show that simple aperture photometry of saturated stellar images, obtained from photo-positives of scanned photographic plates, yield data that are in agreement with simulations using a (saturated) synthetic stellar radius profile. Raw plate magnitudes from this aperture photometry can be easily and satisfactorily transformed to standard magnitudes, as demonstrated in a recent study carried out by the current authors.

  8. High speed low noise multiplexed three color absorbance photometry.

    PubMed

    Dadesh, Khaled M; Kurup, G K; Basu, Amar S

    2011-01-01

    Multispectral photometry is often required to distinguish samples in flow injection analysis and flow cytometry; however, the cost of multiple light detectors, filters, and optical paths contribute to the high cost of multicolor and spectral detection systems. This paper describes frequency division multiplexing (FDM), a simple approach for performing multi-wavelength absorbance photometry with a single light detector and a single interrogation window. In previous efforts, modulation frequencies were <10 KHz, resulting in a detector bandwidth of <20 Hz. This paper presents a high frequency FDM circuit which can increase the oscillation frequencies to several 100 KHz, improving the detection bandwidth by a factor of 10 while still maintaining low cost. Light from 3 different LED sources are encoded into unique frequency channels, passed through the detection cell, and later demodulated using phase-sensitive electronics. Electronic multiplexing couples all light sources into a single optical train without spectral filters. Theory and high frequency considerations are demonstrated. Simultaneous three color absorbance detection is demonstrated in solutions and in flowing droplet microreactors. This technique can potentially reduce the cost of multicolor photometry by replacing expensive optical components with low-cost electronics. PMID:22254245

  9. Precision multi-band photometry with a DSLR camera

    E-print Network

    Zhang, M; Penev, K; Csubry, Z; Hartman, J D; Bhatti, W; de Val-Borro, M

    2015-01-01

    Ground-based exoplanet surveys such as SuperWASP, HATNet and KELT have discovered close to two hundred transiting extrasolar planets in the past several years. The strategy of these surveys is to look at a large field of view and measure the brightnesses of its bright stars to around half a percent per point precision, which is adequate for detecting hot Jupiters. Typically, these surveys use CCD detectors to achieve high precision photometry. These CCDs, however, are expensive relative to other consumer-grade optical imaging devices, such as digital single-lens reflex cameras (DSLRs). We look at the possibility of using a digital single-lens reflex camera for precision photometry. Specifically, we used a Canon EOS 60D camera that records light in 3 colors simultaneously. The DSLR was integrated into the HATNet survey and collected observations for a month, after which photometry was extracted for 6600 stars in a selected stellar field. We found that the DSLR achieves a best-case median absolute deviation (MA...

  10. Theory of wide-angle photometry from standard stars

    NASA Technical Reports Server (NTRS)

    Usher, Peter D.

    1989-01-01

    Wide angle celestial structures, such as bright comet tails and nearby galaxies and clusters of galaxies, rely on photographic methods for quantified morphology and photometry, primarily because electronic devices with comparable resolution and sky coverage are beyond current technological capability. The problem of the photometry of extended structures and of how this problem may be overcome through calibration by photometric standard stars is examined. The perfect properties of the ideal field of view are stated in the guise of a radiometric paraxial approximation, in the hope that fields of view of actual telescopes will conform. Fundamental radiometric concepts are worked through before the issue of atmospheric attenuation is addressed. The independence of observed atmospheric extinction and surface brightness leads off the quest for formal solutions to the problem of surface photometry. Methods and problems of solution are discussed. The spectre is confronted in the spirit of standard stars and shown to be chimerical in that light, provided certain rituals are adopted. After a brief discussion of Baker-Sampson polynomials and the vexing issue of saturation, a pursuit is made of actual numbers to be expected in real cases. While the numbers crunched are gathered ex nihilo, they demonstrate the feasibility of Newton's method in the solution of this overdetermined, nonlinear, least square, multiparametric, photometric problem.

  11. Pushing the precision limit of ground-based eclipse photometry

    E-print Network

    M. Gillon; D. R. Anderson; B. -O. Demory; D. M. Wilson; C. Hellier; D. Queloz; C. Waelkens

    2008-06-30

    Until recently, it was considered by many that ground-based photometry could not reach the high cadence sub-mmag regime because of the presence of the atmosphere. Indeed, high frequency atmospheric noises (mainly scintillation) limit the precision that high SNR photometry can reach within small time bins. If one is ready to damage the sampling of his photometric time-series, binning the data (or using longer exposures) allows to get better errors, but the obtained precision will be finally limited by low frequency noises. To observe several times the same planetary eclipse and to fold the photometry with the orbital period is thus generally considered as the only option to get very well sampled and precise eclipse light curve from the ground. Nevertheless, we show here that reaching the sub-mmag sub-min regime for one eclipse is possible with a ground-based instrument. This has important implications for transiting planets characterization, secondary eclipses measurement and small planets detection from the ground.

  12. M2K Planet Search: Spectroscopic Screening and Transit Photometry

    NASA Astrophysics Data System (ADS)

    Mann, Andrew; Gaidos, E.; Fischer, D.; Lepine, S.

    2010-10-01

    The M2K project is a search for planets orbiting nearby early M and late K dwarf drawn from the SUPERBLINK catalog. M and K dwarfs are highly attractive targets for finding low-mass and habitable planets because (1) close-in planets are more likely to orbit within their habitable zone, (2) planets orbiting them induce a larger Doppler signal and have deeper transits than similar planets around F, G, and early K type stars, (3) planet formation models predict they hold an abundance of super-Earth sized planets, and (4) they represent the vast majority of the stars close enough for direct imaging techniques. In spite of this, only 10% of late K and early M dwarfs are being monitored by current Doppler surveys. As part of the M2K project we have obtained low-resolution spectra for more than 2000 of our sample of 10,000 M and K dwarfs. We vet our sample by screening these stars for high metallicity and low chromospheric activity. We search for transits on targets showing high RMS Doppler signal and photometry candidates provided by SuperWASP project. By using "snapshot” photometry have been able to achieve sub-millimag photometry on numerous transit targets in the same night. With further follow-up observations we will be able to detect planets smaller than 10 Earth masses.

  13. The Chandra COSMOS Survey: Source Detection and Photometry.

    NASA Astrophysics Data System (ADS)

    Puccetti, Simonetta; Fiore, F.; Elvis, M.; Civano, F.; Fruscione, A.; Lanzuisi, G.; Chandra COSMOS Team

    2009-01-01

    We have developed a multi-stage source detection process to deal with the heavily overlapped tiling of the C-COSMOS isurvey. The resulting method combines the ability to separate close pairs of sources with accurate positions and photometry, and so may be useful in other applications. In C-COSMOS every position on the sky was observed in typically 4 overlapping pointings, and so with a corresponding PSFs, in the central 0.5 sq.deg and in two overlapping pointings in most of the outer 0.4 sq.deg. area. To full yexploitthe C-COSMOS data requires a dedicated and accurate analysis focused on three main issues: (1) maximizing the sensitivity when the PSF changes so wildly among different observations of the same source (from few arcsec to 10 arcsec); (2) resolving close pairs; and (3) obtaining the best source localization and count rate accuracy. We made detailed comparisons between different detection algorithms and photometry tools using extensive simulations. Our final method consists of a procedure that takes advantage of the good positional accuracy and ability to separate close groups of sources of PWDETECT, and the accurate photometry and well-defined detection probability of EMLDETECT.

