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1

Internal standard flame photometry  

Microsoft Academic Search

The author's colour wedge photometer has been used to study some aspects of flame photometry as applied to chemical analysis. It has been shown that convenient calibration curves may be obtained with this method. Studies have also been made of the effect of foreign substances and of the optimum operating conditions of the flame.

E G Walsh

1952-01-01

2

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

3

Determination of the Components of Reagent and Buffer Solutions by Flame Photometry.  

National Technical Information Service (NTIS)

An analytical process has been worked out for quantitative determination by flame photometry of sodium-potassium tartrate in a Fehling II and Nylander solution, potassium dehydrophosphate, and sodium monohydrophosphate in buffer phosphate solutions used r...

M. Sarsunova, S. Szuesova

1971-01-01

4

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

5

Use of silicon photovoltaic cells to provide a second channel in flame emission photometry.  

PubMed

Sodium and potassium may be measured simultaneously, using a modified Eppendorf flame photometer. After automatic sampling and dilution of the plasma, the potassium content is measured, using the existing Eppendorf optical and photomultiplier system. The sodium emission is measured by three silicon photovoltaic cells mounted behind an interference filter for sodium, sited on the atomiser casing. The outputs from the photomultiplier and from the silicon cells are recorded by two sensitive recorders. Sixty samples an hour may be estimated, using only 0.12 ml. plasma. Reproducibility tests showed a coefficient of variation of 0.4%. PMID:5928613

Hurst, R J; Bold, A M

1966-11-01

6

Use of silicon photovoltaic cells to provide a second channel in flame emission photometry  

PubMed Central

Sodium and potassium may be measured simultaneously, using a modified Eppendorf flame photometer. After automatic sampling and dilution of the plasma, the potassium content is measured, using the existing Eppendorf optical and photomultiplier system. The sodium emission is measured by three silicon photovoltaic cells mounted behind an interference filter for sodium, sited on the atomiser casing. The outputs from the photomultiplier and from the silicon cells are recorded by two sensitive recorders. Sixty samples an hour may be estimated, using only 0·12 ml. plasma. Reproducibility tests showed a coefficient of variation of 0·4%. Images PMID:5928613

Hurst, R. J.; Bold, A. M.

1966-01-01

7

Candle flame  

NSDL National Science Digital Library

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

Victor Rocha (None;)

2008-02-10

8

Flame Spectra.  

ERIC Educational Resources Information Center

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

Cromer, Alan

1983-01-01

9

Flame Detector  

NASA Technical Reports Server (NTRS)

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

1990-01-01

10

VLT-FLAMES survey of massive stars (Evans+, 2006)  

Microsoft Academic Search

The adopted photometry and astrometry for the targets in NGC 346 and NGC 330 is that from the initial ESO Imaging Survey (EIS) pre-FLAMES release by Momany et al. (2001A&A...379..436M). The N11 region was not covered by the EIS pre-FLAMES Survey and so we obtained 60s B and V images with the Wide Field Imager (WFI) at the 2.2-m Max

C. J. Evans; D. J. Lennon; S. J. Smartt; C. Trundle

2007-01-01

11

Third Workshop on Photometry  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

12

ARCHANGEL: Galaxy Photometry System  

NASA Astrophysics Data System (ADS)

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

Schombert, James

2011-07-01

13

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

14

Candle Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

15

Precision Photometry for Planetary Transits  

NASA Astrophysics Data System (ADS)

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

Pont, F.; Moutou, C.

2007-07-01

16

Oscillation and extinction in flames.  

E-print Network

?? Oscillation phenomena in flames were theoretically investigated for both diffusion and premixed flames. For diffusion flames, oscillations develop intrinsically as a result of thermal-diffusive… (more)

Wang, Heyang

2008-01-01

17

Detection by Transit Photometry  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

18

PHOTOM: Photometry of digitized images  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

19

FLAT FLAME BURNER ANALYSES  

E-print Network

coupled to the detailed fields in the flame, i oe . • the qfflame burner are predicted. An approximate two-dimensional velocity fieldfield around the cooling coil in the sin- tered disk of a Kaskan type flat flame

Pagni, P.J.

2012-01-01

20

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

21

Second Workshop on Improvements to Photometry  

NASA Technical Reports Server (NTRS)

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

Borucki, William J. (editor)

1988-01-01

22

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

E-print Network

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

Farritor, Shane

23

An old flame  

NASA Astrophysics Data System (ADS)

Flames are seen more often in chemistry than in physics laboratories. However, as a continuation of the previous colourful demonstration of a levitating Bunsen flame described recently in this journal (De Carvalho 2012 Phys Educ. 47 517), two short experiments are reported. Firstly, flame rectification is investigated and secondly, the electrical potential around a charged object is measured.

Thompson, Frank

2014-07-01

24

Candle Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

25

CCD photometry of 625 Xenia  

NASA Astrophysics Data System (ADS)

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

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

26

Flame Imaging System  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

27

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

28

Candle flames in microgravity  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

29

Approaches to modeling thermonuclear flames  

Microsoft Academic Search

Turbulence-flame interactions of thermonuclear fusion flames occurring in Type Ia Supernovae were studied by means of incompressible DNS with a highly simplied flame description. The flame is treated as a single diusive scalar eld with a non- linear source term. It is characterized by its Prandtl number, Pr 1, and laminar flame speed, SL. We nd that if SL u0

J. C. Niemeyer; W. K. Bushe; G. R. Ruetsch

1998-01-01

30

Cool Flame Quenching  

NASA Technical Reports Server (NTRS)

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

Pearlman, Howard; Chapek, Richard

2001-01-01

31

Two new flame detectors  

NASA Astrophysics Data System (ADS)

Two new IR flame detectors equipped with pyroelectric sensors are demonstrated. Both detectors are totally new on the world market. With the help of a new method of flame detection it is possible to distinguish flame from all interference radiation with great reliability. Applications: indoor and outdoor fire detection applications such as warehouses, hangars, ships, oil refineries etc. for fires involving all carbonaceous materials such as petrol, oil products, alcohol, wood and plastics.

Tar, D.

1985-02-01

32

Chemical flame heights  

Microsoft Academic Search

A “chemical” flame height has been defined from the ratio of CO to CO2 yields, yCO\\/yCO2, and has been shown to be functionally identical with previous results based on flame luminosity. The chemical flame heights have been determined for propane and acetylene data for fire Froude numbers, Q*, ranging from 0.1 to 60,000. The functional dependence of Zf\\/D on Q*

Jeffrey S Newman; Christopher J Wieczorek

2004-01-01

33

Diffusion Flame Stabilization  

NASA Technical Reports Server (NTRS)

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

Takahashi, Fumiaki; Katta, V. R.

2006-01-01

34

Diffusion Flame Stabilization  

NASA Technical Reports Server (NTRS)

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

Takahashi, Fumiaki; Katta, Viswanath R.

2007-01-01

35

(ELF) Enclosed Laminar Flames  

NASA Technical Reports Server (NTRS)

The goal of the ELF investigation is to improve our fundamental understanding of the effects of the flow environment on flame stability. The flame's stability refers to the position of its base and ultimately its continued existence. Combustion research focuses on understanding the important hidden processes of ignitions, flame spreading, and flame extinction. Understanding these processes will directly affect the efficiency of combustion operations in converting chemical energy to heat and will create a more balanced ecology and healthy environment by reducing pollutants emitted during combustion.

1997-01-01

36

Turbulent flame propagation in partially premixed flames  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

37

Superfast Photometry with MANIA Complex  

NASA Astrophysics Data System (ADS)

We present a hard/software MANIA complex for carrying out superfast photometry. A new type of ``time-code'' converter ``Quantochron'' allows us to measure arrival times of photons registered by a photodetector with time resolutions up to 20 nsec in 2(16) channels (space, colors, polarization, etc.) simultaneously. Special software was developed to investigate variability on a time scale of 2times 10(-8) - 10(3) sec by statistical analysis of the time interval distribution between detected photons and ``classical'' light curves. The results of some observations are presented.

Shvartsman, V. F.; Bernstein, I. N.; Beskin, G. M.; Komarova, V. N.; Neizvestny, S. I.; Plokhotnichenko, V. L.; Popova, M. Yu.; Zhuravkov, A. V.

38

Photometry of astrometric reference stars  

NASA Technical Reports Server (NTRS)

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.

1991-01-01

39

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

40

Candle Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

41

Fast photometry with small telescopes  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

42

Flame Spread Across Liquids  

NASA Technical Reports Server (NTRS)

The principal goal of our recent research on flame spread across liquid pools is the detailed identification of the mechanisms that control the rate and nature of flame spread when the liquid pool is initially at an isothermal bulk temperature that is below the fuel's flash point temperature. In our project, we specialize the subject to highlight the roles of buoyancy-related processes regarding the mechanisms of flame spread, an area of research cited recently by Linan and Williams as one that needs further attention and which microgravity (micro-g) experiments could help to resolve. Toward resolving the effects of buoyancy on this flame spread problem, comparisons - between 1-g and micro-g experimental observations, and between model predictions and experimental data at each of these gravitational levels - are extensively utilized. The present experimental and computational foundation is presented to support identification of the mechanisms that control flame spread in the pulsating flame spread regime for which long-duration, micro-g flame spread experiments have been conducted aboard a sounding rocket.

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

1997-01-01

43

The 2060 Chiron: CCD photometry  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

44

CCD surface photometry of galaxies  

NASA Technical Reports Server (NTRS)

We present here the results based on analysis of broad band optical images of radio loud and radio quiet galaxies selected from a set of x-ray galaxies. Data reduction techniques, and surface photometry using the IRAF data reduction package are described. The radial surface brightness profile of each galaxy is obtained. The disc, bulge, and nucleus of the galaxy are modeled based on the estimated brightness profile. The model of the galaxy is constructed, which is subtracted from the observed image to enhance the small scale features in the galaxy. Color maps of the galaxy are obtained and compared with those of normal galaxies. The optical properties of the galaxy are compared with its x-ray and radio properties.

Anupama, G. C.; Kembhavi, A. K.

1992-01-01

45

Flame-resistant textiles  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

46

"Magic Eraser" Flame Tests  

NASA Astrophysics Data System (ADS)

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.

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

2009-05-01

47

Laminar flames in premixed gases  

NASA Technical Reports Server (NTRS)

Numerical simulation of laminar flames in premixed gases is addressed. Various efforts to solve the laminar flame problem are briefly described, and basic equations to be modeled in a comprehensive description of laminar flames are discussed along with the physical and chemical processes represented by these equations and the numerical requirements to model them. Two flame methods are discussed in some detail: a numerical model for studying transient phenomena and its 2D counterpart method. The various input parameters needed for the models are addressed, and the use of the models is illustrated in several studies of laminar flames in premixed gases. Flammability limits and multidimensional flame propagation are also examined.

Kailasanath, K.

1991-01-01

48

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

49

Meteor44 Video Meteor Photometry  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

50

Dynamics of Swirling Flames  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

51

Strained flamelets for turbulent premixed flames II: Laboratory flame results  

SciTech Connect

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

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

2010-07-15

52

Flame resistant elastic elastomeric fibers  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

53

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

54

Rubens Flame-Tube Demonstration.  

ERIC Educational Resources Information Center

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

Ficken, George W.; Stephenson, Francis C.

