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1

Iontophoresis and Flame Photometry: A Hybrid Interdisciplinary Experiment  

ERIC Educational Resources Information Center

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

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

2010-01-01

2

Releasing effects in flame photometry: Determination of calcium  

USGS Publications Warehouse

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

Dinnin, J. I.

1960-01-01

3

Application of displacement reactions in flame photometry-I: the determination of phosphate by a flame emission method.  

PubMed

Phosphate ions decrease the flame emission of calcium, but this effect can be partly offset by adding a second metal which partly displaces calcium from the non-excitable species. For the determination of phosphate the sample solution is divided into four equal parts; to each of these, various amounts of calcium and barium ions are added such that the total (molar) concentration of the metals is constant. Plotting the intensity measured at 630 nm vs. the calcium content of the solution gives a straight line, the slope of which depends on the concentration of phosphate ions present. The method is suitable for rapid determination of phosphate. Accuracy and precision are within the usual limits characteristic of flame photometric methods. PMID:18960847

Szebényi-Györy, E; Slevin, P J; Svehla, G; Erdey, L

1970-12-01

4

Astronomical Photometry  

NASA Astrophysics Data System (ADS)

Astronomers use the term "photometry" to refer to the precise measurement of the apparent brightness of astronomical objects in particular specified ranges of electromagnetic wavelength in and near the optically visible band. Historically, this task has been most commonly carried out with the human eye, photographic plates, photomultiplier tubes, and - most recently as of this writing - charge-coupled devices. At wavelengths significantly shorter or longer than the optical region, different detector technologies must be used, and some other term than "photometry" is often used to name the process.

Stetson, Peter B.

5

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

PubMed

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

Hamasaki, Tetsuo

2013-05-02

6

The application of separated flames in analytical flame spectroscopy.  

PubMed

Premixed hydrocarbon-air flames invariably show two separate reaction zones. In the primary zone, the combustible gas mixture burns principally to carbon monoxide, hydrogen, and water, and in the outer mantle, or secondary diffusion flame, the hot gases burn with atmospheric oxygen to carbon dioxide and water. Teclu [J. Prakt. Chem. 44, 246 (1891)] and Smithells and Ingle [Trans. Chem. Soc. 61, 204 (1892)] independently demonstrated the existence of these two zones in various premixed hydrocarbon-air flames, using the flame separator. This device consists of a wide glass or silica tube fitted over the bunsen type burner to form an extension above the inner burner port. The primary combustion then occurs at the inner burner port, while the pale blue secondary diffusion flame is maintained at the top of the outer glass tube. An alternative method of separation of premixed hydrocarbon-air flames consists of sheathing the flame with an inert gas to lift off or separate the secondary diffusonzone. The interconal zone of flames separated by these methods are extended in length and exhibit very low radiative background. The interconal zone also contains the hottest part of the flame, and can be viewed without interference from radiation produced in a secondary diffusion zone that would normally surround it in separated flames. It is the hot interconal zone of premixed flames that is most frequently employed in analytical flame photometry, because it is in this region that the greatest population of atoms occurs when elements are introduced into the flame by nebulization of solutions of their salts. Thus, separated flames may be employed with advantage in thermal emission, atomic absorption, and atomic fluorescence spectroscopy. This paper describes the separation of the air-acetylene and nitrous oxide-acetylene flames, and some applications of these flames in analytical flame spectroscopy. PMID:20068791

Kirkbright, G F; West, T S

1968-07-01

7

Photometry of M33  

NASA Astrophysics Data System (ADS)

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

Schlingman, W. M.; Massey, P.

2003-12-01

8

Photometry with FORS  

NASA Astrophysics Data System (ADS)

Photometric calibration observations are routinely carried out with all ESO imaging cameras in every clear night. The nightly zeropoints derived from these observations are accurate to about 10%. Recently, we have started the FORS Absolute Photometry Project (FAP) to investigate, if and how percent-level absolute photometric accuracy can be achieved with FORS1, and how such photometric calibration can be offered to observers. We found that there are significant differences between the sky-flats and the true photometric response of the instrument which partially depend on the rotator angle. A second order correction to the sky-flat significantly improves the relative photometry within the field. We demonstrate the feasibility of percent level photometry and describe the calibrations necessary to achieve that level of accuracy.

Freudling, W.; Møller, P.; Patat, F.; Moehler, S.; Romaniello, M.; Jehin, E.; O'Brien, K.; Izzo, C.; Pompei, E.

9

Premixed Flames  

Microsoft Academic Search

\\u000a Premixed flames refer to the combustion mode that takes place when a fuel and oxidizer have been mixed prior to their combustion.\\u000a Premixed flames are present in many practical combustion devices. Two such applications are a home heating furnace and a spark\\u000a ignited internal combustion engine. In premixed flame combustors, the fuel and oxidizer are mixed thoroughly before being\\u000a introduced

Sara McAllister; Jyh-Yuan Chen; A. Carlos Fernandez-Pello

10

Gaia broad band photometry  

Microsoft Academic Search

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

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

2010-01-01

11

Photometry with GAIA  

NASA Astrophysics Data System (ADS)

The ESA GAIA spacecraft has been approved for launch by a Soyuz-Fregat launcher in December 2011. After five years continuously scanning the sky, astrometric, photometric and spectroscopic data for a billion objects down to V˜20 will be acquired. That huge survey of the Galaxy content and beyond will provide insights to the origin and evolution of the Galaxy, to stellar astrophysics, to solar system objects, to QSOs, and so on. GAIA is the successor of the successful { HIPPARCOS mission and it means a big step forward, both in terms of number of objects and in terms of precision. The final industrial approach to photometry includes two slitless spectrographs, covering the blue and the red parts of the radiation spectrum from 330 to 1050 nm. Photometry will be acquired by a white photometric band, and by two low-dispersion spectra. Now, there is a unique focal plane integrating astrometry, photometry and spectroscopy. In this paper, we review the goals of GAIA photometry, and present as well the new low-dispersion spectrophotometry approach. With the redesign of the mission, the reduction process changes considerably and a great effort must be devoted to this issue in the next years.

Jordi, C.; Carrasco, J. M.

2007-04-01

12

Flame Spectra.  

ERIC Educational Resources Information Center

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

Cromer, Alan

1983-01-01

13

Photometry with NICMOS  

NASA Astrophysics Data System (ADS)

We summarize the performance of the NICMOS instrument and discuss the measured sensitivity, and the photometric performance and stability. We also present a method for removing an instrument artifact termed ``pedestal'', a bias instability that is present at a low level in most NICMOS images. The characteristics of dark frames will also be discussed, in particular as they relate to pedestal correction. NICMOS is capable of achieving the advertised performance in most areas. As an example, typical 3 sigma detection limits for a 5 orbit observation with NIC2 are 1.47 mJy arcsec(-2) in F110W, 1.67 mJy arcsec(-2) in F160W, and 12.6 mJy arcsec(-2) in F222M. The absence of time-dependent backgrounds makes infrared photometry from NICMOS highly stable, reaching an accuracy of 2% or better. NICMOS absolute calibration has been accomplished with a combination of solar analog stars and white dwarf standard stars and achieves 5% absolute photometry. An exception to these accuracies occurs for NIC3 at short wavelengths where intra-pixel sensitivity variations produces variations in relative photometry as large as 20%.

Calzetti, D.; Dickinson, M. E.; Bergeron, L. E.; Colina, L.

1998-12-01

14

Premixed Turbulent Flame Propagation.  

National Technical Information Service (NTIS)

An experimental study has been conducted of turbulence-flame interactions in premixed turbulent flames and their effect on flame-generated turbulence, flame structure and flame propagation. The flame configuration used for this study is that of a freely p...

D. A. Santavicca

1989-01-01

15

Flame photometric determination of salinity in processed foods  

Microsoft Academic Search

The sodium contents determined by flame photometry were used to estimate the salinities of processed foods. The interference effects of potassium and calcium ions on the determination of sodium ion were studied. The threshold interfering patterns of potassium ion and calcium ion for the determination of sodium ion were observed in the model systems. Both of the ions showed enhancement

Min-Jane Chen; Ya-Ting Hsieh; Yih-Ming Weng; Robin Y.-Y. Chiou

2005-01-01

16

Determination of Milk Minerals by Flame Photometry1  

Microsoft Academic Search

This article is an outgrowth of the authors' need for a method for the deter- ruination of the minerals in milk during a milk composition study involving the determination of some 15 to 20 samples per month over a 3-yr. period. The authors sought a method not as laborious nor as time consuming as the standard chemical methods but still

R. J. Keirs; S. J. Speck

1950-01-01

17

CCD Photometry of Variables Stars  

NASA Astrophysics Data System (ADS)

With recent advances in Charged Coupled Devices (CCDs), it is now possible to do high speed CCD photometry. Though photelectric photometry has a rich history and many years of software development, CCDs have several advantages over photometers: They have a higher quantum efficiency and eliminate many of the problems associated with the requirement of a fixed aperture in photoelectric photometry. However, CCD photometry has yet to develop the necessary tools to efficiently reduce and analyze the quantities of time-series data produced. Two other areas where advancement is needed are in decreasing the CCD readout times and producing real time light curves. We present steps taken to address these two issues. Dead times were shortened by examining various CCD geometries and scripts were written to process the data more efficiently. Our work has produced efficient methods for obtaining and reducing high speed CCD observations and brings us a step closer to producing real time light curves.

Jeffery, E. J.; Reed, M. D.

2001-12-01

18

Photometry and the Virtual Observatory  

NASA Astrophysics Data System (ADS)

Building Spectral Energy Distributions combining data from different sources is becoming more important as astronomy takes an increasingly multi-wavelength approach. In order to do this, photometry data must be described in sufficient detail to allow for the conversion to compatible flux density units (including the description of magnitude systems and zero points). Furthermore, comparing observed photometry with the synthetic one for theoretical models allows to infer physical properties from the observed objects. But in order to do that, an even more detailed description of the observed photometric points is needed, including the transmission curves of the filters corresponding to the observed data. In the Virtual Observatory an important effort has been done towards this standardization with the Photometry Data Model. And in the SVO we have developed several services to help in this direction, providing detailed information about filters, synthetic photometry for theoretical models and tools to use all this to analyze observed data and estimate object physical properties.

Rodrigo, C.; Solano, E.

2013-05-01

19

Floating Flame Balls  

NSDL National Science Digital Library

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

2011-04-08

20

Triple flame structure and diffusion flame stabilization  

Microsoft Academic Search

The stabilization of diffusion ñames is studied using asymptotic techniques and numerical tools. The configuration studied corresponda to parallel streams of cold oxidizer and fuel initially separated by a splitter píate. It is shown that stabiliza­ tion of a diffusion flame may only occur in this situation by two processes. First, the flame may be stabilized behind the flame holder

D. Veynante; L. Vervisch; T. Poinsot; A. Liñán; G. Ruetsch

21

Gaia broad band photometry  

NASA Astrophysics Data System (ADS)

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

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

22

Flame Velocity of Cellular Flames at Low Lewis Numbers  

Microsoft Academic Search

The flame velocity of cellular flames at low Lewis numbers is numerically studied, based on the compressible Navier-Stokes equation including a one-step chemical reaction. The flame velocity of a cellular flame is always larger than that of a plane flame and increases as the Lewis number becomes lower. When the Lewis number is unity, the flame velocity is proportional to

SATOSHI KADOWAKI

2001-01-01

23

The Science of Flames.  

ERIC Educational Resources Information Center

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

Cornia, Ray

1991-01-01

24

Turbulence and Flame Propagation.  

National Technical Information Service (NTIS)

The report contains five subreports which all together represent the authors section's recent research in turbulence and flame propagation. Part 1 contains calculations of a turbulent nitrogen diffusion flame based on 'Eddy Dissipation Concept' (EDC), whi...

M. Brostroem S. Byggstoeyl B. Grimsmo J. Holen N. I. Lilleheie

1987-01-01

25

Electrochemistry in flames.  

PubMed

Flames and combustion science are well established fields having contributed to the foundations of engineering and chemistry and led to remarkable achievements in our 'industrial age'. The aim of this paper however is to highlight the electrochemical properties of flames, which are known to a lesser extent. First a historical account on the study on flames is given, followed by a general discussion on the formation and properties of common flames. The core of the discussion deals with the presence of charged species in flames, or else their plasma nature. It is this property that allows us to treat flames as conductive media and even develop flame electrochemical systems that yield voltages in the same fashion as standard batteries. Due to their very interesting plasma properties, therefore, flames can be incorporated with already developed electrochemical methodologies and generate new research areas of great potential. PMID:21047020

Sarantaridis, Dimitris; Fowowe, Toks; Caruana, Daren J

2010-01-01

26

UBV photometry of ER Vulpeculae  

Microsoft Academic Search

UBV photometry of the RS CVn-type eclipsing binary system ER Vulpeculae has been presented. The period comes out to be 0.698093d. The average depths of primary and secondary minima are, respectively, 0.21 and 0.12m. The colors at various phases have been given. A dip is seen around phase 0.73P as was seen in the observations of Arevalo et al. (1988).

R. K. Srivastava; T. D. Padalia; J. B. Srivastava

1991-01-01

27

Aerodynamics of stretched flames  

Microsoft Academic Search

This dissertation presents studies of three distinctive problems associated with the aerodynamics of stretched premixed flames. In Part I, the geometry, stability, and stabilization of premixed flames are studied by treating the entire flame as a structure surface, with emphasis on the importance of appropriately accounting for stretch effects on its propagation velocity. The main objective of Part II is

Chung-Jen Sun

1998-01-01

28

Kinematics and photometry of red clump stars (Vasquez+, 2013)  

NASA Astrophysics Data System (ADS)

The Kinematics and photometry for spectroscopic targets are presented. For each star with proper motions determination, the coordinates in each single epoch is provided. The spectroscopic targets were selected based on the optical V, I photometry of a bulge field centered at (l, b) = (0, -6), obtained with the WFI camera at the 2.2m telescope at ESO La Silla, on April 15th, 1999 as part of the ESO imaging Survey ESO programme (EIS, ESO programme ID 163.O-0741(A)). The resulting CMD has been already presented in Zoccali et al. (2003A&A...399..931Z) and McWilliam & Zoccali (2010ApJ...724.1491M). Based on this CMD the red clump targets were selected among the bright (red dots) and faint red clump stars (blue dots) for spectroscopic follow-up with Magellan IMACS spectrograph at the Las Campanas Observatory on July 10th, 2010 (R~5000) and VLT FLAMES-GIRAFFE spectrograph within the ESO programme ID 385.B-0735(B) (R~6500). In order to derive space velocities for our targets, second epoch images of the same field were obtained on May 6th, 2010 with the same instrument and filters as in the first epoch (ESO program ID 085.D-0143(A)). (1 data file).

Vasquez, S.; Zoccali, M.; Hill, V.; Renzini, A.; Gonzalez, O. A.; Gardner, E.; Debattista, Victor P.; Robin, A. C.; Rejkuba, M.; Baffico, M.; Monelli, M.; Motta, V.

2013-06-01

29

Photocells, photomultipliers, and southern-hemisphere photometry.  

NASA Astrophysics Data System (ADS)

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

Hearnshaw, J. B.

1996-11-01

30

Flame Stretch and the Balance Equation for the Flame Area  

Microsoft Academic Search

When a flame propagates in a nonuniform flow it experiences strain and curvature effects. The fractional rate of change of the flame area constitutes the flame stretch. This quantity is often used to describe the structure and extinction mechanisms of turbulent flames. It also occurs in many recent studies of premixed laminar flames. This article provides a unified view of

SEBASTIEN M. CANDEL; THIERRY J. POINSOT

1990-01-01

31

Stellar photometry with big pixels  

NASA Astrophysics Data System (ADS)

A new software for stellar photometry in crowded fields is presented. This software overcomes the limitations present in a traditional package like ROMAFOT when the pixel size of the detector is comparable to the scale length of point images. This is the case, for instance, with the Hubble Space Telescope-Wide Field Camera and, partially, with the Planetary Camera. The 'numerical' solution presented here is compared to the 'technical' solution of obtaining more exposures of the same field, each shifted by a fraction of pixel. This software will be available in MIDAS.

Buonanno, Roberto; Iannicola, Giacinto

1989-03-01

32

SPA, "The Stellar Photometry Assistant"  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

33

Photometry of astrometric reference stars  

NASA Astrophysics Data System (ADS)

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

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

1991-12-01

34

NIR photometry of Flaring Blazars from CRTS  

NASA Astrophysics Data System (ADS)

Following the Mahabal, A.A. etal, 2011 report (ATel #3321) of flaring blazars from CRTS, we have carried out NIR photometry of these objects. Over all, the objects are brighter in the H band than previous photometry when available. Our results are summarized below, we list the object ID, the Julian Date of our observations, the H magnitude and a brief comment.

Carrasco, L.; Carraminana, A.; Escobedo, G.; Recillas, E.; Porras, A.; Mayya, D. Y.

2011-05-01

35

UBV photometry in Berkeley 32 (Kaluzny+, 1991)  

NASA Astrophysics Data System (ADS)

The observations were performed at Kitt Peak National Observatory using the 0.9m telescope equipped with the CCD camera of TEK2 chip (512x512pixels, 0.774arcsec/pix). The UBV photometry was obtained in the night of 1989-12-04, and the Washington photometry on the night of 1989-12-11. (1 data file).

Kaluzny, J.; Mazur, B.

2010-08-01

36

Flame front geometry in premixed turbulent flames  

SciTech Connect

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.

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

1991-12-01

37

Flame Curvature Statistics in Axisymmetric Turbulent Jet Flames  

Microsoft Academic Search

Flame curvature in axisymmetric turbulent jet flames are obtained experimentally for u'\\/SL from 0.8–1.5. The measurements indicate that the flame curvature statistics exhibit a substantial change as a function of the axial location in turbulent jet flames primarily due to the evolution of flame wrinkle structures. In particular, it is found that the flame curvature tends to be very small

T.-W. LEE; R. SHANKLAND; M. FENTON

1995-01-01

38

Flame Front Curvature Distributions in a Turbulent Premixed Flame Zone  

Microsoft Academic Search

Distributions of flame front curvature obtained by laser sheet tomography agree with those derived from numerical simulations of passive flame propagation within three-dimensional Navier-Stokes turbulence. The experimental configuration is that of grid turbulence impinging upon a plate which stabilizes a premixed methane\\/air flame, planar images of the flame allow construction of flame curvature as a function of flame location within

Wm. T. ASHURST; I. G. SHEPHERD

1997-01-01

39

Early Photometry Studies for Euclid  

NASA Astrophysics Data System (ADS)

The Euclid mission aims to investigate the distance-redshift relationship and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies. Data from the satellite instruments will be merged with ground based imaging data from large surveys such as the Dark Energy Survey and Pan-STARRS. Euclid's weak galaxy lensing experiment requires very accurate photometric redshifts and thus precise galaxy colours. In this contribution we compare the ‘traditional approach’ of fitting object models to co-added images with a new technique that simultaneously fits a model to the ensemble of individual images. Preliminary results indicate that the photometry using individual image fitting is more precise.

Kümmel, M.; Koppenhoefer, J.; Riffeser, A.; Mohr, J.; Desai, S.; Henderson, R.; Paech, K.; Wetzstein, M.

2013-10-01

40

Brominated Flame Retardants  

EPA Science Inventory

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

41

Analysis of flame propagation  

Microsoft Academic Search

We develop a mathematical theory of flame propagation and analyze the stability of a flame front. We consider a premixed, combustible fluid and model the front between the burnt and unburnt regions as an infinitely thin curve propagating in a direction normal to itself at a constant speed. We assume that the specific volume of a fluid particle increases by

J. A. Sethian

1982-01-01

42

Illinois­—Where Astronomical Photometry Grew Up  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

43

Diffusion Flames Based on a Laminar Spray Flame Library  

Microsoft Academic Search

The present paper investigates the structure of turbulent spray diffusion flames by means of numerical simulations. The flamelet model for turbulent diffusion flames has recently been extended to turbulent spray diffusion flames. The model is suitable for considering detailed chemical reactions through use of a laminar flame library consisting of structures of laminar gas diffusion flamelets that are characterized by

C. Hollmann; E. Gutheil

1998-01-01

44

Flame\\/stretch interactions in laminar and turbulent premixed flames  

Microsoft Academic Search

The flame\\/stretch interactions of laminar and turbulent premixed flames are considered both experimentally and computationally. Potentially strong effects of flame\\/stretch interactions due to preferential-diffusion phenomena within practical turbulent premixed flames were suggested by experiments and numerical simulations of spherical outwardly propagating laminar premixed flames. These considerations were limited to conditions where ignition disturbances, pressure variations, intrinsic unsteadiness of propagating spherical

K. T. Aung; M. I. Hassan; S. Kwon; L.-K. Tseng; O.-C. Kwon; G. M. Faeth

2002-01-01

45

NICMOS Photometry of High Redshift Supernovae  

NASA Astrophysics Data System (ADS)

Type Ia supernovae have emerged as excellent cosmological tools. Near infrared photometry becomes increasingly important as observations are pushed to higher redshifts. In particular, near-IR observations can be used to estimate reddening and assess systematic effects such as grey dust. We present infrared photometry of five supernovae obtained using the NICMOS detector on HST. The observed supernovae range in redshift from 0.35 to 0.86. The low background in these images provides more precise photometry than is possible from the ground and the higher resolution allows for a more reliable estimate of host galaxy contamination. We will present data reduction techniques, cosmological implications, and summarize the difficulties of doing absolute photometry using NICMOS. This research is supported by the Department of Energy and by the NASA Space Telescope Science Institute.

Burns, M. S.; Aldering, G.; Amanullah, R.; Antilogus, P.; Astier, P.; Balland, C.; Blanc, G.; Conley, A.; Deustua, S.; Ellis, R.; Fabbro, S.; Folatelli, G.; Fruchter, A.; Garavini, G.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hardin, D.; Hook, I. M.; Howell, D. A.; Irwin, M.; Kasen, D.; Kim, A.; Knop, R. A.; Levy, J.-M.; Lidman, C.; McMahon, R.; Mouchet, M.; Nobili, S.; Nugent, P.; Pain, R.; Panagia, N.; Pécontal, E.; Pennypacker, C. R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Schaefer, B.; Schahmaneche, K.; Spadafora, A. L.; Walton, N.; Wang, L.; Wood-Vasey, W. M.; Supernova Cosmology Project Collaboration

2001-12-01

46

CCD Photometry of UW Coronae Borealis  

Microsoft Academic Search

We present CCD photometry of the low mass X-ray binary UW CrB (MS1603+260) using the McDonald Observatory 107in telescope. These data were obtained on 20 nights during 2002, 2003, and 2004. Hynes, Robinson, and Jeffery (2004) found that UW CrB contains a neutron star exhibiting optical reprocessing of type I X-ray bursts. CCD photometry from that study is included in

Paul A. Mason; E. L. Robinson; C. L. Gray

2006-01-01

47

UBVRI photometry in NGC6791 (Brogaard+, 2012)  

NASA Astrophysics Data System (ADS)

New reduction of photometric B, V, I observations from Stetson et al. (2003, Cat. J/PASP/115/413) with updated photometry zero-points according to Stetson et al. (2005PASP..117..563S), and the same photometry, but empirically corrected for differential reddening using the procedure described in Milone et al. (2012A&A...540A..16M). (1 data file).

Brogaard, K.; Vandenberg, D. A.; Bruntt, H.; Grundahl, F.; Frandsen, S.; Bedin, L. R.; Milone, A. P.; Dotter, A.; Feiden, G. A.; Stetson, P. B.; Sandquist, E.; Miglio, A.; Stello, D.; Jessen-Hansen, J.

2012-06-01

48

Flame characteristics of turbulent lean premixed methane\\/air flames at high pressure: Turbulent flame speed and flame brush thickness  

Microsoft Academic Search

The effects of operating conditions and turbulence on flame front position, turbulent flame speed and flame brush thickness of lean premixed methane\\/air flames at high pressure are investigated experimentally. A comparison of the measured turbulent flame speeds with existing correlations is presented and discussed. The measurements were performed in an axis-symmetric, generic combustor at pressures up to p=1.44MPa, equivalence ratios

P. Griebel; P. Siewert; P. Jansohn

2007-01-01

49

Multicolor Photometry for Mode Identification  

NASA Astrophysics Data System (ADS)

The goal of asteroseismology is to discern the physical conditions of stars by comparing observed pulsations with models. To obtain this goal, the observed pulsation periods and the spherical harmonics (n, l, and m) need to match the theoretical model. Typically the most difficult part in this process is the identification of the pulsation modes in the observations. Multicolour photometry is one method that has proven useful for identifying pulsation modes. By observing stars through various wavebands, and comparing the amplitudes and phases, it is possible to determine the spherical harmonics. This contribution will emphasize the work of Watson (1988), which has since been applied to many different types of variable stars including ? Scuti (Garrido et al., 1990), ? Doradus (Breger et al., 1997), ? Cepheid (Cugier et al., 1994), and EC 14026 (Koen, 1998) stars. I will also discuss the technique of summing spectra (especially UV) into various wavebands which are then used to identify modes as pioneered by Robinson, Kepler, and Nather (1982) and applied to white dwarf stars (Kepler et al., 2000).

Reed, M. D.

50

Calculation of Wrinkled Flames.  

National Technical Information Service (NTIS)

In an earlier work, Sivashinsky derived a nonlinear integro-differential equation for spontaneous hydrodynamic instability of a plane flame front. The simplified form of that equation which describes a steady progressive wave of long period is reconsidere...

H. V. McConnaughey G. S. S. Ludford G. I. Sivashinsky

1982-01-01

51

Differential Photometry at 1612 MHz  

NASA Astrophysics Data System (ADS)

The 1612 MHz light curves of high latitude OH/IR stars have been observed for several years with the Arecibo 305m telescope, to derive the light-travel time diameter of their shells from the phase difference between their red and blue shifted peaks, and to look for secular evolution of their masers. However, direct intensity measurements are always limited by the extent to which the telescope's characteristics can be removed. These, in Arecibo's case, are subject to changes in the weight distribution about the structure over time, to the functioning of the vertical tie-down system, which can be interrupted by thunder storms, and by temperature-related zenith angle effects during daytime observations. Nevertheless, all of these limitations are neutralized when the ratio of the two peaks is used as the observed parameter. This form of differential photometry often results in clean light curves, though the ratio may still be perturbed by RFI, by interstellar scintillation, and more predictably by noise. The increased sensitivity of this observing mode readily detects (1) any differential evolution of the two masers, as well as (2) highlighting changes in masing gain between the two peaks around the pulsation cycle, that in turn are indicative of the operation of partially rather than fully saturated masers. In many of our light-curves there are abrupt changes in the ratio of the peak intensities at a constant pulsation phase. These are interpreted as being due to the onset of dust formation at that phase of the pulsation cycle, with a consequent abrupt change in the reprocessing of the stellar SED, and hence to an abrupt change in the maser pump. This is a feature of the Gray, Howe & Lewis (MN 364, 783 (2005)) maser model. Examples of these effects will be shown.

Lewis, B. Murray

2009-01-01

52

Improved Photometry for the DASCH Pipeline  

NASA Astrophysics Data System (ADS)

The Digital Access to a Sky Century@Harvard (DASCH) project is digitizing the ˜500,000 glass plate images obtained (full sky) by the Harvard College Observatory from 1885 to 1992. Astrometry and photometry for each resolved object are derived with photometric rms values of ˜0.15 mag for the initial photometry analysis pipeline. Here we describe new developments for DASCH photometry, applied to the Kepler field, that have yielded further improvements, including better identification of image blends and plate defects by measuring image profiles and astrometric deviations. A local calibration procedure using nearby stars in a similar magnitude range as the program star (similar to what has been done for visual photometry from the plates) yields additional improvement for a net photometric rms of ˜0.1 mag. We also describe statistical measures of light curves that are now used in the DASCH pipeline processing to identify new variables autonomously. The DASCH photometry methods described here are used in the pipeline processing for the data releases of DASCH data,5 as well as for a forthcoming paper on the long-term variables discovered by DASCH in the Kepler field.

Tang, Sumin; Grindlay, Jonathan; Los, Edward; Servillat, Mathieu

2013-07-01

53

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

54

Wall Flames and Implications For Upward Flame Spread.  

National Technical Information Service (NTIS)

New concepts are addressed for predicting the flame spread on materials from laboratory measurements. It focuses on heat transfer which precipitates and proceeds upward flame spread on a vertical surface. Six materials have been featured in the study as w...

J. Quintiere M. Harkleroad Y. Hasemi

1986-01-01

55

Photometry Studies of Asteroids and Variable Stars  

NASA Astrophysics Data System (ADS)

During the fall semester of 2012, we carried out extensive photometry studies of asteroids to obtain their rotation periods using the 0.9-m SARA North telescope located at the Kitt Peak National Observatory in Arizona and at the 0.6-m SARA South telescope located at the Cerro Tololo Inter-American Observatory in Chile. The asteroids that we carried out photometry studies include: 782 Montefiore, 3024 Hainan, 3842 Harlansmith, 3920 Aubignan, 5542 Moffatt, 5951 AliceMone, 6720 Gifu, 19978 1989VJ. We will present their rotation periods, and compare with previous results where available. During the course of photometry studies, we also discovered several variable stars. We will also present these new variable stars and their periods.

Han, Xianming; Li, B.; Zhao, H.; Liu, W.; Sun, L.; Gao, S.; Shi, J.; Wang, S.; Pan, X.; Jiang, P.; Zhou, H.

2013-01-01

56

An Improved Method for Differential Photometry  

NASA Astrophysics Data System (ADS)

We developed a method to improve the conventional differential photometry by using many auxiliary stars to reduce noise in the reference light curve, which is used to calibrate the light curve of the target star. The data used in this study are taken with the Taiwan Automated Telescope network. The light curves of two ? Scuti, HD 163032 and V830 Her, are shown here as examples. The results are compared with four other methods: conventional differential photometry; ensemble photometry; the method of Tamuz, Mazeh, & Zucker; and trend filtering algorithm. The light curve computed with our method is smoother than the other four methods, while preserving the pulsational signals. The mode frequencies determined from the light curve from our method also has a higher S/N and lower error in comparison with other methods.