  14. Quantification of transient stretch effects on kernel-vortex interactions in premixed methane-air flames

    SciTech Connect

    Marley, S.K.; Danby, S.J.; Roberts, W.L. [Department of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC 27695 (United States); Drake, M.C.; Fansler, T.D. [General Motors Research and Development, Warren, MI 48090 (United States)

    2008-07-15

    Relative flame speeds of time-dependent highly curved premixed methane-air flames (spark-ignited flame kernels) interacting with a laminar vortex have been quantified using high-speed chemiluminescence imaging, particle image velocimetry, and piezoelectric pressure measurements. The goals of this study are to improve fundamental understanding of transient stretch effects on highly curved premixed flames, to provide practical insight into the turbulent growth of spark-ignited flame kernels in internal combustion (IC) engines burning light hydrocarbon fuels, and to provide data for IC engine ignition and combustion model development. Lean and rich CH{sub 4}-O{sub 2}-N{sub 2} flames were tested ({phi}=0.64, 0.90, and 1.13, with nitrogen dilution to equalize the flame speeds (S{sub b}) in the absence of vortex interaction). Transient stretch rates were varied using three different vortex strengths, and the size of the flame kernel at the start of the vortex interaction controlled by time delay between ignition and vortex generation. Vortex interactions with small ({proportional_to}5 mm radius) flame kernels were found to increase burning rates for lean ({phi}=0.64) flame kernels substantially. Burning rates for rich ({phi}=1.13) flames were decreased, with total flame kernel extinction occurring in extreme cases. These small flame kernel-vortex interactions are dominated by transient stretch effects and thermodiffusive stability, in agreement with premixed flame theory. However, vortex interactions with larger methane-air flame kernels ({proportional_to}30 mm radius) led to slight flame speed enhancements for both lean and rich flame kernels, with the flame-vortex process dominated by increased flamefront area generated by vortex-induced flame wrinkling. (author)

  15. Shapes of Nonbuoyant Round Luminous Hydrocarbon/Air Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Lin, K.-C.; Faeth, G. M.; Sunderland, P. B.; Urban, D. L.; Yuan, Z.-G.

    1999-01-01

    The shapes (luminous flame boundaries) of round luminous nonbuoyant soot-containing hydrocarbon/air laminar jet diffusion flames at microgravity were found from color video images obtained on orbit in the Space Shuttle Columbia. Test conditions included ethylene- and propane-fueled flames burning in still air at an ambient temperature of 300 K, ambient pressures of 35-130 kPa, initial jet diameters of 1.6 and 2.7 mm, and jet exit Reynolds numbers of 45-170. Present test times were 100-200 s and yielded steady axisymmetric flames that were close to the laminar smoke point (including flames both emitting and not emitting soot) with luminous flame lengths of 15-63 mm. The present soot-containing flames had larger luminous flame lengths than earlier ground-based observations having similar burner configurations: 40% larger than the luminous flame lengths of soot-containing low gravity flames observed using an aircraft (KC-135) facility due to reduced effects of accelerative disturbances and unsteadiness; roughly twice as large as the luminous flame lengths of soot-containing normal gravity flames due to the absence of effects of buoyant mixing and roughly twice as large as the luminous flame lengths of soot-free low gravity flames observed using drop tower facilities due to the presence of soot luminosity and possible reduced effects of unsteadiness. Simplified expressions to estimate the luminous flame boundaries of round nonbuoyant laminar jet diffusion flames were obtained from the classical analysis of Spalding (1979); this approach provided Successful Correlations of flame shapes for both soot-free and soot-containing flames, except when the soot-containing flames were in the opened-tip configuration that is reached at fuel flow rates near and greater than the laminar smoke point fuel flow rate.

  16. Shapes of Nonbuoyant Round Luminous Hydrocarbon/Air Laminar Jet Diffusion Flames. Appendix H

    NASA Technical Reports Server (NTRS)

    Lin, K.-C.; Faeth, G. M.; Sunderland, P. B.; Urban, D. L.; Yuan, Z.-G.; Ross, Howard B. (Technical Monitor)

    2000-01-01

    The shapes (luminous flame boundaries) of round luminous nonbuoyant soot-containing hydrocarbon/air laminar jet diffusion flames at microgravity were found from color video images obtained on orbit in the Space Shuttle Columbia. Test conditions included ethylene- and propane-fueled flames burning in still air at an ambient temperature of 300 K ambient pressures of 35-130 kPa, initial jet diameters of 1.6 and 2.7 mm, and jet exit Reynolds numbers of 45-170. Present test times were 100-200 s and yielded steady axisymmetric flames that were close to the laminar smoke point (including flames both emitting and not emitting soot) with luminous flame lengths of 15-63 mm. The present soot-containing flames had larger luminous flame lengths than earlier ground-based observations having similar burner configurations: 40% larger than the luminous flame lengths of soot-containing low gravity flames observed using an aircraft (KC-135) facility due to reduced effects of accelerative disturbances and unsteadiness; roughly twice as large as the luminous flame lengths of soot-containing normal gravity flames due to the absence of effects of buoyant mixing and roughly twice as large as the luminous flame lengths of soot-free low gravity flames observed using drop tower facilities due to the presence of soot luminosity and possible reduced effects of unsteadiness, Simplified expressions to estimate the luminous flame boundaries of round nonbuoyant laminar jet diffusion flames were obtained from the classical analysis of Spalding; this approach provided successful correlations of flame shapes for both soot-free and soot-containing flames, except when the soot-containing flames were in the opened-tip configuration that is reached at fuel flow rates near and greater than the laminar smoke point fuel flow rate.

  17. Liquid-oxygen compatible, flame-resistant coating.

    NASA Technical Reports Server (NTRS)

    Bright, C. W.

    1977-01-01

    Polychloroprene rubber composition, using commercially available components, exhibits superior extrusion and durability and is highly flame and corrosion resistant. Material experiences major applications in fields of aeronautics and safety.

  18. Surface wettability studies of PDMS using flame plasma treatment

    E-print Network

    Wang, Xin C

    2009-01-01

    The flame plasma treatment studied in this thesis was able to oxidize the surface of Polydimethylsiloxane (PDMS) in a fraction of a second. It was found to be a much faster way to modify PDMS surface wettability than the ...

  19. Physics-based flame dynamics modeling and thermoacoustic instability mitigation

    E-print Network

    Altay, Hurrem Murat

    2009-01-01

    The objectives of this work are (i) to investigate the coupled unsteady heat release mechanisms responsible for thermoacoustic instabilities under different flame anchoring configurations, (ii) to develop reduced-order ...