1979-01-01

55

NOX FORMATION IN CO FLAMES  

EPA Science Inventory

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

56

Vortex/Flame Interactions in Microgravity Pulsed Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

57

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

58

Ring Flame Stabilizer  

NASA Technical Reports Server (NTRS)

The Ring Flame Stabilizer has been developed in conjunction with Lewis Research Center. This device can lower pollutant emissions (which contribute to smog and air pollution) from natural-gas appliances such as furnaces and water heaters by 90 percent while improving energy efficiency by 2 percent.

1996-01-01

59

Detection of Terrestrial Planets Using Transit Photometry  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

60

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

61

CLEA: Photoelectric Photometry of the Pleiades  

NSDL National Science Digital Library

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

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

2008-12-15

62

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

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Detonation arresters, flame arresters, and flame screens. 154.822 Section 154.822 Navigation...Control Systems § 154.822 Detonation arresters, flame arresters, and flame screens. (a) Each...

2013-07-01

63

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

Code of Federal Regulations, 2011 CFR

... 2011-07-01 false Detonation arresters, flame arresters, and flame screens. 154.822 Section 154.822 Navigation...Control Systems § 154.822 Detonation arresters, flame arresters, and flame screens. (a) Each...

2011-07-01

64

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

Code of Federal Regulations, 2012 CFR

... 2012-07-01 false Detonation arresters, flame arresters, and flame screens. 154.822 Section 154.822 Navigation...Control Systems § 154.822 Detonation arresters, flame arresters, and flame screens. (a) Each...

2012-07-01

65

Flame Retardant Epoxy Resins  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

66

Detecting Problematic Observer Offsets in Sparse Photometry  

NASA Astrophysics Data System (ADS)

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

Calderwood, T.

2014-06-01

67

Combustor flame flashback  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

68

Japan's research on gaseous flames  

NASA Technical Reports Server (NTRS)

Although research studies on gaseous flames in microgravity in Japan have not been one-sided, they have been limited, for the most part, to comparatively fundamental studies. At present it is only possible to achieve a microgravity field by the use of drop towers, as far as gaseous flames are concerned. Compared with experiments on droplets, including droplet arrays, which have been vigorously performed in Japan, studies on gaseous flames have just begun. Experiments on ignition of gaseous fuel, flammability limits, flame stability, effect of magnetic field on flames, and carbon formation from gaseous flames are currently being carried out in microgravity. Seven subjects related to these topics are introduced and discussed herein.

Niioka, Takashi

1995-01-01

69

The Theory of Flame Propagation  

Microsoft Academic Search

The characteristics of steady-state one-dimensional flames are expressed in terms of a set of first-order ordinary differential equations suitable for solution by differential analyzers or high speed digital computing devices. Arbitrary systems of chemical kinetics and reaction rates can be investigated. The effect of ambient temperature, pressure, heat transfer from the flame to the flame holder, diffusion of free radicals,

J. O. Hirschfelder; C. F. Curtiss

1949-01-01

70

Candle Flames in Non-Buoyant Atmospheres  

NASA Technical Reports Server (NTRS)

This paper addresses the behavior of a candle flame in a long-duration, quiescent microgravity environment both on the space Shuttle and the Mir Orbiting Station (OS). On the Shuttle, the flames became dim blue after an initial transient where there was significant yellow (presumably soot) in the flame. The flame lifetimes were typically less than 60 seconds. The safety-mandated candlebox that contained the candle flame inhibited oxygen transport to the flame and thus limited the flame lifetime. 'Me flames on the Mir OS were similar, except that the yellow luminosity persisted longer into the flame lifetime because of a higher initial oxygen concentration. The Mir flames burned for as long as 45 minutes. The difference in the flame lifetime between the Shuttle and Mir flames was primarily the redesigned candlebox that did not inhibit oxygen transport to the flame. In both environments, the flame intensity and the height-to-width ratio gradually decreased as the ambient oxygen content in the sealed chamber slowly decreased. Both sets of experiments showed spontaneous, axisymmetric flame oscillations just prior to extinction. The paper also presents a numerical model of candle flame. The model is detailed in the gas-phase, but uses a simplified liquid/wick phase. 'Me model predicts a steady flame with a shape and size quantitatively similar to the Shuttle and Mir flames. ne model also predicts pre-extinction flame oscillations if the decrease in ambient oxygen is small enough.

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

1999-01-01

71

30 CFR 14.20 - Flame resistance.  

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

2014-07-01

72

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 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...

2011-07-01

73

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

74

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

75

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2012 CFR

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

2012-07-01

76

Flame Feature Model Development and Its Application to Flame Detection  

Microsoft Academic Search

In this study, both linear discriminant technique and logistic regression method are considered and compared to develop a flame feature model. Based on the comparison, the logistic regression method is chosen and plugged into a flame detection system for segmenting the fire regions. Some spurious fire-like regions are then removed by the image difference method and the invented color masking

Tai-fang Lu; Chien-yuan Peng; Wen-bing Horng; Jian-wen Peng

2006-01-01

77

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

78

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

79

Granite flame finishing internal burner  

Microsoft Academic Search

This patent describes an internal burner for producing subsonic air-fuel flame jets for the flame finishing of granite and similar stone; a first nozzle within the body of relatively small diameter d⁠at an exit end of the combustion chamber to expand the products to supersonic velocity, a duct of sufficiently large diameter within the body downstream of the first

1992-01-01

80

Dynamics and structure of stretched flames  

SciTech Connect

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

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

1993-12-01

81

Lightcurve Photometry Opportunities: 2014 July-September  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

82

Lightcurve Photometry Opportunities: 2014 April-June  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

83

Lightcurve Photometry Opportunities: 2013 October-December  

NASA Astrophysics Data System (ADS)

We present lists of asteroid photometry opportunities for objects reaching a favorable apparition and have no or poorly-defined lightcurve parameters. Additional data on these objects will help with shape and spin axis modeling via lightcurve inversion. We also include lists of objects that will be the target of radar observations. Lightcurves for these objects can help constrain pole solutions and/or remove rotation period ambiguities that might not come from using radar data alone.

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

2014-01-01

84

Lightcurve Photometry Opportunities: 2014 October-December  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

85

IC 4651 uvby photometry (Meibom, 2000)  

Microsoft Academic Search

New accurate CCD photometry in the u, v, b and y bands of the Stroemgren system filters has been obtained for 17640 stars to approximately. V=20mag in a approximately 21' x 21' field centered on the intermediate-age open cluster IC 4651. The observations was obtained with the Danish 1.5-m telescope at the European Southern Observatory, La Silla, Chile. Table 1

S. Meibom

2000-01-01

86

Galileo photometry of Asteroid 951 Gaspra  

Microsoft Academic Search

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

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

1994-01-01

87

Hubble Deep Field surface photometry (Fasano+ 1998)  

Microsoft Academic Search

The detailed surface photometry of a sample of early-type galaxies in the Hubble Deep Field is presented as part of a long-term project aimed to settle strong observational constraints to the theories modelling the evolution of elliptical galaxies from the early stages. The sample has been extracted, in the V606 band, from the database provided by the ESO-STECF-HDF Group (Couch,

G. Fasano; M. Filippi; F. Bertola

1997-01-01

88

Surface photometry of WINGS galaxies with GASPHOT  

E-print Network

Aims. We present the B-, V- and K-band surface photometry catalogs obtained running the automatic software GASPHOT on galaxies from the WINGS cluster survey having isophotal area larger than 200 pixels. The catalogs can be downloaded at the Centre de Donnees Astronomiques de Strasbourg (CDS). Methods. We outline the GASPHOT performances and compare our surface photometry with that obtained by SExtractor, GALFIT and GIM2D. This analysis is aimed at providing statistical information about the accuracy generally achieved by the softwares for automatic surface photometry of galaxies. Results. For each galaxy and for each photometric band the GASPHOT catalogs provide the parameters of the Sersic law best-fitting the luminosity profiles. They are: the sky coordinates of the galaxy center (R:A:; DEC:), the total magnitude (m), the semi-major axis of the effective isophote (Re), the Sersic index (n), the axis ratio (b=a) and a flag parameter (QFLAG) giving a global indication of the fit quality. The WINGS-GASPHOT dat...

D'Onofrio, Mauro; Fasano, Gianni; Bettoni, Daniela; Cava, Antonio; Fritz, Jacopo; Gullieuszik, Marco; Kjaergaard, Per; Moretti, Alessia; Moles, Mariano; Omizzolo, Alessandro; Poggianti, Bianca; Valentinuzzi, Tiziano; Varela, Jesus

2014-01-01

89

Photometry with FORS at the ESO VLT  

E-print Network

ESO's two FOcal Reducer and low dispersion Spectrographs (FORS) are the primary imaging cameras for the VLT. Since they are not direct-imaging cameras, the accuracy of photometry which can routinely be obtained is limited by significant sky concentration and other effects. Photometric standard observations are routinely obtained by ESO, and nightly zero points are computed mainly for the purpose of monitoring the instrument performance. The accuracy of these zero points is about 10%. Recently, we have started a program to investigate, if and how percent-level absolute photometric accuracy with FORS can be achieved. The main results of this project are presented in this paper. We first discuss the quality of the flatfields and how it can be improved. We then use data with improved flat-fielding to investigate the usefulness of Stetson standard fields for FORS calibration and the accuracy which can be achieved. The main findings of the FORS Absolute Photometry Project program are as follows. 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. Percent level photometric accuracy can be achieved with FORS1. To achieve this accuracy, observers need to invest some of the assigned science time for imaging of photometric standard fields in addition to the routine nightly photometric calibration.

W. Freudling; M. Romaniello; F. Patat; P. Moller; E. Jehin; K. O'Brien

2006-10-24

90

Asteroid photometry achieved with small telescopes  

NASA Astrophysics Data System (ADS)

Despite very valuable information from space missions (NEAR, Hayabusa,...) extremely important data about asteroids are provided by photometric observations from ground-based telescopes. Because observations are so time-consuming, small telescopes (<2 m) at professional observatories are mostly used. The Community of amateur astronomers also perform extraordinary precise work using even smaller telescopes (>0.2 m). The results of short-term photometry are the rotational period and the amplitude of changes of brightness in a variety of solar phase angles. Medium-term photometry is able to cover eclipses/occultations of binary asteroids very well and to determine the parameters of the primary and the satellite. Long-term photometry detects amplitude variations in different apparitions, determines the direction of rotation axes and the sense of rotation and helps to create a 3D model of the asteroid's shape. By using photometric data from a wider time interval we can study the thermal YORP effect, which affects the trajectory and rotation of asteroids (mainly NEAs). It can be used also in the photometric survey of the paired asteroids.

Husárik, M.

2014-03-01

91

Flame retardant polyphosphazenes  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

92

The Cool Flames Experiment  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

93

Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing  

E-print Network

, and the kinematic response of the flame to this forcing. The near-field flame features are con- trolled by flame anchoring and the far-field by kinematic restoration. In the near-field, the flame response grows. This behavior is strongly non-linear, resulting in significant variation in far-field flame-sheet response

Lieuwen, Timothy C.