Fernández Fernández, Javier; Chou, Dean-Yi; Pan, Yen-Chen; Wang, Li-Hang

2012-05-01

57

The Relationship of the Laminar Flame Width to Flame Speed  

Microsoft Academic Search

The width ( ? ) of a laminar flame is often characterized as a basic property of the flame and is sometimes used in turbulent combustion models to categorize the turbulence scale of the mixture. From computed flame speeds and temperature profiles of C3H8\\/Oa\\/Ns (ø=1) flames we have determined widths, using definitions based on ( dT*sol;dx)max, Q (the heat release

RICHARD J. BLINT

1986-01-01

58

Edge flames and partially premixed combustion in diffusion flame quenching  

Microsoft Academic Search

The aim is to focus on the development of partially premixed combustion after diffusion flame quenching. To this end, the quenching of a planar two-dimensional diffusion flame is studied by using numerical simulation. A flame hole is obtained by submitting the reaction zone to a high strain and scalar dissipation rate resulting from the interaction between vorticity and upstream triple

Valérie Favier; Luc Vervisch

2001-01-01

59

Flame surface densities during spherical turbulent flame explosions  

Microsoft Academic Search

A novel way is presented of deriving the proportionality constant, k (mm?1), for flame surface density. This comprises simultaneous measurements, by Mie scattering, of mean reaction progress variable and the turbulent burning velocity, during explosions in a fan-stirred bomb. Mean effective laminar burning velocities at the wrinkled flame surface are derived theoretically from the distribution of flame stretch rates, the

D. Bradley; M. Lawes; M. S. Mansour

2009-01-01

60

UBVJHKLM photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

We present the results of the optical and IR photometry of Nova Del 2013 obtained at the Crimean Station (Nauchny, Ukraine) of the Sternberg Astronomical Institute. UBV photometry was carried out with 60-cm Zeiss telescope using a photoelectric photometer on August 15.94 UT: U=4.54+/-0.02, B=5.07+/-0.01, V=5.05+/-0.01; on August 16.80 UT: U=4.54+/-0.01, B=4.85+/-0.02, V=4.68+/-0.01; on August 16.86 UT: U=4.66+/-0.01, B=4.92+/-0.01, V=4.73+/-0.01.

Burlak, A. M.; Shenavrin, I. V.; Tatarnikov, M. A.; Tatarnikova, A. A.

2013-08-01

61

Flame Attachement to Vsu 2.  

National Technical Information Service (NTIS)

This instruction manual provides the information necessary for the conversion of the VSU2 spectrophotometer to a flame photometer by use of a flame attachment. With this, the measuring principle of the unregistered radiation photometer, can be basically o...

1973-01-01

62

Flame Cutting Textured Steel Armor.  

National Technical Information Service (NTIS)

Undesirable metallurgical transformations and high tensile residual stresses in the region of flame cut edges have necessitated the use of high preheat temperatures, often in excess of 550, for the flame cutting of high strength steels. In addition, grind...

J. A. Saccoccio W. S. Ricci

1988-01-01

63

Flame propagation through periodic vortices  

SciTech Connect

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

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

1995-02-01

64

Bigger and Brighter Flame Tests.  

ERIC Educational Resources Information Center

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

Dalby, David K.; Mosher, Melvyn M.

1996-01-01

65

Sinusoidal variables from the Tycho Epoch Photometry Annex  

Microsoft Academic Search

The Tycho Epoch Photometry Annex A, a data base of photometry of more than 34 000 bright stars, has been searched for periodic variable stars with approximately sinusoidal light curves. Advantage was taken of special properties of the observing programme (photometry in two wavebands, availability of repeated measurements) to use simple but efficient variable selection criteria. Details of 70 strong

Chris Koen; Robert Schumann

1999-01-01

66

Flames, lasers, and reactive systems  

Microsoft Academic Search

The gasdynamics of flames, lasers, and other reactive systems are explored in contributions (about half by Soviet scientists) to the Eighth International Colloquium on the Gasdynamics of Explosions and Reactive Systems held in Minsk, USSR, in August, 1981. Major areas covered are laminar flames, turbulent flames, combustion of solids, ignition and extinction, nonequilibrium systems, and lasers. Topics discussed include the

J. R. Bowen; N. Manson; A. K. Oppenheim; R. I. Soloukhin

1983-01-01

67

Flame Tests Performed Safely  

NSDL National Science Digital Library

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

Dogancay, Deborah

2005-09-01

68

Photometry of Venus from Mariner 10  

Microsoft Academic Search

Photometry of the upper atmosphere of Venus from Mariner 10 on February 5, 1974 is discussed with respect to in-flight verification of camera linearity, shading, and absolute photometric calibration. Among photometric results are the following: (1) temporal brightness variations were observed in the UV greater than 10% over a few hours due to the rapid rotation of the upper atmosphere,

Bruce Hapke

1976-01-01

69

Walraven photometry of nearby southern OB associations  

NASA Astrophysics Data System (ADS)

Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars in the regions of five nearby southern OB associations: Scorpio Centaurus (Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2. Derived V and (B - V) in the Johnson system are included.

de Geus, E. J.; Lub, J.; van de Grift, E.

1990-10-01

70

Astronomical Photoelectric Photometry for Undergraduate Research  

Microsoft Academic Search

Many college physics departments would welcome the opportunity to initiate a modest research program which could involve their undergraduate students. Astronomical photoelectric photometry is a field in which it is possible to initiate a useful undergraduate oriented research program with relatively modest equipment, some of which can commonly be found in a college physics department. A sketch of the equipment

Albert D. Grauer

1974-01-01

71

CCD Photometry of the Centaur 1995 GO  

Microsoft Academic Search

We present new CCD photometry of the Centaur object 1995 GO obtained in April 1996, including a lightcurve, aV ? Rcolor, and a surface brightness profile. The apparent brightness implies a circular effective radius of 53.5 km, assuming a 4% albedo. The shape of the lightcurve is compatible with an aspherical rotating body, with a rotation period of 8.870 ±

Warren R. Brown; Jane X. Luu

1997-01-01

72

Wise Observatory System of Fast CCD Photometry  

NASA Astrophysics Data System (ADS)

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

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

73

General Photometry of Galaxies (Prugniel+ 1998)  

NASA Astrophysics Data System (ADS)

The tables presented here give the catalogue of aperture photometry of galaxies (UBVRI), the associated bibliography, the weight and systematic corrections applied to individual datasets. A table give the results of the growth curve fits; the net of curves adopted is a linear interpolation between the de Vaucouleurs (r1/4) and exponential laws. This aperture photometry has three different origins: (i) an update of the catalogue of Buta et al. 1995 (Cat. ) (ii) published photometric profiles and (iii) aperture photometry performed on CCD images. Fitting growth curves to aperture photometry of galaxies, in UBVRI, we derive (1) the total magnitude, (2) the effective radius, (3) the color indices and (4) gradients and (5) the photometric type of 5066 galaxies. The photometric type is defined to statistically match the revised morphologic type (numerically coded from -6 to +10) and represents the shape of the growth curve. The catalogue is maintained up-to-date in the database HYPERCAT (http://www-obs.univ-lyon1.fr/~prugniel/cgi-bin/hypercat/). This catalogue supersedes the Longo and de Vaucouleurs (1983) catalogue . (4 data files).

Prugniel, P.; Heraudeau, P.

1998-03-01

74

Flame surface density and burning rate in premixed turbulent flames  

SciTech Connect

The flame surface density has been measured in hydrocarbon/air stagnation point and v-shaped premixed turbulent flames. A method is proposed to determine the flame surface density from the data obtained by laser sheet tomography. The average flame length and flame zone area as a function of the progress variable are calculated from a map of progress variable and a set of flame edges obtained from the tomographs. From these results a surface density estimate in two dimensions is determined. By this technique it is possible to avoid the difficulties which arise when using an algebraic model based on the measurement of the flame front geometry and a scalar length scale. From these results the burning rate can be obtained which compares well with estimates calculated using the fractal technique. The present method, however, is not constrained by a minimum window size as is the case for the fractal determinations.

Shepherd, I.G. [Lawrence Berkeley National Lab., CA (United States). Energy and Environment Div.

1995-10-01

75

Flame Structure and Flame Reaction Kinetics. III. Measurement of Temperature Profiles in Flames at Atmospheric Pressure  

Microsoft Academic Search

The temperature profile m a slow burning, flat hydrogen-nitrogen-oxygen flame at atmospheric pressure has been measured by means of (1) a thermocouple probe which could be moved through the flame zone, and (2) an optical method which mvolves measurement of the deflexion of rays of light passing through the flame in a direction normal to the temperature and refractive index

G. Dixon-Lewis; G. L. Isles

1969-01-01

76

Visible emission of hydrogen flames  

SciTech Connect

The common misconception that hydrogen flames are not visible is examined. Examples are presented of clearly visible emissions from typical hydrogen flames. It is shown that while visible emissions from these flames are considerably weaker than those from comparable hydrocarbon flames, they are indeed visible, albeit at reduced light levels in most cases. Detailed flame spectra are presented to characterize flame emission bands in the ultraviolet, visible and infrared regions of the spectrum that result in a visible hydrogen flame. The visible blue emission is emphasized, and recorded spectra indicate that fine spectral structure is superimposed on a broadband continuum extending from the ultraviolet into the visible region. Tests were performed to show that this emission does not arise from carbon or nitrogen chemistry resulting from carbon-containing impurities (hydrocarbons) in the hydrogen fuel or from CO{sub 2} or N{sub 2} entrainment from the surrounding air. The spectral structure, however, is also observed in methane flames. The magnitude of the broadband emission increases with flame temperature in a highly nonlinear manner while the finer spectral structure is insensitive to temperature. A comparison of diffusion and premixed H{sub 2} flames shows that the fine scale structure is comparable in both flames. (author)

Schefer, R.W.; Kulatilaka, W.D.; Patterson, B.D.; Settersten, T.B. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551-0969 (United States)

2009-06-15

77

Sounding and Sensitive Flames  

Microsoft Academic Search

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

A. S. Herschel

1874-01-01

78

Flame ionization gas analyzers  

Microsoft Academic Search

The paper deals with gas analyzers in which the measured change in conductivity of a standard flame due to the insertion of another gas is used to detect the gas. The application of gas analyzers of this type to the detection of atmospheric pollutants is examined, and some existing gas analyzer designs are discussed.

A. N. Belugin; A. Ia. Bonn; G. V. Verbovskaia; A. M. Drobiz; Iu. G. Khachaturov

1979-01-01

79

Modeling turbulent flame propagation  

SciTech Connect

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

Ashurst, W.T.

1994-08-01

80

"Magic Eraser" Flame Tests  

ERIC Educational Resources Information Center

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

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

2009-01-01

81

Flame retardant polymeric materials  

SciTech Connect

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.

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

1982-01-01

82

Flame Retardation of Polymers.  

National Technical Information Service (NTIS)

The central purpose of this study is to understand the chemical events that may be occurring in the decomposition of a polymer and how a potential flame retardant would in general suppress, alter or modify certain chemical reactions. jg p11.

J. K. Kiang

1979-01-01

83

Incomplete combustion in nonadiabatic premixed gas flames  

Microsoft Academic Search

The inward propagating spherical flame and burner stabilized Bunsen-type flame of low-Lewis-number premixtures are studied numerically. It is shown that reduction of the reaction rate induced by the flame stretch makes the flame vulnerable to the radiative heat losses which may well result in a partial or complete extinction of the flame.

L. Kagan; G. Sivashinsky

1996-01-01

84

Flame characteristics for fires in southern fuels  

Treesearch

Asheville, NC: USDA-Forest Service, Southeast Forest Experiment Station. ... Approximate solutions are used to express flame lengths, angles, heights, and tip velocities of ... controlled burns in southern fuels and with data from the literature. Keywords: Flame length, flame velocity, flame angle, fire intensity, buoyant flames.

85

Flame Front Geometry and Stretch During Interactions of Premixed Flames with Vortices  

Microsoft Academic Search

Flame front geometry and flame stretch during interactions of premixed flames with vortices at various configurations are computationally investigated using a kinematical relationship between vortex-induced velocity and flame propagation velocity, in conjunction with Lagrangian coordinates to represent the flame front. The maximum flame stretch that can occur during an interaction with a single vortex is found to be very close

T.-W. LEE; D. A. SANTAVICCA

1993-01-01

86

Flame Interactions in Turbulent Premixed Twin V-flames  

Microsoft Academic Search

Multiple flame-flame interactions in premixed combustion are investigated using Direct Numerical Simulations of twin turbulent V-flames for a range of turbulence intensities and length scales. Interactions are identified using a novel Automatic Feature Extraction (AFE) technique, based on data registration using the Dual-Tree Complex Wavelet Transform. Information on the time, position and type of interactions, and their influence on the

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

2012-01-01

87

Photometry of faint blue stars - IX  

NASA Astrophysics Data System (ADS)

Stromgren uv by photometry is presented for 129 `faint blue' stars taken from various catalogues. The photometry is used to estimate photometric `classifications' for the stars, which indicate a mixture of hot subdwarfs, horizontal-branch stars, metal-weak subdwarfs and so on. Attention is drawn to stars (from this paper and previous papers in the series) which appear to be somewhat reddened. Some are probably binaries, and others might be objects with peculiar colours, such as cataclysmic variables. One star, LB 9963, almost certainly falls into the latter category. Two stars which, from their colours, are Population II A-F stars are variable; one of these, OM 89, is the known RR Lyrae star, VW Dor.

Kilkenny, D.

1995-12-01

88

The surface photometry of NGC 3379  

NASA Astrophysics Data System (ADS)

Surface photometry is carried out for the photometric standard galaxy NGC 3379 on the basis of two plates in the blue band. The results, including luminosity profiles, photometric parameters, integrated luminosity distribution, ellipticity and position angle variation, are presented. The ellipticity and position angle variations reach up to 5 arc mins, much fainter than any previous study. The accuracy of the present data is checked by comparing them with the surface photometry in the literature. It is found that the zero-point about 0.12 mag brighter than the calibration of de Vaucouleurs and Capaccioli (1979), which agrees with the values 0.10-0.15 mag difference claimed by recent observations. The systematic differences is found to be less than about 0.1 mag.

Hu, F. X.; Hamabe, M.; Okamura, S.; Su, H. J.

1989-08-01

89

Photometry of Variables from Dome A, Antarctica  

NASA Astrophysics Data System (ADS)

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.

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

90

Distant galaxy clusters photometry (Stanford+, 2002)  

NASA Astrophysics Data System (ADS)

We present optical and near-infrared photometry of 45 clusters of galaxies at 0.1photometry has been used in previously published papers to examine the origin and evolution of galaxies in distant clusters. Beginning in 1991, we sought to make use of the advent of relatively large format near-IR detectors to study the galaxy populations of distant clusters. We collected imaging data in both the near-IR and the optical on a large sample of clusters drawn from several samples. These data were analyzed and detailed results were presented on the evolution of early-type galaxies at moderate redshifts in Stanford, Eisenhardt, & Dickinson (1995ApJ...450..512S, 1998ApJ...492..461S), on the evolution of the K-band luminosity function in De Propris et al. (1999AJ....118..719D), on the Butcher-Oemler effect in K-selected galaxy samples in De Propris et al. (2003, ApJ, submitted), and on the evolution of early-type galaxies in high-redshift clusters in Holden et al. (2003, ApJ, in press). So far the photometry for these various studies has been published for only two clusters, Abell 370 and Abell 851 in Stanford et al. (1995ApJ...450..512S). In this paper, we present the photometry on the other 43 clusters used in our published work on distant clusters. (9 data files).

Stanford, S. A.; Eisenhardt, P. R.; Dickinson, M.; Holden, B. P.; de Propris, R.

2002-11-01

91

UBVRIJHK photometry in NGC1624 (Jose+, 2011)  

NASA Astrophysics Data System (ADS)

The CCD UBVRI observations of NGC 1624 were carried out using Hanle Faint Object Spectrograph and Camera (HFOSC) of the 2-m Himalayan Chandra Telescope (HCT) of Indian Astronomical Observatory (IAO), Hanle, India on 2004 November 3. We repeated the observations of NGC 1624 in V and Ic filters to get a deeper photometry on 2006 December 12 using the 104-cm Sampurnanand Telescope (ST) of Aryabhatta Research Institute of observational sciencES (ARIES), Naini Tal, India. (1 data file).

Jose, J.; Pandey, A. K.; Ogura, K.; Ojha, D. K.; Bhatt, B. C.; Samal, M. R.; Chauhan, N.; Sahu, D. K.; Rawat, P. S.

2011-10-01

92

Current Integrator for Astronomical Photoelectric Photometry  

Microsoft Academic Search

An integrator circuit is described, together with programmer and timer, which was constructed for measuring signal-current from a photomultiplier tube as used in astronomical photometry. At the end of a timed run, the voltage data are impressed upon a strip-chart pen recorder. The current-range of such instrument encompasses a span from 10?6 to 10?11 ampere, full scale, with stability and

Robert H. Weitbrecht

1957-01-01

93

100 years of photometry and radiometry  

NASA Astrophysics Data System (ADS)

Measurement of light is an old subject, though the past 100 years have seen significant advances. 100 years ago, photometry - the art and science of measuring light as it is perceived by people - had the greater technological importance. Even today SI (the metric system) retains a base unit for photometry, the candela. However, early work at NBS included pivotal projects in the field of radiometry - the measurement of the physical characteristics of light. These included the validation of Planck's newly-minted theory of blackbody radiation, determining the radiation constants with good accuracy, and the definitive analysis of the spectral responsivity of human vision, so as to relate photometry to radiometry. This latter work has only increased in importance over the past 75 years as the definition of the candela has changed and improved. Today, NIST makes radiometric, and hence photometric measurements, with unprecedented precision. Cryogenic radiometers based on the principle of electrical substitution measure optical flux with uncertainties of 0.02%. Additional facilities enable measurement of spectral responsivity, spectral radiance, and spectral irradiance. Novel detectors, such as light-traps, allow the best accuracy to be transferred from the primary standards to routinely-used instruments and to calibration customers. Filtered detectors are used to realize photometric scales, radiation temperature scales, and other specialized measurements. Indeed, the story of the metrology of light is the story of continuous improvement, both driven by and enabled by advances in technology. We touch upon some of these as a prelude to the other talks in this Conference.

Hardis, Jonathan E.

2001-06-01

94

Astrometry and photometry in high contrast imaging  

NASA Astrophysics Data System (ADS)

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

Galicher, Raphael; Marois, Christian

2011-09-01

95

Nanoclusters produced in flames  

SciTech Connect

Nanotubes have been synthesized by low-pressure fuel-rich benzene-oxygen flames. They were usually solitary and seldom appeared in a bundle. Both closed-end and open-end nanotubes were observed. A new type of nanocluster was also synthesized. We suggest that these nanoclusters are not hollow and are composed of a series of concentric tubes of 6.2 A radius increments. 15 refs., 4 figs.

Duan, H.M.; McKinnon, J.T. (Colorado School of Mines, Golden, CO (United States))

1994-12-08

96

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

97

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Flame resistance. 14.20 Section 14...PRODUCTS REQUIREMENTS FOR THE APPROVAL OF FLAME-RESISTANT CONVEYOR BELTS Technical Requirements § 14.20 Flame resistance. Conveyor belts for...

2009-07-01

98

Modeling of Flame Properties of Methanol.  

National Technical Information Service (NTIS)

Many fuel utilization concepts involve detailed information on flame properties. Processes such as ignition, flame propagation, flame quenching, pollutant formation and others all require the type of fundamental understanding which numerical modeling can ...

C. K. Westbrook F. L. Dryer

1979-01-01

99

Differential Photometry with OSCAAR: Open Source Differential Photometry Code for Amateur Astronomical Research  

NASA Astrophysics Data System (ADS)

We present a cross-platform, open-source differential photometry package written in Python, called OSCAAR (Open Source differential photometry Code for Amateur Astronomical Research). The code is intended for use by undergraduate students or small observatories, or to be used as a scaffolding to be built upon and refined by more advanced users. OSCAAR can be controlled with a graphical user interface for those unfamiliar with Python. OSCAAR makes extensive use of existing astronomical software packages, and the implementation of classes and methods within OSCAAR is designed to be highly modular and interchangeable. The aim of OSCAAR is to provide a free, practical differential photometry toolkit with which users can easily create light curves, and also to encourage the users to work with the source code and refine it for their own purposes.

Morris, Brett M.; Katz, H.; OSCAAR Team

2013-06-01

100

NCN detection in atmospheric flames  

SciTech Connect

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

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

2010-04-15

101

New UBVRI Photometry of 234 M33 Star Clusters  

NASA Astrophysics Data System (ADS)

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 deg2 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 & Kaluzny. Combined with star cluster photometry in previous studies, we present some results: none of the M33 youngest clusters (~107 yr) have masses approaching 105 M ?, and comparisons with models of simple stellar populations suggest a large range of ages for M33 star clusters and some as old as the Galactic globular clusters.

Ma, Jun

2013-04-01

102

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

Microsoft Academic Search

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

Satoshi Kadowaki; Tatsuya Hasegawa

2005-01-01

103

Triaxial Burke-Schumann Flames with Applications to Flame Synthesis  

Microsoft Academic Search

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

B. H. CHAO; R. L. AXELBAUM

2000-01-01

104

Flame retarded asphalt blend composition  

SciTech Connect

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

Walters, R.B.

1987-04-21

105

Not Just Another Old Flame  

NSDL National Science Digital Library

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

2007-07-03

106

Statistics of premixed flame cells  

SciTech Connect

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

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

1991-07-15

107

A Dramatic Flame Test Demonstration  

Microsoft Academic Search

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

Kristin A. Johnson; Rodney Schreiner

2001-01-01

108

Late-2012 Photometry of SN 2009ip  

NASA Astrophysics Data System (ADS)

The object designated SN 2009ip was first noted in NGC 7259 in August 2009. There was evidence of photometric variability in the years preceding discovery and when it brightened again in July 2010 it was classified as a SN impostor. The latest pair of outbursts in July 2012 and September 2012 may have been a terminal SN explosion. We present V, Rc, and Ic-band photometry following the September 2012 event along with an analysis of periodic brightness fluctuations that were recorded during its decline in brightness.

Martin, John C.; Hambsch, F.; Tan, T. G.; Curtis, I. A.

2013-06-01

109

Deep CCD photometry of spiral galaxies  

NASA Astrophysics Data System (ADS)

This study presents deep optical surface photometry in the R-band for the three spiral galaxies NGC 1003, NGC 5533, and NGC 6674. The luminosity profiles, derived by fitting ellipses to the isophotes, are decomposed into bulge and disk contributions using the method proposed by Kent (1986). The intrinsic bulge and disk axis ratios, used in the iterative scheme, are 0.71 and 0.59 for NGC 5533, 0.44 and 0.33 for NGC 1003, and 0.90 and 0.50 for NGC 6674.

Broeils, A. H.; Knapen, J. H.

1991-12-01

110

Charles Nordmann and Multicolour Stellar Photometry  

NASA Astrophysics Data System (ADS)

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

Lequeux, James

2010-11-01

111

uvby photometry in NGC 7419 (Marco+, 2013)  

NASA Astrophysics Data System (ADS)

The open cluster NGC 7419 is known to contain five red supergiants and a very high number of Be stars. However, there are conflicting reports about its age and distance that prevent a useful comparison with other clusters. We intend to obtain more accurate parameters for NGC 7419, using techniques different from those of previous authors, so that it may be used as a calibrator for more obscured clusters. We obtained Stroemgren photometry of the open cluster NGC 7419, as well as classification spectroscopy of ~20 stars in the area. We then applied standard analysis and classification techniques. (3 data files).

Marco, A.; Negueruela, I.

2013-02-01

112

Multicolor photometry of outer Jovian satellites  

NASA Astrophysics Data System (ADS)

Multicolor photometry was obtained of satellites J6 Himalia, J7 Elara, and J10 Lysithea in the prograde cloud of outer Jovian satellites, and of J8 Pasiphae, J9 Sinope, and J11 Carme in the retrograde cloud. The data for J9 are fragmentary; otherwise, the satellites all look like C-class asteroids, except J11, which shows a remarkable brightness in the ultraviolet. The absence of D-class spectra among the outer Jovian satellites suggests that they were not derived from the same population as the outer-belt and Trojan asteroid populations.

Tholen, D. J.; Zellner, B.

1984-05-01

113

Near Infrared Photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

114

Effects of compression and stretch on the determination of laminar flame speeds using propagating spherical flames  

Microsoft Academic Search

The effects of flow compression and flame stretch on the accurate determination of laminar flame speeds at normal and elevated pressures using propagating spherical flames at constant pressure or constant volume are studied theoretically and numerically. The results show that both the compression-induced flow motion and flame stretch have significant impacts on the accuracy of flame speed determination. For the

Z. Chen; M. P. Burke; Y. Ju

2009-01-01

115

Dynamics of weakly stretched flames: quantitative description and extraction of global flame parameters  

Microsoft Academic Search

Generalized expressions for the flame response to weak stretch rate variations were derived based on an integral analysis. Together with values of the laminar flame speed, laminar flame thickness, and the one-step overall reaction order and activation energy determined from the computational results of the one-dimensional planar flame, these expressions for the stretched flames were then used to correlate the

C. J. Sun; C. J. Sung; L. He; C. K. Law

1999-01-01

116

Modelling of lifted turbulent diffusion flames in a channel mixing layer by the flame hole dynamics  

Microsoft Academic Search

The partial quenching structure of turbulent diffusion flames in a turbulent mixing layer is investigated by the method of flame hole dynamics as an effort to develop a prediction model for the turbulent flame lift off. The essence of the flame hole dynamics is derivation of the random walk mapping, from the flame-edge theory, which governs expansion or contraction of

Junhong Kim; J. S. Kim

2006-01-01

117

Numerical study on dynamics of local flame elements in turbulent jet premixed flames  

Microsoft Academic Search

Direct numerical simulations (DNSs) of turbulent jet premixed flames have been conducted to investigate dynamics of local flame elements. Behaviors of turbulent jet flames are discussed by considering characteristics of local flame elements such as flame displacement speed, local turbulent burning velocity, curvature and tangential strain rate. The peak of probability density function (pdf) of the local turbulent burning velocity

K. Yamayaki; Y.-S. Shim; N. Fukushima; M. Shimura; M. Tanahashi; T. Miyauchi

2010-01-01

118

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

Microsoft Academic Search

In non-premixed turbulent combustion the reactive zone is localized at the stoichiometric surfaces of the mixture and may be locally approximated by a diffusion flame. Experiments and numerical simulations reveal a characteristic structure at the edge of such a two-dimensional diffusion flame. This `triple flame' or `edge flame' consists of a curved flame front followed by a trailing edge that

Sandip Ghosal; Luc Vervisch

2000-01-01

119

JHK photometry of CBJC 8 sources (Persi+, 2011)  

NASA Astrophysics Data System (ADS)

Coordinates (J2000) and JHK photometry are given for the 493 sources detected with PANIC on Baade Telescope in an area of 111"x111" centred on G85.40+0.00 as well as photometry in the four IRAC bands measured on archive frames of the same area. (2 data files).

Persi, P.; Tapia, M.; Gomez, M.

2010-11-01

120

WISE photometry of EXor sources and candidates  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

121

A GUI for Aperture Photometry in IRAF  

NASA Astrophysics Data System (ADS)

A graphical user interface for an interactive IRAF application which does fractional pixel aperture photometry through circular, rectangular, or polygonal apertures is presented. The GUI provides facilities for interactively selecting and displaying the image data, selecting and marking the object and background regions to be analyzed, displaying and editing the algorithm parameters, and simultaneously displaying the results both graphically and in text format. Graphical display of the results of the analysis are in the form of a zoomed and marked image display and profile plots of the region of interest, and histogram plots of the associated background region. The GUI uses the new IRAF widget server prototype, which allows the GUI to be well isolated from the photometry code while still permitting a tightly integrated application to be developed. The prototype widget server provides custom IRAF widgets for the graphics and image display plus a selection of standard toolkit widgets such as buttons and menus, allowing IRAF applications to be developed with custom GUIs.

Davis, L. E.

122

Flame Furnace Atomic Absorption Spectrometry: A Review  

Microsoft Academic Search

Flame atomic absorption spectrometry (FAAS) is one of the most widespread traditional analytical techniques for trace element determination, but it often suffers from poor sensitivity due to the low nebulization efficiency and the short residence time of free atoms in the flame. On the basis of conventional FAAS, flame furnace atomic absorption spectrometry (FF-AAS) is developed with a tube (flame

Peng Wu; Shaopan He; Bin Luo; Xiandeng Hou

2009-01-01

123

Acoustic Detection of Blowout in Premixed Flames  

Microsoft Academic Search

Work to develop a practical, fast diagnostic technique to monitor the proximity of a combustor to blowout using measurements of the flame's acoustic signature is described. The feasibility of this approach was demonstrated on three combustors with different flame holding mechanisms that are used in most practical combustion devices: pilot, swirl, and bluff-body stabilized flames. Extensive high-speed flame images were

Suraj Nair; Tim Lieuwen

2005-01-01

124

Pockets in turbulent premixed flames  

NASA Astrophysics Data System (ADS)

We address in this paper the problem of pocket formation in turbulent premixed flames. Pockets of unburnt gases inside the burnt gases, or of burnt gases inside unburnt gases have been observed in experiments, usually in tomographic cuts of a three-dimensional flame. We study here two effects (range of length scales and different time correlations) controlling the number and type of pockets created, on the basis of a two-dimensional numerical study of the thermal-diffusive model subjected to an external turbulent forcing (i.e. we neglect the retroaction of the flame on the flow field).

Denet, Bruno

2001-03-01

125

Flowfield-flame structure interactions in an oscillating swirl flame  

Microsoft Academic Search

A swirling methane-air diffusion flame at atmospheric pressure is stabilized in a gas turbine model combustor with good optical\\u000a access. The investigated flame with a thermal power of 10 kW and an overall equivalence ratio of 0.75 exhibits pronounced\\u000a thermoacoustic oscillations at a frequency of 295 Hz. The main goal of the presented work is a detailed experimental characterization\\u000a of

R. Sadanandan; M. Stöhr; W. Meier

2009-01-01

126

Flame spraying of polymers  

SciTech Connect

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.

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

127

CURVATURE EFFECTS ON EDGE-FLAME PROPAGATION IN THE PREMIXED-FLAME REGIME  

Microsoft Academic Search

We examine the effects of curvature on edge-flame propagation speeds as a function of the fuel Lewis number. The diffusion flame supporting the flame edge is assumed to be in Liñán's “premixed-flame regime” with oxygen leak-age through the flame caused by excessive heat loss to the bounding surface. Adopting an approximate one-dimensional model, we calculate flame-edge propagation velocities in the

VEDHA NAYAGAM; FORMAN A. WILLIAMS

2004-01-01

128

uvby photometry of BH Vir (Clement+ 1997)  

NASA Astrophysics Data System (ADS)

This paper presents new complete uvby light curves of the late-type detached eclipsing binary BH Vir (G0V + G5V, P=0.81687099d). This binary system has been observed during four campaigns at the Calar Alto Observatory (Almeria, Spain) and at the European Southern Observatory (La Silla, Chile). This observations are part of a 6 year uvby and H{beta} monitoring program of low mass eclipsing binaries which main objective is to provide accurate absolute astrophysical parameters for late-type main sequence stars. 1585 points spreaded over the binary period and covering both eclipses are given. The internal accuracy of the standard photometry measured as the mean RMS of the differences between standard value and observed value for the standard stars observed along the program is quoted in a few millimagnitudes. Detailed analysis of BH Vir, based on these light curves, will be published separately. (2 data files).