  20. The effect of fuel composition on flame dynamics

    SciTech Connect

    Hendricks, Adam G.; Vandsburger, Uri [Department of Mechanical Engineering - 0238, Virginia Tech, Blacksburg, VA 24061 (United States)

    2007-10-15

    As fuel sources diversify, the gas turbine industry is under increasing pressure to develop fuel-flexible plants, able to use fuels with a variety of compositions from a large range of sources. However, the dynamic characteristics vary considerably with composition, in many cases altering the thermoacoustic stability of the combustor. We compare the flame dynamics, or the response in heat release rate of the flame to acoustic perturbations, of the three major constituents of natural gas: methane, ethane, and propane. The heat release rate is quantified using OH* chemiluminescence and product gas temperature. Gas temperature is measured by tracking the absorption of two high-temperature water lines, via Tunable Diode Laser Absorption Spectroscopy. The flame dynamics of the three fuels differ significantly. The changes in flame dynamics due to variations in fuel composition have the potential to have a large effect on the thermoacoustic stability of the combustor. (author)

  1. Lean flammability limit of downward propagating hydrogen-air flames

    NASA Technical Reports Server (NTRS)

    Patnaik, G.; Kailasanath, K.

    1992-01-01

    Detailed multidimensional numerical simulations that include the effects of wall heat losses have been performed to study the dynamics of downward flame propagation and extinguishment in lean hydrogen-air mixtures. The computational results show that a downward propagating flame in an isothermal channel has a flammability limit of around 9.75 percent. This is in excellent agreement with experimental results. Also in excellent agreement are the detailed observations of the flame behavior at the point of extinguishment. The primary conclusion of this work is that detailed numerical simulations that include wall heat losses and the effect of gravity can adequately simulate the dynamics of the extinguishment process in downward-propagating hydrogen-air flames. These simulations can be examined in detail to gain understanding of the actual extinction process.

  2. Improved method for flame detection in combustion turbines

    SciTech Connect

    Roby, R.; Hamer, A.J.; Johnsson, E.L. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Mechanical Engineering; Tilstra, S.A.; Burt, T.J. [Rosemount Aerospace, Inc., Eagan, MN (United States)

    1994-12-31

    A fast response chemiluminescent flame detection approach is presented along with field test results from a fiber optic based flame detector device. Chemiluminescence, the light given off by molecules formed in their excited states, has long been recognized as a diagnostics method for use in combustion. The recent advent of higher quality optical fibers with improved transmission properties in the UV, as well as UV optical detectors, has made the use of chemiluminescence for gas turbine diagnostics and monitoring practical. Advances in combustor designs on now low emissions machines as well as reliability issues with some existing machines are creating the need for improved flame dynamics measurements as well as improvements in reliability for existing measurements such as combustor flame detection. This paper discusses the technology, principle of operation, and detectors which operate on the chemiluminescence principle.

  3. Improved method for flame detection in combustion turbines

    SciTech Connect

    Roby, R.J.; Hamer, A.J.; Johnsson, E.L. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States). Dept. of Mechanical Engineering; Tilstra, S.A.; Burt, T.J. [Rosemount Aerospace, Inc., Eagan, MN (United States)

    1995-04-01

    A fast response chemiluminescent flame detection approach is presented along with field test results from a fiber optic based flame detector device. Chemiluminescence, the light given off by molecules formed in their excited states, has long been recognized as a diagnostics method for use in combustion. The recent advent of higher quality optical fibers with improved transmission properties in the UV, as well as UV optical detectors, has made the use of chemiluminescence for gas turbine diagnostics and monitoring practical. Advances in combustor designs on a new low-emissions machines as well as reliability issues with some existing machines are creating the need for improved flame dynamics measurements as well as improvements in reliability for existing measurements such as combustor flame detection. This paper discusses the technology, principle of operation, and detectors that operate on the chemiluminescence principle.

  4. Residence Time Control in Flame Spread over Solid Fuels

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Subrata; Kumar, Chittory

    Flame spread over solid fuels in an opposed-flow environment has been investigated for over four decades for understanding the fundamental nature of hazardous fire spread. The appeal for this configuration stems from the fact that flame spread rate remains steady even if the flame itself may grow in size. For practical fire-safety issues on earth, however, concurrent-flow or wind-assisted flame spread is more relevant. Although there is a good amount of literature on both of these configurations, a connection between the two regimes is yet to be established. The microgravity regime can be thought to be sitting between these two regimes, where the oxidizer flow can be mild or even completely absent, drastically increasing the residence time of the oxidizer flow. It is well established that the dominance of radiation in the microgravity regime stems from the increased residence time -the ratio of the characteristic length of the flame to the characteristic oxidizer velocity -due to small velocity scale. In terrestrial flames, however, the induced flow due to buoyancy reduces the residence time for small flames (as encountered in opposed-flow flame spread) and there is not sufficient time for the radiative transport to become significant compared to advection. Therefore, radiative effects are observed only in large fires, where the residence time goes up due to the increased flame height. Only in large fires does radiative transport become significant when the residence time is high due to size. In this work, we present a simple but novel ground-based experimental set up that allows residence time to be experimentally varied in a controlled manner with the resulting flame transitioning from wind-opposed to wind-aided regime. We have constructed a 8 meter high flame tower at SDSU in which, after a sample is ignited in a downward-spread configuration, the sample holder, placed in an open moveable cart, can be traversed at any desired speed upward or downward. The cart velocity can be controlled to create any desired external flow of oxidizer relative to the sample. When the cart is moved downward, a forced flow equal to the cart velocity is added to the buoyancy induced flow, thereby reducing the residence time. On the other hand, when the cart is moved upward, the forced flow works against the induced flow, possibly increasing the residence time. If the upward velocity is large enough, the downward forced flow experienced by the flame may overwhelm the upward buoyancy induced flow and create a wind-assisted downward flame spread. By varying the cart velocity, it may be possible to go from one extreme regime to another -wind-opposed flame extinction to wind-aided flame extinction with high residence time flames created in the middle. We will present some preliminary results obtained in this experimental set up.

  5. The Rubens Tube: A Flaming Good Way to Teach Waves

    ERIC Educational Resources Information Center

    Sandoval, Christopher

    2013-01-01

    The Ruben Flame Tube is named after H. Ruben, who published the demonstration experiment in "Annalen der Physik" in 1905. This article presents one of the many demonstrations the author uses to engage, motivate, and challenge his students.