94

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

95

Candle Flames in Non-Buoyant Atmospheres  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

96

Conditions for a split diffusion flame  

Microsoft Academic Search

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

Jean R. Hertzberg

1997-01-01

97

Candle Flames in Non-Buoyant Atmospheres  

Microsoft Academic Search

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

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

2000-01-01

98

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

99

Flame Reconstruction Using Synthetic Aperture Imaging  

Microsoft Academic Search

Flames can be formed by burning methane (CH4). When oxygen is scarce, carbon particles nucleate into solid particles called soot. These particles emit photons, making the flame yellow. Later, methane is pre-mixed with air forming a blue flame; burning more efficiently, providing less soot and light. Imaging flames and knowing their temperature are vital to maximizing efficiency and validating numerical

Preston Murray; Jonathon Pendlebury; Dale Tree; Tadd Truscott

2011-01-01

100

Photometry Of The Semi-regular Variable Tx Tau  

Microsoft Academic Search

We report V-band and I-band photometry for the SRA type variable TX Tau. Photometry was obtained using the robotic telescope GORT at the Hume Observatory (NASA funded through Sonoma State University) and the PROMPT robotic telescopes at Cerro Tololo Inter-American Observatory (NSF and NASA funded through the University of North Carolina). Photometry was also obtained using the PI of the

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

2009-01-01

101

Invisible Flame Imaging  

NASA Technical Reports Server (NTRS)

Stennis Space Center uses more than one million gallons of liquid hydrogen per month in its rocket testing program. Firefighters responding to a hydrogen fire had to give the area "the broom test" to determine the presence and location of a fire. This technique has significant safety and accuracy shortfalls. Stennis then developed technology to visually assess the presence, location and extent of hydrogen fires. SafetyScan, LLC. is now manufacturing FIRESCAPE, the first affordable commercial product for invisible (or ashless) fire imaging based on the original technology, to aid firefighters in seeing the invisible flames from alcohol and hydrogen fires during the day and even through smoke. The hand-held device weighs five pounds, is used like a pair of binoculars and can run for up to two hours before recharging.

1997-01-01

102

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...

103

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...

104

Superfast Photometry with the MANIA Complex  

NASA Astrophysics Data System (ADS)

We describe the hard/software MANIA complex for carrying out superfast photometry. A new type of time-code converter Quantochron allows us to measure arrival times of photons registered by a photodetector with time resolution up to 20 ns in 216 channels (space, colours, polarization, etc.) simultaneously. Special software was developed to investigate variability on a time-scale of 2 × 10-8-103 s by statistical analysis of the time inverval distribution between detected photons and classical light curves. The results of some observations are presented.

Shvartsman, V. F.; Bernstein, I. N.; Beskin, G. M.; Komarova, V. N.; Neizvestny, S. I.; Plokhotnichenko, V. L.; Popova, M. Yu.; Zhuravkov, A. V.

105

Simultaneous Filter Photometry of V1727 Cygni  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

106

Flame propagation under partially-premixed conditions  

NASA Technical Reports Server (NTRS)

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 partially premixed combustion, we return to a simple flow field and investigate the behavior of flames in a laminar environment. We solve the compressible Navier-Stokes equations in a two-dimensional domain. At the boundaries, we use an inflow boundary condition on the left and nearly-perfect reflective boundary conditions, required to avoid pressure drift, at the outflow and sides. After the flow and flame are initialized, the mixture fraction is varied at the inlet from its uniform stoichiometric value to a tanh profile varying from zero to one. As the mixture fraction gradient reaches the flame surface only the centerline is exposed to the stoichionetric mixture fraction and locally maintains the planar flame speed and reaction rate. Above this point the mixture is fuel rich, and below fuel lean. As a result, these regions of non-unity equivalence ratio burn less, the reaction rate drops, and the local flame speed is reduced. The excess fuel and oxidizer then combine behind the premixed flame along the stoichiometric surface and burn in a trailing diffusion flame. Thus the 'triple' flame refers to the fuel-rich premixed flame, the fuel-lean premixed flame, and the trailing diffusion flame. Due to heat release, the normal velocity across the flame is increased, whereas the tangential component remains unchanged. Far-field flame speed, local flame speed, and their differences are shown as a function of the local mixing thickness. It was also determined that the lateral position of the flame affects stabilization, and the distribution of the reaction rate along the premixed wings of triple flames affects flame propagation.

Ruetsch, Gregory R.

1994-01-01

107

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

108

Chemical limits to flame inhibition  

Microsoft Academic Search

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

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

1998-01-01

109

Coupling of wrinkled laminar flames with gravity  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

110

On the theory of turbulent flame velocity  

E-print Network

The renormalization ideas of self-similar dynamics of a strongly turbulent flame front are applied to the case of a flame with realistically large thermal expansion of the burning matter. In that case a flame front is corrugated both by external turbulence and the intrinsic flame instability. The analytical formulas for the velocity of flame propagation are obtained. It is demonstrated that the flame instability is of principal importance when the integral turbulent length scale is much larger than the cut off wavelength of the instability. The developed theory is used to analyse recent experiments on turbulent flames propagating in tubes. It is demonstrated that most of the flame velocity increase measured experimentally is provided by the large scale effects like the flame instability, and not by the small-scale external turbulence.

Vitaly Bychkov; Vyacheslav Akkerman; Arkady Petchenko

2012-10-19

111

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

112

Globular Cluster Ages and Stromgren CCD Photometry  

E-print Network

Stromgren uvby CCD photometry can be used in a variety of ways to constrain the absolute and relative ages of globular clusters. The reddening corrected (v-y, c1) diagram offers the means to derive ages that are completely independent of distance. Very precise differential ages for clusters of the same chemical composition may also be determined from such 2-color plots, or from measurements of the magnitude difference, Delta_u, between the subgiant and horizontal branches on the $u-y, u$ plane (where both of these features are flat and well-defined, even for clusters like M13 that have extremely blue HBs on the (B-V, V) diagram). Based on high-quality photometry we find that: (1) M92 is 15 Gyr old, (2) M3 and M13 differ in age by < 1 Gyr, and (3) NGC 288, NGC 362, and NGC 1851 are coeval to within ~1.5 Gyr. These results strongly suggest that age cannot be the only ``second parameter''. Finally, we suggest that the observed variations in c1 among giant branch stars in all the metal-poor clusters that we have studied so far are likely due to star-to-star C and N abundance variations, and potentially indicate that most (if not all) globular clusters have ``primordial'' variations in at least these elements.

Frank Grundahl

1999-09-23

113

An invariant derivation of flame stretch  

NASA Technical Reports Server (NTRS)

The flame stretch factor is derived using an invariant formulation in a consistent manner. The derived generalized expression has two terms and completely describes the flame area evolution with its movement. One term represents the stretch due to the nonuniform tangential velocity field and the other represents the effect of the curvature of the propagating flame. The effect of curvature for stationary flames is implicitly included in the former term through variations of the tangential velocity. The flame sheet assumption, and thereby the stretch factor, are uniquely defined. Another expression is derived under the assumption that the tangential velocity of the flame equals the tangential component of the fluid velocity.

Chung, S. H.; Law, C. K.

1984-01-01

114

Ten Recent Enhancements To Aperture Photometry Tool  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

115

The Dynamics of Flame Flicker in Conical Premixed Flames: An Experimental and Numerical Study  

E-print Network

and phase-averaged velocity fields, centerline axial velocities and the flame flicker frequency (10.2 HzThe Dynamics of Flame Flicker in Conical Premixed Flames: An Experimental and Numerical Study I Fax: (510) 486-7303 Email: igshepherd@lbl.gov Colloquium: 4. LAMINAR FLAMES Total length: 5674 words

Bell, John B.

116

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

117

Transient flame propagation process and flame-speed oscillation phenomenon in a carbon dust cloud  

E-print Network

flame, because the charac- teristic time scale of the chemical reactions is longer than that of gaseousTransient flame propagation process and flame-speed oscillation phenomenon in a carbon dust cloud in revised form 28 June 2011 Accepted 24 July 2011 Available online xxxx Keywords: Flame propagation

Qiao, Li

118

Transient flame propagation process and flame-speed oscillation phenomenon in a carbon dust cloud  

E-print Network

flame, because the charac- teristic time scale of the chemical reactions is longer than that of gaseousTransient flame propagation process and flame-speed oscillation phenomenon in a carbon dust cloud in revised form 28 June 2011 Accepted 24 July 2011 Available online 19 August 2011 Keywords: Flame

Qiao, Li

119

Chemical Kinetics in Flames—a Review  

Microsoft Academic Search

The importance of chemical kinetics (heat release rates) in the laminar flame front are discussed. The need and possibilities of studying complex reactions in the flame front for large extents of conversion are considered.

L. A. LOVACHEV

1981-01-01

120

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

121

Radiant Extinction of Gaseous Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

122

Unsteady Spherical Diffusion Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

123

Radiant Extinction Of Gaseous Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

124

Displacement speeds in turbulent premixed flame simulations  

SciTech Connect

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

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

2007-07-01

125

Oscillatory Extinction Of Spherical Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

126

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

127

Production of fullerenic nanostructures in flames  

DOEpatents

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

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

1999-01-01

128

Granite flame finishing internal burner  

SciTech Connect

This patent describes an internal burner for producing subsonic air-fuel flame jets for the flame finishing of granite and similar stone; a first nozzle within the body of relatively small diameter d{sub 1} at an exit end of the combustion chamber to expand the products to supersonic velocity, a duct of sufficiently large diameter within the body downstream of the first nozzle and open thereto to convert the jet of hot gases to subsonic velocity by shock action for discharging hot gas product of combustion, and a second nozzle having a larger diameter d{sub 2} than the diameter d{sub 1} of the first nozzle within the body open to the duct and at the end of the duct opposite the first nozzle whereby a subsonic flame jet is produced to be directed against the rock surface.

Browning, J.A.

1992-06-30

129

Spherical Diffusion Flames: Structure and Dynamics  

NASA Technical Reports Server (NTRS)

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

Matalon, Moshe

1997-01-01

130

Studies of Flame Structure in Microgravity  

NASA Technical Reports Server (NTRS)

The present research endeavor is concerned with gaining fundamental understanding of the configuration, structure, and dynamics of laminar premixed and diffusion flames under conditions of negligible effects of gravity. Of particular interest is the potential to establish and hence study the properties of spherically- and cylindrically-symmetric flames and their response to external forces not related to gravity. For example, in an earlier experimental study of the burner-stabilized cylindrical premixed flames, the possibility of flame stabilization through flow divergence was established, while the resulting one-dimensional, adiabatic, stretchless flame also allowed an accurate means of determining the laminar flame speeds of combustible mixtures. We have recently extended our studies of the flame structure in microgravity along the following directions: (1) Analysis of the dynamics of spherical premixed flames; (2) Analysis of the spreading of cylindrical diffusion flames; (3) Experimental observation of an interesting dual luminous zone structure of a steady-state, microbuoyancy, spherical diffusion flame of air burning in a hydrogen/methane mixture environment, and its subsequent quantification through computational simulation with detailed chemistry and transport; (4) Experimental quantification of the unsteady growth of a spherical diffusion flame; and (5) Computational simulation of stretched, diffusionally-imbalanced premixed flames near and beyond the conventional limits of flammability, and the substantiation of the concept of extended limits of flammability. Motivation and results of these investigations are individually discussed.

Law, C. K.; Sung, C. J.; Zhu, D. L.