Clement, R.; Garcia, M.; Reglero, V.; Clausen, J. V.; Bravo, A.; Suso, J.; Fabregat, J.

1996-09-01

129

Techniques for Automated Single-Star Photometry  

NASA Astrophysics Data System (ADS)

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

Henry, Gregory W.

2001-02-01

130

Gaia photometry: methods, performances and problems  

NASA Astrophysics Data System (ADS)

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

Jordi, C.

2011-02-01

131

VBLUW photometry of some halo field giants  

NASA Astrophysics Data System (ADS)

Walraven photometry has been obtained for a sample of 43 metal-deficient halo giants and 35 stars with known values of Teff, log g and [Fe/H]. A calibration of Walraven photometric indices in terms of ? = 5040K/Teff and [Fe/H] is established. The metallicities derived for the sample of halo giants are in good agreement with those of Kraft et al. (1982). In contrast to the metallicities derived by Bond (1980), the authors find a considerably lower number of stars with [Fe/H] < -2.7 dex. The calibration yields a metallicity of -2.9 dex for CoD-38°245, which is in contrast to the extremely low value of -4.6 dex based on a spectroscopic abundance determination by Bessell and Norris (1981). The importance of this star for the calibration of photometric metallicities in the domain of extreme metal deficiency is discussed.

Nelles, B.; Richtler, T.; Seggewiss, W.

1984-10-01

132

TERMS PHOTOMETRY OF KNOWN TRANSITING EXOPLANETS  

SciTech Connect

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

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

2011-10-15

133

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...

134

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...

135

Flame Retardant Organic Fibrous Materials.  

National Technical Information Service (NTIS)

In the patent application organic fibrous materials especially cellulosic and other textiles are rendered flame resistant upon treatment with an emulsion containing (1) a tetrakis(hydroxymethyl)phosphonium salt, (2) an amide, (3) a salt of a strong base a...

D. J. Donaldson F. L. Normand G. L. Drake W. A. Reeves

1973-01-01

136

Time Series Photometry of the Youngest Stars - MIPS24 Photometry for IC1396A  

NASA Astrophysics Data System (ADS)

We have recently obtained IRAC time-series photometry of the embedded, very young cluster of young stellar objects (YSOs) in the Elephant's Trunk Nebula (a.k.a. IC1396A). About 20% of the YSOs, including about half of the Class I stars, showed relatively large amplitude (> 0.1 mag) variability with characteristic timescales of 4 to 15 days, and with very little difference in light curve shape and amplitude between 3.6 and 8 microns. The most plausible physical model for these variations is that we are seeing these stars primarilyin scattered light all the way out to 8 microns, and that the sources of the variability are hot spots (from accretion flows) on the surfaces of these stars. In order to place further constraints on models for these stars, we propose to obtain MIPS24 photometric observations of the 5'x5' "head" of the IC1396A star-forming globule at sixteen epochs, about twice per day, during a single MIPS campaign. We will also obtain a small amount of new IRAC time-series photometry in an adjacent campaign in order to place the MIPS photometry in better context with the existing IRAC light curves obtained in February 2008. The entire set of observations requires 3.6 hours of observing time.

Stauffer, John; Carey, Sean; Hartmann, Lee; Hillenbrand, Lynne; Morales, Maria; Rebull, Luisa; Werner, Michael

2008-08-01

137

Difference image photometry with bright variable backgrounds  

NASA Astrophysics Data System (ADS)

Over the last two decades the Andromeda galaxy (M31) has been something of a test-bed for methods aimed at obtaining accurate time-domain relative photometry within highly crowded fields. Difference imaging methods, originally pioneered towards M31, have evolved into sophisticated methods, such as the optimal image subtraction (OIS) method of Alard & Lupton, that today are most widely used to survey variable stars, transients and microlensing events in our own Galaxy. We show that modern difference image analysis (DIA) algorithms such as OIS, whilst spectacularly successful towards the Milky Way bulge, may perform badly towards high surface brightness targets such as the M31 bulge. Poor results can occur in the presence of common systematics which add spurious flux contributions to images, such as internal reflections, scattered light or fringing. Using data from the Angstrom Project microlensing survey of the M31 bulge, we show that very good results are usually obtainable by first performing careful photometric alignment prior to using OIS to perform point spread function (PSF) matching. This separation of background matching and PSF matching, a common feature of earlier M31 photometry techniques, allows us to take full advantage of the powerful PSF matching flexibility offered by OIS towards high surface brightness targets. We find that difference images produced this way have noise distributions close to Gaussian, showing significant improvement upon results achieved using OIS alone. We show that with this correction light curves of variable stars and transients can be recovered to within ~10arcsec of the M31 nucleus. Our method is simple to implement and is quick enough to be incorporated within real-time DIA pipelines. We also demonstrate that OIS is remarkably robust even when, as in the case of the central regions of the M31 bulge, the sky density of variable sources approaches the confusion limit.

Kerins, E.; Darnley, M. J.; Duke, J. P.; Gould, A.; Han, C.; Newsam, A.; Park, B. G.; Street, R.

2010-11-01

138

Laser speckle photometry: contactless nondestructive testing technique  

NASA Astrophysics Data System (ADS)

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

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

139

A Dramatic Flame Test Demonstration  

NASA Astrophysics Data System (ADS)

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

Johnson, Kristin A.; Schreiner, Rodney

2001-05-01

140

FLAME reentry systems test vehicle  

Microsoft Academic Search

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

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

1976-01-01

141

Turbulent Oxygen Flames in Type Ia Supernovae  

NASA Astrophysics Data System (ADS)

In previous studies, we examined turbulence-flame interactions in carbon-burning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damköhler numbers (Da16) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when Da16 < 1, and the flame burns inductively some distance behind the carbon flame. However, for Da16>1, turbulence enhances heat transfer and drives the propagation of a flame that is narrower than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen turbulent flame with complex compound structure. The simulations do not appear to support the possibility of a transition to detonation in the oxygen flame, but do not preclude it either.

Aspden, A. J.; Bell, J. B.; Woosley, S. E.

2011-04-01

142

TURBULENT OXYGEN FLAMES IN TYPE Ia SUPERNOVAE  

SciTech Connect

In previous studies, we examined turbulence-flame interactions in carbon-burning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damkoehler numbers (Da{sub 16}) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when Da{sub 16} < 1, and the flame burns inductively some distance behind the carbon flame. However, for Da{sub 16}>1, turbulence enhances heat transfer and drives the propagation of a flame that is narrower than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen turbulent flame with complex compound structure. The simulations do not appear to support the possibility of a transition to detonation in the oxygen flame, but do not preclude it either.

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

2011-04-01

143

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

National Technical Information Service (NTIS)

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 fl...

Z. Dai A. M. El-Leathy K. C. Lin P. B. Sunderland F. Xu G. M. Faeth

2000-01-01

144

The role of boron in flame-retardant treatments  

Treesearch

Forest Products Laboratory ... 39-41 : ill. Description: Flame retardants for wood alter the combustion properties of wood to reduce surface flame spread. Flame ... Two types of fire tests were used to evaluate flame retardancy. Clearwood and ...

145

The flaming funis.  

PubMed

The authors observed a Nicaraguan traditional birth attendant burn the fetal end of the umbilical cord with camphor. They review this practice and reflect on the role of foreign medical volunteers in the developing world. There is a long history to the use of camphor in rituals and medicine. No print references to burning the umbilical cord with camphor, its effectiveness, or its safety could be identified. Interviews with Nicaraguan traditional birth attendants revealed that the practice is passed from generation to generation and that it is believed to decrease infections through the medicinal properties of camphor as well as the flame it produces. It is continued in modern times because it is easy and inexpensive and because there are no clearly better and sustainable alternatives available. Gradual and culturally sensitive modernization to improve the health for mothers and babies is appropriate, but it will be a slow process. Health care volunteers in the developing world struggle with doing the best they can despite the limited resources and sometimes the local traditions. Volunteering as a medical worker in the developing world provides inspiring rewards, teaches powerful lessons, and exposes challenging conflicts. PMID:15292015

Young, William W; Dedam, Jean-Paul; Conley, Sarah; Wickner, Paige

2004-08-01

146

VI photometry of the Leo II galaxy (Bellazzini+, 2005)  

NASA Astrophysics Data System (ADS)

V and I photometry and astrometry for 2715 stars in a 9.4'x9.4' field centered on the Leo II dwarf spheroidal galaxy. Photometric system: Johnson-Kron-Cousins (Landolt's photometric standards). (1 data file).

Bellazzini, M.; Gennari, N.; Ferraro, F. R.

2005-06-01

147

SYNMAG Photometry: Catalog-level Matched Colors of Extended Sources  

NASA Astrophysics Data System (ADS)

SYNMAG is a tool for producing synthetic aperture magnitudes to enable fast matched photometry at the catalog level without reprocessing imaging data. Aperture magnitudes are the most widely tabulated flux measurements in survey catalogs; obtaining reliable, matched photometry for galaxies imaged by different observatories represents a key challenge in the era of wide-field surveys spanning more than several hundred square degrees. Methods such as flux fitting, profile fitting, and PSF homogenization followed by matched-aperture photometry are all computationally expensive. An alternative solution called "synthetic aperture photometry" exploits galaxy profile fits in one band to efficiently model the observed, point-spread-function-convolved light profile in other bands and predict the flux in arbitrarily sized apertures.

Bundy, Kevin; Hogg, David W.; Higgs, Tim D.; Nichol, Robert C.; Yasuda, Naoki; Masters, Karen L.; Lang, Dustin; Wake, David A.

2013-02-01

148

Feasibility Study of Coal Dust Measurement by Light Reflectance Photometry.  

National Technical Information Service (NTIS)

This report describes the design, fabrication, and testing of a proto-type instrument that demonstrates the feasibility of determining respirable coal dust concentrations by light reflectance photometry. Coal dust is collected on a filter and the amount c...

I. Pritts G. A. Bertone

1981-01-01

149

Improved Asteroid Astrometry and Photometry with Trail Fitting  

NASA Astrophysics Data System (ADS)

We present the trail fitting algorithm that introduces the trail equation. Our demonstration of trail and PSF fitting on synthetic and Pan-STARRS PS1 detected asteroid detections leads to improved astrometry and photometry of trailed detections.

Vereš, P.; Jedicke, R.; Denneau, L.; Wainscoat, R.; Holman, M. J.

2012-05-01

150

Binary Star Synthetic Photometry and Distance Determination Using BINSYN  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

151

Large-Scale Errors in CCD Photometry of M67  

Microsoft Academic Search

The accuracy of new CCD photometry in the Vilnius system of the M67 cluster is analyzed. The observational material is obtained during six observing runs in 1994--2001 with the 1 meter telescope of the USNO Flagstaff Station. The main task was to establish CCD standards of high accuracy and to eliminate large-scale errors from our CCD photometry. We compare our

V. Laugalys; R. P. Boyle; A. Kazlauskas; F. J. Vrba; A. G. Davis Philip; V. Straizys

2003-01-01

152

FIXING THE U-BAND PHOTOMETRY OF TYPE Ia SUPERNOVAE  

SciTech Connect

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

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

2013-01-01

153

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

Microsoft Academic Search

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

O. C. KWON; G. M. FAETH

2001-01-01

154

Stability of inclined planar flames as a local approximation of weakly curved flames  

Microsoft Academic Search

To evaluate the effect of vorticity usually generated by curved flames on the flame stability, laminar premixed planar flames inclined in the gravitational field is asymptotically examined. The flame structure is resolved by a large activation energy asymptotics and a long wave approximation. The coupling between hydrodynamics and diffusion processes is included and near-unity Lewis number is assumed. The results

Dae Keun Lee; Moon-Uhn Kim; Hyun Dong Shin

2005-01-01

155

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

Microsoft Academic Search

Chemical inhibition of laminar propane flames by organophosphorus compounds has been studied experimentally, using a laboratory Mache Hebra nozzle burner and a flat flame burner with molecular beam mass spectrometry (MBMS), and with a computational flame model using a detailed chemical kinetic reaction mechanism. Both fuel-lean and fuel-rich propane flames were studied to examine the role of equivalence ratio in

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

2003-01-01

156

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

Microsoft Academic Search

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

Yuji Nakamura; Ryosuke Nozaki; Akio Kitajima

2011-01-01

157

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames  

Microsoft Academic Search

The flame base structures of laminar lifted flames are numerically investigated in order to develop a model of triple flame applicable to the flamelet model. The lifted flames formed in the downstream expanded duct developed by Kioni et al.are calculated systematically in terms of the fuel concentration gradient at the inlet using a variant of the HSMAC method, modified so

Susumu Noda; Shuhei Yamamoto

2006-01-01

158

A new flame detector using the latest research on flames and fuzzy-wavelet algorithms  

Microsoft Academic Search

The detection of a fire with a flame detector relies upon the analysis of the flame flickering at several wavelengths. In order to improve the quality of the detection, a number of open questions have been addressed: What is the physical effect responsible for the flame pulsation of a diffusion flame? How does the main frequency depend on the location

M. Thuillard

2002-01-01

159

Flame Structure of a Jet Flame with Penetration of Side Micro-jets  

Microsoft Academic Search

In this paper, an innovative jet lifted flame with side micro-jets has been proposed and its effects on the flame structure have also been investigated. Due to the changes of the initial combustion conditions, mixing and aerodynamics which resulted from the perturbation of the side micro-jets, such a lifted jet flame has different flame structure compared with the common premixed

Yuchun CAO; Jinxing WU; Jianchun MI; Yu ZHOU

2008-01-01

160

Radiant Extinction of Gaseous Diffusion Flames.  

National Technical Information Service (NTIS)

The absence of buoyancy-induced flows in microgravity significantly alters the fundamentals of many combustion processes. Substantial differences between normal-gravity and microgravity flames have been reported during droplet combustion, flame spread ove...

A. Atreya S. Agrawal T. Shamim K. Pickett K. R. Sacksteder

1995-01-01

161

Flame Propagation under Partially-Premixed Conditions.  

National Technical Information Service (NTIS)

This study concentrates on developing a better understanding of triple flames. We relax the assumption of zero heat release, address the issue of stabilization, and, in order to investigate the role that heat release plays in flame propagation in partiall...

G. R. Ruetsch

1994-01-01

162

Mechanistic Studies of Phosphorus Containing Flame Retardants.  

National Technical Information Service (NTIS)

A combination of mass spectrometric and optical spectroscopic studies has been made to establish a mechanism for phosphorus controlled flame retardancy in thermoplastics. It is shown that a vapor phase mode of flame inhibition can account for the known fl...

C. L. McBee J. W. Hastie

1976-01-01

163

Flame-Sprayed Polymeric Protective Coatings.  

National Technical Information Service (NTIS)

A silicone, polyimide prepolymer, and a carborane-modified polybenzimidazole resin were evaluated as flame-and arc plasma-sprayed protective coatings. Considerable decomposition of the silicone powder into carbonaceous material was observed in flame-spray...

R. J. Janowieck M. C. Willson

1966-01-01

164

Synthetic IR Photometry of Main Sequence Stars  

NASA Astrophysics Data System (ADS)

We describe results on the calculation and comparison of synthetic photometry in 40 IR and sub-mm bands conducted using three different libraries of theoretical stellar spectra: MARCS, ATLAS9 and PHOENIX. Discrepancies of photometric magnitudes obtained with these libraries are less than 3% over the wavelength range 1-160?m. We use PHOENIX fluxes to construct an extensive grid of nearly 9000 points that cover the effective temperature interval 5000-7000 K (step of 200 K), surface gravity, log(g) = 3.5 to 5.0 (step of 0.5 dex), and [M/H] = -2.0 to +0.0 (step of 0.5 dex). We use PHOENIX theoretical fluxes and simple disk emission models to construct a series of diagnostic diagrams that allow a direct identification of an IR-submm excess and a preliminary determination of the properties of the material originating that excess. The grid is aimed at providing a handy access to photospheric fluxes for the analysis of IR excesses of solar like stars.

Cruz Saenz de Miera, F.; Chavez, M.; Bertone, E.; Vega, O.

2013-04-01

165

BATC photometry on A119 (Tian+, 2012)  

NASA Astrophysics Data System (ADS)

This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 (z=0.0442) with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58'x58', there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions of 1376 galaxies brighter than iBATC=19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segregations is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario. (3 data files).

Tian, J.-T.; Yuan, Q.-R.; Zhou, X.; Jiang, Z.-J.; Ma, J.; Wu, J.-H.; Wu, Z.-Y.; Fan, Z.; Zhang, T.-M.; Zou, H.

2012-11-01

166

BV photometry of quadrupole system ET Bootis  

NASA Astrophysics Data System (ADS)

In this study, we present the first Johnson BV photometry of the eclipsing binary star ET Bootis, which is member of a physically connected visual pair. Analysis of times of light minima enables us to calculate accurate ephemeris of the system via O-C analysis and observed an increase in period which we believe is a result of the light-time effect in the outer visual orbit. Secondly, we determined the total brightness and color of the system in light maxima and minima. Photometric solution of the system indicates that the contribution of the visual pair to the total light is about 40% in Johnson V band. Furthermore, photometric analysis shows that the primary star in the eclipsing binary has F8 spectral type while it confirms the G5 spectral type for the visual pair. Masses of the components in eclipsing binary are M1 = 1.109 ± 0.014 M? and M2 = 1.153 ± 0.011 M?. Absolute radii of the components are R1 = 1.444 ± 0.007 R? and R2 = 1.153 ± 0.007 R?. Physical properties of the components leads 176 ± 7 pc distance for the system and suggests an age of 6.5 billion years.

Özdarcan, O.; Evren, S.

2012-10-01

167

Multicolor Photometry of Trans-neptunian Objects  

NASA Astrophysics Data System (ADS)

We are continuing our photometric survey of the trans-neptunian and Centaur populations started in 1997. We report multicolor photometry for 17 objects. With these results combined with previous data (M. A. Barucci, A. Doressoundiram, M. Fulchignoni, D. Tholen, and M. Lazzarin 1999. Icarus142, 476-481; M. A. Barucci, J. Romon, A. Doressoundiram, and D. Tholen 2000. Astron. J.120, 496-500), we have at our disposal a homogeneous and high-quality set of color indices for 29 objects, numerous enough to make significant studies. The color-color diagrams confirm the wide and continuous spread of colors in the trans-neptunian object population. This diversity may be explained by the combined action of space weathering and collisional resurfacing. We do not find any correlation of colors with size or heliocentric distance, but we note an excess of red objects for perihelion distance greater than 40 AU. Furthermore, our results suggest also that highly inclined (e.g., i>17°) and eccentric objects are preferentially neutral. These objects may have suffered more collisional resurfacing than others.

Doressoundiram, A.; Barucci, M. A.; Romon, J.; Veillet, C.

2001-12-01

168

Infrared Photometry of beta Pictoris Type Systems  

NASA Astrophysics Data System (ADS)

We obtained small-aperture (4"-5" diameter) infrared (2-20 ?m) photometry of 10 early-type main-sequence stars with infrared excesses from circumstellar dust. These systems possibly exemplify the beta Pictoris phenomenon. We observed them with either the NASA Marshall Space Flight Center bolometer array camera (``Big Mac'') or the Infrared Telescope Facility 2-30 ?m single-channel bolometer system. Measurements were obtained in the KLMNQ filters and the narrowband (Deltalambda ~ 1 ?m) 10 ?m ``silicate'' filters. We fitted Kurucz photospheric models to the photometric data to determine excess-emission spectra. We report the nondetection of small-aperture circumstellar dust emission from HR 10 and 21 LMi. We confirmed previous nondetections of near-infrared or 10 ?m excess emission from 68 Oph, alpha PsA, and HR 4796A. We did not detect prominent silicate emission from any of the sources. The spectra of gamma Oph, sigma Her, HR 2174A, beta UMa, and zeta Lep show weak 10 ?m excesses. We fitted simple models to these data, together with IRAS excess fluxes, to determine plausible distributions of temperature and density of circumstellar dust grains. Significant quantities of these grains around HR 2174A, zeta Lep, and beta UMa are at temperatures similar to terrestrial material in the solar system.

Fajardo-Acosta, S. B.; Telesco, C. M.; Knacke, R. F.

1998-05-01

169

BVI CCD photometry of 47 Tucanae  

SciTech Connect

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

Alcaino, G.; Liller, W.

1987-08-01

170

Production Of Fullerenic Soot In Flames  

DOEpatents

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

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

2000-12-19

171

A Note on Flame-Length  

Microsoft Academic Search

THREE years ago, whilst endeavouring to make use of flame-length as a means of testing the economic values of different qualities of coal-gas by the determination of their specific flame-lengths, I was led to the discovery of some simple relations, the further study of which will perhaps one day help to simplify the theory of flames. By specific flame-length I

Lewis T. Wright

1881-01-01

172

Diffusional-Thermal Theory of Cellular Flames  

Microsoft Academic Search

It is shown that the formation of cellular structure in a flame is conditioned by diffusion and heat conduction effects and is independent of the hydrodynamics of the perturbed flame. It is proved that cellular flames are formed only when a sufficiently light reactant of the combustible mixture is present in a low concentration. If there is an excess of

G. I. SIVASHINSKY

1977-01-01

173

Email Flaming Behaviors and Organizational Conflict  

Microsoft Academic Search

This study explores whether the attributes listed in the literature on flaming in email are considered characteristic of flaming by actual email users. Through the creation of a semantic differential scale—called the Message Invectives Scale—the study took eight concepts found in more than 20 research articles on flaming and examined email users' responses to a set of 20 messages in

Anna K. Turnage

2007-01-01

174

The structure of inhibited counterflowing nonpremixed flames  

SciTech Connect

Recent international agreements call for a halt to the manufacture of CF[sub 3]Br, a commonly used fire suppressant, due to its high ozone depletion potential. Ideally, the search for replacement compounds should be guided by fundamental studies of the detailed inhibition mechanisms of halogenated agents in flames. Numerical simulations of the structure of laminar counterflow methane-air nonpremixed flames with chemical (chloromethane) and inert (nitrogen) agents added to the oxidizer stream were performed using a previously developed computer code. The computations were substantiated by measurements of the temperature and velocity fields. The simulated flame structure demonstrated that the addition of chloromethane to the oxidizer side of the nonpremixed flame leads to a broadened reaction zone, increased flame temperatures, decreased concentrations of key flame radicals, and decreased rates of important exothermic chemical reactions. The addition of nitrogen to the oxidizer side of the flame had a very different impact on the flame structure, leading to decreased flame temperatures and decreased concentrations of key flame radicals. The reaction pathways associated with inhibition by chloromethane were identified through an analysis of the calculated flame structure. Simulated flames inhibited by molecular chlorine and hydrochloric acid are also discussed.

Yang, M.H.; Hamins, A.; Puri, I.K. (Univ. of Illinois, Chicago, IL (United States). Dept. of Mechanical Engineering National Inst. of Standards and Technology, Gaithersburg, MD (United States). Building and Fire Research Lab.)

1994-07-01

175

Study of laminar-jet diffusion flames  

Microsoft Academic Search

Based on the Shvab-Zeldovich formulation, the mass, momentum, and species equations for a laminar-jet diffusion flame are simplified. These equations are observed to be identical to those of a laminar hot jet and can be readily solved. Utilizing analytical results and general behaviors of experimental data, closed form correlations for flame height and flame shape are generated and shown to

Yuen

1980-01-01

176

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

177

Analysis of flame shapes in turbulent hydrogen jet flames with coaxial air  

Microsoft Academic Search

This paper addresses the characteristics of flame shapes and flame length in three types of coaxial air flames realizable\\u000a by varying coaxial air and\\/or fuel velocity. Forcing coaxial air into turbulent jet flames induces substantial changes in\\u000a flame shapes and NOx emissions through the complex flow interferences that exist within the mixing region. Mixing enhancement\\u000a driven by coaxial air results

Hee-Jang Moon

2009-01-01

178

Edge flame instability in low-strain-rate counterflow diffusion flames  

Microsoft Academic Search

Experiments in low-strain-rate methane-air counterflow diffusion flames diluted with nitrogen have been conducted to study flame extinction behavior and edge flame oscillation in which flame length is less than the burner diameter and thus lateral conductive heat loss, in addition to radiative loss, could be high at low global strain rates. The critical mole fraction at flame extinction is examined

June Sung Park; Dong Jin Hwang; Jeong Park; Jeong Soo Kim; Sungcho Kim; Sang In Keel; Tae Kwon Kim; Dong Soon Noh

2006-01-01

179

Edge flame instability in low-strain-rate counterflow diffusion flames  

Microsoft Academic Search

Experiments in low-strain-rate methane–air counterflow diffusion flames diluted with nitrogen have been conducted to study flame extinction behavior and edge flame oscillation in which flame length is less than the burner diameter and thus lateral conductive heat loss, in addition to radiative loss, could be high at low global strain rates. The critical mole fraction at flame extinction is examined

June Sung Park; Dong Jin Hwang; Jeong Park; Jeong Soo Kim; Sungcho Kim; Sang In Keel; Tae Kwon Kim; Dong Soon Noh

2006-01-01

180

Ionization in Flames and Identification of the Negative Flame Ions.  

National Technical Information Service (NTIS)

A summary is given of the most representative actual data concerning the measurement of the chemi-ion concentration in the flame reaction zone, the identification of these ions and the rate of their recombination in the afterburning zone. A few possible p...

A. van Tiggelen

1964-01-01

181

Electric-field-induced flame speed modification  

SciTech Connect

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

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

2005-10-01

182

Mesopic luminance assessed with minimum motion photometry.  

PubMed

We measured the relative contribution of rods and cones to luminance across a range of photopic, mesopic, and scotopic adaptation levels and at various retinal eccentricities. We isolated the luminance channel by setting motion-based luminance nulls (minimum motion photometry) using annular stimuli. Luminance nulls between differently colored stimuli require equality in a weighted sum of rod and cone excitations. The relative cone weight increases smoothly from the scotopic range, where rods dominate, to photopic levels, where rod influence becomes negligible. The change from rod to cone vision does not occur uniformly over the visual field. The more peripheral the stimulus location, the higher is the light level required for cones to participate strongly. The relative cone contribution can be described by a sigmoid function of intensity, with two parameters that each depend on the eccentricity and spatial frequency of the stimulus. One parameter determines the "meso-mesopic" luminance--the center of the mesopic range, at which rod and cone contributions are balanced. This increases with eccentricity, reflecting an increase in the meso-mesopic luminance from 0.04 scotopic cd/m(2) at 2° eccentricity to 0.44 scotopic cd/m(2) at 18°. The second parameter represents the slope of the log-log threshold-versus-intensity curve (TVI curve) for rod vision. This parameter inversely scales the width of the mesopic range and increases only slightly with eccentricity (from 0.73 at 2° to 0.78 for vision at 18° off-axis). PMID:21868482

Raphael, Sabine; MacLeod, Donald I A

2011-08-25

183

HST BVI photometry of Triton and Proteus  

NASA Astrophysics Data System (ADS)

BVI photometry of Triton and Proteus was derived from HST images taken in 1997. The VEGAMAG photometric technique was used. Triton was found to be brighter by a few percent than observations of the 1970's and 1980's, as expected due to the increasingly greater exposure of the bright south polar region. The leading side was also found to be brighter than the trailing side by 0.09 mag in all filters—50% larger than reported by Franz [Franz, O.G., 1981. Icarus 45, 602 606]. Contrary to our previous results [Pascu, D., et al., 1998. Bull. Am. Astron. Soc. 30, 1101], we found no episodic reddening. Our previous conclusions were based on an inaccurate early version of the Charge Transfer Efficiency (CTE) correction. The present result limits the start of the reddening event reported by Hicks and Buratti [Hicks, M.D., Buratti, B.J., 2004. Icarus 171, 210 218]. Our (B V) result of 0.70±0.01 supports the global blueing described by Buratti et al. [Buratti, B.J., Goguen, J.D., Gibson, J., Mosher, J., 1994. Icarus 110, 303 314]. Our observations of July 1997 agree with the Voyager results and are among the bluest colors seen. We found Proteus somewhat brighter than earlier studies, but in good agreement with the recent value given by Karkoschka [Karkoschka, E., 2003. Icarus 162, 400 407]. A leading/trailing brightness asymmetry was detected for Proteus, with the leading side 0.1 mag brighter. The unique differences in action of the endogenic and exogenic processes on Triton and Proteus provides an opportunity to separate the endogenic and exogenic effects on Triton.

Pascu, Dan; Storrs, Alex D.; Wells, Eddie N.; Hershey, John L.; Rohde, James R.; Seidelmann, P. Kenneth; Currie, Douglas G.

2006-12-01

184

Flame stabilizer for stagnation flow reactor  

DOEpatents

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

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

1999-01-01

185

Using SysRem as an Alternative Photometry Technique  

NASA Astrophysics Data System (ADS)

In SysRem, a statistical photometric algorithm for the search for new variable objects (Tamuz et al. 2005; Mazeh et al. 2007), the correction for systematic errors for star i on frame j is expressed as the product of two coefficients, a_j and c_i. SysRem introduces some distortion to the light curves, because unknown variations of variable objects influence c_i and a_j. Shporer et al. (2007) applied SysRem for photometry of a known star with transiting planet, WASP-1b. To minimize the influence of target's variability, only the comparison stars were used for finding a_j; then c_t for the target was determined by minimizing the residuals from the best fitting model of the transit. We investigated further the possibility of using modified SysRem for precise photometry of known targets. Here we report on the results obtained with a version similar to that used by Shporer et al. (2007, hereafter ``SysRem-ph''). The target was a constant V = 11.12 star from Landolt cluster SA98 (Landolt 1992). Observations were performed on the 0.6-m MMO reflector with the Princeton Instruments E2V, 512× 512, CCD camera, on two nights, with filters V (74 frames) and I (76 frames), with 90 s and 40 s exposures per frame, respectively. The reductions were made by JW and GW. JW compared SysRem-ph with the ``grey'' differential photometry (in which the differences in colors and positions of stars are not taken into account) and with the regular SysRem, and GW - the results of ``grey'' and ``color'' differential photometry (Hardie 1962). Eight comparison stars were used by JW and 12 by GW. The results for the four data sets can be summarized as follows: (1) Regular SysRem produced standard deviations (STDEV) of 3-5 mmag, close to the predicted photon noise (? 4 mmag); (2) SysRem-ph gave larger STDEV than regular SysRem (by 0.8-0.9 mmag) but smaller than ``grey'' photometry (by 0.5-1.6 mmag); and (3) ``Color'' differential photometry was better than ``grey'' photometry by 1-2 mmag. We conclude that for one-color photometry of variable objects with identifiable periods of constancy, SysRem-ph can be a good alternative to the traditional ``grey'' differential photometry. The higher precision of SysRem-ph is due to the capability of SysRem to account for the differences in color and position of the involved stars, without prior knowledge of these differences (Mazeh et al. 2007).