  6. Burning To Learn: An Introduction to Flame Retardants.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 2001

    2001-01-01

    Presents an activity that demonstrates the effectiveness of flame retardants--substances added to combustible materials to slow down or hinder burning--that can be introduced when discussing combustion reactions or during a practical or everyday chemistry unit. (ASK)

  7. Probing flame chemistry with MBMS, theory, and modeling

    SciTech Connect

    Westmoreland, P.R. [Univ. of Massachusetts, Amherst (United States)

    1993-12-01

    The objective is to establish kinetics of combustion and molecular-weight growth in C{sub 3} hydrocarbon flames as part of an ongoing study of flame chemistry. Specific reactions being studied are (1) the growth reactions of C{sub 3}H{sub 5} and C{sub 3}H{sub 3} with themselves and with unsaturated hydrocarbons and (2) the oxidation reactions of O and OH with C{sub 3}`s. This approach combines molecular-beam mass spectrometry (MBMS) experiments on low-pressure flat flames; theoretical predictions of rate constants by thermochemical kinetics, Bimolecular Quantum-RRK, RRKM, and master-equation theory; and whole-flame modeling using full mechanisms of elementary reactions.

  8. Calculations of premixed turbulent flames by pdf methods

    SciTech Connect

    Anand, M.S.; Pope, S.B.

    1987-02-01

    Idealized premixed turbulent flames are studied using probability density function (pdf) methods. A modeled transport equation for the joint pdf of velocity and the reaction progress variable is solved by a Monte Carlo method. Detailed calculations of flame properties and flow statistics, including the flame speed, the scalar flux, the turbulence intensities, the kinetic energy budget and conditional statistics are presented for different density ratios. Results are compared with the limited available experimental data and the calculations based on the Bray-Moss-Libby (BML) model. Compared to the BML model, the present pdf approach has several advantages: few processes have to be modeled, more information can be extracted from the solution, and the method is directly applicable to multidimensional flames.

  9. PDF calculations of piloted turbulent nonpremixed flames of methane

    SciTech Connect

    Masri, A.R. (Dept. of Mechanical Engineering, Univ. of Sydney, Sydney (AU)); Pope, S.B. (Sibley School of Mechanical Aerospace Engineering, Cornell Univ., Ithaca, NY (US))

    1990-07-01

    A velocity-composition joint pdf transport equation has been solved by the Monte Carlo method to calculate the structure of pilot-stabilized turbulent nonpremixed flames of methane. Three components of velocity and a conserved scalar, namely, mixture fraction, {xi} are jointly represented in the pdf. A new model is used for turbulent frequency. Turbulent dissipation and the fluctuating pressure gradient terms are conditionally modeled. Two simple models for thermochemistry are used. In one, density is a piecewise function of {xi}, and in the other, density is obtained from calculations of a laminar counterflow diffusion flame of methane with a stretch rate, a = 100 s{sup {minus}1}. Calculations are compared with the corresponding experimental measurements performed on a number of flames ranging from flames with low mixing rates to ones close to extinction. The velocity, turbulence, and mixing fields are predicted with reasonable accuracy down to {chi}/D{sub j} {approximately} 30.

  10. Cat Health Problem Might Be Linked to Flame Retardants

    MedlinePLUS

    ... nlm.nih.gov/medlineplus/news/fullstory_152327.html Cat Health Problem Might Be Linked to Flame Retardants ... linked to a common health problem in pet cats, a new study from Sweden says. Researchers found ...

  11. View down into vertical flame channel of Test Stand 'A' ...

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

    View down into vertical flame channel of Test Stand 'A' from superstructure. Wooden platform open side faces west. - Jet Propulsion Laboratory Edwards Facility, Test Stand A, Edwards Air Force Base, Boron, Kern County, CA

  12. 1. FLAME DEFLECTOR FROM FERROCEMENT APRON, VIEW TOWARDS NORTHEAST. ...

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

    1. FLAME DEFLECTOR FROM FERROCEMENT APRON, VIEW TOWARDS NORTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  13. 4. CLOSE UP OF FLAME DEFLECTOR, VIEW TOWARDS SOUTHEAST. ...

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

    4. CLOSE UP OF FLAME DEFLECTOR, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  14. 10. STATIC TEST TOWER CLOSEUP OF COOLING PIPES OF FLAME ...

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

    10. STATIC TEST TOWER CLOSE-UP OF COOLING PIPES OF FLAME DEFLECTOR PIT ON NORTH ELEVATION. - Marshall Space Flight Center, Saturn Propulsion & Structural Test Facility, East Test Area, Huntsville, Madison County, AL

  15. 6. FLAME DEFLECTOR, VIEW TOWARDS NORTHWEST. Glenn L. Martin ...

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

    6. FLAME DEFLECTOR, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  16. 1. FLAME DEFLECTOR AT LEFT, COUNTERFORT AT RIGHT, VIEW TOWARDS ...

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

    1. FLAME DEFLECTOR AT LEFT, COUNTERFORT AT RIGHT, VIEW TOWARDS SOUTH. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  17. 5. CLOSE UP OF FLAME DEFLECTOR, COUNTERFORT VISIBLE AT REAR, ...

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

    5. CLOSE UP OF FLAME DEFLECTOR, COUNTERFORT VISIBLE AT REAR, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  18. 4. DETAIL SHOWING FLAME DEFLECTOR. Looking southeast. Edwards Air ...

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

    4. DETAIL SHOWING FLAME DEFLECTOR. Looking southeast. - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Test Stand 1-A, Test Area 1-120, north end of Jupiter Boulevard, Boron, Kern County, CA

  19. 25. STATIC TEST TOWER WEST SIDE STANDING ON FLAME ...

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

    25. STATIC TEST TOWER WEST SIDE - STANDING ON FLAME DEFLECTOR GRILL LOOKING UP TOWARDS F-1 ENGINE SET UP. - Marshall Space Flight Center, Saturn Propulsion & Structural Test Facility, East Test Area, Huntsville, Madison County, AL

  20. 8. NORTH FLAME DEFLECTOR, VIEW TOWARDS WEST. Glenn L. ...

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

    8. NORTH FLAME DEFLECTOR, VIEW TOWARDS WEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  1. 3. FLAME DEFLECTOR AT CENTER, CONNECTING TUNNEL AT CENTER RIGHT, ...

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

    3. FLAME DEFLECTOR AT CENTER, CONNECTING TUNNEL AT CENTER RIGHT, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  2. 7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR ...

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

    7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR AT RIGHT, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  3. Flame Deflector Section, Elevation, Water Supply Flow Diagram, Exploded ...

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

    Flame Deflector - Section, Elevation, Water Supply Flow Diagram, Exploded Deflector Manifolds, and Interior Perspective - Marshall Space Flight Center, F-1 Engine Static Test Stand, On Route 565 between Huntsville and Decatur, Huntsville, Madison County, AL

  4. 7. FLAME DEFLECTOR, VIEW TOWARDS SOUTHWEST. Glenn L. Martin ...

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

    7. FLAME DEFLECTOR, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  5. 6. FLAME DEFLECTOR AT LEFT, COUNTERFORT AT RIGHT, VIEW TOWARDS ...

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

    6. FLAME DEFLECTOR AT LEFT, COUNTERFORT AT RIGHT, VIEW TOWARDS EAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  6. 2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW ...

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

    2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  7. 5. SOUTHEAST FLAME DEFLECTOR, VIEW TOWARDS NORTHWEST. Glenn L. ...

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

    5. SOUTHEAST FLAME DEFLECTOR, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  8. 9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS ...