1997-01-01

131

Numerical simulations of flames and detonations  

Microsoft Academic Search

Time-dependent numerical simulations of multidimensional flames and detonations are discussed in this paper. The differences in the processes which must be modelled and the approaches adopted in simulating flames and detonations are highlighted. A two-dimensional flame model is described and then results of calculations are presented that show the effects of gravity on the structure and propagation of laminar, premixed

K. Kailasanath; E. Oran; J. Boris

132

Premixed and diffusion flames in a centrifuge  

SciTech Connect

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

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

1995-09-01

133

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

134

Chemical kinetics in hydrogen-air flames  

Microsoft Academic Search

This report describes a chemical reaction mechanism for hydrogen-air flames. The mechanism includes the minimum number of elementary reactions that are necessary to reproduce macroscopic flame properties. The elementary reactions, their rate coefficients, and a qualitative description of their contributions to the structure of the flame are given. It is suggested that the flammability limits are determined primarily by the

1984-01-01

135

The Flame Challenge What is Time?  

E-print Network

to our Flame Challenge sponsors, the American Chemical Society and the American AssociationThe Flame Challenge What is Time? Alan Alda, the Center for Communicating Science -- and 11- year? That is the question for this year's edition of the Flame Challenge, an international contest that asks scientists

136

Turbulent Flame Speeds of G-equations  

E-print Network

with transport equations (chemical reaction). Simplified models proposed to characterize flame propagation. (E of flame front is described by a velocity field (flow) and a laminar speed (chemical reaction): dx dt = V of flame front is described by a velocity field (flow) and a laminar speed (chemical reaction): dx dt = V

137

To appear in Combustion and Flame (2006) Propagation rates of non-premixed edge-flames  

E-print Network

a condensed-phase fuel surface, or flames in highly turbulent flow fields where "holes" in the flame sheet mayTo appear in Combustion and Flame (2006) Propagation rates of non-premixed edge-flames Min Suk Cha1-42-868-7284 E-mail: mscha@kimm.re.kr #12;i Propagation rates of non-premixed edge-flames Min Suk Cha1* and Paul

138

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

Microsoft Academic Search

Turbulent diffusion flames consist of countless vortex-flame interactions with length- and time-scales that vary over several orders of magnitude. These vortex-flame interactions are the fundamental building blocks of turbulent diffusion flames. In this experiment, a hydrogen jet diffusion flame is driven with a loud speaker located below a cylindrical fuel tube. The modulation of the fuel velocity in the tube

Sivaram Gogineni; Robert Hancock; Frederick Schauer; Robert Lucht

1997-01-01

139

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

140

Flame Speed and Spark Intensity  

NASA Technical Reports Server (NTRS)

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

Randolph, D W; Silsbee, F B

1925-01-01

141

The TAOS Project: High-Speed Crowded Field Aperture Photometry  

NASA Astrophysics Data System (ADS)

We have devised an aperture photometry pipeline for data reduction of image data from the Taiwanese-American Occultation Survey (TAOS). The photometry pipeline has high computational performance, and is capable of real-time photometric reduction of images containing up to 1000 stars, within the sampling rate of 5 Hz. The pipeline is optimized for both speed and signal-to-noise performance, and in the latter category it performs nearly as well as DAOPHOT. This paper provides a detailed description of the TAOS aperture photometry pipeline.

Zhang, Z.-W.; Kim, D.-W.; Wang, J.-H.; Lehner, M. J.; Chen, W. P.; Byun, Y.-I.; Alcock, C.; Axelrod, T.; Bianco, F. B.; Coehlo, N. K.; Cook, K. H.; Dave, R.; de Pater, I.; Giammarco, J.; King, S.-K.; Lee, T.; Lin, H.-C.; Marshall, S. L.; Porrata, R.; Protopapas, P.; Rice, J. A.; Schwamb, M. E.; Wang, S.-Y.; Wen, C.-Y.

2009-12-01

142

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

143

Azimuthal structure of an annular diffusion flame  

SciTech Connect

An annular diffusion flame was studied using planar laser induced fluorescence. The insitu concentration of one of the combustion products, hydroxyl radical, was used as an indicator of the combustion structure. The flame structure was studied both in axial and radial cross-sections. Phased average data, as well as instantaneous measurements of 18 nsec duration, revealed details on the highly three-dimensional features of the axisymmetric flame. The characteristics of these structures at different regions of the flame and their response to forcing were studied. The three-dimensional structures have a significant effect on the fine-scale mixing rate and flame stability limits.

Gutmark, E.; Parr, T.P.; Hanson-Parr, D.M.; Schadow, K.C.

1989-03-01

144

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

145

Studies on upward flame spread  

E-print Network

Ratio of the average flame height over pyrolysis height as a function of heat-release rate per unitRelease Rate per unit Width (kW/m) Figure 3.10: Ratio of theratio, then a mass balance indicates that the burning rate per unit

Gollner, Michael J.

2012-01-01

146

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

147

Flame Challenge Science Communication Contest  

NASA Astrophysics Data System (ADS)

What is color? That is the question for this year's Flame Challenge, an international contest started by actor Alan Alda that asks scientists to communicate complex science in a way that would educate and spark the interest of an 11-year-old.

Showstack, Randy

2014-02-01

148

Burning Laminar Jet Diffusion Flame  

NASA Technical Reports Server (NTRS)

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

2003-01-01

149

Arnold Flames Resonance Surface Folds*  

E-print Network

Arnold Flames and Resonance Surface Folds* Richard P. McGehee School of Mathematics University parameter plane bifurcation diagrams are "(Arnold) resonance horns" emanating from zero forcing ampli- tude families by Arnold [1983] and Hall [1984] indi- cate the presence of (Arnold) resonance horns emanating

Peckham, Bruce B.

150

Detection of Extrasolar Planets by Transit Photometry  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

151

Hubble Deep Field surface photometry (Fasano+ 1998)  

NASA Astrophysics Data System (ADS)

The detailed surface photometry of a sample of early-type galaxies in the Hubble Deep Field is presented as part of a long-term project aimed to settle strong observational constraints to the theories modelling the evolution of elliptical galaxies from the early stages. The sample has been extracted, in the V606 band, from the database provided by the ESO-STECF-HDF Group (Couch, 1996, ). The selection criteria involve the total magnitude, the number of pixels detected above the background level and an automatic star/galaxy classifier. Moreover, form visual inspection of the frames, we excluded the galaxies showing unambiguous late-type morphology. The analysis of the luminosity and geometrical profiles, carried out on the 162 candidates obeying our selection criteria, resulted in a list of 99 'bona fide' early-type galaxies, for which accurate total magnitudes and effective radii were computed on the basis of the equivalent luminosity profiles. The comparison with the magnitudes given by Williams et al. (1996, Cat. ) indicates that the automated photometry tends to underestimate the total luminosity of the ellipticals. The luminosity profiles of most of galaxies in our sample follow fairly well the de~Vaucouleurs law ('Normal' profiles). However, a relevant fraction of galaxies, even following the r1/4 law in the main body light distribution, exhibit in the inner region a flattening of the luminosity profile not attributable to the PSF (`Flat' profiles) or, in some cases, a complex (multi-nucleus) structure (`Merger' profiles). A statistically significant correlation is found between the shapes of the luminosity profiles and the ellipticity distribution. In particular, the average ellipticity of galaxies belonging to the `Flat' and `Merger' classes is significantly higher than that of the `Normal' galaxies. Finally, even taken into account the relevant uncertainty of the outer position angle profiles, the amount of isophotal twisting of HDF ellipticals turns out to be significantly larger with respect to that of the local samples. (2 data files).

Fasano, G.; Filippi, M.; Bertola, F.

1997-11-01

152

Flame Reconstruction Using Synthetic Aperture Imaging  

E-print Network

Flames can be formed by burning methane (CH4). When oxygen is scarce, carbon particles nucleate into solid particles called soot. These particles emit photons, making the flame yellow. Later, methane is pre-mixed with air forming a blue flame; burning more efficiently, providing less soot and light. Imaging flames and knowing their temperature are vital to maximizing efficiency and validating numerical models. Most temperature probes disrupt the flame and create differences leading to an inaccurate measurement of the flame temperature. We seek to image the flame in three dimensions using synthetic aperture imaging. This technique has already successfully measured velocity fields of a vortex ring [1]. Synthetic aperture imaging is a technique that views one scene from multiple cameras set at different angles, allowing some cameras to view objects that are obscured by others. As the resulting images are overlapped different depths of the scene come into and out of focus, known as focal planes, similar to tomogr...

Murray, Preston; Tree, Dale; Truscott, Tadd

2011-01-01

153

Soot Formation in Laminar Premixed Flames  

NASA Technical Reports Server (NTRS)

Soot processes within hydrocarbon-fueled flames affect emissions of pollutant soot, thermal loads on combustors, hazards of unwanted fires and capabilities for computational combustion. In view of these observations, the present study is considering processes of soot formation in both burner-stabilized and freely-propagating laminar premixed flames. These flames are being studied in order to simplify the interpretation of measurements and to enhance computational tractability compared to the diffusion flame environments of greatest interest for soot processes. In addition, earlier studies of soot formation in laminar premixed flames used approximations of soot optical and structure properties that have not been effective during recent evaluations, as well as questionable estimates of flow residence times). The objective of present work was to exploit methods of avoiding these difficulties developed for laminar diffusion flames to study soot growth in laminar premixed flames. The following description of these studies is brief.

Xu, F.; Krishnan, S. S.; Faeth, G. M.

1999-01-01

154

A catalogue of IJK photometry of Planetary Nebulae with DENIS  

E-print Network

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

S. Schmeja; S. Kimeswenger

2001-05-15

155

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry,  

E-print Network

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry, and minimally distinct border: implications for the neural mechanisms underlying induction Karen L. Gunther manuscript received April 21, 2005; accepted April 24, 2005 Brightness induction refers to the finding

Dobkins, Karen R.

156

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

SciTech Connect

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

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

2009-09-15

157

BINARY STAR SYNTHETIC PHOTOMETRY AND DISTANCE DETERMINATION USING BINSYN  

SciTech Connect

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

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

2013-09-15

158

The discrete regime of flame propagation  

NASA Astrophysics Data System (ADS)

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

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

159

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

160

NEW UBVRI PHOTOMETRY OF 234 M33 STAR CLUSTERS  

SciTech Connect

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

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

2013-04-15

161

Noise characteristics of LCOGT time series photometry  

NASA Astrophysics Data System (ADS)

The Las Cumbres Observatory Global Telescope (LCOGT) facility consists of a network of robotic telescopes located at multiple sites in both the northern and southern hemispheres. We have deployed and commissioned nine 1.0m telescopes. Eight of these are distributed longitudinally at three sites to provide continuous night-time coverage in the south. LCOGT's unique capabilities can contribute to a wide range of research in the field of time-domain astronomy. To ensure optimal data quality for individual as well as combined multi-telescope time series, it is essential that we understand and correct - whenever possible - the instrument systematics affecting LCOGT network observations. We identify physical sources of noise present in LCOGT 1.0m photometry, and we use singular value decomposition (SVD) to filter correlated noise patterns common to an ensemble of stars in a given time series data set. We quantify and compare the levels of uncorrelated and correlated noise before and after SVD filtering using power spectral analysis. Finally, we discuss the properties of and methods to reduce any remaining post-SVD red noise that is due to instrumental systematics.

Dragomir, Diana; Brown, T. M.

2014-01-01

162

Microlensing for extrasolar planets : improving the photometry  

NASA Astrophysics Data System (ADS)

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

Bajek, David J.