Marshall, S.; Williams, J.; Mazeh, T.; Walker, G.; Strelnitski, V.

2010-02-01

186

Pulsed Turbulent Diffusion Flames in a Coflow  

NASA Astrophysics Data System (ADS)

Fully modulated diffusion flames were studied experimentally in a co-flow combustor using unheated ethylene fuel at atmospheric pressure. A fast solenoid valve was used to fully modulate (completely shut-off) the fuel flow. The fuel was released from a 2 mm diameter nozzle with injection times ranging from 2 to 750 ms. The jet exit Reynolds number was 2000 to 10,000 with a co-flow air velocity of up to 0.02 times the jet exit velocity. Establishing the effects of co-flow for the small nozzle and short injection times is required for future tests of pulsed flames under microgravity conditions. The very short injection times resulted in compact, burning puffs. The compact puffs had a mean flame length as little as 20flame for the same Reynolds number. As the injection time and fuel volume increased, elongated flames resembling starting jets resulted with a flame length comparable to that of a steady flame. For short injection times, the addition of an air co-flow resulted in an increase in flame length of nearly 50flames with longer injection times was correspondingly smaller. The effects of interaction of successive pulses on the flame length were most pronounced for the compact puffs. The emissions of unburned hydrocarbon and NOx from the pulsed flames were examined.

Usowicz, James E.; Hermanson, James C.; Johari, Hamid

2000-11-01

187

Soda Flames in Coal Fires  

Microsoft Academic Search

IF a coal-fire be looked into with some attention after a fresh supply of coals has nearly ceased to give out its gases, there will be seen here and there in the hottest parts, and coming out of them through crannies and round dark corners, a pale translucent yellow flame, which one soon gets to recognise easily. What does it

J. Herschel

1882-01-01

188

An Improved Calcium Flame Test.  

ERIC Educational Resources Information Center

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

Pearson, Robert S.

1985-01-01

189

Analysis of diffusion flame tests  

Microsoft Academic Search

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

1987-01-01

190

Flex-flame burner and combustion method  

DOEpatents

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.

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

2010-08-24

191

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

SciTech Connect

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

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

2004-03-01

192

Experimental study of turbulent flame kernel propagation  

SciTech Connect

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

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

2008-07-15

193

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

SciTech Connect

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

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

2004-03-01

194

Flame Lift-off and Stabilization Mechanisms of Nonpremixed Jet Flames on a Bluff-body Burner  

Microsoft Academic Search

A detailed regime diagram for bluff-body stabilized flames is proposed for the flame lift-off and stabilization limits. At low fuel velocities, the flame structure is classified into three stable modes: recirculation zone flames, jet-dominated flames, and jet-like flames according to the velocity ratio of annular to central jets. Two different flame stability limits can be identified between cold and combusting

Yung-cheng Chen; Chia-chi Chang; Kuo-Long Pan; Jing-Tang Yang

1998-01-01

195

Near-IR Photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

196

Photometry of UCM galaxies (Perez-Gonzalez+, 2000)  

NASA Astrophysics Data System (ADS)

We present Johnson B CCD photometry for the whole sample of galaxies of the Universidad Complutense de Madrid (UCM) Survey Lists I and II (Cat. and ). They constitute a well-defined and complete sample of galaxies in the Local Universe with active star formation. The data refer to 191 S0 to Irr galaxies at an averaged redshift of 0.027, and complement the already published Gunn r, J and K photometries. (B-r) colours are also computed. (2 data files).

Perez-Gonzalez, P. G.; Zamorano, J.; Gallego, J.; Gil de Paz, A.

1999-11-01

197

High-Resolution Surface Photometry of NGC 4314 : Cycle 0  

NASA Astrophysics Data System (ADS)

We propose to obtain ST WF/PC surface photometry of NGC 4314. NGC 4314 exhibits anomalous nuclear activity indicative of on-going star formation. Multicolor surface photometry with 0.1 to 0.4 arcsec resolution will afford an opportunity to explore the global interrelationships between gas clouds, dust, star formation, and stellar populations with detail never before obtained. The expected maximum resolution for for NGC 4314 is 10 parsecs. While most of the data will be secured after the refurb mission with WFPC II, these early I-band exposures will allow studies of structures.

Jefferys

1990-07-01

198

Automated photographic photometry of stars in globular clusters  

NASA Astrophysics Data System (ADS)

An automatic method for stellar photometry in crowded fields is presented. The reduction procedure, based on a multicomponent fitting routine, applies to PDS scans of a photographic plate and gives accurate magnitudes of all the objects with a detectable maximum (the estimated internal error is ? ? 0.02 m). The extended objects (galaxies or extremely blended stellar images) are recognized and passed to an interactive procedure. An application to the photometry of 2344 stars in the field of the globular cluster NGC 2808 is also shown.

Buonanno, R.; Buscema, G.; Corsi, C. E.; Ferraro, I.; Iannicola, G.

1983-10-01

199

Propagation of curved stationary flames in tubes  

NASA Astrophysics Data System (ADS)

Dynamics of a curved flame propagating in a tube is investigated by means of two-dimensional numerical simulations. The complete system of hydrodynamical equations including thermal conduction, viscosity, equation of chemical kinetics, and fuel diffusion is solved with the ideally adiabatic and slippery boundary conditions at the tube walls. It is found that only a planar flame can propagate in a narrow tube of width smaller than a half of the cutoff wavelength determined from the linear theory of the hydrodynamic instability of a flame front. In a wider tube, stationary curved flames are obtained, which propagate with the velocities larger than the corresponding velocity of a planar flame. The velocity of a curved flame front is studied as a function of the tube width and the expansion coefficient of the fuel. The influence of viscosity on the velocity of a curved flame front is found to be negligible. The configuration of a curved flame propagating upwards in a gravitational field is also investigated. It is shown that gravity leads to an additional increase of the flame velocity due to the effect of rising bubbles of light burning products. The analytical formulas for the velocity of a flame front are proposed for the cases of both zero and nonzero gravity.

Bychkov, V. V.; Golberg, S. M.; Liberman, M. A.; Eriksson, L. E.

1996-10-01

200

A numerical study of thin flame representations  

SciTech Connect

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.

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

1989-08-11

201

Flame detection in video using hidden Markov models  

Microsoft Academic Search

ABSTRACT This paper proposes a novel method to detect flames in video by processing the data generated by an ordinary camera monitoring a scene. In addition to ordinary motion and color clues, flame flicker process is also detected by using a hidden Markov model. Markov models representing the flame and flame colored ordinary moving,objects are used to distinguish flame flicker

B. Ugur Töreyin; Yigithan Dedeoglu; A. Enis Çetin

2005-01-01

202

Stretch in Premixed Laminar Flames Under IC Engine Conditions  

Microsoft Academic Search

Flamelet models for turbulent combustion provide an approach (via the laminar flame) to include detailed flame chemistry into fluid dynamic simulations of IC engines. The flamelet model postulates that a turbulent flame is a statistical distribution of premixed, laminar flames. However. turbulence affects the laminar flames through strain (a) and curvature. The effect of positive strains (outflow condition) on counter-flow

Richard J. Blint

1991-01-01

203

Microwave Techniques for the Combustion Enhancement of Laminar Flames  

Microsoft Academic Search

An experimental technique for using microwave power to increase the flame speed of laminar premixed flames is discussed. The microwave energy is applied by means of a rectangular resonant cavity. A laminar flame burner is used to produce a free floating flame sheet within the confines of the rectangular cavity. Upon application of microwave power, the flame sheet is observed

Daniel J. Sullivan; S. H. Zaidi; S. O. Macheret

204

Adhesion of flame-treated polyolefins to styrene butadiene rubber  

Microsoft Academic Search

Samples of polyethylene and polypropylene have been submitted to repeated short duration (75 ms) flame treatments, at optimum flaming conditions. Surface energies of untreated and flamed specimens were determined by liquid contact angle measurements. It appears that the surface energy of polyethylene increases much more than that of polypropylene after flame treatment. The flamed polymer surfaces were further examined by

E. Papirer; D. Y. Wu; J. Schultz

1993-01-01

205

Characterization of the local flame structure and the flame surface density for freely propagating premixed flames at various lewis numbers  

Microsoft Academic Search

The local flame structure and the flame surface density for freely propagating premixed turbulent flames are measured by laser sheet tomography and image processing techniques. Different fuel\\/air mixtures (methane, propane, and hydrogen) have been successively spark-ignited at atmospheric pressure in order to evaluate the influence of thermodiffusive effects characterized by the Lewis number, at quasi-constant ratio u?S L 0 .

B. Renou; A. Mura; E. Samson; A. Boukhalfa

2002-01-01

206

Structure of Lean Turbulent Partially-Premixed Flames Stabilized in a Co-Axial Jet Flame Burner  

Microsoft Academic Search

Lean premixed flames at very low equivalence ratios and high mean flow velocities can be sustained in a co-axial jet flame burner. The flame shape involves a thin, highly turbulent flame region where most of the lean combustion occurs, and a base flame region which burns at the initial equivalence ratio. Due to the entrainment velocity induced by the high-speed

T.-W. Lee; A. Mitrovic

1997-01-01

207

Numerical investigations of gaseous spherical diffusion flames  

NASA Astrophysics Data System (ADS)

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

Lecoustre, Vivien R.

208

Wrinkled flames and geometrical stretch  

NASA Astrophysics Data System (ADS)

Localized wrinkles of thin premixed flames subject to hydrodynamic instability and geometrical stretch of uniform intensity (S) are studied. A stretch-affected nonlinear and nonlocal equation, derived from an inhomogeneous Michelson-Sivashinsky equation, is used as a starting point, and pole decompositions are used as a tool. Analytical and numerical descriptions of isolated (centered or multicrested) wrinkles with steady shapes (in a frame) and various amplitudes are provided; their number increases rapidly with 1/S>0. A large constant S>0 weakens or suppresses all localized wrinkles (the larger the wrinkles, the easier the suppression), whereas S<0 strengthens them; oscillations of S further restrict their existence domain. Self-similar evolutions of unstable many-crested patterns are obtained. A link between stretch, nonlinearity, and instability with the cutoff size of the wrinkles in turbulent flames is suggested. Open problems are evoked.

Denet, Bruno; Joulin, Guy

2011-07-01

209

Interferometric visualization of jet flames  

Microsoft Academic Search

This paper presents visualizations of reacting, round jets of the premixed and nonpremixed type realized by using interferometry\\u000a and, complementarily, direct photography. The available interferometer, proposed by Carlomagno (1986), employs low-cost components\\u000a and is flexible and robust to geometrical misalignments, allowing the drawbacks limiting the application of traditional interferometric\\u000a systems to be overcome. Several flames are produced by varying the

A. Stella; G. Guj; A. Mataloni

2000-01-01

210

Galileo Photometry of Asteroid 951 Gaspra  

USGS Publications Warehouse

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

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

1994-01-01

211

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

SciTech Connect

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

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

1999-02-01

212

Formation of Cellular Flames and Increase in Flame Velocity Generated by Intrinsic Instability  

Microsoft Academic Search

The formation of cellular flames and the increase in flame velocity generated by intrinsic instability are studied by two-dimensional (2-D) and three-dimensional (3-D) unsteady calculations of reactive flows based on the compressible Navier-Stokes equation. We consider three basic types of phenomena to be responsible for the intrinsic instability of premixed flames, i.e., hydrodynamic, diffusive-thermal, and body-force instabilities. Cellular flames are

Satoshi Kadowaki

2005-01-01

213

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

SciTech Connect

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)

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

2010-11-15

214

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

Microsoft Academic Search

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

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

2007-01-01

215

Synthetic hydromagnesite as flame retardant. Evaluation of the flame behaviour in a polyethylene matrix  

Microsoft Academic Search

Synthetic hydromagnesite obtained from an industrial by-product was evaluated as a non-halogenated flame retardant. It was used in combination with aluminium hydroxide (ATH) and compared with commercial flame retardants like magnesium hydroxide (MH) and natural hydromagnesite–huntite (U) in a polyolefin system of low-density polyethylene\\/poly(ethylene-co-vinyl acetate) (LDPE\\/EVA).The thermal stability and flame behaviour of the halogen free flame retarded composites were studied

Laia Haurie; Ana Inés Fernández; José Ignacio Velasco; Josep Maria Chimenos; José-Marie Lopez Cuesta; Ferran Espiell

2006-01-01

216

Flame acceleration due to flame-induced instabilities in large-scale explosions  

Microsoft Academic Search

Large-scale explosions of initially quiescent methane-air and propane-air mixtures at atmospheric pressure are reported, in which the flame speed of a hemispherical flame is measured up to radii just beyond 3 m. A cellular flame is developed fairly soon and thereafter the flame speed increases continually with the square root of the time. The range of unstable wavelengths that wrinkle

D. Bradley; T. M. Cresswell; J. S. Puttock

2001-01-01

217

Flame extinction in compressible flow  

NASA Astrophysics Data System (ADS)

The structure of the compressible stagnation flow at the forward point of a cylinder in a uniform stream is examined. Such flows are used in the laboratory to characterize the structure and stability limits of counterflow diffusion flames, where the fuel is emitted radially from the surface of the cylinder against the uniform approach flow. While hydrocarbon fuels are extinguished at relatively low strain rates, corresponding to low approach velocities, hydrogen requires much larger strain rates for extinction. The corresponding approach flow is in the compressible range and requires analysis as such. Solutions and estimates are developed for the cases of subsonic and supersonic flow. In particular, a Rayleigh-Janzen expansion of the potential function is carried out to six terms, using a symbolic manipulation language, and the analytical results are differentiated to obtain the strain field in subsonic flow. Compressibility is shown to decrease the strain rate for constant approach velocity and cylinder radius. This counter-intuitive result is shown to be a near-field phenomenon due to higher-order singularities; the strain further upstream is shown to increase. Estimates made for the case of supersonic flow indicate a lower level of strain compared with that in subsonic compressible flow. These results indicate that compressibility of the free stream offers a potential for increased flame stability. The conclusions are relevant to flame stability in high-speed combustors, such as those in supersonic combustion ramjets.

Correa, S. M.

1988-10-01

218

Transient response of premixed methane flames  

SciTech Connect

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

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

2006-08-15

219

Liquid flame spraying for glass coloring  

Microsoft Academic Search

The liquid flame spraying process has been developed to uniformly color hot glass objects. A solution consisting of a metal\\u000a nitrate dissolved in alcohol or water is fed to an oxyfuel torch and atomized in the flame. The liquid evaporates from the\\u000a droplet, and subsequent reactions produce metals or metallic oxides that impact the hot glass surface. Flame spraying of

K. A. Gross; J. Tikkanen; J. Keskinen; V. Pitkänen; M. Eerola; R. Siikamaki; M. Rajala

1999-01-01

220

Computational and experimental study of laminar flames  

SciTech Connect

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

Smooke, M.; Long, M.

1991-01-01

221

40 CFR 1065.260 - Flame-ionization detector.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Flame-ionization detector. 1065.260 Section 1065.260 ...Measurements § 1065.260 Flame-ionization detector. (a) Application. Use a flame-ionization detector (FID) analyzer to measure...

2013-07-01

222

The Coherent Flame Model for Turbulent Chemical Reactions.  

National Technical Information Service (NTIS)

A description of the turbulent diffusion flame is proposed in which the flame structure is composed of a distribution of laminar diffusion flame elements, whose thickness is small in comparison with the large eddies. These elements retain their identity d...

F. E. Marble J. E. Broadwell

1977-01-01

223

Stabilization and Blowout of Gaseous- and Spray-Jet Flames.  

National Technical Information Service (NTIS)

This Final Report surveys our results under ARO support in the areas of Spray and Gas-Flame Research. Flame liftoff blowout is witnessed in spray combustion systems encountered in practical devices. Understanding the governing parameters for flame structu...

K. M. Lyons

2004-01-01

224

Combined Photometry and Spectroscopy of Globular Cluster Tidal Streams  

Microsoft Academic Search

Globular cluster tidal streams are of interest for what they can tell us of the dynamical evolution of the clusters and our Galaxy. Recent studies have used photometric and statistical subtraction methods to attempt to separate potential streams from the field stars that contaminate the samples. We chose instead to use photometry to select blue stars that match the horizontal

W. L. Powell; R. Wilhelm; A. McWilliam; A. Westfall; A. Lauchner

2005-01-01

225

Two-Color Photoelectric Photometry of the Earthshine  

Microsoft Academic Search

digcult to assess to what extent this value varies with changing meteorological conditions and differing observing locations. Ranjon's observations were carried out only in France, and both he and Fritz [1949] have indicated the benefits of photometry from other stations. Wildey [1964], although beset by various uncertainties, has obtained from a photometer carried in Mariner 2 results that differ from

F. A. Franklin

1967-01-01

226

Photometry of Restored Full-Disk Solar Images  

NASA Astrophysics Data System (ADS)

The San Fernando Observatory (SFO) Cartesian Full Disk Telescope (CFDT) has been taking full-disk 512 square photometric images of the Sun through a 100 Angstroms bandpass red filter since 1985, and through a 10 Angstroms bandpass K-line filter since 1989. We have recently begun a project to attempt to remove the effects of atmospheric blurring and scattered light on the photometry of these images. Specifically, we are fitting the convolution of a limb darkening profile expansion and a model point spread function (PSF) to the radial profiles of SFO CFDT images, using a technique similar to that of Toner and Jeffries (Ap. J. 1996, submitted) to remove the PSF from the images. The blurring-free limb darkening profile is the sum of an expansion in orthogonal (Legendre) polynomials, and the PSF model is the sum of three Gaussian components plus a Lorentzian, normalized so that its integral over the sky is unity. Tests with artificially generated images with sunspots show that we can recover the sunspot photometric quantities with excellent results. Comparison of the original and restored photometry from eight actual red images taken hourly also show that correlations between the PSF and the photometry disappear after the restoration. We have been less successful at recovery of facular photometry in the K line images, and are continuing to investigate this. We will present details of our fitting procedure and results. This project was partly supported by NSF Grant ATM-9115111 and NASA grant NAGW-3017.

Walton, S. R.; Preminger, D. G.; Toner, C. G.

1996-05-01

227

Flaring on RS CVn systems: Results from EUVE Photometry  

Microsoft Academic Search

We present broadband EUV photometry for a sample of RS CVn systems observed with the Deep Survey Spectrometer and Right Angle Program (RAP) Scanners on the Extreme Ultraviolet Explorer (EUVE). We have developed robust data analysis and light curve software for the interpretation of these data. Large-scale flaring activity is seen on 15 of the 18 systems studied. These binaries

R. A. Osten; A. Brown; T. R. Ayres

1998-01-01

228

General Catalog of Photometry of Galaxies (Longo+ 1983)  

Microsoft Academic Search

Details of the integrated photometry of galaxies in the UBV system (generally through circular apertures centered at the nucleus) published prior to 1963 were given in three appendices to the (First) Reference Catalogue of Bright Galaxies (RCBG = RC1). The publication of an updated listing in the Second Reference Catalogue (RC2) has been requested since then. The present catalogue contains

G. Longo; A. de Vaucouleurs

1994-01-01

229

Photometry of Three Fields in the Orion Nebula Cluster  

Microsoft Academic Search

We have initiated a program of repeated R and I photometry of three fields in the Orion Nebula Cluster. Our observations were 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 Research Observatory. These three fields and several others covering

K. L. McFarland; R. J. Boyle; B. W. Taylor; E. B. Zamkoff

1997-01-01

230

JHK photometry of carbon stars and their effective temperature  

Microsoft Academic Search

Infrared photometry in the J, H, and K bands of 24 carbon stars from Stephenson's (1973) General Catalog of Carbon Stars (GCCS) is presented. The observations were carried out on four nights in late November 1982, using the near-infrared photometer attached to the Yunnan 1-meter telescope. The photometric system constants used in the observations are given in a table. The

Heng Gao; Pei-Sheng Chen; Yun Zhang

1985-01-01

231

BVRI Photometry of Blazar PKS 0507+179  

NASA Astrophysics Data System (ADS)

We present optical broadband photometry (Bessel BVRI) in response of recent reports (ATel #4424, #4528, #4531) showing increased brightening of blazar PKS 0507+179. The images are obtained with the 50/70 cm Schmidt telescope at NAO Rozhen, Bulgaria. The available magnitudes are:

Ovcharov, E.; Metodieva, Y.; Kurtenkov, A.; Dineva, E.; Bogdanov, K.; Teodossiev, S.; Bozhilov, V.

2012-11-01

232

HST photometry of Sculptor group dwarf galaxies (Lianou+, 2013)  

NASA Astrophysics Data System (ADS)

Position and photometry for the resolved stars of five dwarf galaxies in the Sculptor Group. The dwarf galaxies are: ESO540-G030; ESO540-G032; ESO294-G010; ESO410-G005; SCL-DE1. The catalogue includes only those stars in which all selection criteria described in the companion paper were applied. (6 data files).

Lianou, S.; Grebel, E. K.; da Costa, G. S.; Rejkuba, M.; Jerjen, H.; Koch, A.

2013-05-01

233

A new look at photometry of the Moon  

Microsoft Academic Search

We use ROLO photometry (Kieffer, H.H., Stone, T.C. [2005]. Astron. J. 129, 2887-2901) to characterize the before and after full Moon radiance variation for a typical highlands site and a typical mare site. Focusing on the phase angle range 45° < alpha < 50°, we test two different physical models, macroscopic roughness and multiple scattering between regolith particles, for their

Jay D. Goguen; Thomas C. Stone; Hugh H. Kieffer; Bonnie J. Buratti

2010-01-01

234

VI photometry of 5 open clusters (Carraro+, 2007)  

Microsoft Academic Search

The stellar populations in the outer Galactic disk are a subject of wide interest nowadays. To contribute to a better picture of this part of the Galaxy, we have studied the nature of five marginally investigated star clusters (Collinder 74, Berkeley 27, Haffner 8, NGC 2509, and VdB-Hagen4) by means of accurate CCD photometry in the V and I passbands.

G. Carraro; E. Costa

2007-01-01

235

Characterizing New Eclipsing Binaries Identified from STEREO Photometry  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

236

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

Microsoft Academic Search

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

P. Cinzano

2003-01-01

237

JHK Photometry of CN-Rich Field Giants. Abstract Only.  

National Technical Information Service (NTIS)

Infrared JHK photometry was obtained for a sample of CN-rich Population I field giants. On average, the CN-rich giants show a modest color separation from more typical field giants of near solar abundance in the J-H, H-K two-color diagram. Many of the CN ...

G. H. Smith

1987-01-01

238

The interaction of high-speed turbulence with flames: Global properties and internal flame structure  

SciTech Connect

We study the dynamics and properties of a turbulent flame, formed in the presence of subsonic, high-speed, homogeneous, isotropic Kolmogorov-type turbulence in an unconfined system. Direct numerical simulations are performed with Athena-RFX, a massively parallel, fully compressible, high-order, dimensionally unsplit, reactive flow code. A simplified reaction-diffusion model represents a stoichiometric H{sub 2}-air mixture. The system being modeled represents turbulent combustion with the Damkoehler number Da=0.05 and with the turbulent velocity at the energy injection scale 30 times larger than the laminar flame speed. The simulations show that flame interaction with high-speed turbulence forms a steadily propagating turbulent flame with a flame brush width approximately twice the energy injection scale and a speed four times the laminar flame speed. A method for reconstructing the internal flame structure is described and used to show that the turbulent flame consists of tightly folded flamelets. The reaction zone structure of these is virtually identical to that of the planar laminar flame, while the preheat zone is broadened by approximately a factor of two. Consequently, the system evolution represents turbulent combustion in the thin reaction zone regime. The turbulent cascade fails to penetrate the internal flame structure, and thus the action of small-scale turbulence is suppressed throughout most of the flame. Finally, our results suggest that for stoichiometric H{sub 2}-air mixtures, any substantial flame broadening by the action of turbulence cannot be expected in all subsonic regimes. (author)

Poludnenko, A.Y.; Oran, E.S. [Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington, DC 20375 (United States)

2010-05-15

239

Influence of differential diffusion on maximum flame temperature in turbulent nonpremixed hydrogen\\/air flames  

Microsoft Academic Search

A turbulent nonpremixed H2\\/air flame is simulated using 2D direct numerical simulations coupled with a complete chemical scheme and a detailed transport model. The influence of differential diffusion is evidenced by comparing these results in terms of scatterplots and local flame structures with similar computations using a Lewis number unity hypothesis. The fast chemistry limit and thus the maximum flame

R. Hilbert; D. Thévenin

2004-01-01

240

Influence of nitrogen dilution and flame temperature on soot formation in diffusion flames  

Microsoft Academic Search

This paper reports the line-of-sight soot surface temperatures and soot volume fractions that were measured as a function of axial position in overventilated coflow laminar diffusion flames. A comparison of the influence of nitrogen dilution and the flame temperature on soot formation in diffusion flames of ethylene was made, and the relative importance of the two effects was quantified. To

O. L. Gulder; D. R. Snellin

1993-01-01

241

Confined superadiabatic premixed flame-flow interaction  

SciTech Connect

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

Najm, H.N.

1995-12-31

242

Laser Ionization Studies of Hydrocarbon Flames.  

NASA Astrophysics Data System (ADS)

Resonance-enhanced multiphoton ionization (REMPI) and laser induced fluorescence (LIF) are applied as laser based flame diagnostics for studies of hydrocarbon combustion chemistry. rm CH_4/O_2, C _2H_4/O_2, and rm C_2H_6/O_2 low pressure ( ~20 Torr), stoichiometric burner stabilized flat flames are studied. Density profiles of intermediate flame species, existing at ppm concentrations, are mapped out as a function of distance from the burner head. Profiles resulting from REMPI and LIF detection are obtained for HCO, CH_3, H, O, OH, CH, and CO flame radicals. The above flame systems are computer modeled against currently accepted combustion mechanisms using the Chemkin and Premix flame codes developed at Sandia National Laboratories. The modeled profile densities show good agreement with the experimental results of the CH_4/O_2 flame system, thus confirming the current C1 kinetic flame mechanism. Discrepancies between experimental and modeled results are found with the C2 flames. These discrepancies are partially amended by modifying the rate constant of the rm C_2H_3+rm O_2 to H_2CO + HCO reaction. The modeled results computed with the modified rate constant strongly suggest that the kinetics of several or possibly many reactions in the C2 mechanism need refinement.

Bernstein, Jeffrey Scott

243

Novel Methods for Flame Pulsation Frequency Measurement with Image Analysis  

Microsoft Academic Search

To characterize the periodic pulsation of flame from the flame image sequence, several novel methods for flame pulsation measurement\\u000a were introduced and demonstrated based on flame image analysis. Results show that moment function of flame image, such as\\u000a weighted Euclidean distance and cross correlation coefficient, could represent the geometric and periodic flame pulsation;\\u000a and that both the vertical and horizontal

Ying-chun Wu; Xue-cheng Wu; Shou-xiang Lu; Jia-qing Zhang; Ke-fa Cen

244

SPA, "The Stellar Photometry Assistant", a New Software Package Specializing in High Speed Photometry of White Dwarfs  

NASA Astrophysics Data System (ADS)

SPA, "The Stellar Photometry Assistant", is a new program for photometry reduction and analysis slated for initial release in early 2008. Development was fueled by high speed photometry of white dwarfs, mainly EC20058-5235, a pulsating DB white dwarf. The stability of EC20058-5235's primary mode, along with the relatively short timescales of DB cooling may allow a measurement of dP/dt. EC20058-5235 has 2 companions of comparable magnitude within 5'', which adds significant noise to simple aperture photometry. This, combined with the relatively steep learning curve of IRAF, and IRAF like tools sparked the beginning of SPA. SPA combines powerful, proven, methods with an easy to use interface. Currently SPA is written in MATLAB, but future plans include a cross platform stand alone application. SPA tackles many issues such as auto-tracking jumps in star location and crowded field reduction. SPA will also provide easy to use tools for viewing and manipulating data. The interface is intuitive and is suitable for both amateur and professorial astronomers. SPA is being developed by The University of Delaware in collaboration with the Delaware Asteroseismic Research Center (DARC) and the Mt. Cuba Astronomical Observatory.

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

2007-12-01

245

Flame acceleration studies in the MINIFLAME facility  

SciTech Connect

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.

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

1989-07-01

246

Comprehensive modeling of turbulent flames with the coherent flame-sheet model. Part 1: Buoyant diffusion flames  

SciTech Connect

A modified version of the computational fluid dynamics code KIVA-II was used to model the transient behavior of buoyant turbulent diffusion flames burning in still air. Besides extensions to the range of permitted boundary conditions and the addition of buoyancy terms to the turbulence model, KIVA-II was augmented by a version of the coherent flame-sheet model, Tesner`s soot generation model, Magnussen`s soot oxidation model, and an implementation of the discrete transfer radiation model that included both banded and continuum radiation. The model captured many of the features of buoyant turbulent flames. Its predictions supported experimental observations regarding the presence and frequency of large-scale pulsations, and regarding axial distributions of temperature, velocity, and chemical species concentrations. The radial structure of the flame was less well represented. The axial radiative heat flux distribution from the flame highlighted deficiencies in the soot generation model, suggesting that a model of soot particle growth was required.

Blunsdon, C.A.; Beeri, Z.; Malalasekera, W.M.G.; Dent, J.C. [Loughborough Univ. of Technology (United Kingdom). Dept. of Mechanical Engineering

1996-03-01

247

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

PubMed Central

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

Pearce, E M; Liepins, R

1975-01-01

248

Silencing the Flame Channelling Process. Volume I.  

National Technical Information Service (NTIS)

Conventional flame channeling operates continuously at over 120 db--flame drill channeling operates at a maximum of 95 db. The latter process was developed under this program. Individual drill holes are spaced to leave narrow rock webs. Sound and dust pas...

J. A. Browning

1980-01-01

249

Cup Burner Flame Extinguishment by Brominated Compounds.  

National Technical Information Service (NTIS)

Experiments and calculations have been performed for a methane-air cup-burner flame with added CF3Br or Br2. The time-dependent, two-dimensional numerical code, which includes a detailed kinetic model and diffusive transport, has predicted the flame extin...