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

    9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  9. 2. CLOSE UP OF FLAME DEFLECTOR FROM FERROCEMENT APRON, VIEW ...

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

    2. CLOSE UP OF FLAME DEFLECTOR FROM FERROCEMENT APRON, VIEW TOWARDS NORTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  10. 3. SOUTH FLAME DEFLECTOR FROM THE REINFORCED CONCRETE ROOF, VIEW ...

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

    3. SOUTH FLAME DEFLECTOR FROM THE REINFORCED CONCRETE ROOF, VIEW TOWARDS EAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  11. DEMONSTRATION BULLETIN: FLAME REACTOR - HORSEHEAD RESOURCE DEVELOPMENT COMPANY, INC.

    EPA Science Inventory

    The Horsehead Resource Development Company, Inc. (HRD) Flame Reactor is a patented and proven high temperature thermal process designed to safely treat industrial residues and wastes containing metals. During processing, the waste material is introduced into the hottest portio...

  12. Improving Kepler Pipeline Sensitivity with Pixel Response Function Photometry.

    NASA Astrophysics Data System (ADS)

    Morris, Robert L.; Bryson, Steve; Jenkins, Jon Michael; Smith, Jeffrey C

    2014-06-01

    We present the results of our investigation into the feasibility and expected benefits of implementing PRF-fitting photometry in the Kepler Science Processing Pipeline. The Kepler Pixel Response Function (PRF) describes the expected system response to a point source at infinity and includes the effects of the optical point spread function, the CCD detector responsivity function, and spacecraft pointing jitter. Planet detection in the Kepler pipeline is currently based on simple aperture photometry (SAP), which is most effective when applied to uncrowded bright stars. Its effectiveness diminishes rapidly as target brightness decreases relative to the effects of noise sources such as detector electronics, background stars, and image motion. In contrast, PRF photometry is based on fitting an explicit model of image formation to the data and naturally accounts for image motion and contributions of background stars. The key to obtaining high-quality photometry from PRF fitting is a high-quality model of the system's PRF, while the key to efficiently processing the large number of Kepler targets is an accurate catalog and accurate mapping of celestial coordinates onto the focal plane. If the CCD coordinates of stellar centroids are known a priori then the problem of PRF fitting becomes linear. A model of the Kepler PRF was constructed at the time of spacecraft commissioning by fitting piecewise polynomial surfaces to data from dithered full frame images. While this model accurately captured the initial state of the system, the PRF has evolved dynamically since then and has been seen to deviate significantly from the initial (static) model. We construct a dynamic PRF model which is then used to recover photometry for all targets of interest. Both simulation tests and results from Kepler flight data demonstrate the effectiveness of our approach. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA’s Science Mission Directorate.Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA’s Science Mission Directorate.

  13. Gravity effects on flame spreading over solid surfaces

    NASA Technical Reports Server (NTRS)

    Andracchio, C. R.; Cochran, T. H.

    1976-01-01

    The effects of gravity on the spreading of a flame over a solid combustible surface were determined. Flame propagation rates were measured from specimens of thin cellulose acetate sheets burning in both normal gravity (1 g) and reduced gravity (0 g) environments; the specimens were burned in various quiescent mixtures of oxygen, helium, argon, and nitrogen. A correlation for normal gravity and reduced gravity burning was obtained based on theoretical models of previous investigators.

  14. Spectral flame radiance from a tubular-can combustor

    NASA Technical Reports Server (NTRS)

    Claus, R. W.

    1981-01-01

    An experimental investigation was conducted to determine the effects of fuel type, fuel-air ratio, and inlet-air pressure on the spectral flame radiance emanating from a JT8D can combustor. Spectral radiance measurements from 1.55 to 5.5 micrometers of wavelength were recorded and analyzed to determine soot concentration and flame temperature at various axial locations in the combustor. Two fuels differing in volatility, viscosity, and chemical composition were used in this investigation.

  15. Structure and Stability of Burke-Schumann Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Lee, Yong G.; Chen, Lea-Der; Brooker, John E.; Stocker, Dennis P.

    1997-01-01

    The general goal of this NASA Grant is twofold: to improve our understanding of (1) the influence of buoyancy on the stability and structure of Burke-Schumann type diffusion flames, and (2) the effects of buoyancy on vortex-flame interactions in co-flow diffusion flames. A numerical code with a higher order accuracy for spatial discretization is developed in this project for simulation of time-dependent diffusion flames by Sheu and Sheu and Chen, and an extended reduced mechanism is incorporated for prediction of methane oxidation and NO(x)(NO, NO2, and N2O) formation and emission from methane Burke-Schumann diffusion flame (BSDF) as reported in Sheu, and Sheu and Chen. Initial investigation of vortex and flame interaction within the context of fast chemistry is reported. Experiments are conducted in reduced pressure to study the lift-off and stabilization of methane-fueled BSDF in reduced buoyancy environments due to reduced pressure. Measurements of temperature and species concentrations are made in normal and reduced pressure environments to study the effects of buoyancy on the structure of BSDF, and will be reported in this paper. To study the buoyancy effects on the lift-off and stabilization of methane-fueled jet diffusion flames in coflowing air, a glovebox investigation, Enclosed Laminar Flames (ELF), has been proposed and approved for space-based testing on the fourth United States Microgravity Payload (USMP-4) mission, scheduled for October 1997. A brief description of the ELF investigation is also presented.

  16. Spherically Symmetric Flame Propagation in Hydrogen-Air Mixtures

    Microsoft Academic Search

    G. Dixon-Lewis

    1983-01-01

    Abstract–A Lagragian finite difference procedure is outlined for the modelling of constant pressure, spherically summetric, laminar flames, with detailed chemistry and transport property representation. The procedure is used for modelling spherically expanding hydrogen-air flames such as are obtained during the early, pre-pressure period of constant volume bomb explosions with single spark ignition at the centre. For modelling purposes, such explosions

  17. Efficiencies of low-momentum jet diffusion flames in crosswinds

    Microsoft Academic Search

    M. R. JOHNSON; L. W. KOSTIUK

    2000-01-01

    Low-momentum propane, natural gas, and propane\\/CO2 diffusion flames in a crosswind were studied experimentally using a closed-loop wind tunnel. Flames were established at the exit of a burner tube mounted vertically in the wind tunnel and perpendicular to the airflow, a configuration that is relevant to continuous gas flaring in the atmosphere. Analysis of the products of combustion showed that

  18. Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

    NASA Technical Reports Server (NTRS)

    Sun, Z.; Huertas, J. I.; Axelbaum, R. L.