163

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

164

Recent Advances in Video Meteor Photometry  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

165

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

SciTech Connect

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

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

2005-08-01

166

Theory of interactive combustion of counterflow premixed flames  

NASA Technical Reports Server (NTRS)

The framework of large activation energy asymptotics is used in an investigation of the extinction characteristics of two interacting premixed flames in counterflow configuration, analyzing the interactive combustion modes of two lean premixed flames, two rich premixed flames, and one of each type of flame separated by a diffusion flame. Regions corresponding to symbiotic combustion of two lean or two rich premixed flames exist in which either flame will be extinguished in the absence of the other. Conditions for the existence of superadiabatic flames within mixtures outside of the conventional flammability limit compositions are established, and practical implications of flame interaction for combustion in inhomogeneous mixtures are discussed.

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

1986-01-01

167

Fully Modulated Turbulent Diffusion Flames in Microgravity*  

NASA Astrophysics Data System (ADS)

Fully modulated, turbulent diffusion flames are studied in microgravity in 2.2 s drop-tower tests with a co-flow combustor. The fuel consists of pure ethylene or a 50/50 mixture with nitrogen; the oxidizer is either normal air or up to 40% oxygen in nitrogen. A fast solenoid valve is used to fully modulate (completely shut off) the fuel flow. The injection times range from 5 to 400 ms with a duty-cycle of 0.1 - 0.5. The fuel nozzle is 2 mm in diameter with a jet Reynolds number of 5000. The shortest injection times yield compact puffs with a mean flame length as little as 20% of that of the steady-state flame. The reduction in flame length appears to be somewhat greater in microgravity than in normal gravity. As the injection time increases, elongated flames result with a mean flame length comparable to that of a steady flame. The injection time for which the steady-state flame length is approached is shorter for lower air/fuel ratios. For a given duty-cycle, the separation between puffs is greater in microgravity than in normal gravity. For compact puffs, increasing the duty-cycle appears to increase the flame length more in microgravity than in normal gravity. The microgravity flame puffs do not exhibit the vortex-ring-like structure seen in normal gravity.

Sangras, Ravikiran; Hermanson, James C.; Johari, Hamid; Stocker, Dennis P.; Hegde, Uday G.

2001-11-01

168

Structure of laminar sooting inverse diffusion flames  

SciTech Connect

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

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

2007-06-15

169

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

170

Flame\\/Flow Interaction in Oscillating Flow Field  

Microsoft Academic Search

A numerical study on the premixed wrinkled flame front has been conducted in order to examine the motion of the wrinkled flame front and flame\\/flow interaction in an oscillating flow field. The conventional G-equation is solved to determine the time dependent behavior of the flame front by using a model in which the flame front is regarded as a source

B. I. CHOI; H. D. SHIN

2000-01-01

171

Dynamics of turbulent premixed flames in acoustic fields  

Microsoft Academic Search

This thesis describes computational and theoretical studies of fundamental physical processes that influence the heat-release response of turbulent premixed flames to acoustic forcing. Attached turbulent flames, as found in many practical devices, have a non-zero mean velocity component tangential to the turbulent flame brush. Hence, flame surface wrinkles generated at a given location travel along the flame sheet while being

Santosh Hemchandra

2009-01-01

172

FLAME DETECTION IN VIDEO USING HIDDEN MARKOV MODELS  

Microsoft Academic Search

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; Yigithan Dedeoglu; A. Enis

173

Radiative extinction of gaseous spherical diffusion flames in microgravity  

Microsoft Academic Search

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

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

2007-01-01

174

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

175

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

2011-01-01

176

Distant Comets Photometry and Dust Modeling  

NASA Astrophysics Data System (ADS)

Several comets have been observed to develop coma on their in-bound leg at heliocentric distances from 5.84 to 11.49 AU. We will present the observational evidence for their activity and propose an explanation based on experiments carried out on amorphous, gas-laden ice samples that are 0.1 to 100 microns thick and formed by flowing water vapor and CO onto a cold surface. The considerable gas emission occurs when the amorphous ice anneals before 135K, where it transforms into a crystalline structure. This activity was found experimentally to be associated with gas release during annealing of the gas-laden amorphous ice. We observed and measured optical CCD photometry for two short-period and five long-period, dynamically new comets, that have enter the inner solar system directly from the Oort cloud for the first time. All of these comets have been observed pre-perihelion. Observations were done with the University of Hawaii 2.2-m telescope on Mauna Kea with the Tektronix 2x2K CCD camera through the Kron-Cousins B, V, R, I filter system. In order to observationally distinguish the physical causes of activity, not only is it important to observe comets at large heliocentric distances, but also those that are dynamically new and on the in-bound leg of their orbits at distances beyond where the amorphous to crystalline ice phase transition can occur. This research includes observations of the level of nucleus activity as a function of distance. We also would like to present Finson-Probstein (FP) dust modeling investigation on select comets. From the FP dust modeling of a cometary tail we can determine three basic parameters: the dust production rate, the particle distribution, and the emission velocity of the grains.

Pittichova, Jana; Meech, K. J.; Bar-Nun, A.; Notesco, G.

2008-09-01

177

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

178

Effects of confinement on partially premixed flames  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

179

Violent folding of a flame front in a flame-acoustic resonance.  

PubMed

The first direct numerical simulations of violent flame folding because of the flame-acoustic resonance are performed. Flame propagates in a tube from an open end to a closed one. Acoustic amplitude becomes extremely large when the acoustic mode between the flame and the closed tube end comes in resonance with intrinsic flame oscillations. The acoustic oscillations produce an effective acceleration field at the flame front leading to a strong Rayleigh-Taylor instability during every second half period of the oscillations. The Rayleigh-Taylor instability makes the flame front strongly corrugated with elongated jets of heavy fuel mixture penetrating the burnt gas and even with pockets of unburned matter separated from the flame front. PMID:17155402

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

2006-10-20

180

Laminar Jet Diffusion Flame Burning  

NASA Technical Reports Server (NTRS)

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

2003-01-01

181

Heat and mass transfer in flames  

NASA Technical Reports Server (NTRS)

Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

Faeth, G. M.

1986-01-01

182

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

1999-02-01

183

Microgravity Turbulent Gas-Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

A gas-jet diffusion flame is similar to the flame on a Bunsen burner, where a gaseous fuel (e.g., propane) flows from a nozzle into an oxygen-containing atmosphere (e.g., air). The difference is that a Bunsen burner allows for (partial) premixing of the fuel and the air, whereas a diffusion flame is not premixed and gets its oxygen (principally) by diffusion from the atmosphere around the flame. Simple gas-jet diffusion flames are often used for combustion studies because they embody the mechanisms operating in accidental fires and in practical combustion systems. However, most practical combustion is turbulent (i.e., with random flow vortices), which enhances the fuel/air mixing. These turbulent flames are not well understood because their random and transient nature complicates analysis. Normal gravity studies of turbulence in gas-jet diffusion flames can be impeded by buoyancy-induced instabilities. These gravitycaused instabilities, which are evident in the flickering of a candle flame in normal gravity, interfere with the study of turbulent gas-jet diffusion flames. By conducting experiments in microgravity, where buoyant instabilities are avoided, we at the NASA Lewis Research Center hope to improve our understanding of turbulent combustion. Ultimately, this could lead to improvements in combustor design, yielding higher efficiency and lower pollutant emissions. Gas-jet diffusion flames are often researched as model flames, because they embody mechanisms operating in both accidental fires and practical combustion systems (see the first figure). In normal gravity laboratory research, buoyant air flows, which are often negligible in practical situations, dominate the heat and mass transfer processes. Microgravity research studies, however, are not constrained by buoyant air flows, and new, unique information on the behavior of gas-jet diffusion flames has been obtained.

1996-01-01

184

Kinetics of Chemical Reactions in Flames  

NASA Technical Reports Server (NTRS)

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

Zeldovich, Y.; Semenov, N.

1946-01-01

185

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

186

The Interaction of High-Speed Turbulence with Flames: Turbulent Flame Speed  

Microsoft Academic Search

The interaction of flames with background turbulence occurs in systems ranging from chemical flames on Earth to thermonuclear burning fronts in supernovae. We present an analysis of a set of numerical simulations aimed at studying the dynamics and properties of turbulent flames formed under the action of high-speed turbulence in stoichiometric hydrogen-air mixture. The simulations were performed using the massively

Alexei Poludnenko; Elaine Oran

2010-01-01

187

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

188

Spectroscopic Studies of Low-Pressure Flames; Temperature Measurements in Acetylene Flames  

Microsoft Academic Search

Flames at very low pressure have a relatively thick reaction zone (or flame front) and are especially suitable for detailed study of the combustion processes and of the distribution of energy during the reaction. Temperature measurements have been made, by various spectroscopic methods, on flames of acetylene with air, oxygen and nitrous oxide, in some cases down to a pressure

A. G. Gaydon; H. G. Wolfhard

1948-01-01

189

Planar imaging of vortex dynamics in flames  

SciTech Connect

The interaction between the fluid dynamics and the combustion process in an annular diffusion flame was studied experimentally using the Planar Laser Induced Fluorescence (PLIF) technique. The local temperature and OH radical fluorescence signals were mapped in the entire flame cross section. The flame was forced at different instability frequencies, thus enabling the study of the evolution and interaction of large-scale structures in the flame shear layer. The present study of the effect of fluid dynamics on combustion is part of a more comprehensive program aimed at understanding and controlling the effect of heat release, density variations, and reaction parameters on the shear layer evolution.

Gutmark, E.; Parr, T.P.; Parr, D.M.; Schadow, K.C.

1989-02-01

190

Mechanisms and enhancement of flame stabilization  

SciTech Connect

During the reporting period, useful contributions have been made in understanding the structure of laminar premixed and diffusion flames, with emphasis on the influence of aerodynamics and chemical kinetics. These contributions include (1) derivation of the missing closure condition for the activation energy asymptotic analysis of premixed flames, (2) identification of a dual extinction mode for radiation-affected flames, (3) formulation of a unified theory of fundamental flammability limits, and (4) demonstration that flame stabilization can be achieved in the absence of heat loss. These investigations have been conducted via experimental, analytical and computational approaches, with strong coupling between the individual components.

Law, C.K.

1993-01-01

191

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Smoking or open flames. 195.438 Section 195...Operation and Maintenance § 195.438 Smoking or open flames. Each operator shall prohibit smoking and open flames in each pump station...

2012-10-01

192

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2011 CFR

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

2011-10-01

193

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Smoking or open flames. 195.438 Section 195...Operation and Maintenance § 195.438 Smoking or open flames. Each operator shall prohibit smoking and open flames in each pump station...

2013-10-01

194

49 CFR 195.438 - Smoking or open flames.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

195

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

196

30 CFR 75.600 - Trailing cables; flame resistance.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Trailing cables; flame resistance. 75.600 Section 75...Cables § 75.600 Trailing cables; flame resistance. [Statutory Provisions...requirements established by the Secretary for flame-resistant...

2012-07-01

197

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

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Approved cables; flame resistance. 75.600-1 Section 75...Cables § 75.600-1 Approved cables; flame resistance. Cables shall be accepted or approved by MSHA as flame resistant. [57 FR 61223, Dec....