F. Takahashi G. T. Linteris V. R. Katta

2006-01-01

250

Flame aerosol synthesis of ceramic powders  

Microsoft Academic Search

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

Sotiris E. Pratsinis

1998-01-01

251

Propagation Velocity of Premixed Turbulent Flames  

Microsoft Academic Search

The problem of propagation of turbulent premixed flame is analyzed using the field equation introduced recently by Kerstein, Ashurst and Williams (1987). The dynamic renormalization group method is applied to this equation and the formula for the turbulent flame velocity is derived in the lowest order in the ?-expansion. The formula, which does not include adjustable parameters, agrees well with

VICTOR YAKHOT

1988-01-01

252

Flame retarding polymer nanocomposites: Synergism, cooperation, antagonism  

Microsoft Academic Search

Three systems of FR treatments of polyamide 6 with conventional flame retarding additives in the absence and in the presence of nanoparticles are discussed: I. ammonium sulfamate (AS) and dipentaerythritol (Di) II. melamine cyanurate (MC) III. pentabromobenzyl acrylate in the monomeric (PMA) and the polymeric (PPA) form. Depending on the concentration of the nanoparticles; synergism, antagonism, and cooperation in flame

Menachem Lewin

2011-01-01

253

Flame fronts with complex chemical networks  

SciTech Connect

For laminar flame fronts with general complex chemistry networks, we present a systematic method to reduce the detailed chemistry in the limit of high-activation-energy asymptotics. We detail the method on a global multistep hydrocarbon model. Generic flame profile structures are discussed, and extensions to networks with zero activation energies are outlined.

Fife, P.C.; Nichols, B.

1983-01-01

254

Flaming in CMC: Prometheus' Fire or Inferno's?  

ERIC Educational Resources Information Center

|Reports on a descriptive study with 75 intermediate college learners of German participating in two sessions of synchronous computer mediated communication during the course of a semester that investigated students' flaming behavior--aggressive interpersonal language and rude behavior. Shows that not only is flaming a very infrequent occurrence,…

Abrams, Zsuzsanna Ittzes

2003-01-01

255

Extinction Theory of Spray Premixed Flames  

Microsoft Academic Search

Recent advances in the understandings on extinction of spray premixed flames under the influence of internal heat transfer, external heat transfer, flow stretch and preferential diffusion by using activation energy asymptotics are reviewed and discussed. In the theoretical model, a completely prevaporized mode and a partially prevaporized mode of flame propagation are identified. The internal heat transfer, which results from

Ta-Hui Lin

256

Simple Flame Test Techniques Using Cotton Swabs  

ERIC Educational Resources Information Center

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

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

2004-01-01

257

Flow Structure of Lifted Swirling Jet Flames  

Microsoft Academic Search

Swirling combustion is widely applied in various applications such as gas turbines, utility boilersor waste incinerators. This article contributes to the ongoing research by providing experimentaldata that are gathered in the mixing zone of a lifted swirling premixed natural gas flame. Theobjective of this paper is fivefold: (1) to introduce the lifted swirling flame featuring lowNOx emissions (2) to provide

K. Vanoverberghe; E. Van den Bulck; M. Tummers

2004-01-01

258

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...

259

Simple Flame Test Techniques Using Cotton Swabs  

ERIC Educational Resources Information Center

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

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

2004-01-01

260

Jet flames of a refuse derived fuel  

SciTech Connect

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

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

2009-04-15

261

Cellular flame structure and turbulent combustion  

Microsoft Academic Search

Knowledge of flame interaction with perturbation of the surrounding medium is insufficient. This study investigates various parameters and methods for clarifying the combustion mechanism. The conditions for the appearance of a cellular structure were formed by analysis of diffusion phenomenon. Because such a spontaneous transition is characteristic of laminar regimes, photographs of laminar flames of hydrogen 2H2 plus (alpha) 2

V. P. Karpov

1982-01-01

262

Analysis of Stabilization Mechanisms in Lifted Flames  

NASA Astrophysics Data System (ADS)

Flame stabilization and the mechanisms that govern the dynamics at the flame base have been subject to numerous studies in recent years. Recent results using a combined Large Eddy Simulation-Conditional Moment Closure (LES-CMC) approach to model the turbulent flow field and the turbulence-chemistry interactions has been successful in predicting flame ignition and stabilization by auto-ignition, but LES-CMCs capability of the accurate modelling of the competition between turbulent quenching and laminar and turbulent flame propagation at the anchor point has not been resolved. This paper will consolidate LES-CMC results by analysing a wide range of lifted flame geometries with different prevailing stabilization mechanisms. The simulations allow a clear distinction of the prevailing stabilization mechanisms for the different flames, LES-CMC accurately predicts the competition between turbulence and chemistry during the auto-ignition process, however, the dynamics of the extinction process and turbulent flame propagation are not well captured. The averaging process inherent in the CMC methods does not allow for an instant response of the transported conditionally averaged reactive species to the changes in the flow conditions and any response of the scalars will therefore be delayed. Stationary or quasi-stationary conditions, however, can be well predicted for all flame configurations.

Navarro-Martinez, S.; Kronenburg, A.

2009-12-01

263

Characterization of flame stabilization technologies  

NASA Astrophysics Data System (ADS)

To experimentally explore and characterize a V-gutter stabilized flame, this research study developed a Combustion Wind Tunnel Test Facility capable of effectively simulating the freestream Mach #'s and temperatures achieved within the back end of a gas turbine jet engine. After validating this facility, it was then used to gain a better understanding of the flow dynamics and combustion dynamics associated with the V-gutter configuration. The motivation for studying the V-gutter stabilized flame is due to the concern in industry today with combustion instabilities that are encountered in military aircraft. To gain a better understanding of the complex flow field associated with the V-gutter stabilized flame, this research study utilized Particle Image Velocimetry to capture both non-reacting and reacting instantaneous and mean flow structures formed in the wake region of the three dimensional V-gutter bluff body. The results of this study showed significant differences between the non-reacting and reacting flow fields. The non-reacting case resulted in asymmetric shedding of large scale vortices from the V-gutter edges while the reacting case resulted in a combination of both symmetric and asymmetric shedding of smaller scale vortical structures. A comparison of the mean velocity components shows that the reacting case results in a larger region of reversed flow, experiences an acceleration of the freestream flow due to combustion, and results in a slower dissipation of the wake region. Simultaneous dynamic pressure and CH* chemiluminescence measurements were also recorded to determine the coupling between the flow dynamics and combustion dynamics. The results of this study showed that only low frequency combustion instabilities were encountered at various conditions within the envelope of stable operation because of the interaction between longitudinal acoustic waves and unsteady heat release. When approaching rich blow out, rms pressure amplitudes were as high as 2 psi, and approaching lean blow out lead to rms pressure amplitudes around 0.2 psi. These studies also showed the instability frequency increasing with increases in either inlet temperature or inlet Mach #. Additionally, increasing the inlet velocity or the DeZubay parameter reduced the stability limits of operation for the V-gutter stabilized flame.

Bush, Scott Matthew

264

Explosion triggering by an accelerating flame  

NASA Astrophysics Data System (ADS)

The analytical theory of explosion triggering by an accelerating flame is developed. The theory describes the structure of a one-dimensional isentropic compression wave pushed by the flame front. The condition of explosion in the gas mixture ahead of the flame front is derived; the instant of the explosion is determined provided that a mechanism of chemical kinetics is known. As an example, it is demonstrated how the problem is solved in the case of a single reaction of Arrhenius type, controlling combustion both inside the flame front and ahead of the flame. The model of an Arrhenius reaction with a cutoff temperature is also considered. The limitations of the theory due to the shock formation in the compression wave are found. Comparison of the theoretical results to the previous numerical simulations shows good agreement.

Bychkov, Vitaly; Akkerman, V.'Yacheslav

2006-06-01

265

Propagating edge-flame response to multiple stoichiometry gradients  

SciTech Connect

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)

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

266

Acoustically perturbed turbulent premixed swirling flames  

NASA Astrophysics Data System (ADS)

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 underlying physical mechanisms identified experimentally are investigated numerically. Simulations confirm that swirl number fluctuations and vortex roll-up govern the flame response. It is also confirmed that the first mechanism is associated with a mode conversion process taking place when acoustic waves impinge on the swirler unit. The axial acoustic velocity disturbance on the upstream side of the swirler generates an axial acoustic wave and an azimuthal convective disturbance in the downstream flow. These combined disturbances are retrieved in the simulation and their effect on the swirl number is extracted. Calculations also indicate that vortex shedding synchronized by the acoustic forcing takes place at the injector lip outlet. Vortices originating from this region are convected in the jet shear layer, impinge on the flame, and roll-up the flame tip. This process interferes with oscillations in the flame angle induced by swirl number fluctuations. The phasing of the flame angle with respect to the instant of vortex shedding from the injector lips determines the lifetime of the vortex before interaction with the flame and controls the strength of this interaction. When this lifetime is reduced, the vortex cannot fully develop and the flame response remains weak. For larger lifetimes, the vortex can fully develop and produce larger heat release rate perturbations. This process depends on the forcing frequency, which determines the phasing between swirl number fluctuations and vortices generation.

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

2011-03-01

267

Infrared photometry and spectroscopy in L1641N (Galfalk+, 2008)  

NASA Astrophysics Data System (ADS)

Space-based photometry of sources in our L1641N catalogue, with Spitzer (3.6, 4.5, 5.8, and 8.0 microns) and ISO satellite (6.7 and 14.3 microns), and ground-based photometry with 2.56m Nordic Optical Telescope (NOT) in JHks. Optical spectra (5780-8340{AA}) of Young Stellar Object (YSO) candidates in our L1641N source catalogue. The spectra were taken with the 2.56m Nordic Optical Telescope (NOT) Dec 02-04 2003 and Jan 08-10 2005 (added from both epochs). Each spectrum is contained in a 2052x2 FITS file. The first row in each file is the wavelength [{AA}]. The second row in each file is the flux [erg/s/cm2/{AA}] (3 data files).

Galfalk, M.; Olofsson, G.

2008-05-01

268

UBV photometry of FK Com and HD 199178 (Panov+, 2007)  

NASA Astrophysics Data System (ADS)

We report previously unpublished photometric observations of FK Com (1990-2005) and HD 199178 (1991-2004). The observations have been carried out with the 60cm telescope of the Rozhen National Astronomical Observatory (Bulgaria). Observations contain measurements in the Johnson U,B and V bands. The observations are differential. For FK Com, the differential photometry is with respect to HD 117567. For HD 199178, the differential photometry is with respect to HD 199206. Table 2a,b contains a summary of subsets for FK Com and HD 199178, respectively. Table 3a,b contains UBV data for FK Com and HD 199178, respectively, obtained at Rozhen Observatory. Missing data are substituted with 99.000. Table 5a,b contains results of light-curve modelling for FK Com and HD 199178, respectively. (6 data files).

Panov, K.; Dimitrov, D.

2007-03-01

269

High Precision Differential Photometry with CCDs: A Brief History  

NASA Astrophysics Data System (ADS)

I present a brief history of the hunt for high photometric precision using CCDs in astronomy. CCDs were invented in 1969 and only 7 years later they started to appear at the major observatories of the time. The next 10 years constituted a steep learning curve for astronomers as they developed an understanding of CCDs as instruments and analysis techniques for use with digital images. In 1985, differential photometry with CCDs began producing light curves with precisions near 0.01 magnitude. By 2008, ground-based telescopes armed with CCDs and using differential techniques consistently can provide photometric precisions of 1 millimagnitude or better. The challenge now is to continue to improve the photometry using new types of CCD detectors and other advanced digital imagers.

Howell, Steve B.

270

Galaxy photometry at faint light levels - Interaction with the environment  

NASA Astrophysics Data System (ADS)

Interactions of two disk galaxies are considered, taking into account findings which suggest that violent relaxation in the stellar component of a merging system operates on a shorter time scale than dissipation in the gaseous component. Interactions between disk and elliptical galaxies are also discussed along with tidal distension of the envelopes of galaxies, cD galaxies, the halos of spiral galaxies, isophotometry, interacting spiral galaxies, dust lanes, the environment of radio galaxies, and future work. It is pointed out that photometry, particularly panoramic surface photometry, can provide important evidence on the effects of mergers, accretion, and tides on galaxies. More sensitive X-ray telescopes will make it possible to observe the accretion by galaxies of the hot intergalactic medium. Such an accretion is, perhaps, the most important environmental effect on galaxies.

Carter, D.

271

Photometry of a complete sample of faint galaxies  

NASA Astrophysics Data System (ADS)

Techniques are developed for the automatic measurement of the colors and magnitudes of a complete sample of very faint galaxies. The observations consist of photographic surface photometry in two wavebands for approximately 20,000 galaxies in two widely separated, high-latitude fields, each having an area of approximately 1080 sq arcmin. The photometric zero points are derived directly from faint stars in the same fields measured photoelectrically by other observers. The photometry of the galaxy sample is complete to a limit about 10 times fainter than has been systematically investigated before. The sample is characterized by a population of galaxies which becomes bluer with increasing faintness and which increases steeply in number with increasing faintness in the blue waveband.

Kron, R. G.

1980-06-01

272

Photometry of low-mass stars in Praesepe  

NASA Astrophysics Data System (ADS)

The results of a program of BVRI photometry of a set of relatively faint stars in the Praesepe cluster are reported. The program stars were selected to be high-probability members of the cluster based on a new proper-motion study by Jones and Cudworth (1982). Those membership identifications appear to have been quite accurate, since all but two of the stars observed have colors and magnitudes consistent with cluster membership. The new photometry, combined with previous data from Upgren, Weis, and DeLuca (1979) and Weis (1981) are used to show that the intrinsic width of the Praesepe main sequence remains quite narrow within 0.15 magnitude up to at least magnitude 10.5.

Stauffer, J.

1982-08-01

273

Millimeter-to-Far-Infrared Photometry of Cygnus A  

NASA Astrophysics Data System (ADS)

We present precision photometry and imaging of the core and two radio lobes of the galaxy Cygnus A at a wavelength of 2 millimeters, taken using the GISMO camera at the IRAM 30m telescope. We also present new 350 micron photometry using the SHARC-II camera at the CSO, archival Spitzer data, and WISE data, all with the aim of producing a precision spectral energy distribution of the synchrotron emission from the two radio lobes along with a single-dish size of the synchrotron-emitting regions. Using a sophisticated mapping approach and with attention to an accurate beamwidth measurement, we are able to determine that the two lobes have an effective emission scale of around 9+/-0.5 arcseconds, and are therefore roughly 10kpc in scale.

Benford, Dominic J.; Staguhn, J.; Kovacs, A.; Sharp, E.; Maher, S.

2013-01-01

274

Photometry of Variable Stars from Dome A, Antarctica  

NASA Astrophysics Data System (ADS)

Dome A on the Antarctic plateau is likely one of the best observing sites on Earth thanks to the excellent atmospheric conditions present at the site during the long polar winter night. We present high-cadence time-series aperture photometry of 10,000 stars with i < 14.5 mag located in a 23 deg2 region centered on the south celestial pole. The photometry was obtained with one of the CSTAR telescopes during 128 days of the 2008 Antarctic winter. We used this photometric data set to derive site statistics for Dome A and to search for variable stars. Thanks to the nearly uninterrupted synoptic coverage, we found six times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% were unclassified, 27% were likely binaries, and 17% were likely pulsating stars. The latter category includes ? Scuti, ? Doradus, and RR Lyrae variables. One variable may be a transiting exoplanet.

Wang, Lingzhi; Macri, Lucas M.; Krisciunas, Kevin; Wang, Lifan; Ashley, Michael C. B.; Cui, Xiangqun; Feng, Long-Long; Gong, Xuefei; Lawrence, Jon S.; Liu, Qiang; Luong-Van, Daniel; Pennypacker, Carl R.; Shang, Zhaohui; Storey, John W. V.; Yang, Huigen; Yang, Ji; Yuan, Xiangyan; York, Donald G.; Zhou, Xu; Zhu, Zhenxi; Zhu, Zonghong

2011-11-01

275

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

NASA Astrophysics Data System (ADS)

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.

Liao, Ying-Hao

276

The flaming gypsy skirt injury.  

PubMed

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

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

2006-11-01

277

Walraven Photometry of southern OB associations (de Geus+ 1990)  

NASA Astrophysics Data System (ADS)

Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars in the region of five nearby southern OB associations: Sco-Cen (Sco OB2), Ori OB1, CMa OB1, Mon OB1, and Sct OB2. Note that the tables have been prepared at Lausanne/Geneve Observatory (star names in Lausanne/Geneva system, coordinates absent) For details about the Walraven photometric system, see (1 data file).

de Geus, E. J.; Lub, J.; van de Grift, E.

1994-05-01

278

WIYN Open Cluster Study: UBVRI CCD Photometry of M34  

Microsoft Academic Search

M34 is a thoroughly studied open cluster on its way to becoming a fundamental WOCS cluster. We provide photometry of M34 in the U, B, V, R, and I filters in order to re-evaluate its fundamental properties. Observations were made on the WIYN 0.9m telescope on 17 January 2003 using a field of 20' x 20' on the S2KB CCD.

J. L. Windschitl; H. Gneiser; Constantine P. Deliyannis; A. Sarajedini; I. Platais

2004-01-01

279

Precise Photometry Mission -- Measuring Stellar Microvariability from Space  

Microsoft Academic Search

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

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

1995-01-01

280

Using a Web Cam CCD to do V Band Photometry  

NASA Astrophysics Data System (ADS)

With the plethora of cheap web cam based CCD cameras in the market today, it seemed expedient to find out if they can be used to do photometry. An experiment was planned to determine if it was possible to do this kind of exacting measurement. Arne Henden (AAVSO) believed it would be possible to do V band photometry to 0.05 mag accuracy with a web cam CCD. Using a 6" refractor, the heart of M42 was repeatedly imaged. Theta 2 and SAO 132322 were the comparison stars and V361 Orion was the target variable. Since the 1/4 HAD CCD chip only allows for a field of 10x7 arc minutes using the 6" refractor, the number targets was limited. The RGB on the chip itself provides the filters needed for photometry. The G band pass on the chip ranges from 425-650 nm with a peak band pass at 540, V band pass is 475-645 with a peak at 525. The results indicate that a web cam CCD can be used for V band photometry. With a 10 second calibrated exposure without the Peltier cooling being engaged, the results for the 2 target stars were ± 0.18 mag. The star Theta 2 was 0.18 brighter in V than the actual measurement from the Tycho catalog. SAO 132322 was -0.012 mag dimmer than the listed Tycho measurement. Then using SAO 132322 and Theta 2 as comparison stars, V361 Orion was estimated at 7.786 magnitudes. This is inline with visual estimates received before and after this date. With more estimates of known magnitude comparison stars, a correction factor should be estimated and applied to the variable work that will make it more accurate. This correction factor should bring it close to Arne Henden's estimate of 0.05 mag accuracy.

Temple, Paul

2009-05-01

281

GASPHOT: a tool for Galaxy Automatic Surface PHOTometry  

Microsoft Academic Search

In this paper we present a new tool for automatic, blind surface photometry of galaxies in deep and\\/or wide fields. The tool (GASPHOT) favors the robustness of results with respect to the details of galaxy modeling. To this aim, a single Sersic-law for the models and a hybrid 1D\\/2D approach for the best-fitting algorithm were adopted. GASPHOT is heavily based

E. Pignatelli; G. Fasano; P. Cassata

2006-01-01

282

A new look at photometry of the Moon  

Microsoft Academic Search

We use ROLO photometry (Kieffer, H.H., Stone, T.C. [2005]. Astron. J. 129, 2887–2901) to characterize the before and after full Moon radiance variation for a typical highlands site and a typical mare site. Focusing on the phase angle range 45°

Jay D. Goguen; Thomas C. Stone; Hugh H. Kieffer; Bonnie J. Buratti

2010-01-01

283

Wide metal-poor binaries BVRI photometry (Zapatero Osorio+, 2004)  

NASA Astrophysics Data System (ADS)

Observing dates, differential photometry and astrometry (rho and position angle) of companion candidates around 473 nearby, low-metallicity G- to M-type stars are provided in the Table. The target stars were mainly taken from the Carney-Latham surveys. Also provided are exposure times, the FWHM of the CCD images, and the telescope used for collecting the observations. The last column contains a flag indicating whether the candidate is a confirmed physical companion. (2 data files).

Zapatero Osorio, M. R.; Martin, E. L.

2004-04-01

284

UBV photometry of V379 Cep (Harmanec+, 2007)  

NASA Astrophysics Data System (ADS)

Reduction of new spectra was carried out in the IRAF and SPEFO programs. New photometry was reduced and transformed to the standard system using the HEC22 program. Orbital elements were derived with the FOTEL program and via disentangling with the program KOREL. The final combined solution was obtained with the program PHOEBE. Some initial period searches were carried out using the phase dispersion minimalization technique. (4 data files).

Harmanec, P.; Mayer, P.; Prsa, A.; Bozic, H.; Eenens, P.; Guinan, E. F.; McCook, G.; Koubsky, P.; Ruzdjak, D.; Engle, S.; Sudar, D.; Skoda, P.; Slechta, M.; Wolf, M.; Yang, S.

2006-11-01

285

Bibliography of Surface Photometry of galaxies (Davoust+ 1982)  

NASA Astrophysics Data System (ADS)

(adapted from the "Documentation for the Machine-Readable Version of the Detailed bibliography of the surface photometry of galaxies by Lee E. Brotzman and Robert S. Hill (ADC), SASC-T-1-5810-5006-84, July 1984) The bibliography supplies coded information about the methods of observation and reduction, types of photometric data, limiting surface brightness, and the general purpose of each paper for about 650 galaxies and 300 references. (3 data files).

Davoust, E.; Pence, J. D.

1995-06-01

286

M5 (NGC5904) UBVRI photometry (Viaux+, 2013)  

NASA Astrophysics Data System (ADS)

We have carried out crowded-field, point-spread function (PSF) photometry for M5 using the DAOPHOT II/ALLFRAME suite of programs (Stetson 1987PASP...99..191S, 1994PASP..106..250S). The current corpus of observations for M5 consists of 2840 CCD images obtained during 40 observing runs on 12 telescopes over a span of 27 years. (1 data file).

Viaux, N.; Catelan, M.; Stetson, P.; Raffelt, G.; Redondo, J.; Valcarce, A.; Weiss, A.

2013-08-01

287

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

288

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

SciTech Connect

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

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

2011-02-15

289

Blue stars with disk photometry in NGC 6611 (Guarcello+, 2010)  

NASA Astrophysics Data System (ADS)

This catalog contains coordinates and both optical and infrared photometry, plus usefull tags, of the Blue Stars With Disk (BWE stars) discussed in detail in Guarcello et al. (2010, in prep): "Pre-main sequence stars with disks in the Eagle nebula observed in scattered light". The optical photometry in BVI bands comes from observations with WFI@ESO (Guarcello et al. 2007, Cat. J/A+A/462/245); JHK photometry have been obtained from 2MASS/PSC and UKIDSS/GPS catalogs (Bonatto et al., 2006A&A...445..567B, Guarcello et al., 2007, Cat. J/A+A/462/245 and 2010, in prep); IRAC data are from GLIMPSE public survey (Indebetouw 2007ApJ...666..321I, Guarcello et al., 2009, Cat. J/A+A/496/453); X-ray data from observations with Chandra/ACIS-I (Linsky et al. 2007, Cat. J/ApJ/654/347, Guarcello et al., 2007, Cat. J/A+A/462/245, Guarcello et al., 2010, in prep). BWE stars have been studied by analizing their Spectral Energy Distribution (SED) using the grid of YSO models developed by Robitaille et al. 2006ApJS..167..256R. (1 data file).

Guarcello, M. G.; Damiani, F.; Micela, G.; Peres, G.; Prisinzano, L.; Sciortino, S.

2010-06-01

290

Ultra-High Precision, Ultra-Wide-Field Optical Photometry  

NASA Astrophysics Data System (ADS)

The low scintillation noise and the long continuous darkness are among the unique properties of the Dome-C site on the east Antarctic plateau. Ultra-high precision optical photometry is therefore among the techniques best suited for this particular site. We propose a telescope (ICE-T) optimized for ultra-high and ultra wide field photometry for Dome C. It consists of two 60cm optical ultra-wide-field Wynne-Schmidt telescopes and one 18cm narrow-field Maksutov spectrophotometric telescope on a single mount. ICE-T is currently a team effort of the German Alfred-Wegener-Institute for Polar Research, the Italian Universities of Padova and Perugia, the INAF Observatory Catania, and the Catalonian IEEC in Barcelona, Spain, and the AIP, with collaboration from the University of New South Wales, Australia and the University of St. Andrews, UK. In this paper, I discuss some of the many problems associated with sub-milli-mag photometry.

Strassmeier, K. G.

291

Surface Photometry of Nearby Field Galaxies: The Data  

NASA Astrophysics Data System (ADS)

We have obtained integrated spectra and multifilter photometry for a representative sample of ~200 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (MB=-14 to -22) and colors (B-R=0.4-1.8). Here we describe the sample selection criteria and the U, B, R surface photometry for these galaxies. The spectrophotometric results will be presented in a companion paper. Our goals for the project include measuring the current star formation rates and metallicity of these galaxies, and elucidating their star formation histories, as a function of luminosity and morphology. We thereby extend the work of Kennicutt to lower luminosity systems. We anticipate that our study will be useful as a benchmark for studies of galaxies at high redshift. We discuss the observing, data reduction, and calibration techniques and show that our photometry agrees well with previous work in those cases in which earlier data are available. We present an atlas of images, radial surface brightness profiles, and color profiles as well as tables of derived parameters. The atlas and tables of measurements will be made available electronically. We study the correlations of galaxy properties determined from the galaxy images. Our findings include the following: (1) colors determined within the effective radius correlate better with morphological type than with MB and (2) 50% of the low-luminosity galaxies are bluest in their centers.

Jansen, Rolf A.; Franx, Marijn; Fabricant, Daniel; Caldwell, Nelson

2000-02-01

292

Improved Asteroid Astrometry and Photometry with Trail Fitting  

NASA Astrophysics Data System (ADS)

Asteroid detections in astronomical images may appear as trails due to a combination of their apparent rate of motion and exposure duration. Nearby asteroids in particular typically have high apparent rates of motion and acceleration. Their recovery, especially on their discovery apparition, depends upon obtaining good astrometry from the trailed detections. We present an analytic function describing a trailed detection under the assumption of a Gaussian point spread function (PSF) and constant rate of motion. We have fit the function to both synthetic and real trailed asteroid detections from the Pan-STARRS1 survey telescope to obtain accurate astrometry and photometry. For short trails our trailing function yields the same astrometric and photometry accuracy as a functionally simpler two-dimensional Gaussian but the latter underestimates the length of the trail - a parameter that can be important for measuring the object's rate of motion and assessing its cometary activity. For trails longer than about 10 pixels (˜3× PSF) our trail fitting provides ˜3× better astrometric accuracy and up to two magnitudes improvement in the photometry. The trail fitting algorithm can be implemented at the source detection level for all detections to provide trail length and position angle that can be used to reduce the false tracklet rate.

Vereš, Peter; Jedicke, Robert; Denneau, Larry; Wainscoat, Richard; Holman, Matthew J.; Lin, Hsing-Wen

2012-11-01

293

Theory of wide-angle photometry from standard stars  

NASA Astrophysics Data System (ADS)

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.

Usher, Peter D.

1989-10-01

294

Multi-feature fusion based fast video flame detection  

Microsoft Academic Search

A video flame detection method based on the multi-feature fusion is presented in this paper. The temporal and spatial characteristics of flames, such as ordinary flame movement and color clues, a flame flickering detection algorithm is incorporated into the scheme to detect fires in color video sequences. An improved Gaussian mixture model method is firstly adopted to extract moving foreground

Juan Chen; Yaping He; Jian Wang

2010-01-01

295

Nonlinear effects of stretch on the flame front propagation  

Microsoft Academic Search

In all experimental configurations, the flames are affected by stretch (curvature and\\/or strain rate). To obtain the unstretched flame speed, independent of the experimental configuration, the measured flame speed needs to be corrected. Usually, a linear relationship linking the flame speed to stretch is used. However, this linear relation is the result of several assumptions, which may be incorrected. The

F. Halter; T. Tahtouh; C. Mounaïm-Rousselle

2010-01-01

296

Observations on the leading edge in lifted flame stabilization  

Microsoft Academic Search

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

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

1999-01-01

297

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

ERIC Educational Resources Information Center

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

Wang, Hongjie

1996-01-01

298

APPLICATION OF THE MARKSTEIN NUMBER CONCEPT TO CURVED TURBULENT FLAMES  

Microsoft Academic Search

Effects of large-scale stretching of premixed turbulent flames on flame speed are discussed and an extension of the classical Markstein number concept is proposed to parameterize flame speed modifications by the stretch rate. The concept is applied to fit various experimental data on the growth of the radius of expanding, statistically spherical, premixed, turbulent flames, obtained by different groups under

A. N. LIPATNIKOV; J. CHOMIAK

2004-01-01

299

STUDYING FLAME DILUTION BY BURNT GASES USING NUMERICAL COMBUSTION  

Microsoft Academic Search

Laminar unstrained and freely propagating premixed oxy-flames diluted by burnt gases are simulated with detailed chemistry. The temperature of the burnt gases is varied with the level of dilution. The response of global flame properties, as flame speed and flame thick- ness, is reported along with the behavior of major species. In a second part, Direct Numerical Simulation of partially

S. Payet; A. Naudin; P. Domingo; B. Labegorre; L. Vervisch

2006-01-01

300

Flame image segmentation algorithm based on background subtraction  

NASA Astrophysics Data System (ADS)

Considering the defect and imperfection of flame pixel point extraction and the bad environmental adaptability in the field of the present fire flame image segmentation algorithm, we put forward a kind of new algorithm based on the background difference method and fire flame color criterion. The adaptive background differencing method can detect and find objects which are moving or changing in the view field. The color criterion of fire flame can judge the color of flame of the moving objects, and then extract the flame image. Finally, the experimental results show that this algorithm has better adapt to the changing environment, and the flame extracting more accurately, perfect and stable.