    1999-01-01

    Two critical challenges facing the application of flames for synthesis of nanopowder materials are: (1) overcoming formation of agglomerates and (2) ensuring that the highly reactive nanopowders that are synthesized in flames can be produced in such a manner that their purity is maintained during subsequent processing. Agglomerates are produced in flames because particle formation occurs in a high temperature and high number density environment. They are undesirable in most advanced applications of powders. For example, agglomerates have a deleterious effect on compaction density, leading to voids when nanopowders are consolidated. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Powder purity must also be maintained during subsequent handling of nanopowders and this poses a significant challenge for any synthesis route because nanopowders, particularly metals and non-oxide ceramic powders, are inherently reactive. Impurities acquired during handling of nanopowders have slowed the advancement of the nanostructured materials industry. One promising approach that has been proposed to address these problems is nano-encapsulation. In this approach, the core particles are encapsulated in a removable material while they are within the flame but before excessive agglomeration has occurred. Condensation can be very rapid so that core particles are trapped within the condensed material and agglomeration is limited. Nano-encapsulation also addresses the handling concerns for post-synthesis processing. Results have shown that when nano-encapsulated powders are exposed to atmosphere the core particles are protected from oxidation and/or hydrolysis. Thus, handling of the powders does not require extreme care. If, for example, at the time of consolidation the encapsulation material is removed by vacuum annealing, the resulting powder remains unagglomerated and free of impurities. In this work, we described a novel aerosol model that has been developed to simulate particle encapsulation in flames. The model will ultimately be coupled to a one-dimensional spherical flame code and compared to results from microgravity flame experiments.

  19. The O stars sample of the Tarantula-FLAMES survey

    NASA Astrophysics Data System (ADS)

    Sabín-Sanjulián, C.; Herrero, A.; Simón-Díaz, S.; Lennon, D. J.; Evans, C. J.

    2011-11-01

    The Tarantula FLAMES Survey is an ESO Large Program aimed at disentangling the role of binarity in the evolution of massive stars. We have multiepoch, high resolution and SNR observations of about 1000 massive OB stars in 30 Dor secured with the FLAMES spectrograph at VLT. In this poster we present a general view of the project and the main characteristics of the O star subsample.

  20. Combustion synthesis of titania nanoparticles in a premixed methane flame

    Microsoft Academic Search

    Hsiao-Kang Ma; Hsiung-An Yang

    2010-01-01

    Previous studies have shown that titanium tetra-isopropoxide (TTIP) can be a substitute in the production of non-poisonous and inexpensive nanostructured titania (TiO2) particles. This study discusses the combustion characteristics of synthesized titania obtained while adding TTIP into the premixed methane\\/air flames. As the TTIP concentration increased, a bright yellow flame brush, representing a region of titania nanoparticles production, appeared on

  1. Formation and Combustion of Smoke in Laminar Flames

    NASA Technical Reports Server (NTRS)

    Schalla, Rose L; Clark, Thomas P; Mcdonald, Glen E

    1954-01-01

    The nature and formation of smoke and its combustion were investigated. Smoke, which consist of tiny mesomorphous crystals tightly packed into popcorn-ball-like particles that agglomerate to give filaments, was found to contain about 5 percent of the hydrogen originally present in the fuel. Factors affecting smoke formation were studied in both diffusion flames and premixed Bunsen flames. It is suggested that smoking tendency increases with increasing stability of the carbon skeleton of the molecule, as determined by relative bond strength.

  2. Flame retardancy of paulownia wood and its mechanism

    Microsoft Academic Search

    Peng Li; Juhachi Oda

    2007-01-01

    Paulownia wood (Pauloumia tomentosa) is a special kind of wood material in that it has especially excellent flame retardancy.\\u000a Using this property, it has been commonly used to make clothing wardrobes for a long time in Japan. In this research, the\\u000a flame retardancy of paulownia wood has been verified by heating experiments and cone calorimeter testing. The structure and\\u000a tissue

  3. Development of Flame Retardants for Engineering Polymers and Polyurethanes

    NASA Astrophysics Data System (ADS)

    Desikan, Anantha

    2013-03-01

    With a broad portfolio of brominated, organophosphorus and inorganic flame retardants, ICL Industrial Products (ICL-IP) is engaged in the development of new flame retardants by exploiting the synergism between bromine based, phosphorus based and other halogen-free flame retardants. ICL-IP is also focusing on the development of polymeric and reactive flame retardants. This presentation will give examples of existing and new polymeric and reactive products for applications in thermoplastics, thermosets and polyurethane foam. This presentation will also show examples of phosphorus-bromine synergism allowing partial or complete elimination of antimony trioxide in many thermoplastics for electronic applications. New synergistic combinations of magnesium hydroxide with phosphorus and other halogen-free FRs will be presented. With a broad portfolio of brominated, organophosphorus and inorganic flame retardants, ICL Industrial Products (ICL-IP) is engaged in the development of new flame retardants by exploiting the synergism between bromine based, phosphorus based and other halogen-free flame retardants. ICL-IP is also focusing on the development of polymeric and reactive flame retardants. This presentation will give examples of existing and new polymeric and reactive products for applications in thermoplastics, thermosets and polyurethane foam. This presentation will also show examples of phosphorus-bromine synergism allowing partial or complete elimination of antimony trioxide in many thermoplastics for electronic applications. New synergistic combinations of magnesium hydroxide with phosphorus and other halogen-free FRs will be presented. Work done in collaboration with S. Levchik, ICL-IP America, 430 Saw Mill Rriver Rd., Ardsley, NY, 10502, USA and M. Leifer, ICL-IP, P. O. Box 180, Beer Sheva 84101, Israel.

  4. Infrared Flame Detection System Using Multiple Neural Networks

    Microsoft Academic Search

    Javid J. Huseynov; Shankar B. Baliga; Alan Widmer; Zvi Boger

    2007-01-01

    A model for an infrared (IR) flame detection system using multiple artificial neural networks (ANN) is presented. The present work offers significant improvements over our previous design (1). Feature extraction only in the relevant frequency band using joint time-frequency analysis yields an input to a series of conjugate-gradient (CG) method-based ANNs. Each ANN is trained to distinguish all hydrocarbon flames

  5. Active control of lifted diffusion flames with arrayed micro actuators

    Microsoft Academic Search

    N. Kurimoto; Y. Suzuki; N. Kasagi

    2005-01-01

    Active control of a lifted flame issued from a coaxial nozzle is investigated. Arrayed micro flap actuators are employed to\\u000a introduce disturbances locally into the initial shear layer. Shedding of large-scale vortex rings is modified with the flap\\u000a motion, and the flame characteristics such as liftoff height, blowoff limit, and emission trend, are successfully manipulated.\\u000a Spatio-temporal evolution of large-scale vortical

  6. Soot formation in hydrocarbon\\/air laminar jet diffusion flames

    Microsoft Academic Search

    P. B. Sunderland; G. M. Faeth

    1996-01-01

    Soot processes along the axes of round laminar jet diffusion flames were studied, considering ethane, propane, n-butane, ethylene, propylene, and 1,3-butadiene burning in air at pressures of 25–99 kPa. Measurements included soot volume fractions, temperatures, soot structure, concentrations of major gas species and gas velocities. As distance increased along the axes of the flames, significant soot formation began when temperatures

  7. Numerical simulation of a premixed turbulent V-flame

    SciTech Connect

    Bell, John B.; Day, Marc S.; Grcar, Joseph F.; Lijewski, Michael J.; Johnson, Matt R.; Cheng, Robert K.; Shepherd, Ian G.