2012-07-01

198

30 CFR 75.600 - Trailing cables; flame resistance.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Trailing cables; flame resistance. 75.600 Section 75...Cables § 75.600 Trailing cables; flame resistance. [Statutory Provisions...requirements established by the Secretary for flame-resistant...

2011-07-01

199

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Approved cables; flame resistance. 75.600-1 Section 75...Cables § 75.600-1 Approved cables; flame resistance. Cables shall be accepted or approved by MSHA as flame resistant. [57 FR 61223, Dec....

2013-07-01

200

46 CFR 151.03-23 - Flame arrestor.  

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

2014-10-01

201

46 CFR 151.03-23 - Flame arrestor.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

202

30 CFR 75.600 - Trailing cables; flame resistance.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Trailing cables; flame resistance. 75.600 Section 75...Cables § 75.600 Trailing cables; flame resistance. [Statutory Provisions...requirements established by the Secretary for flame-resistant...

2013-07-01

203

30 CFR 75.600 - Trailing cables; flame resistance.  

...2014-07-01 false Trailing cables; flame resistance. 75.600 Section 75...Cables § 75.600 Trailing cables; flame resistance. [Statutory Provisions...requirements established by the Secretary for flame-resistant...

2014-07-01

204

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

205

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

206

30 CFR 75.600 - Trailing cables; flame resistance.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

207

46 CFR 151.03-23 - Flame arrestor.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

208

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

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Approved cables; flame resistance. 75.600-1 Section 75...Cables § 75.600-1 Approved cables; flame resistance. Cables shall be accepted or approved by MSHA as flame resistant. [57 FR 61223, Dec....

2011-07-01

209

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

...2014-07-01 false Approved cables; flame resistance. 75.600-1 Section 75...Cables § 75.600-1 Approved cables; flame resistance. Cables shall be accepted or approved by MSHA as flame resistant. [57 FR 61223, Dec....

2014-07-01

210

Flame spread Analysis using a Variable B-Number  

E-print Network

than the chemical reaction time and thus the flame sheetand flame spread is controlled by mixing and gas-phase chemical-chemical reaction time) is used to study the two limits that are observed in flame

Rangwala, Ali S.

2006-01-01

211

First time-series optical photometry from Antarctica  

E-print Network

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

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

2008-07-18

212

CCD photometry of bright stars using objective wire mesh  

E-print Network

Obtaining accurate photometry of bright stars from the ground remains tricky because of the danger of overexposure of the target and/or lack of suitable nearby comparison star. The century-old method of the objective wire mesh used to produce multiple stellar images seems attractive for precision CCD photometry of such stars. Our tests on beta Cep and its comparison star differing by 5 magnitudes prove very encouraging. Using a CCD camera and a 20 cm telescope with objective covered with a plastic wire mesh, located in poor weather conditions we obtained differential photometry of precision 4.5 mmag per 2 min exposure. Our technique is flexible and may be tuned to cover as big magnitude range as 6 - 8 magnitudes. We discuss the possibility of installing a wire mesh directly in the filter wheel.

Kami?ski, Krzysztof; Zgórz, Marika

2014-01-01

213

Unsteady planar diffusion flames: Ignition, travel, burnout  

NASA Technical Reports Server (NTRS)

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

Fendell, F.; Wu, F.

1995-01-01

214

Flame temperature and location measurements of sooting premixed Bunsen flames by rainbow schlieren deflectometry.  

PubMed

Rainbow schlieren deflectometry (RSD) provides a simple and nonintrusive way of determining the temperature field of axisymmetric flames. This technique is specially suited for the detection of large temperature gradients, such as those near the flame location. We explore the feasibility and accuracy of using RSD to obtain the flame location and thermal structure of premixed Bunsen flames for varying fuel types, equivalence ratios, and soot loadings. Uncertainty analysis is also carried out to provide various ways to reduce RSD experimental error. The RSD technique is demonstrated to give useful data even for moderately and heavily sooting flames. PMID:16007857

Ibarreta, Alfonso F; Sung, Chih-Jen

2005-06-10

215

UBV(RI)c photometry of Stock 16 (Vazquez+, 2005)  

NASA Astrophysics Data System (ADS)

CCD UBV(RI)c imaging photometry was carried out in the field of Stock 16 along two observational runs at the University of Toronto Southern Observatory, Las Campanas, Chile, using the Hellen Sawyer Hogg 60-cm telescope: on the nights of 1994 April 13, 14 and 16, we obtained UBVRI photometry for four frames with the nitrogen-cooled detector PM METHACROME UV coated (0.45"/pix) covering 4' on a side; three more frames were exposed on the nights of 1996 February 25 and 26 in the UBV(I)c bands (this time, the detector was glycol-refrigerated). (1 data file).

Vazquez, R. A.; Baume, G. L.; Feinstein, C.; Nunez, J. A.; Vergne, M. M.

2005-02-01

216

Characterization of transiting exoplanets by way of differential photometry  

NASA Astrophysics Data System (ADS)

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

Cowley, Michael; Hughes, Stephen

2014-05-01

217

Flame surface statistics of constant-pressure turbulent expanding premixed flames  

NASA Astrophysics Data System (ADS)

In this paper we investigate the local flame surface statistics of constant-pressure turbulent expanding flames. First the statistics of local length ratio is experimentally determined from high-speed planar Mie scattering images of spherically expanding flames, with the length ratio on the measurement plane, at predefined equiangular sectors, defined as the ratio of the actual flame length to the length of a circular-arc of radius equal to the average radius of the flame. Assuming isotropic distribution of such flame segments we then convolute suitable forms of the length-ratio probability distribution functions (pdfs) to arrive at the corresponding area-ratio pdfs. It is found that both the length ratio and area ratio pdfs are near log-normally distributed and shows self-similar behavior with increasing radius. Near log-normality and rather intermittent behavior of the flame-length ratio suggests similarity with dissipation rate quantities which stimulates multifractal analysis.

Saha, Abhishek; Chaudhuri, Swetaprovo; Law, Chung K.

2014-04-01

218

Monitoring Atmospheric Transmission with FLAME  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

219

Temperature Measurements of Flames containing Incandescent Particles  

Microsoft Academic Search

Colour temperatures measured on photoflash powders are higher than expected from theoretical calculations Determinations of the true temperature of stationary flames of aluminium flakes suspended in air have been made (a) by a line reversal method and (b) by measuring the absolute light intensity. The experimental values obtained were very close to the theoretical flame temperature of about 3,000° C.,

H G Wolfhard; W G Parker

1949-01-01

220

Active control for turbulent premixed flame simulations  

SciTech Connect

Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.

Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.

2004-03-26

221

Flame Heat Fluxes in Pmma Pool Fires  

Microsoft Academic Search

A simple one-dimensional analytical model has been developed to describe the processes involved in the transient burning of non-charring thermoplastic materials. The model includes conduction, convection, and radiation effects for flaming materials. The burning rate solution is obtained by numerically solving an ordinary differential equation and an algebraic equation with flame radiative heat flux as a specified variable. The effect

Naeem Iqbal; James Quintiere

1994-01-01

222

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

223

Flame propagation in partially premixed conditions  

Microsoft Academic Search

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

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

1996-01-01

224

Transient Supersonic Methane-Air Flames  

E-print Network

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

Richards, John L.

2012-07-16

225

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

226

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...

227

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

228

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

229

Propagation of a Free Flame in a Turbulent Gas Stream  

NASA Technical Reports Server (NTRS)

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

Mickelsen, William R; Ernstein, Norman E

1956-01-01

230

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

231

The Rate of Expansion of Spherical Flames  

E-print Network

In this paper we investigate the acceleration of the expansion of premixed spherical flames and evolution of the cellular patterns on their surfaces. An asymptotic model is used for the simulations and a spectral numerical algorithm is employed to study flames over large time intervals. Numerous numerical experiments indicate that for large enough time intervals the acceleration of two-dimensional expanding flame ceases and the expansion rate stabilizes to a value significantly exceeding the burning rate. The importance of the effect of forcing was also confirmed and the validity of sectorial simulations of closed flames was studied in order to justify prospective use of the Fourier spectral model for the three-dimensional spherical flames.

V. Karlin; G. Sivashinsky

2005-05-14

232

Particle Cloud Flames in Acoustic Fields  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

233

Interaction Between Flames and Electric Fields Studied  

NASA Technical Reports Server (NTRS)

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

Yuan, Zeng-Guang; Hegde, Uday

2003-01-01

234

Flame-vortex interactions imaged in microgravity  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

235

Edge Diffusion Flame Propagation and Stabilization Studied  

NASA Technical Reports Server (NTRS)

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

Takahashi, Fumiaki; Katta, Viswanath R.

2004-01-01

236

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

237

The flaming gypsy skirt injury.  

PubMed

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

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

2007-01-01

238

NIR photometry of MASTER OTJ013135.43+555831.5  

NASA Astrophysics Data System (ADS)

Following the report on MASTER OTJ013135.43+555831.5 by Denisenko et al.,2014 (Atel #6432). We carried out NIR photometry recently, On October 4th,2014 (JD2456934.8775), we found the object with fluxes corresponding to J = 14.879 +/- 0.05, H = 13.431 +/- 0,05 and Ks = 12.236 +/- 0.05.

Carrasco, L.; Porras, A.; Recillas, E.; Leon-Tavares, J.; Chavushyan, V.; Carraminana, A.

2014-10-01

239

Characterization of Transiting Exoplanets by Way of Differential Photometry  

ERIC Educational Resources Information Center

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

Cowley, Michael; Hughes, Stephen

2014-01-01

240

Far-ultraviolet stellar photometry: A field in Orion  

Microsoft Academic Search

Far-ultraviolet photometry for 625 objects in Orion is presented. These data were extracted from electrographic camera images obtained during sounding rocket flights in 1975 and 1982. The 1975 images were centered close to the belt of Orion while the 1982 images were centered approximately 9 deg further north. One hundred and fifty stars fell in the overlapping region and were

Edward G. Schmidt; George R. Carruthers

1993-01-01

241

Photometry of the Under Observed RR Lyrae Star GM Orionis  

NASA Astrophysics Data System (ADS)

We report photometric observations of the under-observed RR Lyrae variable star GM Orionis. Earlier observations show an inconsistency in the star’s observed brightness, while the amplitude of variability has remained constant. We show photometry that has been collected over a three-year period demonstrating a continued increase in brightness. We discuss possible explanations.

Brown, Justin; Boyle, R. J.

2014-01-01

242

Multicolor CCD Photometry of the Open Cluster IC 361  

Microsoft Academic Search

CCD photometry in the eight-color Vilnius + I system for 7250 stars down to I = 19.6 mag has been obtained in the 20 arcmin × 26' field of the open cluster IC 361 in Camelopardalis. The catalog of 1420 stars down to V ˜ 18.5 mag is presented. It contains the coordinates, V magnitudes, seven color indices, quantitative photometric

J. Zdanavicius; S. Bartasiute; R. P. Boyle; F. J. Vrba; K. Zdanavicius

2010-01-01

243

BVRI CCD Photometry of the Open Cluster IC 4996  

Microsoft Academic Search

CCD observations in the BVRI system of 126 stars in the central part of the open cluster IC 4996 are presented. The precision of the photometry and the parameters of the cluster are discussed. A distance of r = 1620 pc and an age t = 9 Myr of the cluster are determined.