Zhang, Jie; Wang, Xikang; Lv, Ming

301

Particle clustering in turbulent premixed flames  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

302

Numerical study of turbulent flame velocity  

SciTech Connect

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)

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

303

Pressure effects on nonpremixed strained flames  

SciTech Connect

This article deals with the effect of pressure on the structure and consumption rate of nonpremixed strained flames. An analysis based on the fast chemistry limit indicates that the flame thickness is inversely proportional to the square root of pressure and that the flame structure may be described in terms of a similarity variable that scales like the product of pressure and the strain rate to the power 1/2. This scaling rule also applies to flames submitted to a time-variable strain rate provided that the frequencies characterizing these changes are low compared to the mean strain rate. It is also confirmed that reactants consumption rates per unit flame surface vary like the square root of pressure and that this rule holds for time-variable strain rates of arbitrary nature. Complex chemistry calculations carried out over a broad range of operating pressures indicate that the pressure dependences deduced analytically are remarkably accurate and can be used for a broad range of strain rates, excluding values in the near vicinity of extinction conditions, where finite rate chemistry effects become important and influence the flame response to pressure. Thus, it appears that the pressure exponent characterizing the heat release rate in nonpremixed strained flames is essentially constant and equal to 1/2. This exponent is independent of finite rate chemistry effects, except when conditions are close to extinction. (author)

Pons, Laetitia; Darabiha, Nasser [Ecole Centrale Paris, Laboratoire EM2C, CNRS, 92295 Chatenay-Malabry Cedex (France); Candel, Sebastien [Ecole Centrale Paris, Laboratoire EM2C, CNRS, 92295 Chatenay-Malabry Cedex (France); Institut Universitaire de France (France)

2008-01-15

304

Velocity statistics in premixed turbulent flames  

SciTech Connect

Laser Doppler velocimetry was used to measure velocity statistics in six unconfined v-shaped premixed ethylene/air turbulent flames with incident turbulence generated by grid or perforated plate. Also obtained were high speed schlieren movies of the turbulent flames. The results discussed include two components of mean and rms velocities, probability density functions, macroscales, and Reynolds stress. In most cases, turbulent intensities increase within the flame zone. This increase is attributed to the intermittent measurement of the flow velocities in the burned and unburned states as the thin flame sheet fluctuates about the stationary measurement point. Reynolds stress also increases in the flame zone, but its sign suggests removal of turbulent kinetic energy. Therefore, conventional gradient transport modeling would break down for these flames. The sign of the Reynolds stress is in qualitative agreement with contributions due to intermittent measurement of the turbulent components in the burned and unburned states. These results show that the intermittency effect is a major influence on turbulent statistics in premixed flames and should require careful consideration in numerical models.

Cheng, R.K.; Ng, T.T.

1983-01-01

305

Progress and challenges in swirling flame dynamics  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

306

PLIF investigation of the evolution of premixed turbulent flame structures  

SciTech Connect

Planar Laser Induced Fluorescence (PLIF) technique of OH has been used to investigate premixed turbulent flame structures under moderate and intense isotropic turbulence. The goal is to test and verify theoretical assumptions regarding classification of premixed turbulent flames. The experiments use a weak-swirl burner that supports stable combustion in laminar and turbulent flames with incident turbulence intensities exceeding 20%. OH-PLIF results obtained for a flame with Ka = 0.8 (i.e. corrugated flamelet regime) show that the flame forms deep flame cusps but not flame pockets. For a flame with Ka = 3.1 (i.e. distributed reaction zone regime), the flame front is more fragmented with pockets form both in the products and in the reactants. Sharp rises in the OH fluorescence intensity profiles deduced from both flames suggest flamelet behavior even for conditions well within the regime of {open_quotes}distributed reaction zones{close_quotes}.

Bedat, B.; Shepherd, I.G.; Cheng, R.K.

1996-03-01

307

High-Quality Broadband BVRI Photometry of Benchmark Open Clusters  

NASA Astrophysics Data System (ADS)

Photometric techniques are often used to observe stars and it can be demonstrated that fundamental stellar properties can be observationally determined using calibrated sets of photometric data. Many of the most powerful techniques utilized to calibrate stellar photometry employ the use of stars in clusters since the individual stars are believed to have many common properties such as age, composition, and approximate distance. Broadband photometric Johnson/Cousins BVRI observations are presented for several nearby open clusters. The new photometry has been tested for consistency relative to archival work and shown to be both accurate and precise. The careful use of a regular routine when making photometric observations, along with the monitoring of instrumental systems and the use of various quality control techniques when making observations or performing data reductions, will enhance an observer's ability to produce high-quality photometric measurements. This work contains a condensed review of the history of photometry, along with a brief description of several popular photometric systems that are often utilized in the field of stellar astrophysics. Publications written by Taylor or produced during the early Taylor and Joner collaboration are deemed especially relevant to the current work. A synopsis of seven archival publications is offered, along with a review of notable reports of VRI photometric observations for the nearby Hyades open star cluster. The body of this present work consists of four publications that appeared between the years 2005 and 2008, along with a soon to be submitted manuscript for a fifth publication. Each of these papers deals specifically with high-quality broadband photometry of open clusters with new data being presented for the Hyades, Coma, NGC 752, Praesepe, and M67. It is concluded that the VRI photometry produced during the Taylor and Joner collaborative investigations forms a high-quality data set that has been: (1) stable for a period of more than 25 years; (2) monitored and tested several times for consistency relative to the broadband Cousins system, and (3) shown to have well-understood transformations to other versions of broadband photometric systems. Further work is suggested for: (1) the transformation relationships for the reddest stars available for use as standards; (2) the standardization of more fields for use with CCD detectors; (3) a further investigation of transformations of blue color indices for observations done using CCD detectors with enhanced UV sensitivity, and (4) a continuation of work on methods to produce high-quality observations of assorted star clusters (both open and globular) with CCD-based instrumentation and intermediate-band photometric systems.

Joner, Michael D.

308

Stochastic subgrid modeling of turbulent premixed flames  

NASA Astrophysics Data System (ADS)

A comprehensive modeling approach for simulating flamelet premixed combustion is formulated. The subgrid version of the linear eddy mixing model is refined and used to model flame wrinkling by the fine scale eddies. The advection of the flame by the larger eddies is modeled using a Lagrangian volume tracking scheme. The subgrid model and the advection scheme are independently validated and coupled effectively to produce a two-scale modeling approach. The resulting approach is free of any empiricisms, needs no calibration and fits into the large eddy simulation framework which is used to model the fluid dynamics. The new modeling approach is used to study premixed flames stabilized by stagnating turbulence and turbulent wakes. The results for the stagnation flames predicted using the proposed approach compare better with experimental results than the results obtained using more conventional modeling approaches. Simulations also show that the flamelet nature of combustion, which is not often captured by most approaches, is well captured by the present approach. The simulations of wake stabilized flames suffer from inaccuracies in modeling flame-wall interactions. However, these simulations show that the numerical scheme used to capture the flame evolution has a very significant effect on the predictions of flame structure and its interaction with turbulence in flows dominated by large scale vortex structures. Specifically, the thin-flame model proposed here predicts that the heat release due to combustion weakens the Kelvin-Helmholtz instability and the related von-Karman instability in the near wakes. Such weakening is, however, not predicted by the more conventional methods. The method proposed here has some inherent limitations. Possible ways to overcome these limitations are proposed.

Chakravarthy, Veerathu Kalyana

2000-10-01

309

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

Microsoft Academic Search

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

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

1997-01-01

310

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

PubMed

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

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

2012-01-27

311

Physical Mechanism of Ultrafast Flame Acceleration  

NASA Astrophysics Data System (ADS)

We explain the physical mechanism of ultrafast flame acceleration in obstructed channels used in modern experiments on detonation triggering. It is demonstrated that delayed burning between the obstacles creates a powerful jetflow, driving the acceleration. This mechanism is much stronger than the classical Shelkin scenario of flame acceleration due to nonslip at the channel walls. The mechanism under study is independent of the Reynolds number, with turbulence playing only a supplementary role. The flame front accelerates exponentially; the analytical formula for the growth rate is obtained. The theory is validated by extensive direct numerical simulations and comparison to previous experiments.

Bychkov, Vitaly; Valiev, Damir; Eriksson, Lars-Erik

2008-10-01

312

Particle size distribution function of incipient soot in laminar premixed ethylene flames: effect of flame temperature  

Microsoft Academic Search

Particle size distribution functions (PSDFs) of incipient soot formed in laminar premixed 24.2% ethylene–37.9% oxygen-diluent (nitrogen and\\/or argon) flames with an equivalence ratio of 1.92 were studied by online sampling and scanning mobility particle sizer. Two series of flames were studied to quantify the effect of flame temperature on the characteristics of PSDFs. In the first series, the variation of

Bin Zhao; Zhiwei Yang; Zhigang Li; Murray V. Johnston; Hai Wang

2005-01-01

313

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

SciTech Connect

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

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

1997-12-01

314

Diffusion edge-flame: approximation of the flame tip Damköhler number  

Microsoft Academic Search

A relation is provided to approximate the Damköhler number at the tip of an edge-flame. The reaction zone extremity is modeled as a one-dimensional diffusion flame to which additional transverse fluxes are added. The Damköhler number at the flame tip is then characterized by a relation that involves the quenching Damköhler number of a one-dimensional diffusion flamelet. In this expression,

Joan Boulanger; Luc Vervisch

2002-01-01

315

A numerical study of the superadiabatic flame temperature phenomenon in HN3 flames  

Microsoft Academic Search

The phenomenon of superadiabatic flame temperature (SAFT) was discovered and investigated in a low-pressure HN3\\/N2 flame using numerical modelling. A previously developed mechanism of chemical reactions in the HN3\\/N2 flame at the pressure 50 Torr and the initial temperature T0 = 296 K was revised. Rate constants of several important reactions involving HN3 (HN3 (+N2) = N2 + NH (+N2), R1;

Oleg P. Korobeinichev; Alexander A. Paletsky; Tatyana A. Bolshova; Vadim D. Knyazev

2012-01-01

316

Structure and Flame Length of Fully-Modulated, Turbulent Diffusion Flames  

Microsoft Academic Search

The turbulent flame structure and flame length of fully-modulated diffusion flames was examined over a range of pulsing frequencies, injection flow rates, and duty-cycles. An injection system employing an electronically-controlled solenoid value was used to discharge puffs of unhealed natural gas and ethylene fuel into still air at one atmosphere pressure. Video imaging of the luminosity from the sooting regions

J. C. HERMANSON; R. DUGNANI; H. JOHARI

2000-01-01

317

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

Microsoft Academic Search

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

G. W. Sidebotham; I. Glassman

1992-01-01

318

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

Microsoft Academic Search

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

H. Pitsch; H. Steiner

2000-01-01

319

Cyclic phosphines as flame retardants  

US Patent & Trademark Office Database

The present invention is related to the use of specific cyclic and/or polymeric aryl-phosphines as flame retardants and to a method for reducing the flammability of organic material by incorporating into the material these specific cyclic and/or polymeric phosphines. Moreover, the invention is related to a polymeric composition containing a polymeric material and at least one of the specific cyclic and/or polymeric phosphines in an amount of from 1 to 15% by weight, based on the weight of the polymeric material. The invention also relates to a composition comprising at least one of the specific cyclic and/or polymeric phosphines and at least one polymerizable monomer.

2013-08-27

320

Flame Structure and Flame Reaction Kinetics. I. Solution of Conservation Equations and Application to Rich Hydrogen-Oxygen Flames  

Microsoft Academic Search

The time dependent heat conduction and diffusion equations have been set up for some simplified reaction mechanisms representing a fuel-rich hydrogen-nitrogen-oxygen flame, and have been solved by finite difference methods. The effects on the flame properties of changes in some of the reaction parameters and the transport properties of the gas mixture have been examined and some comparisons made with

G. Dixon-Lewis

1967-01-01

321

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

SciTech Connect

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

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

1998-03-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

323

The interaction of high-speed turbulence with flames: Turbulent flame speed  

SciTech Connect

Direct numerical simulations of the interaction of a premixed flame with driven, subsonic, homogeneous, isotropic, Kolmogorov-type turbulence in an unconfined system are used to study the mechanisms determining the turbulent flame speed, S{sub T}, in the thin reaction zone regime. High intensity turbulence is considered with the r.m.s. velocity 35 times the laminar flame speed, S{sub L}, resulting in the Damkoehler number Da=0.05. The simulations were performed with Athena-RFX, a massively parallel, fully compressible, high-order, dimensionally unsplit, reactive-flow code. A simplified reaction-diffusion model, based on the one-step Arrhenius kinetics, represents a stoichiometric H{sub 2}-air mixture under the assumption of the Lewis number Le=1. Global properties and the internal structure of the flame were analyzed in an earlier paper, which showed that this system represents turbulent combustion in the thin reaction zone regime. This paper demonstrates that: (1) The flame brush has a complex internal structure, in which the isosurfaces of higher fuel mass fractions are folded on progressively smaller scales. (2) Global properties of the turbulent flame are best represented by the structure of the region of peak reaction rate, which defines the flame surface. (3) In the thin reaction zone regime, S{sub T} is predominantly determined by the increase of the flame surface area, A{sub T}, caused by turbulence. (4) The observed increase of S{sub T} relative to S{sub L} exceeds the corresponding increase of A{sub T} relative to the surface area of the planar laminar flame, on average, by {approx}14%, varying from only a few percent to as high as {approx}30%. (5) This exaggerated response is the result of tight flame packing by turbulence, which causes frequent flame collisions and formation of regions of high flame curvature >or similar 1/{delta}{sub L}, or ''cusps,'' where {delta}{sub L} is the thermal width of the laminar flame. (6) The local flame speed in the cusps substantially exceeds its laminar value, which results in a disproportionately large contribution of cusps to S{sub T} compared with the flame surface area in them. (7) A criterion is established for transition to the regime significantly influenced by cusp formation. In particular, at Karlovitz numbers Ka >or similar 20, flame collisions provide an important mechanism controlling S{sub T}, in addition to the increase of A{sub T} by large-scale motions and the potential enhancement of diffusive transport by small-scale turbulence. (author)

Poludnenko, A.Y.; Oran, E.S. [Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington, DC 20375 (United States)

2011-02-15

324

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

Microsoft Academic Search

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

Ashoke De; Sumanta Acharya

2009-01-01

325

Influence of oblique angle and heating height on flame structure, temperature field and efficiency of an impinging laminar jet flame  

Microsoft Academic Search

An experimental study is performed to determine the combined effects of oblique angle (?) and heating height (H) on the flame structure, temperature field and thermal efficiency of a laminar premixed methane–air flame impinging on a plane surface. A double-flame burning of a Bunsen flame under a fuel-rich condition is used. It is found that the flame structure, temperature distribution

Shuhn-Shyurng Hou; Yung-Chang Ko

2005-01-01

326

Flame Retardant Formulations and Products Produced Therefrom.  

National Technical Information Service (NTIS)

An elastomeric coating is presented that significantly increases the flame resistance of a flammable polyurethane foam, without adversely affecting the desirable physical properties of the foam. The coating does not produce smoke, a very significant impro...

K. R. Sidman P. Monaghan

1978-01-01

327

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...

328

Light collection device for flame emission detectors  

DOEpatents

This report describes a light collection device for use in a flame emission detection system such as an on-line, real-time alkali concentration process stream monitor. The device 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. 2 figs.

Woodruff, S.D.; Logan, R.G.; Pineault, R.L.

1989-04-14

329

Light collection device for flame emission detectors  

DOEpatents

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

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

1990-01-01

330

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...

331

Flat Flame Olympics: Test Problem A.  

National Technical Information Service (NTIS)

This report discusses a test problem for a computer program for numerically solving the equations governing a laminar, premixed, one-dimensional flame. The problem was proposed by GAMM (Committee for Numerical Methods in Fluid Mechanics), and has been sol...

T. P. Coffee

1982-01-01

332

Kinetical Study of Hydrogen - Nitrous Oxide Flames.  

National Technical Information Service (NTIS)

Flames propagating in hydrogen-nitrous oxide mixtures have been investigated in widely varying conditions of composition and dilution with different inert gases. The kinetical interpretation of the experimental values, obtained for burning velocities, the...

A. Duval P. J. Van Tiggelen

1967-01-01

333

Characterization of flame radiosity in shrubland fires  

Microsoft Academic Search

The present study is aimed at quantifying the flame radiosity vertical profile and gas temperature in moderate to high intensity spreading fires in shrubland fuels. We report on the results from 11 experimental fires conducted over a range of fire rate of spread and frontal fire intensity varying respectively between 0.04–0.35ms?1 and 468–14,973kWm?1. Flame radiosity, or radiant emissive power, and

Miguel G. Cruz; Bret W. Butler; Domingos X. Viegas; Pedro Palheiro

2011-01-01

334

Thermally Stable and Flame Retardant Elastomeric Nanocomposites  

Microsoft Academic Search

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

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

335

An elementary discussion of propellant flame geometry  

SciTech Connect

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

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

1999-05-01

336

Formation and properties of distributed flames  

NASA Astrophysics Data System (ADS)

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

Poludnenko, Alexei; Gamezo, Vadim; Oran, Elaine

2008-11-01

337

Characterisation of an oxy-coal flame through digital imaging  

SciTech Connect

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

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

2010-06-15

338

Blowoff dynamics of bluff body stabilized turbulent premixed flames  

SciTech Connect

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

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

2010-04-15

339

Auroral images from space - Imagery, spectroscopy, and photometry  

NASA Astrophysics Data System (ADS)

The design of the Auroral Ionospheric Remote Sensor (AIRS), a multimodal instrument comprising imagery, spectroscopy, and photometry subsystems, is described, with attention given to its electrooptics, mechanics, and electronics. The AIRS is a four-channel system that operates simultaneously in the vacuum UV (VUV), near-UV, and visible spectral bands. The sensor produces auroral images in both dark and sunlit hemispheres and enables the remote sensing of ionospheric airglows. The results of AIRS VUV spectrometer detectors sensitivity measurements for the two VUV channels are presented together with the AIRS optical schematic and the block diagram of its electrical system.

Schenkel, Frederick W.; Ogorzalek, Bernard S.

1987-09-01

340

Surface photometry of ellipticals: Radio and cluster galaxies  

NASA Astrophysics Data System (ADS)

Broad-band surface photometry in V, R and I colors is presented for three elliptical galaxies immersed in hot intracluster gas emitting X-rays due to thermal bremsstrahlung. The galaxies are (1) a cD galaxy, and (2) a radio bright galaxy with a narrow angle tail in the cluster of galaxies, 2A0335+096, and (3) NGC 3607 in a small nearby group of galaxies. Strong H-alpha emission from NGC 3607 has also been imaged. Detection of a dust ring in NGC 3607 is being reported here for the first time.

Singh, K. P.; Bhat, P. N.; Prabhu, T. P.; Kembhavi, A. K.

1993-09-01

341

BVI photometry of 5 CVn cloud galaxies (Karachentsev+ 1998)  

NASA Astrophysics Data System (ADS)

We present results of CCD imaging in B, V of five late-type galaxies with radial velocities V0<350km/s in the Canes Venatici cloud. Based on the photometry of their brightest blue stars we derived the following distances to the galaxies: 9.7Mpc for NGC 4144, 4.5Mpc for NGC 4244, 4.2Mpc for NGC 4395, 2.9Mpc for NGC 4449, and 8.2Mpc for UGC 8331. (1 data file).

Karachentsev, I. D.; Drozdovsky, I. O.

1998-01-01

342

Early Photometry of the Type IIP supernova SN 2013ej  

NASA Astrophysics Data System (ADS)

We report an early photometric observation of the Type IIP supernova SN 2013ej taken 15 hours before the official discovery (CBET #3606). We observed the field of M74 on 2013 July 24.80 - 24.83 UT using the 1m telescope at the Lulin Observatory in Taiwan. The supernova 2013ej was clearly detected in our multi-color observations. By comparing with the USNO and GSC2.3 catalogs, we derived the following optical (B, V, and R) photometry: B=13.8, V=14.0, and R=14.3.

Lee, M.; Li, K. L.; Wang, J.-W.; Kong, A. K. H.; Liu, H. B.; Huang, H.-J.; Huang, Y.-H.; Lin, Y.-M.; Yang, K.-C.; Program, on behalf of the Taipei First Girls'High School High Scope

2013-10-01

343

Analysis of RGU Photometry in Selected Area 51  

Microsoft Academic Search

A low-latitude anticenter field (l=189 °, b=+21 °) is investigated by using the full calibration tools of RGU photometry. The observed RGU data are reduced to the standard system and the separation of dwarfs and evolved stars is carried out by an empirical method. Stars are categorized into three metallicity classes, i.e. -0.25<[M\\/H]<=+0.50, $-1.00<[M\\/H]<=-0.25, and [M\\/H]<=-1.00 dex, and their absolute

S. Bilir; S. Karaali; R. Buser

2004-01-01

344

An algorithm for precise aperture photometry of critically sampled images  

NASA Astrophysics Data System (ADS)

We present an algorithm for performing precise aperture photometry on critically sampled astrophysical images. The method is intended to overcome the small-aperture limitations imposed by point sampling. Aperture fluxes are numerically integrated over the desired aperture, with sinc interpolation used to reconstruct values between pixel centres. Direct integration over the aperture is computationally intensive, but the integrals in question are shown to be convolution integrals and can be computed ? 10 000 times faster as products in the wavenumber domain. The method works equally well for annular and elliptical apertures and could be adapted for any geometry. A sample of code is provided to demonstrate the method.

Bickerton, S. J.; Lupton, R. H.

2013-05-01

345

Optical photometry and spectroscopy of Nova Del 2013  

NASA Astrophysics Data System (ADS)

We report optical BV photometry and spectroscopy of Nova Del 2013, carried out between August 14.88 UT and August 15.08 UT. Using a 60 cm Cassegrain telescope at the Nicolaus Copernicus University Observatory (Torun, Poland) we estimated the V brightness of the Nova to be 6.31+/-0.02 mag and 6.18+/-0.03 mag on Aug. 14.94 UT and Aug. 15.02 UT respectively. HD 194113 (F2, V=8.00 mag) was used as a comparison star.

Tomov, T.; Ilkiewicz, K.; Swierczynski, E.; Belcheva, M.; Dimitrov, D.

2013-08-01

346

Flame Structure and Flame Reaction Kinetics. VII. Reactions of Traces of Heavy Water, Deuterium and Carbon Dioxide Added to Rich Hydrogen + Nitrogen + Oxygen Flames  

Microsoft Academic Search

The overall reactions of traces of heavy water, deuterium and carbon dioxide added to some fuel-rich hydrogen + nitrogen + oxygen flames have been examined both experimentally and theoretically. The mechanism and most of the controlling rate constants for the flames both without and with the additives are now sufficiently firmly established for computation of the detailed flame profiles to

G. Dixon-Lewis

1972-01-01

347

Vorticity in unsteady premixed flames: vortex pair–premixed flame interactions under imposed body forces and various degrees of heat release and laminar flame thickness  

Microsoft Academic Search

The dynamics of vortical structures are investigated when a vortex pair propagates into a premixed flame under different imposed body forces in the direction of mean flame propagation and various degrees of heat release and laminar flame thicknesses. The direct numerical simulation assumes zero Mach number, adiabatic, simple chemistry equations, and constant diffusivities. Visual pictures of the qualitatively different behaviors

D. S. Louch; K. N. C. Bray

2001-01-01

348

Burning velocities, markstein lengths, and flame quenching for spherical methane-air flames: A computational study  

Microsoft Academic Search

Computations are for three modes of spherical laminar flame propagation: explosion, implosion, and stationary. The reduced kinetic, C1, scheme of Mauss and Peters is employed for a range of equivalence ratios under atmospheric conditions, with flame propagation at constant pressure. Save for the richest mixture, the scheme is fully adequate for present purposes. Two burning velocities are computed, one based

Derek Bradley; P. H. Gaskell; X. J. Gu

1996-01-01

349

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

SciTech Connect

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

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

2007-04-15

350

STUDY ON FLAME HEIGHT OF MERGED FLAME FROM MULTIPLE FIRE SOURCES  

Microsoft Academic Search

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

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

2004-01-01

351

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

Microsoft Academic Search

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

Jianjun Wang; Li Wang; Anguo Xiao

2009-01-01

352

Effect of steam on flame temperature, burning velocity and carbon formation in hydrocarbon flames  

Microsoft Academic Search

The effect on flame temperature, burning velocity and carbon limit of adding water vapor to a premixed flame has been investigated using a Bunsen-type burner operated at atmospheric pressure and employing propane and ethylene as fuels. The results indicate that water vapor does not act as an inert diluent but instead inhibits carbon formation and gives rise to a greater

K. Mueller-Dethlefs; A. F. Schlader

1976-01-01

353

Calculations of explosion deflagrating flames using a dynamic flame surface density model  

Microsoft Academic Search

Explosion deflagrating flames in a small scale vented chamber, with repeated obstacles are simulated using the large eddy simulation (LES) technique for turbulent reacting flows. A novel dynamic flame surface density (DFSD) combustion model, based on the laminar flamelet concept has been used to account for the mean chemical reaction rate. All cases considered here start with a stagnant, stoichiometric

S. S. Ibrahim; S. R. Gubba; A. R. Masri; W. Malalasekera

2009-01-01

354

24 CFR 3280.203 - Flame spread limitations and fire protection requirements.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Flame spread limitations and fire protection requirements...STANDARDS Fire Safety § 3280.203 Flame spread limitations and fire protection requirements. (a) Establishment of flame spread rating. The surface flame...

2009-04-01

355

24 CFR 3280.203 - Flame spread limitations and fire protection requirements.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Flame spread limitations and fire protection requirements...STANDARDS Fire Safety § 3280.203 Flame spread limitations and fire protection requirements. (a) Establishment of flame spread rating. The surface flame...

2010-04-01

356

The wrinkling of a flame due to viscosity  

SciTech Connect

The authors present a numerical study of flame wrinkling due to viscosity. They model a flame propagating in a swirling, viscous, premixed combustible fuel inside a closed, rectangular vessel, and analyze the influence of vorticity produced by the no-slip condition along solid walls on the motion of the flame. They show that viscosity wrinkles the flame front, increasing the surface area available for burning and thus accelerating the combustion process. They perform experiments over a range of nondimensional burning velocities, and show that the slower the flame speed, the greater the effect of viscosity on the rate of combustion, when compared to an inviscid calculation with the same flame speed.

Sethian, J.A.; Alpert, R.L.; Altenkirch, R.A.

1983-07-01

357

Investigation of flame-generated turbulence in premixed flames at low and high burning velocities  

SciTech Connect

Knowledge of the dependence of turbulent flame velocity on such parameters as fuel properties, turbulent fluctuations, and length scales is of central importance for industrial applications such as combustion in motors, gas turbine combustors, and domestic burners. Two unanswered questions concern how aerodynamic turbulence influences the reaction and/or flame speed and how the reaction intensity influences the aerodynamic turbulence values. The reaction velocity has been measured in a stagnation point flame, the turbulence intensities and length scales before and after the flame front being recorded by an LDV system. Laminar burning velocity was varied by using different concentrations of methane-hydrogen-air mixtures. The results show under certain conditions an immense increase in turbulent fluctuations in and after the flame front, measured using conditioned and unconditioned LDV techniques. 6 refs.

Liu, Yanson; Lenze, B. (Karlsruhe, Universitaet, (Germany))

1992-05-01

358

An evaluation of flame surface density models for turbulent premixed jet flames  

SciTech Connect

The authors report a computational study of a turbulent premixed jet flame stabilized in a laminar coflow of a reactant mixture at the same stoichiometric ratio as the turbulent flame. The performance of four different flame surface density (FSD) models, earlier used by Duclos et al. for studying flame propagation in constant density frozen turbulence, and that of the reaction progress variable approach of Bray and Moss (BM) is evaluated by comparison with existing experimental data. The authors also describe a sensitivity analysis of predictions to inlet turbulence quantities and inlet flame surface density. The predictions of the Mantel and Borghi (MB) model are observed to be highly sensitive to inlet turbulence quantities, while those of the coherent flame (CF) model and BM models are less sensitive. The mean velocity and temperature predictions are insensitive to the inlet FSD distribution because of the strong production and dissipation terms in the transport equation for FSD. The predictions of mean velocity and temperature profiles are compared with the experimental data of Chen et al. Among the FSD models, the CF and MB models gave good estimates of mean velocity and temperature. The Cant, Pope, and Bray (CPB) model overpredicted the mean temperatures slightly. The flame surface density model of Cheng and Diringer (CD) predicted too high temperatures. This is shown to be resulting from an overprediction of the generation of flame surface density. All the models predict the increase in flame brush thickness with distance from the injector exit, but the MB model provides the best quantitative estimates of the flame brush thickness.

Prasad, R.O.S.; Gore, J.P. [Purdue Univ., West Lafayette, IN (United States)

1999-01-01

359

The Chrysalis Opens? Photometry from the eta Carinae Hubble Space Telescope Treasury Project, 2002-2006  

Microsoft Academic Search

During the past decade eta Car has brightened markedly, possibly indicating a change of state. Here we summarize photometry gathered by the Hubble Space Telescope (HST) as part of the HST Treasury Project on this object. Our data include Space Telescope Imaging Spectrograph (STIS) CCD acquisition images, Advanced Camera for Surveys HRC images in four filters, and synthetic photometry in

J. C. Martin; Kris Davidson; M. D. Koppelman

2006-01-01

360

The AAVSO Photoelectric Photometry Program in its Scientific and Socio-Historic Context  

Microsoft Academic Search

Photoelectric photometry began in the 1900s through the work of Guthnick, Stebbins, and others who constructed and used photometers based on the recently-discovered photoelectric effect. The mid 20th century saw a confluence of several areas of amateur interest: astronomy, telescope making, radio and electronics, and general interest in space. This is the time when AAVSO photoelectric photometry (PEP) began, with

John R. Percy

2011-01-01

361

ESO large program on physical studies of Transneptunian Objects and Centaurs: Visible photometry - First results  

Microsoft Academic Search

We present the first results of BVRI photometry of Transneptunian Objects (TNOs) and Centaurs obtained through the ESO Large Program on physical studies of these icy bodies in the outer solar system. In total 28 objects were observed of which 18 are new measurements. Combining our new BVRI photometry with the data summary published by Hainaut & Delsanti (\\\\cite{Hainaut2002}) results

H. Boehnhardt; A. Delsanti; A. Barucci; O. Hainaut; A. Doressoundiram; M. Lazzarin; L. Barrera; C. de Bergh; K. Birkle; E. Dotto; K. Meech; J. E. Ortiz; J. Romon; T. Sekiguchi; N. Thomas; G. P. Tozzi; J. Watanabe; R. M. West

2002-01-01

362

High-Speed CCD Photometry of White Dwarfs with a Small Telescope  

NASA Astrophysics Data System (ADS)

Small telescopes face a mission crisis and lack of funding in this age of bigger and bigger telescopes. High speed photometry of white dwarfs and other variables is a field in which these telescopes can be vital participants. We present high speed photometry taken at Mt. Cuba Observatory in Wilmington, Delaware, in collaboration with the Whole Earth Telescope.

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

2003-12-01

363

Laminar flame speeds of moist syngas mixtures  

SciTech Connect

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

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

364

Infrared surface photometry of dwarf galaxies in Fornax  

NASA Astrophysics Data System (ADS)

Despite its utility in exploring possible spatial variations in the stellar populations in galaxies, infrared surface photometry of low-luminosity dwarf elliptical (dE) galaxies is generally lacking, due to the technical difficulties in observing low surface brightness objects against the bright infrared sky. Here we attempt to remedy this shortfall to some extent by presenting K-band photometry at arcsecond resolution, including radial profiles, 1D and 2D model fits and the quantification of nuclear components, for a small sample of dE galaxies, with absolute magnitudes MB?-15 to -13, in the Fornax Cluster. In the second part of the paper, we explore the comparison of these data with corresponding optical observations and attempt to interpret this in terms of stellar population models and their radial trends. A significant range of global optical-infrared colours is present in our sample, but radial colour gradients in the galaxies are usually small. However, while the nuclear regions tend to be bluer in optical colours, they are systematically redder than the surrounding galaxy in (R-K). The stellar population modelling suggests that these colour differences are probably an effect of both higher metallicity and younger age in the nuclei. Excluding the nuclear regions, the global colour profiles typically change in the same direction, again indicating older, more metal-poor stellar populations in the outskirts of the galaxies.