    2003-07-27

    We present three-dimensional, time-dependent simulations of a full-size laboratory-scale rod-stabilized premixed turbulent V-flame. The computations use an adaptive projection method based on a low Mach number formulation that incorporates detailed chemical kinetics and transport. The simulations are performed without introducing models for turbulence or turbulence chemistry interaction. We outline the numerical procedure and experimental setup, and compare computed results to mean flame location and surface wrinkling statistics gathered from experiment.

  8. A detailed numerical investigation of Burke-Schumann gaseous and spray flames

    NASA Technical Reports Server (NTRS)

    Mawid, M. A.; Aggarwal, S. K.

    1991-01-01

    The classical Burke-Schumann gaseous diffusion flame, and the effect of introducing fuel in the form of liquid sprays are investigated numerically. The time-dependent two-dimensional, axisymmetric conservation equations are solved for the gas phase. A Lagrangian approach is used for the dispersed phase. The chemical reactions are modeled through the one-step global reaction scheme. The numerical results show that the computed flame structure is significantly different from that given by the analytical solution. The computed flame is about 15 percent longer and 5 percent narrower than the classical Burke-Schumann flame. The predicted flame shape is, however, in better agreement with experimental observations than the Burke-Schumann flame. The effects of introducing liquid sprays is found to produce thinner and longer flames than its counterpart gaseous flame. A detailed comparison of the structures of gaseous and spray flames is made, and the differences are discussed.

  9. Influence of gas compression on flame acceleration in the early stage of burning in tubes

    E-print Network

    Valiev, Damir; Kuznetsov, Mikhail; Eriksson, Lars-Erik; Law, Chung K; Bychkov, Vitaly

    2012-01-01

    The mechanism of finger flame acceleration at the early stage of burning in tubes has been observed experimentally by Clanet and Searby [Combust. Flame 105: 225 (1996)] for slow propane-air flames, and elucidated analytically and computationally by Bychkov et al. [Combust. Flame 150: 263 (2007)] in the limit of an incompressible flow. We analytically, experimentally and computationally study herein the finger flame acceleration for fast burning flames, when the gas compressibility assumes an important role. Specifically, we have developed a theory through small Mach number expansion up to the first-order terms, demonstrating that gas compression reduces the acceleration rate and thereby moderates the finger flame acceleration noticeably. We have also conducted experiments for hydrogen-oxygen mixtures with considerable initial values of the Mach number, showing finger flame acceleration with the acceleration rate much smaller than those obtained previously for hydrocarbon flames. Furthermore, we have performed...

  10. Combustion Research Program: Flame studies, laser diagnostics, and chemical kinetics

    SciTech Connect

    Crosley, D.R.

    1992-09-01

    This project has comprised laser flame diagnostic experiments, chemical kinetics measurements, and low pressure flame studies. Collisional quenching has been investigated for several systems: the OH radical, by H{sub 2}0 in low pressure flames; the rotational level dependence for NH, including measurements to J=24; and of NH{sub 2} at room temperature. Transition probability measurements for bands involving v{prime} = 2 and 3 of the A-X system of OH were measured in a flame. Laser-induced fluorescence of vinyl radicals was unsuccessfully attempted. RRKM and transition state theory calculations were performed on the OH + C{sub 2}H{sub 4} reaction, on the t-butyl radical + HX; and transition state theory has been applied to a series of bond scission reactions. OH concentrations were measured quantitatively in low pressure H{sub 2}/N{sub 2}O and H{sub 2}/O{sub 2} flames, and the ability to determine spatially precise flame temperatures accurately using OH laser-induced fluorescence was studied.

  11. Flame Spread and Extinction in Partial-Gravity Environments

    NASA Technical Reports Server (NTRS)

    Sacksteder, Kurt; Ferkul, P. V.; T'ien, J. S.

    1999-01-01

    Considerable progress has been made in understanding the mechanisms of spreading flames under certain conditions, nearly all under the influence of normal Earth gravity. Recently, several investigators have studied some aspects of flame spread in purely forced flows in microgravity. However, very few have considered (especially experimentally) purely-buoyant flow influences, using gravity as a variable. In addition to the scientific interest in understanding how variable gravity affects flame spread in purely-buoyant flow, prospective human exploration of the Moon and Mars provides an incentive to obtain practical knowledge for use in fire-safety related engineering and mission operations in those partial-gravity environments. The purpose of this research effort is to conduct a focused experimental effort to observe the behavior of flames spreading both upward (concurrent flow) and downward (opposed flow) over thin fuels in partial-gravity environments, and to extend an existing numerical model of flame spread to predict flammability and flame spread behavior in these two regimes. A significant aspect of the experimental effort is to use a special device to improve the simulated partial-gravity environment achievable aboard reduced-gravity aircraft facilities.

  12. Flame Spread Along Free Edges of Thermally Thin Samples in Microgravity

    NASA Technical Reports Server (NTRS)

    Mell, W. E.; Olson, S. L.; Kashiwagi, T.

    2000-01-01

    The effects of imposed flow velocity on flame spread along open edges of a thermally thin cellulosic sample in microgravity are studied experimentally and theoretically. In this study, the sample is ignited locally at the middle of the 4 cm wide sample and subsequent flame spread reaches both open edges of the sample. The following flame behaviors are observed in the experiments and predicted by the numerical calculation; in order of increased imposed flow velocity: (1) ignition but subsequent flame spread is not attained, (2) flame spreads upstream (opposed mode) without any downstream flame, and (3) the upstream flame and two separate downstream flames traveling along the two open edges (concurrent mode). Generally, the upstream and downstream edge flame spread rates are faster than the central flame spread rate for an imposed flow velocity of up to 5 cm/s. This is due to greater oxygen supply from the outer free stream to the edge flames than the central flames, For the upstream edge flame, the greater oxygen supply results in a flame spread rate that is nearly independent of, or decreases gradually, with the imposed flow velocity. The spread rate of the downstream edge, however, increases significantly with the imposed flow velocity.

  13. Experimental and Computational Study of Flame Inhibition Mechanisms of Halogenated Compounds in C1-C3 Alkanes Flames

    E-print Network

    Osorio Amado, Carmen H

    2013-07-30

    EXPERIMENTAL AND COMPUTATIONAL STUDY OF FLAME INHIBITION MECHANISMS OF HALOGENATED COMPOUNDS IN C1-C3 ALKANES FLAMES A Dissertation by CARMEN HELENA OSORIO AMADO Submitted to the Office of Graduate Studies of Texas A&M University... Chair, Ibrahim Karaman August 2013 Major Subject: Materials Science and Engineering Copyright 2013 Carmen Helena Osorio Amado ii ABSTRACT After the restriction of different halogenated fire suppressants by the Montreal Protocol...