V. Vansevicius; A. Bridzius; A. Pucinskas; T. Sasaki Sasaki

1996-01-01

244

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

245

CCD Photometry of Nova V1500 Cygni Twenty Years After  

E-print Network

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

I. Semeniuk; A. Olech; M. Nalezyty

1995-12-14

246

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

247

Simulation of premixed turbulent flames M. Day and J. Bell  

E-print Network

-emissions burners for a variety of industrial applications. However, it is difficult to design lean premixed systems spanning a circular nozzle, and a piloted Bunsen flame anchored on a rectangular nozzle. These flames span, colored by mean flame surface curvature. The V-flame inlet nozzle is 5 cm in diameter; the simulation

248

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

249

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

250

Opposed Flow Impact on Flame Spread Above Liquid Fuel Pools  

E-print Network

the effects of gravity level, pool depth, fluid properties, and chemical kinetic coefficients on flame spreadOpposed Flow Impact on Flame Spread Above Liquid Fuel Pools Jinsheng Cai, Feng Liu, and William A and flame propagation above a liquid fuel (propanol) pool in an airflow duct. Pulsating flame spread

Liu, Feng

251

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

E-print Network

diffusion flames. We con­ sider a flame sheet problem with one­step chemical reaction. The governingPreconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda Samir Karaa of an elliptic flame sheet problem. By selecting the generalized minimum residual method as the linear smoother

Zhang, Jun

252

Asymptotic Structure of Rich Methane-Air Flames K. SESHADRI*  

E-print Network

-rich, premixed methane flame is analyzed by using a reduced chemical-kinetic mechanism made up of three global of these flames was presumed to be made up of two layers, for rich flames analyzed here all chemical reaction of unstrained premixed methane flames obtained using chemical-kinetic mechanisms made up of elementary reactions

Pitsch, Heinz

253

The Interaction of High-Speed Turbulence with Flames  

Microsoft Academic Search

Interaction of flames with turbulence occurs in systems ranging from chemical flames on Earth to thermonuclear burning fronts, which are presently believed to be the key component of the explosion mechanism powering the type Ia supernovae. A number of important questions remains concerning the dynamics of turbulent flames in the presence of high-speed turbulence, the flame structure and stability, as

Alexei Y. Poludnenko; E. S. Oran

2010-01-01

254

Swirl effects on global and chemical behavior of flames  

Microsoft Academic Search

Flame characteristics are reported for four lean direct injection (LDI) method flames using direct flame photography and optical emission spectroscopy (OES). The flames included three counter-swirl and one coswirl configuration using a double concentric swirl burner. The chemiluminescent images for the OES technique are acquired using an intensified charge coupled device (ICCD) camera and narrow bandpass filters centered at wavelengths

S. Archer; A. K. Gupta

2002-01-01

255

THREE-DIMENSIONAL FLAME PROPAGATION ABOVE LIQUID FUEL POOLS  

E-print Network

properties, and chemical kinetic coefficients on flame spread across liquid fuel pools. Pulsating flameTHREE-DIMENSIONAL FLAME PROPAGATION ABOVE LIQUID FUEL POOLS JINSHENG CAI, FENG LIU, AND WILLIAM A, USA Ignition and flame spread above liquid fuels initially below the flashpoint temperature

Liu, Feng

256

Formation mechanism for polycyclic aromatic hydrocarbons in methane flames  

E-print Network

of the flame. The yellow color shows the presence of soot particles in the flame as they radiate due to PlanckFormation mechanism for polycyclic aromatic hydrocarbons in methane flames K. Siegmanna) Swiss 96822 Received 24 August 1999; accepted 13 October 1999 A laminar diffusion flame of methane

Sattler, Klaus

257

Application of multispectral color photography to flame flow visualization  

Microsoft Academic Search

For flames of short duration and low intensity of radiation a spectroscopical flame diagnostics is difficult. In order to find some other means of extracting information about the flame structure from its radiation, the feasibility of using multispectral color photography was successfully evaluated. Since the flame photographs are close-ups, there is a considerable parallax between the single images, when several

G. Stoffers

1974-01-01

258

FLAME DETECTION IN VIDEO USING HIDDEN MARKOV MODELS  

Microsoft Academic Search

Thispaperproposesa novelmethodtodetectflames invideo 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 andflame coloredordinarymovingobjects areused to distinguish flame flicker process from motion of flame col- ored moving objects. Spatial color variations in

A. Enis Cetin

259

Fire-Flame Detection Based on Fuzzy Finite Automation  

Microsoft Academic Search

This paper proposes a new fire-flame detection method using probabilistic membership function of visual features and Fuzzy Finite Automata (FFA). First, moving regions are detected by analyzing the background subtraction and candidate flame regions then identified by applying flame color models. Since flame regions generally have an irregular pattern continuously, membership functions of variance of intensity, wavelet energy and motion

SunJae Ham; ByoungChul Ko; Jae Yeal Nam

2010-01-01

260

Application of multispectral color photography to flame flow visualization  

Microsoft Academic Search

For flames of short duration and low intensity of radiation a spectroscopical flame diagnostics is difficult. In order to find some other means of extracting information about the flame structure from its radiation, the feasibility of using multispectral color photography was successfully evaluated. Since the flame photographs are close-ups, there is a considerable parallax between the single images, when several

G. Stoffers

1979-01-01

261

The cellular nature of confined spherical propane-air flames  

Microsoft Academic Search

Cellular structures of hydrodynamic origin are observed in laminar propane-air flames confined in a constant volume vessel. The flame structure is observed and the flame speed measured by high speed Schlieren photography. Measured pressure and time data are also used to compute the flame speeds, utilizing a two-zone thermodynamic combustion model. Results show that the onset of the observed cellular

E GROFF

1982-01-01

262

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

E-print Network

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

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

2014-01-01

263

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

NASA Technical Reports Server (NTRS)

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

Matalon, Moshe

2003-01-01

264

Premixed turbulent flame propagation in microgravity  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

265

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

266

Structure of Propagating and Attached Hydrocarbon Flames  

NASA Technical Reports Server (NTRS)

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

Takahashi, Fumiaki; Katta, Viswanath

2004-01-01

267

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

268

Flame-Generated Vorticity Production in Premixed Flame-Vortex Interactions  

NASA Technical Reports Server (NTRS)

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

Patnaik, G.; Kailasanath, K.

2003-01-01

269

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

270

Aromatics oxidation and soot formation in flames  

SciTech Connect

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

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

1993-12-01

271

Flaming alcoholic drinks: flirting with danger.  

PubMed

Alcohol-related burn injuries carry significant mortality and morbidity rates. Flaming alcoholic beverages served in trendy bars and clubs are becoming increasingly popular. The dangers associated with an ignited alcoholic drink are often underestimated by party goers whose risk assessment ability is already impaired by heavy alcohol consumption. The authors present two cases demonstrating the varied severity of burn injuries associated with flaming alcoholic drinks, and their clinical management. Consumption of flaming alcoholic drinks poses potential risks for burn injuries. Further support is required to enable national and local agencies to implement effective interventions in drinking environments. PMID:24043236

Tan, Alethea; Frew, Quentin; Yousif, Ali; Ueckermann, Nicola; Dziewulksi, Peter

2014-01-01

272

Lewis Number Effects on Partially Premixed Flames  

NASA Technical Reports Server (NTRS)

Combustion is generally categorized as either premixed, where flames propagate into homogeneous mixtures of reactants, or as nonpremixed, where initially separated reactants diffuse into the reaction zones. Although these approaches are applicable to many combustion devices, there are cases not in either of these two limiting regimes. Under such circumstances, one must consider partially premixed combustion. In partially premixed combustion, mechanisms from both premixed and nonpremixed regimes coexist and, as a result, some interesting phenomena arise. One such phenomenon is flame stabilization in laminar mixing layers by triple flames.

Ruetsch, G. R.; Ferziger, J.

1996-01-01

273

Studies of Premixed Laminar and Turbulent Flames at Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

274

Unsolved problems and unanswered questions in flame retardance of polymers  

Microsoft Academic Search

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

Menachem Lewin

2005-01-01

275

Structure and chemical kinetics of flames supported by nitrogen oxides  

Microsoft Academic Search

This paper is a report on efforts to model burner-stabilized and free-standing flames supported by nitrogen oxides. A 272-reaction mechanism has been used as a basis for modeling flames supported by the oxidizers N,O, NO, and NO. Results have been compared with recent experimental data for burner-stabilized flames and free-standing flames. For burner-stabilized flames, comparisons between modeling and experimental data

MELVYN C. BRANCH; JOSEPH J. COR

1993-01-01

276

Laminar diffusion flames under micro-gravity conditions  

NASA Technical Reports Server (NTRS)

Laminar methane and propane gas-jet diffusion flames have been theoretically and experimentally studied at NASA-Lewis under microgravity conditions. It is noted that laminar diffusion flames are strongly affected by the combined effects of kinetics, radiation, and such transient phenomena as flame ignition, stabilization, and extinction. Observations on the distinctive nature of the flame color and luminosity parameters in microgravity are presented, and flame behavior under transient, high-deceleration rates is discussed. Test hardware and instrumentation design are described.

Edelman, Raymond B.; Bahadori, Yousef; Olson, Sandra L.; Stocker, Dennis P.

1988-01-01

277

Ultraviolet Imaging Of Hydrogen Flames  

NASA Astrophysics Data System (ADS)

We have assembled an ultraviplet-sensitive intensified camera for observing hydrogen combustion by imaging the OH, A2?+ - x2II 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 polarization effects for 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.

Yates, George J.; Wilke, Mark; King, Nick; Lumpkin, Alex

1988-08-01

278

Flame resistant nontoxic polymer development  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

279

Application of flame monitoring system for flame spectrum analysis in industrial conditions  

NASA Astrophysics Data System (ADS)

The flame monitoring system is intended to use in industrial condition for controlling pulverized coal combustion in power boiler. Placing the fiber-optic probes close to the each burner, one can obtain detailed information of the coal combustion process within the single burner. In order to enhance flame-monitoring system sensitivity for detection of fuel's composition changes, we have measured flame emission spectra.

Wojcik, Waldemar; Golec, Tomasz; Kotyra, Andrzej; Cieszczyk, Slawomir; Duk, Mariusz; Komada, Pawel

2004-09-01

280

Flame driving of axial acoustic fields - Comparison between flame radiation and acoustic intensity measurements  

Microsoft Academic Search

The paper describes results of an ongoing investigation of the mechanisms responsible for the driving of axial instabilities in solid-propellant rocket motors. Specifically, the results of two experimental methods for measuring the driving of axial acoustic fields by sidewall-stabilized diffusion flames are compared. Driving of acoustic fields by diffusion flames was investigated using LDV and C-H flame-radiation measurements. These studies

T. Y. Chen; U. G. Hegde; B. R. Daniel; B. T. Zinn

1990-01-01

281

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

282

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

283

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

SciTech Connect

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

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

2009-04-15

284

Numerical and experimental studies of ethanol flames and autoignition theory for higher alkanes  

E-print Network

extinction of H 2 /air flames: Chemical Kinetics andchemical-kinetic mechanism for hydrocarbon combustion”, Combustion and Flame,chemical-kinetic mechanism for hydrocarbon combustion”, Combustion and Flame,

Saxena, Priyank

2007-01-01

285

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

286

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...