Smith, Rachel; Phillipps, S.; Jones, J. B.; Morris, R. A. H.; Smith, R. M.; Drinkwater, M. J.; Karick, A. M.

2012-03-01

365

BVR photometry of the resolved dwarf galaxy Ho IX  

NASA Astrophysics Data System (ADS)

We present BVR CCD photometry down to limiting magnitude B=23.5 mag for 232 starlike objects and 11 diffuse objects in a 5.4 arcmin × 5.4 arcmin field of Ho IX. The galaxy is a gas-rich irregular dwarf galaxy possibly very close to M 81, which makes it especially interesting in the context of the evolution of satellite galaxies and the accretion of dwarf galaxies. Investigations of Ho IX were hampered by relatively large contradictions in the magnitude scale between earlier studies. With our new photometry we resolved these discrepancies. The color magnitude diagram (CMD) of Ho IX is fairly typical of a star-forming dwarf irregular, consistent with earlier results. Distance estimates from our new CMD are consistent with Ho IX being very close to M 81 and therefore being a definite member of the M 81 group, apparently in very close physical proximity to M 81. This work is a part of a joint project between the Astronomical Institute of the Ruhr-University in Bochum and the Institute of Astronomy of the Bulgarian Academy of Sciences for the study of nearby dwarf galaxies.

Georgiev, T. B.; Bomans, D. J.

2004-08-01

366

A new look at photometry of the Moon  

USGS Publications Warehouse

We use ROLO photometry (Kieffer, H.H., Stone, T.C. [2005]. Astron. J. 129, 2887-2901) to characterize the before and after full Moon radiance variation for a typical highlands site and a typical mare site. Focusing on the phase angle range 45??. ) to calculate the scattering matrix and solve the radiative transfer equation for I/. F. The mean single scattering albedo is ??=0.808, the asymmetry parameter is ???cos. ?????=0.77 and the phase function is very strongly peaked in both the forward and backward scattering directions. The fit to the observations for the highland site is excellent and multiply scattered photons contribute 80% of I/. F. We conclude that either model, roughness or multiple scattering, can match the observations, but that the strongly anisotropic phase functions of realistic particles require rigorous calculation of many orders of scattering or spurious photometric roughness estimates are guaranteed. Our multiple scattering calculation is the first to combine: (1) a regolith model matched to the measured particle size distribution and index of refraction of the lunar soil, (2) a rigorous calculation of the particle phase function and solution of the radiative transfer equation, and (3) application to lunar photometry with absolute radiance calibration. ?? 2010 Elsevier Inc.

Goguen, J. D.; Stone, T. C.; Kieffer, H. H.; Buratti, B. J.

2010-01-01

367

Changes on Pluto's Surface Revealed with Long Timebase Photometry  

NASA Astrophysics Data System (ADS)

We are continuing to monitor the long-term photometric behavior of Pluto in order to constrain volatile surface migration. As Pluto passes near the center of the galaxy, the fields are too crowded for normal aperture photometric techniques. We approached this problem with a combination of point-spread function (PSF) photometry and optimal image subtraction (OIS). Our data are from the 0.8-m robotic telescope at Lowell Observatory, the 1-m robotic telescope at New Mexico State Observatory, and the Faulkes 2-m robotic telescope at Siding Spring, part of Las Cumbres Observatory. Our latest results add photometric data up through 2012 to the data collected since discovery. Our new reduction scheme consists of background catalogs, image subtraction using deep templates, and Pluto photometry extraction. We also use the known photometric properties of Charon determined with HST to remove Charon's contribution from old and new data and compare these results with the HST data where Pluto is measured by itself. Data since 2002 show marked departures from the behavior prior to that time. These results provide clear evidence for time evolution of Pluto's surface albedo. We will present these results along with implications for present-day processes that are altering the surface of Pluto. This work also provides crucial insight into the effort required to provide ground-based support observations for the upcoming New Horizons flyby of Pluto in 2015. Support for this work was provided by NASA Planetary Astronomy Program, grant number NNX09AB43G.

George, Erin; Buie, M.

2013-10-01

368

Optical and NIR Photometry of Open Cluster NGC 7790  

NASA Astrophysics Data System (ADS)

We present BVRI CCD photometry and near-infrared K photometry of the intermediate-aged open cluster NGC 7790. The reddening, E(B-V)=0.54 +/- 0.05 and the distance modulus, (m-M)_o=12.45 +/- 0.10 for the cluster were determined by zero-age-main-sequence fitting and theoretical isochrone fitting using not only (V, B-V), (V, V-I), (V, V-R) but also (V, V-K) color-magnitude diagrams. The reddening corresponded approximately to the average value derived from previous studies, while the distance modulus was found to be almost midway between the CCD photometric results of Romeo et al. (1989) and those of Mateo & Madore (1988). We have used four colors to distinguish members from field stars. The expected colors were calculated using the derived distance modulus, and were then were compared with the observed colors (B-V), (V-I), (V-R), and (V-K). Thus, a color excess E(B-V) for each star was determined which could give the minimum difference between the calculated and observed colors. Single and binary members of the cluster were determined on the basis of the E(B-V) distribution of stars.

Lee, Jung-Deok; Lee, Sang-Gak

1999-10-01

369

Multicolor photometry of triple system b Per requested  

NASA Astrophysics Data System (ADS)

Dr. Bob Zavala (U.S. Naval Observatory, Flagstaff) has requested AAVSO assistance in obtaining multicolor photometry of the bright triple system b Per in order to prepare for and detect a possible eclipse of the AB components by the C component predicted for 2013 January 23. Multi-color photometric observations of 4.5V b Per are requested 2013 January 23 through February 04. Based on a revised period of 702.45 ± 0.05 days, the next time of minimum light is predicted for HJD = 2456321.35 ± 0.05 (UT 2013 January 28 20:24UT ± 1.5 hours). The eclipse may last for up to four days, so the coverage requested will provide both a baseline out-of-eclipse light curve and a multi-color eclipse light curve for analysis. Photometry is needed at the level of 0.02-0.03 magnitude or better, as the eclipse may be as deep as 0.1 magnitude. For PEP observers, V coverage, and B if possible, is requested. DSLR observers should use whatever band(s) are available to them. Finder charts 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 and links.

Waagen, Elizabeth O.

2013-01-01

370

Ultraviolet imaging of hydrogen flames  

SciTech Connect

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

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

1988-01-01

371

Engineering Flame Retardant Biodegradable Nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

372

A Study of the Interaction Between a Jet Flame and a Lateral Wall  

Microsoft Academic Search

The dynamic process of the interaction between a jet flame and a lateral wall is experimentally studied. The evolution of the outer buoyant vortices, which are involved in the jet flame bulge and flame tip-cutting phenomena, is found to play the central role in the flame-wall interaction process for low speed jet flames. The flame response as the lateral wall

YEI-CHIN CHAO; CHIH-YUNG WU

2000-01-01

373

Aromatics oxidation and soot formation in flames  

SciTech Connect

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

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

1993-04-01

374

Chaotic radiation/turbulence interactions in flames  

SciTech Connect

In this paper, the authors present a review of their recent efforts to model chaotic radiation-turbulence interactions in flames. The main focus is to characterize soot volume fraction fluctuations in turbulent diffusion flames, as they strongly contribute to these interaction. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames are deterministic in nature, rather than random. The authors first discuss the theoretical details and then they briefly outline the experiments conducted to measure the scattered light signals from fluctuating soot particles along the axis of an ethylene-air diffusion flame. They compare the power spectra and time series obtained from experiments against the ad-hoc and rigorous models derived using a series of logistic maps. These logistic maps can be used in simulation of the fluctuations in these type of flames, without extensive computational effort or sacrifice of physical detail. Availability of accurate models of these kinds allows investigation of radiation-turbulence interactions at a more fundamental level than it was previously possible.

Menguec, M.P.; McDonough, J.M.

1998-11-01

375

A Weakly Turbulent Flame with High Activation Energy.  

National Technical Information Service (NTIS)

A previously outlined approach to turbulent flame theory is extended to premixed combustibles with high activation energy. Emphasis is placed primarily on turbulence whose integral scale is large compared with the thickness of the laminar flame. Only the ...

F. A. Williams

1973-01-01

376

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

377

Mixing and Ignition of Enclosed Supersonic Diffusion Flames.  

National Technical Information Service (NTIS)

An experimental study has been made of the effect of combustor geometry on the ignition and combustion of enclosed supersonic diffusion flames. A short film was made of a hydrogen supersonic diffusion flame within a quartz combustor, which indicated that ...

R. A. Cookson

1973-01-01

378

An Improved Method for Students' Flame Tests in Qualitative Analysis  

NASA Astrophysics Data System (ADS)

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

Bare, William D.; Bradley, Tom; Pulliam, Elizabeth

1998-04-01

379

An Improved Method for Students' Flame Tests in Qualitative Analysis  

Microsoft Academic Search

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

William D. Bare; Tom Bradley; Elizabeth Pulliam

1998-01-01

380

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

NASA Astrophysics Data System (ADS)

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

Schmidt, Jacob B.; Ganguly, Biswa N.

2012-02-01

381

Numerical studies of curved stationary flames in wide tubes  

NASA Astrophysics Data System (ADS)

The nonlinear problem of the propagation of curved stationary flames in tubes of different widths is studied by means of direct numerical simulation of the complete system of hydrodynamic equations including thermal conduction, viscosity, fuel diffusion and chemical kinetics. While only a planar flame can propagate in a narrow tube of width smaller than half of the cut-off wavelength determined by the linear theory of the hydrodynamic instability of a flame front, in wider tubes stationary curved flames propagate with velocities considerably larger than the corresponding velocity of a planar flame. It is shown that only simple 'single-hump' slanted stationary flames are possible in wide tubes, and 'multi-hump' flames are possible in wide tubes only as a nonstationary mode of flame propagation. The stability limits of curved stationary flames in wider tubes and the secondary Landau Darrieus instability are investigated. The dependence of the velocity of the stationary flame on the tube width is studied. The analytical theory describes the flame reasonably well when the tube width does not exceed some critical value. The dynamics of the flame in wider tubes is shown to be governed by a large-scale stability mechanism resulting in a highly slanted flame front. In wide tubes, the skirt of the slanted flame remains smooth with the length of the skirt and the flame velocity increasing progressively with the increase of the tube width above the second critical value. Results of the analytical theory and numerical simulations are discussed and compared with the experimental data for laminar flames in wide tubes.

Liberman, Michael A.; Ivanov, Mikhail F.; Peil, Oleg E.; Valiev, Damir M.; Eriksson, Lars-Erik

2003-12-01

382

Intrinsic low-dimensional manifolds of strained and unstrained flames  

Microsoft Academic Search

The intrinsic low-dimensional manifolds of strained and unstrained premixed CH4-air flames are analysed. We show that in typical flame applications only a small domain of the state space is accessed. This is found by simple one-dimensional flame computations using different strain rates. Secondly, in the different flame regions a different number of time scales is rate limiting. This means that

D. Schmidt; T. Blasenbrey; U. Maas

1998-01-01

383

Impact of curvature on the kinematic response of small flames  

Microsoft Academic Search

The objective of the study is to investigate the impact of curvature on the kinematic response of an axisymmetric curved laminar\\u000a premixed flame, utilizing a phenomenological relationship between the curvature and the laminar burning velocity. The reference\\u000a and the perturbed flame shapes are obtained by numerically or analytically integrating the flame kinematics equations. The\\u000a steady reference flame shape deviates gradually

Daehyun Wee; Ahmed F. Ghoniem

384

Residence Time Control in Flame Spread over Solid Fuels  

Microsoft Academic Search

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

Subrata Bhattacharjee; Chittory Kumar

2010-01-01

385

Conditional analysis of lifted hydrogen jet diffusion flame experimental data and comparison to laminar flame solutions  

SciTech Connect

Simultaneous point measurements of temperature, mixture fraction, major species, and OH concentrations in a lifted turbulent hydrogen jet flame are reprocessed to obtain the Favre average and conditional mean profiles. Large discrepancies between the Favre average and the ensemble average temperature, H{sub 2}O, and OH mole fractions are found at the lifted flame base, due to density weighting of fairly large samples of unreacted mixtures. Conditional statistics are used to reveal the reaction zone structure in mixture fraction coordinates. The cross-stream dependence of conditional reactive scalars, which is most notable at the lifted flame base and decreases to negligible levels with increasing streamwise positions, could be attributed to radial differences in both the Damkoehler number and the level of partial premixing. Conditional results indicate that the lifted flame is stabilized at the outer region of the jet characterized by low strain rates and lean mixtures. Comparison of the measured conditional mean OH vs H{sub 2}O with a series of stretched laminar partially premixed flame and diffusion flame calculations reveals that strong partial premixing takes place at the lifted flame base and the strain rates vary from a=14,000 to 100 s{sup -1}. The level of partial premixing and the strain rate decrease with increasing downstream locations. The range of estimated scalar dissipation rates ({chi}{approx}1-0.13 s{sup -1}) at a further downstream location (x/D=33.3) is in agreement with reported values and the flame composition reaches an equilibrium condition at x/D=194.4. These results combined with previously reported data provide a benchmark data set for evaluation and refinement of turbulent combustion models for lifted hydrogen jet flame predictions. (author)

Cheng, T.S. [Department of Mechanical Engineering, Chung Hua University, Hsinchu 300 (China); Wehrmeyer, J.A. [Aerospace Testing Alliance, Arnold Air Force Base, TN 37389 (United States); Pitz, R.W. [Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235 (United States)

2007-09-15

386

The Flame Challenge and Communicating Science  

NASA Astrophysics Data System (ADS)

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

Ames, Ben

2013-04-01

387

Liquid flame spraying for glass coloring  

NASA Astrophysics Data System (ADS)

The liquid flame spraying process has been developed to uniformly color hot glass objects. A solution consisting of a metal nitrate dissolved in alcohol or water is fed to an oxyfuel torch and atomized in the flame. The liquid evaporates from the droplet, and subsequent reactions produce metals or metallic oxides that impact the hot glass surface. Flame spraying of Co, Cu, and Ag solutions onto soda-lime silica glass at 900 to 1000 °C have produced blue, blue-green, and yellow colors. Typical spraying times are 5 to 20 s. Other colors have been produced by using a combination of transition metal ions. This method has found application in studio production and in volume manufacturing of glassware.

Gross, K. A.; Tikkanen, J.; Keskinen, J.; Pitkänen, V.; Eerola, M.; Siikamaki, R.; Rajala, M.

1999-12-01

388

Flame Tests Using Improvised Alcohol Burners  

NASA Astrophysics Data System (ADS)

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

Dragojlovic, Veljko

1999-07-01

389

Pentan isomers compound flame front structure  

SciTech Connect

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

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

1995-08-13

390

White Flame Energy switches to backhoes  

SciTech Connect

The mountaintop coal operator, White Flame Energy has switched to different truck-shovel arrangement. Along with many surface mining operations throughout central Appalachia, the company is using hoe-configured hydraulic excavators as opposed to the traditional front-shovel arrangements. Located in Varney, WV, White Flame Energy uses two Terex O & K mining shovels, an RH170 and an RH 200, which have the capacity to move 2 million cu yards per month from five seams, primarily the Coalburg, Stockton, and No 5 Block and associated rider seams. The article records conversations on the operations with Mike Vines, the general manager, and Don Nicewonder, the owner of White Flame Energy. 2 photos.

Fiscor, S.

2005-06-01

391

Measurement of Flame Spectrum and Estimation of Flame Temperature in Diesel Combustion by Means of Optical Fibers.  

National Technical Information Service (NTIS)

Some difficulties have been experienced to analyze Diesel combustion flame spectroscopically. The authors experimented with optical fibers inserted into the combustion chambers to detect the flame image. The spectroscopic characteristics of the light is d...

K. Nagase K. Funatsu

1986-01-01

392

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

393

Characteristics of hydrogen–hydrocarbon composite fuel turbulent jet flames  

Microsoft Academic Search

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

Ahsan R. Choudhuri; S. R. Gollahalli

2003-01-01

394

49 CFR 392.25 - Flame producing devices.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Flame producing devices. 392.25 Section...Commercial Motor Vehicles § 392.25 Flame producing devices. No driver shall use or permit the use of any flame-producing emergency signal...

2011-10-01

395

46 CFR 151.03-23 - Flame arrestor.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Flame arrestor. 151.03-23 Section 151...CARGOES Definitions § 151.03-23 Flame arrestor. Any device or assembly...type used for preventing the passage of flames into enclosed...

2012-10-01

396

49 CFR 392.25 - Flame producing devices.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Flame producing devices. 392.25 Section...Commercial Motor Vehicles § 392.25 Flame producing devices. No driver shall use or permit the use of any flame-producing emergency signal...

2012-10-01

397

49 CFR 392.24 - Emergency signals; flame-producing.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Emergency signals; flame-producing. 392.24 Section 392...Vehicles § 392.24 Emergency signals; flame-producing. No driver shall attach...person to attach a lighted fusee or other flame-producing emergency signal to any...

2012-10-01

398

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Smoking or open flames. 195.438 Section 195.438 Transportation...Maintenance § 195.438 Smoking or open flames. Each operator shall prohibit smoking and open flames in each pump station area and each...

2012-10-01

399

49 CFR 392.24 - Emergency signals; flame-producing.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Emergency signals; flame-producing. 392.24 Section 392...Vehicles § 392.24 Emergency signals; flame-producing. No driver shall attach...person to attach a lighted fusee or other flame-producing emergency signal to any...

2011-10-01

400

27 CFR 555.212 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2010-04-01 true Smoking and open flames. 555.212 Section 555.212 Alcohol...EXPLOSIVES Storage § 555.212 Smoking and open flames. Smoking, matches, open flames, and spark producing devices are not...

2011-04-01

401

Laminar flame speeds of hydrocarbon + air mixtures with hydrogen addition  

Microsoft Academic Search

Using the symmetrical, adiabatic, counterflow arrangement, the laminar flame speeds of methane + air and propane + air mixtures, with and without the addition of stoichiometrically small amounts of hydrogen, have been determined by first measuring the flame speeds with stretch and then linearly extrapolating these values to zero stretch. The results show that the flame speed is substantially increased

G. Yu; C. K. Law; C. K. Wu

1986-01-01

402

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2011 CFR

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

2011-10-01

403

46 CFR 151.03-23 - Flame arrestor.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Flame arrestor. 151.03-23 Section 151...CARGOES Definitions § 151.03-23 Flame arrestor. Any device or assembly...type used for preventing the passage of flames into enclosed...

2011-10-01

404

FLAME DENITRATION AND REDUCTION OF URANIUM NITRATE TO URANIUM DIOXIDE  

DOEpatents

A process is given for converting uranyl nitrate solution to uranium dioxide. The process comprises spraying fine droplets of aqueous uranyl nitrate solution into a hightemperature hydrocarbon flame, said flame being deficient in oxygen approximately 30%, retaining the feed in the flame for a sufficient length of time to reduce the nitrate to the dioxide, and recovering uranium dioxide. (AEC)

Hedley, W.H.; Roehrs, R.J.; Henderson, C.M.

1962-06-26

405

30 CFR 56.6904 - Smoking and open flames.  

Code of Federal Regulations, 2013 CFR

... 1 2013-07-01 2013-07-01 false Smoking and open flames. 56.6904 Section 56.6904...Explosives General Requirements § 56.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2013-07-01

406

30 CFR 57.7805 - Smoking and open flames.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Smoking and open flames. 57.7805 Section...Piercing-Surface Only § 57.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2013-07-01

407

30 CFR 56.7805 - Smoking and open flames.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Smoking and open flames. 56.7805 Section... Rotary Jet Piercing § 56.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2013-07-01

408

30 CFR 57.6904 - Smoking and open flames.  

Code of Federal Regulations, 2013 CFR

... 1 2013-07-01 2013-07-01 false Smoking and open flames. 57.6904 Section 57.6904...Requirements-Surface and Underground § 57.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2013-07-01

409

WASTE MANAGEMENT OF PLASTICS CONTAINING BROMINATED FLAME RETARDANTS  

Microsoft Academic Search

Bromine is used as the building block for some of the most effective flame retarding agents available to the plastics industry today. They are used to protect against the risk of accidental fires in a wide range of electrical and electronic equipment (EEE). Brominated flame retardants (BFRs), as all flame retardants, act to decrease the risk of fire by increasing

Lein Tange; Dieter Drohmann

2002-01-01

410

Flame-Retarding Plastics and Elastomers with Melamine  

Microsoft Academic Search

Melamine has shown broad utility as a flame retardant in plastics although its commercial use to date as a flame retardant additive has been principally in coatings and flexible urethane foams. Its mode of action appears to involve endothermic sublimation and vapor-phase dissociation, but it also undergoes conversion to non-volatile products and ammonia. Combinations of melamine with other flame retardants

Edward D. Weil; Veena Choudhary

1995-01-01

411

The visualization and mapping of turbulent premixed impinging flames  

Microsoft Academic Search

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

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

2001-01-01

412

Fire flame detection algorithm using a color camera  

Microsoft Academic Search

In fire detection using image processing, it is required that a system has enough robustness and elimination of an influence of a disturbance. The authors have developed a method which fire flame can be detected by calculating a space-time fluctuation data on a contour of the flame area extracted by a color information. In this paper, the fire flame detection

H. Yamagishi; J. Yamaguchi

1999-01-01

413

Real-time smoke and flame detection in video  

Microsoft Academic Search

This paper proposes a novel method to detect fire and\\/or flame by processing the video data generated by an ordi- nary camera monitoring a scene. In addition to ordinary motion and color clues, flame and fire flicker is detected by analyzing the video in wavelet domain. Periodic behav- ior in flame boundaries is detected by performing tempo- ral wavelet transform.

B. U. Toreyin; U. Gudukbay; A. E. Cetin

2005-01-01

414

Detection of Oil in Water by a Flame Emission Technique.  

National Technical Information Service (NTIS)

A flame emission technique and basic instrument design is presented for measuring low concentrations of oil in oil-contaminated water. The flame emission instrument developed in this report would be useful as a detector for petroleum oils. The flame emiss...

M. Pragar D. Stainken

1981-01-01

415

An experimental study of air-assist atomizer spray flames  

Microsoft Academic Search

It is noted that air-assisted atomizer spray flames encountered in furnaces, boilers, and gas turbine combustors possess a more complex structure than homogeneous turbulent diffusion flames, due to the swirling motion introduced into the fuel and air flows for the control of flame stability, length, combustion intensity, and efficiency. Detailed comparisons are presented between burning and nonburning condition measurements of

Chien-Pei Mao; Geng Wang; Norman Chigier

1988-01-01

416

Effect of Fluorochemicals on Flame-Retardant Fibers  

Microsoft Academic Search

To develop durable flame, water and oil repellent fabrics, a study was undertaken using fluorochemicals as water and oil repellent agents on inherently flame-retardant fibers. The treated samples were leached for 30 and 60 min to evaluate durability of the chemical treatment. The fluorochemical treatments produced durable fabrics that were simultaneously flame retardant and water and oil repellent. The effect

NISHKAM KASTURIYA; PRIYANKA KATIYAR; G. S. BHARGAVA; ANITA NISHKAM

2003-01-01

417

A numerical study of reignition induced by a diffusion flame  

Microsoft Academic Search

We present a numerical study of the reignition of a cold reactant mixture by the interaction with a nearby diffusion flame. This reignition mechanism may be an important process in turbulent non-premixed flames at high rates of strain where quenched sections of the stoichiometric surface are folded by the turbulent flow and come in close proximity with other burning flame

K.-P. Liao; C. Pantano

2009-01-01

418

A numerical and experimental investigation of ``inverse'' triple flames  

Microsoft Academic Search

Tribrachial or triple flames represent a class of partially premixed flames that generally contain three spatially distinct but synergistically coupled reaction zones, namely a rich premixed, a lean premixed, and a nonpremixed reaction zone. The generally considered flow arrangement for burner-stabilized triple flames involves a rich mixture issuing from a central port and a lean mixture from two outer ports,

Suresh K. Aggarwal; Ishwar K. Puri; Xiao Qin

2001-01-01

419

On the low-frequency limit of flame transfer functions  

Microsoft Academic Search

The response of a premixed flame to quasi-steady flow perturbations is considered. It is found that in this low-frequency limit, constraints on the flame transfer function can be established from global conservation laws for mass, energy, and momentum. For example, the transfer function between velocity fluctuations and heat release of a perfectly premixed flame without fluctuations of equivalence ratio should

Wolfgang Polifke; Chris Lawn

2007-01-01

420

Analysis of Methane-Air Edge Flame Sturcture using CSP  

Microsoft Academic Search

We study the structure of a methane-air edge flame stabilized against an incoming mixing layer. The flame is computed using detailed chemical kinetics, and the analy- sis is based on computational singular perturbation theory. We focus on examination of the low-dimensional structure of the flame, analyzing the number of exhausted modes, along with the distribution of fast and active timescales.

Habib N. Najm; Mauro Valorani; Dimitris A. Goussis

421

VELOCITY AND SCALAR MEASUREMENTS IN NEIGHBORING LIFTED EDGE FLAMES  

Microsoft Academic Search

Laminar lifted edge flames stabilized above a five-exit slot burner are examined experimentally using particle imaging velocimetry and OH planar laser-induced fluorescence. In the present study, partially premixed methane and air are used to create a single lifted tribrachial flame that replicates many previous studies. Utilizing the same burner, two neighboring lifted tribrachial flames whose flow fields interact are also

AMIT WASON; WILLIAM F. CARNELL JR; MICHAEL W. RENFRO

2006-01-01

422

The Effects of Flame Weeding on Soil Microbial Biomass  

Microsoft Academic Search

The effects of liquefied petroleum gas (LPG) flaming on soil microbial biomass and soil temperature were studied in a laboratory trial. The trial was arranged to imitate the most common weed flaming practice, non-selective flaming pre-emergence of the crop. Soil samples were taken, without disturbing the soil surface, before the germination of the crop from a field cultivated and sown

J. Rahkonen; J. Pietikäinen; H. Jokela

1999-01-01

423

Halogen free flame retardants for Epoxy substrate in electronic applications  

Microsoft Academic Search

Epoxy resins together with glass fibers had been extensively used as the core substrate in electronic applications due to its superior mechanical properties and chemical resistance. Due to its application in high heat environment, flame retardants became a required additive for the epoxy resins to prevent any flame mishaps. In this paper, intumescent and nitrogen based flame retardants, specifically the

W. K. P. Lim; M. Mariatti; W. S. Chow; K. T. Mar

2010-01-01

424

Measurement of flame temperature distribution by IR emission computed tomography  

Microsoft Academic Search

Noncontact and nondestructive measurements for determining flame temperature distribution are under investigation. This paper proposes a new method we have called infrared emission computed tomography to measure the temperature distribution in arbitrary transaxial layers of the flame by calculating the infrared radiation intensity emitted from a flame as the projection data. The authors developed an experimental system using an infrared

Hiroki Uchiyama; Masato Nakajima; Hiyoshi Kouhokuku

1985-01-01

425

Flame propagation in hybrid mixture of coal dust and methane  

Microsoft Academic Search

To investigate the flame propagation through hybrid mixture of coal dust and methane in a combustion chamber, a high-speed video camera with a microscopic lens and a Schlieren optical system were used to record the flame propagation process and to obtain the direct light emission photographs. Flame temperature was detected by a fine thermocouple. The suspended coal dust in the

Yi Liu; Jinhua Sun; Dongliang Chen

2007-01-01

426

Advanced 3D Emission Tomography Flame Temperature Sensor  

Microsoft Academic Search

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

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

2001-01-01

427

30 CFR 18.65 - Flame test of hose.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Flame test of hose. 18.65 Section 18...Inspections and Tests § 18.65 Flame test of hose. (a) Size of test specimen...by thickness of the hose. (b) Flame-test apparatus. The principal...

2010-07-01

428

30 CFR 18.65 - Flame test of hose.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Flame test of hose. 18.65 Section 18...Inspections and Tests § 18.65 Flame test of hose. (a) Size of test specimen...by thickness of the hose. (b) Flame-test apparatus. The principal...

2009-07-01

429

30 CFR 7.406 - Flame test apparatus.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Flame test apparatus. 7.406 Section...Cable Splice Kits § 7.406 Flame test apparatus. The principal parts of the apparatus used to test for flame resistance of electric...

2013-07-01

430

Watch out for those variables in flame testing!  

Microsoft Academic Search

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

C. N. Keeney

1978-01-01

431

Recyclable flame retardant nonwoven for sound absorption; RUBA®  

Microsoft Academic Search

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

Kazuhiko Kosuge; Akira Takayasu; Teruo Hori

2005-01-01

432

Thermal and flame retardant properties of novel intumescent flame retardant low-density polyethylene (LDPE) composites  

Microsoft Academic Search

A char-forming agent (CFA) and silica-gel-microencapsulated ammonium polyphosphate (MCAPP) were selected to form novel intumescent\\u000a flame retardant system (IFRs), and then the influence of this novel IFRs on the thermal and flame retardant properties of\\u000a low-density polyethylene (LDPE) were studied. The results of cone calorimetry show that the flame retardant properties of\\u000a LDPE with 30 wt% novel IFR (CFA\\/MCAPP = 1:3) improve remarkably.

Shibin Nie; Mingxu Zhang; Shujie Yuan; Guanglong Dai; Ningning Hong; Lei Song; Yuan Hu; Xueli Liu

433

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

NASA Astrophysics Data System (ADS)

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.

Steinberg, Adam M.

434

Velocity profiles in laminar diffusion flames  

NASA Astrophysics Data System (ADS)

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

Lyons, Valerie J.; Margle, Janice M.