  14. Quantitative measurement of soot particle size distribution in premixed flames - The burner-stabilized stagnation flame approach

    SciTech Connect

    Abid, Aamir D.; Camacho, Joaquin; Sheen, David A.; Wang, Hai [Aerospace and Mechanical Engineering Department, University of Southern California, Los Angeles, CA 90089 (United States)

    2009-10-15

    A burner-stabilized, stagnation flame technique is introduced. In this technique, a previously developed sampling probe is combined with a water-cooled circular plate such that the combination simultaneously acts as a flow stagnation surface and soot sample probe for mobility particle sizing. The technique allows for a rigorous definition of the boundary conditions of the flame with probe intrusion and enables less ambiguous comparison between experiment and model. Tests on a 16.3% ethylene-23.7% oxygen-argon flame at atmospheric pressure show that with the boundary temperatures of the burner and stagnation surfaces accurately determined, the entire temperature field may be reproduced by pseudo one-dimensional stagnation reacting flow simulation using these temperature values as the input boundary conditions. Soot particle size distribution functions were determined for the burner-stabilized, stagnation flame at several burner-to-stagnation surface separations. It was found that the tubular probe developed earlier perturbs the flow and flame temperature in a way which is better described by a one-dimensional stagnation reacting flow than by a burner-stabilized flame free of probe intrusion. (author)

  15. Interaction of a flame front with its self-generated flow in an enclosure; The tulip flame phenomenon

    SciTech Connect

    Gonzalez, M.; Borghi, R.; Saouab, A. (Univ. de Rouen, Mont-Saint-Aignan (FR))

    1992-02-01

    This paper reports on the propagation of a flame front under nonturbulent condition in a closed tube ignited at one end which is numerically investigated using a computing procedure based on finite volumes technique and devoted to two-dimensional, compressible, reacting flows. A global one-step reaction for the chemical process and an Arrhenius law for fuel consumption are assumed. The detailed analysis of the results of computations in which wall friction, tube aspect ratio and initial flame configuration are varied allows to highlight the influence of different parameters and to get more insight into the tulip-shaped flame phenomenon. In particular, Darrieus-landau instability is examined by comparing the shape variations of an initially perturbed flat front in a tube closed at both ends to those in a tube in which the ignition end is open while the opposite one is closed. Attention is also given to the computed flame generated flowfield; the flame front-confined flow interaction is specially scrutinized. Furthermore, the oscillatory acoustic regime occurring during tulip flame appearance, as well as the collapse of the tulip shape in tubes of large aspect ratio, already experimentally put into evidence but never numerically addressed, have also been simulated and discussed.

  16. LDA study of non-steady flame propagation in a constant volume duct

    SciTech Connect

    Dunn-Rankin, D.; Cheng, R.K.; Sawyer, R.F.

    1984-09-01

    This work investigates the development of tulip shaped flames during laminar flame propagation in a closed duct. In particular the interaction of a laminar flame front with its self-induced non-steady flow field is examined as a possible source of the tulip phenomenon. The flame generated flow is measured with a laser Doppler anemometer (LDA). The flame shape and its position are recorded with high-speed schlieren cinematography. Comparison of the qualitative schlieren and the quantitative LDA data records provides insight into the flame/flow relationship.

  17. Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

    NASA Technical Reports Server (NTRS)

    Sun, Z.; Huertas, J. I.; Axelbaum, R. L.

    1999-01-01

    Gas-phase combustion (flame) synthesis has been an essential industrial process for producing large quantities of powder materials such as carbon black, titanium dioxide, and silicon dioxide. Flames typically produce simple oxides, with carbon black being the noted exception because the oxides of carbon are gaseous and are easily separated from the particulate matter that is formed during fuel pyrolysis. Furthermore, the powders produced in flames are usually agglomerated, nanometer-sized particles (nanoparticles). This composition and morphology is acceptable for many applications. However, the present interest in nanoparticles for advanced materials application has led to efforts to employ flames for the synthesis of unagglomerated nanoparticles (2 to 100 nm) of metals and non-oxide ceramics. Sodium-halide chemistry has proven to be viable for producing metals and non-oxide ceramics in flames. Materials that have been produced to date include Si (Calcote and Felder, 1993), TiN, TiB2, TiC, TiSi2, SiC, B4C (Glassman et al, 1993) Al, W, Ti, TiB2, AlN, and W-Ti and Al-AlN composites (DuFaux and Axelbaum, 1995, Axelbaum et al 1996,1997). Many more materials are possible. The main challenge that faces application of flame synthesis for advanced materials is overcoming formation of agglomerates in flames (Brezinsky, 1997). The high temperatures and high number densities in the flame environment favor the formation of agglomerates. Agglomerates must be avoided for many reasons. For example, when nanopowders are consolidated, agglomerates have a deleterious effect on compaction density, leading to voids in the final part. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Another critical challenge that faces all synthesis routes for nanopowders is ensuring that the powders are high purity and that the process is scaleable. Though the containerless, high temperature environment of a flame is excellent for producing high-purity simple compounds, ultrafine metals and non-oxide ceramic powders are inherently reactive in the presence of oxygen and/or moisture. Thus, the handling of these powders after synthesis poses a challenging problem. Impurities acquired during handling of nanoparticles have plagued the advancement of nanostructured materials technology.

  18. Comparison of ozone determinations by ultraviolet photometry and gas-phase titration

    NASA Technical Reports Server (NTRS)

    Demore, W. B.; Patapoff, M.

    1976-01-01

    A comparison of ozone determinations based on ultraviolet absorption photometry and gas-phase titration (GPT) shows good agreement between the two methods. Together with other results, these findings indicate that three candidate reference methods for ozone, UV photometry, IR photometry, and GPT are in substantial agreement. However, the GPT method is not recommended for routine use by air pollution agencies for calibration of ozone monitors because of susceptibility to experimental error.

  19. A Test of the Use of Hot DA White Dwarfs to Calibrate AB-Magnitude Photometry

    Microsoft Academic Search

    Tim Axelrod; Edward Olszewski; Abi Saha; Chuck Claver

    2007-01-01

    Proposed all-sky surveys wish to have photometry on an energy-based system (AB magnitudes, for instance). Two important projects requiring such photometry are luminosity distances of supernovae and high quality photometric redshifts. In order to achieve sub-1% energy-based photometry, hot DA White Dwarfs (WDs) with spectroscopically determined T_eff and log(g) and model-atmosphere spectral-energy distributions (SEDs) are needed as standards. What is

  20. How to reach sub-1% photometry in an all-sky survey such as LSST

    Microsoft Academic Search

    Tim Axelrod; Edward Olszewski; Abi Saha; Jay Holberg

    2008-01-01

    Proposed all-sky surveys wish to have photometry on an energy-based system (AB magnitudes, for instance). Two important projects requiring such photometry are luminosity distances of supernovae and high quality photometric redshifts. In order to achieve sub-1% energy-based photometry, hot DA White Dwarfs (WDs) with spectroscopically determined T_eff and log(g) and model-atmosphere spectral-energy distributions (SEDs) are needed as standards. What is