1986-05-01

435

VUV laser photoionization studies of selected flames  

NASA Astrophysics Data System (ADS)

A new laser based diagnostic, Vacuum Ultraviolet Photoionization Mass Spectrometry (VUV-PIMS) has been developed and applied to several laboratory flames. VUV- PIMS utilizes nonlinear optical techniques to convert visible laser radiation into narrow band, broadly tunable VUV radiation (120-160 nm). This light is ideal as a soft, sensitive and selective ionization source for time of flight mass spectromehry (TOFMS). VUV-PIMS can simultaneously detect several radicals such as CH3, HCO, C2H3, and C3H3, even when these radicals are present in the flame in trace quantities (parts per million). The concentration of these and other species may be mapped out through the flame front. These species 'profiles' were successfully utilized in the construction and validation of detailed chemical kinetic models for the combustion of two species studied in detail trichloroethylene (TCE), C2Cl3H, and dimethyl methyl phosphonate (DMMP), PO(OCH3)2CH3. A total of 14 radical and stable chemical species (six of these phosphorus bearing) were detected and modeled in a H2/O2 flame doped with trace amounts of DMMP. Over 30 radical and stable species were detected, identified, and modeled in studies of a CH4/O2 flame doped with 2% TCE. VUV-PIMS, applied to flames containing DMMP, have directly verified the existence and prominence of the phosphorane species CH3PO2 and CH3OPO2. Both had eluded direct detection before this study. Measurements of the ionization potentials of each were undertaken, revealing an IP of 9.24 ± 0.01 for CH3PO2 and 8.97 ± 0.02 for CH3OPO2. Applied to chlorocarbon combustion, VUV-PIMS allowed the first measurements in a flame environment to be taken on both the dichloro vinyl radical, C2HCl2 and dichloroethenol, C2H(OH)Cl2. This study determined the ionization potential of dichloroethenol to be 9.09 ± 0.02 eV; this is the first IP measurement on this species. Dichloroethenol has only been detected in one other experimental study. This study advances the use and validity of semi- empirical methods to estimate photoionization cross sections, which allow quantification of the flame sampled VUV-PIMS data. Several species had their one-photon ionization cross sections measured in this study to test the accuracy of the semi-empirical estimation procedure. The semi-empirical method agreed with the measured cross sections to within ±20%.

Werner, James Henry

1998-05-01

436

Photometry of UCM galaxies. II. (Perez-Gonzalez+, 2001)  

NASA Astrophysics Data System (ADS)

We present Johnson B surface photometry for the UCM Survey galaxies. One-dimensional bulge-disk decomposition is attempted, discussing on fitting functions and computational procedures. The results from this decomposition, jointly with concentration indices and an asymmetry coefficient, are employed to study the morphological properties of these galaxies. We also compare our results with the previous morphological classification established using Gunn r imaging data and with other samples of galaxies. No major statistical differences in morphology are found between red and blue data, although some characteristics such as size and luminosity concentration vary. We find a correlation between luminosity and size. Several parameters are used to segregate the objects according to their morphological type. (2 data files).

Perez-Gonzalez, P. G.; Gallego, J.; Zamorano, J.; Gil de Paz, A.

2000-11-01

437

Optical and infrared photometry of TX Canum Venaticorum  

SciTech Connect

UBVRJHK photometry during 1979--1982 indicates significant variability in the TX CVn binary system, with the optical brightness diminishing and the object growing redder. In the U band the amplitude was roughly-equal0/sup m/.6, while in the near infrared the brightness declined by 0/sup m/.1, on the average. To within +- 1 subtype, in 1981 the radiation of the system comprised that of a normal K5 giant and a B9 main-sequence star. The rest of the time excess optical emission was present, probably coming from a hot spot. The K-band flux density of the K5 giant implies a distance for TX CVn of roughly-equal1.1 kpc.

Taranova, O.G.; Yudin, B.F.

1983-01-01

438

UVBY photometry of blue stragglers in NGC 7789  

NASA Astrophysics Data System (ADS)

uvby photometry of 28 blue stragglers in the open cluster NGC 7789 is presented and analyzed. A rediscussion of the fundamental cluster parameters is presented. Comparison of these results with those from the blue stragglers indicates that standard photometric calibrations do apply to the stragglers. It is found that the extended halo of blue stragglers around NGC 7789 is composed predominantly of field stars, and that the radial distribution of the stragglers is similar to that of the red giants, implying that the progenitors of both classes of stars have the same mass, i.e., single stars near the cluster turnoff. When combined with weak photometric evidence for a lower bound to the luminosity distribution of the stragglers in the C-M diagram, it is concluded that the best current model for these enigmatic stars is that of a single star which has mixed internally, as delineated in the work of Saio and Wheeler (1980). Possibilities for future research are outlined.

Twarog, B. A.; Tyson, N.

1985-07-01

439

Vilnius photometry of IC1805 stars (Straizys+, 2013)  

NASA Astrophysics Data System (ADS)

Table 1 contains the results of photometry of 242 stars down to V=18mag in the Vilnius seven-color system in the direction of a young open cluster IC 1805. Photometric data are used to classify stars in spectral and luminosity classes. The identification numbers, coordinates, V magnitudes and six color indices in the Vilnius system, photometric spectral types and membership estimates are given. VSA are numbers from Vasilevskis et al. (1965AJ.....70..806V), and MJD are numbers from Massey et al. (1995, Cat. J/ApJ/454/151). The coordinates are from the PPMXL catalog (Roeser et al., 2010AJ....139.2440R, Cat. I/317>. (1 data file).

Straizys, V.; Boyle, R. P.; Janusz, R.; Laugalys, V.; Kazlauskas, A.

2013-04-01

440

Three Years of Photometry of the Delta Cepheid T Vulpecula  

NASA Astrophysics Data System (ADS)

Three years of UBV photoelectric photometry are presented for the Delta Cepheid, T Vulpecula. The observations were made by the Phoenix-10 automatic photoelectric telescope at the Fairborn Observatory in southern Arizona. T Vul was observed on over 100 different nights during this three-year period. Determination of times of maxima is proceeding using the "master curve" technique suggested by David G. Turner (Saint Mary's University, Halifax). We are thankful for the assistance of Louis J. Boyd (Fairborn Observatory) for telescope operations, Michael A. Seeds (Franklin and Marshall College) for telescope management and initial automated data reduction, and Russell M. Genet (Orion Observatory) and James R. Mueller (California Polytechnic State University) for technical advice. We acknowledge financial support by the Orion Observatory (observation funds) and the Department of Mathematics, California Polytechnic State University (conference and travel funds).

Nguyen, H. T.; Kyaw, T. T.

2004-12-01

441

Metallicity estimates of Galactic cepheids based on Walraven photometry .  

NASA Astrophysics Data System (ADS)

We present new empirical and theoretical calibrations of two photometric metallicity indices based on Walraven photometry. The empirical calibration relies on a sample of 48 Cepheids for which iron abundances based on high resolution spectra are available in the literature. They cover a broad range in metal abundance (-0.5 le [Fe/H]le +0.5) and the intrinsic accuracy of the Metallicity Index Color (MIC) relations is better than 0.2 dex. The theoretical calibration relies on a homogeneous set of scaled-solar evolutionary tracks for intermediate-mass stars and on pulsation predictions concerning the topology of the instability strip. The metal content of the adopted evolutionary tracks ranges from Z=0.001 to Z=0.03 and the intrinsic accuracy of the MIC relations is better than 0.1 dex.

Pedicelli, S.; Lub, J.; Pel, J. W.; Lemasle, B.; Bono, G.; François, P.

442

The Fast-Photometry Facilities at La Silla  

NASA Astrophysics Data System (ADS)

We briefly present in this note the available programme (and its environment) to perform fast photometry at La Silla. This facility has become available on the mountain a lang time aga already but recent discussions with same Visiting Astronomers tend to show that potential users are not yet weil aware of it. Many programmes have already been carried out with this mode of observing, mainly in the infrared but also in the visible. Let us mention, for instance: - Occultations of stars by planets to discover and/or study rings as weil as to determinate the temperatures and variations of the atmospheres of the planets. (See for instance: Bauchet et al., The Messenger No. 26, Dec. 1981 and Haefner et al., The Messenger No. 42, Dec.1985)

Bouchet, P.; Gutierrez, F.

1986-09-01

443

Exoplanet Photometry and Spectroscopy with HII/L2  

NASA Astrophysics Data System (ADS)

With the recent discovery of extrasolar planets (exoplanets) around nearby stars by indirect methods, one of the next goals of the exoplanet study is to directly detect the giant exoplanets and to make photometry and spectroscopy. The next decade will be the time to move from discovery to characterization of exoplanet systems. This, however, requires all of high sensitivity, high spatial resolution, and high dynamic range observations at infrared wavelengths, which will be difficult to achieve from the ground. In this paper, we describe a coronagraphic camera and spectrometer for the HII/L2 mission for mid- and far-infrared astronomy and show the photometry and spectroscopy of exoplanets to be one of the most important scientific aims for this mission. The proposed HII/L2 coronagraph will cover the wavelength between 4 and 27 micron, optimized at 5 micron. The plate scale is about 0.06 arcsec, covering a field-of-view of about 1 arcmin by 1 arcmin with a 1024x1024 array detector. Occulting masks of diameter greater than 0.72 arcsec will be available, which enables the observations of exoplanets beyond ~2 AU around nearby (d~5 pc) stars. The coronagraph greatly takes advantage of the single (non-segmented) mirror of the HII/L2 telescope design. A high-efficiency Ge or CdTe grism with a resolution of a few hundreds will be installed for the coronagraphic spectroscopy of the exoplanet atmosphere. Rich spectral features at mid-infrared wavelengths enable us to study various atmospheric components and to make a comparative study of the exoplanets and our solar system planets.

Tamura, M.

2000-12-01

444

Four Decades of TiO/CN Classification Photometry  

NASA Astrophysics Data System (ADS)

Photometry on the writer's eight-color narrow-band system has entered its 40th year. This poster, in connection with the HAD Special Session on "Photometry: Past and Present," reviews the history of the system and its applications. Employing interference filters approximately 50 Å in width to measure the strongest bands of TiO, VO, and CN as well as continuum points in the 7000 -- 11000 Å spectral region, the system is used primarily to provide two-dimensional spectral classifications for M stars. A precision of 0.1 spectral subtype is routinely obtained for normal stars of type K4.0 or later. The first two sets of filters were manufactured in 1969, and the first observations were made with the Perkins 1.8-m telescope at Lowell Observatory. A decade later, after some of the original filters had deteriorated, new filter sets were made for several individuals and observatories including KPNO and CTIO. During the 1970s, observations were made with S-1 photomultipliers and the emphasis was on bright stars. Later, with the acquisition of the more sensitive Varian LSE photocells by both KPNO and CTIO, observations extended to red giant cluster members, K and M supergiants in the Magellanic Clouds, and faint suspected Galactic supergiants. Observations were briefly interrupted when the ASCAP photometer at CTIO was taken out of service in 2001, but were resumed in 2003 with the establishment of the SMARTS consortium. Large-format filters representing the first 6 filters of the 8-color system have been acquired to allow work by CCD imaging. At least 15 observers have contributed an estimated 16,000 sets of narrow-band data for approximately 5000 different stars to date.

Wing, Robert F.

2009-01-01

445

DIVA, the Next Global Astrometry and Photometry Mission  

NASA Astrophysics Data System (ADS)

The small German satellite DIVA is intended to provide highest-quality astrometric and multi-band spectrophotometric data for a complete sky survey of about 35 million stars. The satellite is planned to operate for two years, starting early 2004. Final results will be generally available in 2008. With about 300 times as many stars as Hipparcos, typically five times the astrometric precision, and the provision of multi-colour photometry in several dozen optical and near-UV bands, DIVA will be the next milestone in the series of global astrometric data sets that started with the Hipparcos Catalogue in 1997 and which will culminate in the GAIA data products around 2018. The talk will present a brief description of the project and its planned products. DIVA's scientific potential for galactic astronomy and stellar astrophysics will be outlined by examples from different fields of research. DIVA's applications will generally cover similar areas as those of Hipparcos, but at a greatly increased scale. While Hipparcos provided about 20,000 parallaxes of 10 percent relative precision (out to about 100 pc), DIVA will yield about 250,000 of them, out to about 600 pc. Proper motions will have precisions up to 0.1 milli-arcsec/year, corresponding to a tangential velocity of 1 km/s at a distance of 2 kpc. The multi-colour photometry will give a fairly clear physical characterization of a large proportion of the observed stars, largely eliminating the need of extensive ground-based parallel observation campaigns for the selection of specific stellar samples within the DIVA data.

Röser, S.; Bastian, U.

446

Recovering physical properties from narrow-band photometry  

NASA Astrophysics Data System (ADS)

Our aim in this work is to answer, using simulated narrow-band photometry data, the following general question: What can we learn about galaxies from these new generation cosmological surveys? For instance, can we estimate stellar age and metallicity distributions? Can we separate star-forming galaxies from AGN? Can we measure emission lines, nebular abundances and extinction? With what precision? To accomplish this, we selected a sample of about 300k galaxies with good S/N from the SDSS and divided them in two groups: 200k objects and a template library of 100k. We corrected the spectra to z = 0 and converted them to filter fluxes. Using a statistical approach, we calculated a Probability Distribution Function (PDF) for each property of each object and the library. Since we have the properties of all the data from the STARLIGHT-SDSS database, we could compare them with the results obtained from summaries of the PDF (mean, median, etc). Our results shows that we retrieve the weighted average of the log of the galaxy age with a good error margin (? ? 0.1 - 0.2 dex), and similarly for the physical properties such as mass-to-light ratio, mean stellar metallicity, etc. Furthermore, our main result is that we can derive emission line intensities and ratios with similar precision. This makes this method unique in comparison to the other methods on the market to analyze photometry data and shows that, from the point of view of galaxy studies, future photometric surveys will be much more useful than anticipated.

Schoenell, W.; Cid Fernandes, R.; Benítez, N.; Vale Asari, N.

2013-05-01

447

One-Dimensional Propagation of a Premixed Turbulent Flame With a Balance Equation for the Flame Surface Density  

Microsoft Academic Search

A transport equation for the flame surface density is used to describe premixed turbulent combustion in the simple case of a one-dimensional propagation in a homogeneous mixture. An analytical method of the type devised by Kolmogorov, Petrovski and Piskunov, as well as numerical simulations, are exploited to study the influence of turbulence and laminar flame speed on the turbulent flame

FLORIAN FICHOT; FRANÇOIS LACAS; DENIS VEYNANTE; SÉBASTIEN CANDEL

1993-01-01

448

The Effects of Fuel Sooting Tendency and the Flow on Flame Radiation in Luminous Turbulent Jet Flames  

Microsoft Academic Search

In this paper two observations are emphasized with regard to flame radiation in luminous turbulent jet flames: (a) the radiant fraction in turbulent buoyant jet flames is a weak function of the fuel sooting tendency as expressed by the laminar smoke-point heat release rate; and (b) moreover, for very sooty fuels, the radiant fraction saturates to a constant value which

M. A. DELICHATSIOS; L. Orloff; M. M. DELICHATSIOS

1992-01-01

449

PREDICTION OF FLAME LIFTOFF HEIGHT OF DIFFUSION\\/PARTIALLY PREMIXED JET FLAMES AND MODELING OF MILD COMBUSTION BURNERS  

Microsoft Academic Search

In this article, a new flame extinction model based on the k\\/? turbulence time scale concept is proposed to predict the flame liftoff heights over a wide range of coflow temperature and O2 mass fraction of the coflow. The flame is assumed to be quenched, when the fluid time scale is less than the chemical time scale (Da < 1). The chemical

SUDARSHAN KUMAR; P. J. PAUL; H. S. MUKUNDA

2007-01-01

450

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

Microsoft Academic Search

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

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

1986-01-01

451

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

Microsoft Academic Search

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

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

1972-01-01

452

Calculations of Burning Velocity of Turbulent Premixed Flames Using a Flame Surface Density Model  

NASA Astrophysics Data System (ADS)

The objective of the present paper is to develop and validate a newly formulated Flame Surface Density (FSD) model able to predict realistic turbulent burning velocities of premixed turbulent propagating flames over a wide range of flow conditions. Non-iterative transient numerical calculations of turbulent flame propagation in one-dimensional space are carried out over a range of turbulence Reynolds number using stoichiometric methane-air mixture. It is found that the new model closely predicts experimental data of turbulent burning velocity by Abdel-Gayed et al. (1987) as well as results from KPP (Kolmogorov, Petrovski, Piskonov) analytical method. The model formulation, and subsequent results of turbulent burning velocity and combustion regimes are presented and discussed in terms of the various physical processes that control flame/flow interactions in premixed combustion.

Patel, Samir N. D. H.; Ibrahim, Salah S.

453

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

National Technical Information Service (NTIS)

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 th...

R. L. Axelbaum D. L. Urban P. B. Sunderland B. H. Chao

2000-01-01

454

An experimental study of air-assist atomizer spray flames  

NASA Astrophysics Data System (ADS)

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

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

455

IMF, Extinction Law, and Stellar Populations in Dwarf Galaxies - Global Photometry of the LITTLE THINGS Galaxies  

NASA Astrophysics Data System (ADS)

We have assembled a multi-wavelength dataset, including deep interferometric HI maps, on a representative sample of 41 relatively nearby gas-rich dwarf irregular galaxies (LITTLE THINGS or LT). These data trace stellar populations, gas content, and dynamics for the purpose of testing and modifying star formation models. Here we present preliminary analysis of global photometry for 37 galaxies (two are not included in the LT sample). We include GALEX FUV/NUV, optical UBV, and IRAC 3.6?m photometry. Surface photometry was done for all bands with the same elliptical apertures.

Zhang, H.; Hunter, D.; Little Things Team

2011-06-01

456

The AAVSO Photoelectric Photometry Program in Its Scientific and Socio-Historic Context  

NASA Astrophysics Data System (ADS)

In this paper, I review the work of the AAVSO in the area of photoelectric photometry (PEP). This work was influenced by several trends: in science, in technology, and in the sociology of amateur astronomy. Through the 1980s, the AAVSO photoelectric photometry program competed with other such programs and, in recent years, has been overshadowed by CCD photometry programs. Nevertheless, the AAVSO PEP program has, through careful organization, motivation, and feedback, produced extensive scientific results, and can continue to do so. In the case of my own research, AAVSO PEP observations have also contributed significantly to the education of my students.

Percy, J. R.

2012-06-01

457

STRÖMGREN Photometry of the Supergiants HD 4841 (B5 Ia) and HD 194279 (B2 Ia)  

NASA Astrophysics Data System (ADS)

We investigated the variability of the B Ia supergiants HD 4841 and HD 194279 using Strömgren photometry obtained with the Four College Automated Photoelectric Telescope, Arizona and the 0.4-m telescope of TÜB?TAK National Observatory (TUG), Turkey. Both stars are definitely variable with amplitudes of order 0.10 mag in u, v, b and y. The Turkish photometry with several observations per night suggests a more rapid variability than the once per night American photometry. The periods of variability are likely to be of the order of one day.

Adelman, Saul J.; Yüce, Kutluay

458

Flame Facility: Effect of Obstacles and Transverse Venting on Flame Acceleration and Transition to Detonation for Hydrogen-Air Mixtures at Large Scale.  

National Technical Information Service (NTIS)

The report describes research on flame acceleration and deflagration-to-detonation transition (DDT) for hydrogen-air mixtures carried out in the FLAME facility, and describes its relevance to nuclear reactor safety. Flame acceleration and DDT can generate...

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

1989-01-01

459

Flame behavior and flame-induced flow in a closed rectangular duct with a 90° bend  

Microsoft Academic Search

A 3-D premixed laminar flame propagation, ignited at one end in a closed rectangular duct with a 90° bend, has been investigated by both experimental and numerical methods. A high-speed camera was used to capture the flame shapes and propagation speed in the experiments, and a computational fluid dynamics (CFD) code KIVA-3V was employed to simulate the 3-D transient laminar

Biao Zhou; Andrzej Sobiesiak; Peng Quan

2006-01-01

460

Experimental Study on Local Flame Properties of Hydrogen Added Hydrocarbon Premixed Turbulent Flames  

Microsoft Academic Search

This experimental study is performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition (u'\\/SL0=1.4), in order to clarify basically the influence of the addition of hydrogen to lean and rich methane or propane mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different rates

Masaya Nakahara; Takamori Shirasuna; Jun Hashimoto

2009-01-01

461

Autoignition and flame stabilisation processes in turbulent non-premixed hot coflow flames  

Microsoft Academic Search

Temporarily only a part of the thesis is presented. \\u000aThis dissertation examines stabilisation processes in turbulent non-premixed jet flames, created by injecting gaseous fuel into a co-flowing stream of hot, low-oxygen combustion products. Being able to predict whether and how a flame achieves stable and reliable combustion is a matter of great practical relevance, and a challenging scientific problem. Several

E. Oldenhof

2012-01-01

462

The effects of gravity on wrinkled laminar flames  

SciTech Connect

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

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

1992-09-01

463

The effects of gravity on wrinkled laminar flames  

SciTech Connect

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

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

1992-09-01

464

Freely propagating open premixed turbulent flames stabilized by swirl  

SciTech Connect

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

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

1991-12-01

465

Study of Microwave Plasma Enhanced Methane Flame at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

Non-thermal plasma assisted combustion can provide potential accommodation in improving fuel efficiency, contaminant reduction, faster ignition time, etc. A 2.45 GHz microwave (MW) plasma source was used with a premixed He/CH4 gases to study the effect of MW power coupling and hence OH radical generation. UV pulsed laser cavity ringdown spectroscopy was employed to measure absolute number density of OH (A-X) (0-0) band in plasma enhanced flame. Emission species such as OH(A-X), N2(C-B), N2^+(B-X) and C2 swan band were observed using optical emission spectroscopy. Depending on the mixing ratio of CH4 and MW power, two kinds of CH4 flames were obtained; (1) Flame with coupled MW energy but no pre-flame (flame and plasma interaction region); at high CH4/He mixing ratios and low MW energies, detached flame were obtained with detaching gap depended on MW power. (2) Flame with visible pre-flame region: at low CH4/He mixing ratios and high MW energies. In both the cases total flame volume increased with increase in MW energy. Compared to the flame, OH concentration was higher in the pre-flame.

Srivastava, Nimisha; Wang, Chuji

2011-11-01

466

On the dynamics of anchored flames  

SciTech Connect

The dynamic and the shape of anchored premised flame are analyzed as the result of the sum of wrinkles convected along the flame and of the wrinkles locally induced by the flow. The linear approximation leads to an interference integral that describes the shape as a function of time. Three applications are given: An homogeneous oscillation of the flow induces a traveling wave propagating inside a stationary envelope. Its main feature is a spatial modulation with bottlenecks (nodes in one case) regularly spaced with a wavelength equal to the convecting velocity times the period of the modulation. Experiments are presented and discussed. The modulation of the flame by a Bernard Von Karman street is calculated for small wrinkling and compared to experiments. The turbulent thickness of anchored flames is calculated for homogeneous and isotropic turbulence. The result is given as a function of the R{sub 11} space-time correlation function. The conclusion points out the new insight from a physical point of view and the limitation of such an approach.

Boyer, L.; Quinard, J. (Laboratoire de Recherche en Combustion, CNRS/ Universite de Provence, S.252, Centre St. Jerome, 13397 Marseille Cedex 13 (FR))

1990-10-01

467

Zeeman effect in flame atomic absorption spectrometry  

Microsoft Academic Search

An electromagnet is used to apply a modulated transverse magnetic field to a 6-cm length burner. A fixed linear polarizer is used to eliminate the ..pi.. component. Sixty-six elements are examined in the appropriate acetylene fuelled flame, using either nitrous oxide or air as the supporting gas. Zeeman sensitivity ratios range from 36% to 94%. The accuracy of background correction

K. G. Brodie; P. R. Liddell

1980-01-01

468

Spark Ignited Turbulent Flame Kernel Growth.  

National Technical Information Service (NTIS)

An experimental study of the effects of spark power and of incomplete fuel-air mixing on spark-ignited flame kernel growth was conducted in turbulent propane-air mixtures at 1 atm, 300K conditions. The results showed that increased spark power resulted in...

D. A. Santavicca

1995-01-01

469

Can we characterize turbulence in premixed flames?  

Microsoft Academic Search

Modeling of premixed turbulent combustion involves averaging reaction rates in turbulent flows. The focus of most approaches to resolving this problem has been placed on determining the dependence of the mean rate w of product creation on the laminar flame speed S{sub L}, the rms turbulence velocity u', etc. The goal of the present work is to draw attention to

Lipatnikov

2009-01-01

470

Stability of planar flames as gasdynamic discontinuities  

NASA Astrophysics Data System (ADS)

The stability of a steadily propagating planar premixed flame has been the subject of numerous studies since Darrieus and Landau showed that in their model flames are unstable to perturbations of any wavelength. Moreover, the instability was shown to persist even for very small wavelengths, i.e. there was no high-wavenumber cutoff of the instability. In addition to the Darrieus Landau instability, which results from thermal expansion, analysis of the diffusional thermal model indicates that premixed flames may exhibit cellular and pulsating instabilities as a consequence of preferential diffusion. However, no previous theory captured all the instabilities including a high-wavenumber cutoff for each. In Class, Matkowsky & Klimenko (2003) a unified theory is proposed which, in appropriate limits and under appropriate assumptions, recovers all the relevant previous theories. It also includes additional new terms, not present in previous theories. In the present paper we consider the stability of a uniformly propagating planar flame as a solution of the unified model. The results are then compared to those based on the models of Darrieus Landau, Sivashinsky and Matalon Matkowsky. In particular, it is shown that the unified model is the only model to capture the Darrieus Landau, cellular and pulsating instabilities including a high-wavenumber cutoff for each.

Class, Andreas G.; Matkowsky, B. J.; Klimenko, A. Y.

2003-09-01

471

Computational model of flame-cutting  

Microsoft Academic Search

A computational model for simulation of flame-cutting has been developed. Two different cutting conditions are compared with respect to the residual stresses. The first case is a plate cut at room temperature and the other is the cutting of a preheated plate. The model depends on measured micro-structure to estimate the required heat input. The model is verified by comparing

L. E. Lindgren; M. Jonsson; A. Carlestam

1993-01-01

472

Can we characterize turbulence in premixed flames?  

Microsoft Academic Search

Modeling of premixed turbulent combustion involves averaging reaction rates in turbulent flows. The focus of most approaches to resolving this problem has been placed on determining the dependence of the mean rate w˜ of product creation on the laminar flame speed SL, the rms turbulence velocity u?, etc. The goal of the present work is to draw attention to another

A. N. Lipatnikov

2009-01-01

473

Ignition and Flame Propagation in Sprays.  

National Technical Information Service (NTIS)

A theoretical model of ignition and flame propagation in a spray consisting of a number of parallel droplet streams is presented. The analysis is based on a simplified representation of the fluid-mechanic aspects of the flow while focusing on the details ...

S. C. Yao W. A. Sirignano M. Queiroz R. H. Rangel

1987-01-01

474

Flame Retardancy of Cellular Polymeric Materials  

Microsoft Academic Search

The combustion behavior of cellular polymeric materials is reviewed. The correlations between the structure and thermophysical properties of cellular polymers are discussed. The tests for potential fire hazard of cellular polymeric materials are reviewed. The approaches to flame retardancy of rigid foams based on reactive polyfunctional olygomers (phenolformaldehyde and urea formaldehyde ones, polyurethane) are demonstrated.

R. M. Aseeva; G. E. Zaikov

1996-01-01

475

Flame Retardancy Behavior of Zinc Borate  

Microsoft Academic Search

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

Youming Yang; Xichang Shi; Ruirong Zhao

1999-01-01

476

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...

477

Some Laminar-Flame Modelling Problems.  

National Technical Information Service (NTIS)

In the paper the effect of radiation-heat loss on the structure and extinction limits of laminar CO/H2/N2 counterflow diffusion flames is investigated. From the fundamental integro-differential equation governing radiation transport a simplified radiation...

Y. Liu B. Rogg

1990-01-01

478

Heterogeneous flame propagation and flammability limits  

Microsoft Academic Search

This research was performed to study characteristics of wheat dust flame propagation with a 5 x 5 x 214.1 cm 3 square tube. Dust particle size used is a diameter of 106 mu m--300 mum and as a supplementary, the dust particle size of 300 mum--325 mum was used. The dust particles were fed from the top of the tube

Insang Moon

2003-01-01

479

From Spark Ignition to Flame Initiation  

Microsoft Academic Search

The process of spark ignition and the subsequent flame propagation in an internal combustion engine have been investigated. A unique theoretical model which considers the various physical and chemical phenomena associated with the ignition process has been developed. It employs a two-dimensional cylindrical coordinate system and assumes axial and radial symmetry. The model employs also a detailed chemical reaction scheme

T. KRAVCHIK; E. SHER; J. B. HEYWOOD

1995-01-01

480

Extinction and relight in opposed flames  

Microsoft Academic Search

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

E. Korusoy; J. H. Whitelaw

2002-01-01

481

Measurements of Flame Lengths Under Ceilings,  

National Technical Information Service (NTIS)

Measurements of luminous flame extensions beneath ceilings under steady burning conditions are presented. Tests were conducted using both axisymmetric and corner-wall-ceiling configurations for a range of energy supply rates up to 400 kW and burner-to-cei...

D. Gross

1988-01-01

482

Hot Flame Cut Study. Volume III.  

National Technical Information Service (NTIS)

The hot shearing and hot flame cutting concepts of billet separation for use in projectile forging applications were investigated during this project. The hot parting concept of billet separation involves heating 20 to 24 foot lengths of billet stock to f...

D. O. Gustad

1977-01-01

483

Polybrominated diphenyl ether (PBDE) flame retardants  

Microsoft Academic Search

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

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

2001-01-01

484

Spectra and Latent Energy in Flame Gases  

Microsoft Academic Search

PROF. W. T. DAVID in the first paragraph of his letter under this title1 makes two points about the afterglow in the gases from names or explosive reactions; the first that the temperatures determined by the sodium flame reversal method are too high, compared presumably with the platinum resistance method, the second that `long-lived' luminous products account for a considerable

A. Egerton; A. R. Ubbelohde

1934-01-01

485

Method for Suppressing Rocket Motor Exhaust Flame.  

National Technical Information Service (NTIS)

The jet-actuated device includes, in combination, a rocket motor having at least one exit nozzle, a propellant grain within the motor and a flame-suppressing disk bonded to the nozzle end of the grain. The disk consists essentially of potassium sulfate, p...

R. A. Breitengross W. E. Donaldson

1965-01-01

486

Brominated flame retardants and endocrine disruption  

Microsoft Academic Search

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

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

2003-01-01

487

Flaming Gorge Unit: Colorado River Storage Project.  

National Technical Information Service (NTIS)

One of the first sights John Wesley Powell encountered on his journey down the Colorado and Green Rivers in 1869 was a beautiful canyon which he christened Flaming Gorge Canyon because of its fiery colors. Today the canyon retains its fiery colors, undimi...

T. R. Linenberger

1998-01-01

488

New Developments with Flame Resistant Cottons  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

489

Photovoltaic module spread-of-flame testing  

Microsoft Academic Search

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

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

1984-01-01

490

Simple Flame Test Techniques Using Cotton Swabs  

Microsoft Academic Search

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

Michael J. Sanger; Amy J. Phelps

2004-01-01

491