287

Analytical investigation of acoustically perturbed Bunsen flames  

E-print Network

to the burner rim is essential for modeling and understanding the dynamical response of flames to velocity in the theoretical models. To test this hypothesis, here we extend the kinematic models proposed previously [4, 3

Eindhoven, Technische Universiteit

288

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...

289

Dynamics and structure of turbulent premixed flames  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

290

Environmentally Benign Flame Retardant Nanocoatings for Fabric  

E-print Network

percent PSP coating after burning. In several instances, a direct flame on the fabric was extinguished. The peak HRR and THR of coated fabric has 30 percent and 65 percent reduction, respectively, compared to the uncoated control fabric. These anti...

Li, Yu-Chin

2012-07-16

291

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

292

Flame resistant fibrous materials. [developed from chlorofluoropolymers  

NASA Technical Reports Server (NTRS)

Four chlorofluoropolymer systems were developed that satisfactorily met the criteria for classification as self-extinguishing. Three of these systems consisted of Halar (a copolymer of chlorotrifluoroethylene and ethylene) and tin-based flame retardants. The fourth system was a copolymer of chlorotrifluoroethylene and tetrafluoroethylene with no flame retardants added. Production of fibers from all four candidates, by melt extrusion, was demonstrated. Fibers produced from the chlorotrifluoroethylene tetrafluoroethylene copolymer showed the most promise.

1973-01-01

293

Chemical processes in the HNF flame  

Microsoft Academic Search

Results of modeling the HNF flame structure are presented. From an analysis of literature data on the thermal decomposition\\u000a and combustion of HNF, it is concluded that the dissociative vaporization of HNF proceeds via the route HNFliq ? (N2H4)g + (HC(NO2)3)g. The flame structure is modeled using a detailed kinetic mechanism consisting of 47 species and 283 elementary reactions.\\u000a Its

N. E. Ermolin; V. E. Zarko; H. H. Keizers

2006-01-01

294

Optical measurements of soot in premixed flames  

Microsoft Academic Search

Two laser diagnostic techniques were used to measure soot volume fractions, number densities and soot particle radii in premixed propane\\/oxygen flat flames. The two techniques were two wavelength extinction, using 514.5 to 632.8 nm and 457.9 to 632.8 nm wavelength combinations, and extinction\\/scattering using 514.5 nm light. The flames were fuel rich and had cold gas velocities varying from 3.4

Valerie J. Lyons

1988-01-01

295

Digital image-based flame emission spectrometry  

Microsoft Academic Search

A digital image-based flame emission spectrometric (DIB-FES) method for the quantitative chemical analysis is proposed here for the first time. The DIB-FES method employs a webcam to capture the digital images which are associated to a radiation emitted by the analyte into an air-butane flame. Since the detection by webcam is based on the RGB (red–green–blue) colour system, a novel

Wellington Silva Lyra; Vagner Bezerra dos Santos; Amália Geiza Gama Dionízio; Valdomiro Lacerda Martins; Luciano Farias Almeida; Edvaldo Nóbrega Gaião; Paulo Henrique Gonçalves Dias Diniz; Edvan Cirino Silva; Mário César Ugulino Araújo

2009-01-01

296

Flame failure detection and modern boilers  

Microsoft Academic Search

The safe operation of fossil-fuel-fired boilers is dependent to a large extent on the stability of the combustion process. Flame instability can be both inefficient and pollutant forming. but in extreme cases flame extinction can occur. Unless immediate action is taken in such circumstances, large quantities of unburnt fuel can be admitted to the combustion chamber and subsequently re-ignite explosively

A. R. Jones

1988-01-01

297

Photometry on Metal-Poor Stars with HST Parallaxes  

NASA Astrophysics Data System (ADS)

Stellar evolution models and isochrones of metal-poor stars are widely used in astrophysics. However, there are few observational tests of the validity of these models below metallicities of [Fe/H] = -1.5. To remedy this situation, HST has determined parallaxes for 9 metal-poor main sequence stars. Here, we present new ground-based photometry of these stars. The observations were obtained at MDM observatory in March of 2012 over the course of five nights. Our photometry is compared to literature values and combined with parallax results to obtain absolute magnitudes for these stars. The locations of the stars on a color-magnitude diagram are compared to theoretical models.

Joyce, Meridith; Chaboyer, Brian C.; Feiden, Gregory A.; Matthews, Morgan; Benedict, G. Fritz; McArthur, Barbara; Harrison, Thomas E.; McWilliam, Andrew; Nelan, Edmund P.; Patterson, Richard J.; Sarajedini, Ata

2014-06-01

298

Absolute stellar photometry on moderate-resolution FPA images  

USGS Publications Warehouse

An extensive database of star (and Moon) images has been collected by the ground-based RObotic Lunar Observatory (ROLO) as part of the US Geological Survey program for lunar calibration. The stellar data are used to derive nightly atmospheric corrections for the observations from extinction measurements, and absolute calibration of the ROLO sensors is based on observations of Vega and published reference flux and spectrum data. The ROLO telescopes were designed for imaging the Moon at moderate resolution, thus imposing some limitations for the stellar photometry. Attaining accurate stellar photometry with the ROLO image data has required development of specialized processing techniques. A key consideration is consistency in discriminating the star core signal from the off-axis point spread function. The analysis and processing methods applied to the ROLO stellar image database are described. ?? 2009 BIPM and IOP Publishing Ltd.

Stone, T. C.

2009-01-01

299

UBVI and Ha Photometry of the h & chi Persei cluster  

E-print Network

UBVI and Ha photometry is presented for 17319 stars in vicinity of the young double cluster h & chi Persei. Our photometry extends over a 37arcmin x 1arcdeg field centered on the association. We construct reddening contours within the imaged field. We find that the two clusters share a common distance modulus of 11.75$\\pm$0.05 and ages of log age(yr) = 7.1$\\pm$0.1. From the V-Ha colour, a measure of the Ha emission strength, we conduct a survey for emission line objects within the association. We detect a sample of 33 Be stars, 8 of which are new detections. We present a scenario of evolutionary enhancement of the Be phenomenon to account for the peak in Be fraction towards the top of the main-sequence in the population of h & chi Persei and similar young clusters.

Stefan C. Keller; Eva K. Grebel; Grant Miller; Kenneth Yoss

2001-04-10

300

From Spitzer Galaxy Photometry to Tully-Fisher Distances  

E-print Network

This paper involves a data release of the observational campaign: Cosmicflows with Spitzer (CFS). Surface photometry of the 1270 galaxies constituting the survey is presented. An additional ~ 400 galaxies from various other Spitzer surveys are also analyzed. CFS complements the Spitzer Survey of Stellar Structure in Galaxies, that provides photometry for an additional 2352 galaxies, by extending observations to low galactic latitudes (|b|calibrators, selected in K band, of the Tully-Fisher relation. The addition of new calibrators demonstrate the robustness of the previously released calibration. Our estimate of the Hubble constant using supernova host galaxies is unchanged, H0 = 75.2 +/- 3.3 km/s/Mpc. Distance-derived radial peculiar velocities, for the 1935 galaxies with all the available parameters, will be incorporated into a new data release of the Cosmicflows project. The size of the previous catalog will be increased by 20%, including spatial regions close to t...

Sorce, J G; Courtois, H M; Jarrett, T H; Neill, J D; Shaya, E J

2014-01-01

301

The Spitzer Local Volume Legacy (LVL) global optical photometry  

NASA Astrophysics Data System (ADS)

We present the global optical photometry of 246 galaxies in the Local Volume Legacy (LVL) survey. The full volume-limited sample consists of 258 nearby (D < 11 Mpc) galaxies whose absolute B-band magnitude span a range of -9.6 < MB < -20.7 mag. A composite optical (UBVR) data set is constructed from observed UBVR and Sloan Digital Sky Survey ugriz imaging, where the ugriz magnitudes are transformed into UBVR. We present photometry within three galaxy apertures defined at UV, optical, and IR wavelengths. Flux comparisons between these apertures reveal that the traditional optical R25 galaxy apertures do not fully encompass extended sources. Using the larger IR apertures, we find colour-colour relationships where later type spiral and irregular galaxies tend to be bluer than earlier type galaxies. These data provide the missing optical emission from which future LVL studies can construct the full panchromatic (UV-optical-IR) spectral energy distributions.

Cook, David O.; Dale, Daniel A.; Johnson, Benjamin D.; Van Zee, Liese; Lee, Janice C.; Kennicutt, Robert C.; Calzetti, Daniela; Staudaher, Shawn M.; Engelbracht, Charles W.

2014-11-01

302

Premixed Turbulent Flame Propagation in Microgravity  

NASA Technical Reports Server (NTRS)

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

Menon, Suresh

1999-01-01

303

NO concentration imaging in turbulent nonpremixed flames  

SciTech Connect

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

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

1993-12-01

304

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

NASA Astrophysics Data System (ADS)

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

Rosenberg, David Ari

305

ISOCAM Photometry of Narrow-Line X-ray Galaxies  

E-print Network

Mid-infrared photometry of the hosts of Narrow-Line X-ray Galaxies at 6 microns and 12 microns has been attempted with ISOCAM. No conclusive detections have been made. This implies that these are quiescent objects with little or no active star-formation. Neither X-ray binaries nor starburst-driven superwinds are consistent explanations for the X-ray emission in these objects. We conclude that these NLXGs are predominantly AGN-powered.

J. D. Law-Green; A. Zezas; M. J. Ward; C. Boisson

1998-12-23

306

CCD time-resolved photometry of faint cataclysmic variables. IV  

NASA Technical Reports Server (NTRS)

Time-resolved CCD photometry in V, B, and the near-IR has been obtained, with average time-series length of 3 hours, for 15 certified or candidate cataclysmic-variable faint stars. Orbital periods are found in three of the stars, and nine others are noted to exhibit evidence leading toward confirmation of cataclysmic-variable status. The characteristics of PG 0917+342 and PG 2240+193 are as yet unclear.

Howell, Steve B.; Dobrzycka, Danuta; Szkody, Paula; Kreidl, Tobias J.

1991-01-01

307

BV photographic and CCD photometry of IC 4651  

Microsoft Academic Search

A BV photometric survey in IC 4651 based on photographic and CCD material calibrated with photoelectric photometry from Eggen (1971) and Anthony-Twarog and Twarog (1987) has been completed. The color-magnitude diagram is consistent with an age of 2.4 + or - 0.3 x 10 to the 9th yr derived by comparison with the isochrones of VandenBerg (1985) if the apparent

Barbara J. Anthony-Twarog; Krishna Mukherjee; Bruce A. Twarog; Nelson Caldwell

1988-01-01

308

CCD Photometry of Galactic Globular Clusters.III.IC 4499  

Microsoft Academic Search

The variable star population of the Oosterhoff Type I galactic globular cluster IC 4499 (C1452-820) has been studied by CCD photometry, from observations in the B, V, R, and I passbands made during the period 1987-1994. Light curves have been prepared for 97 RR Lyrae variables and one variable blue-straggler (SX Phe) star. The RR Lyraes have =17.65±0.01, and via

Alistair R. Walker; James M. Nemec

1996-01-01

309

CCD Photometry of SW Ursae Majoris during the 1996 Superoutburst  

E-print Network

We present CCD R photometry of SW Ursae Majoris - an SUUMa type cataclysmic variable - obtained during its April 1996 superoutburst. The mean value of the superhump period derived from our observations is 0.05818(+/-2) days (83.8 min). The analysis of times of superhump maxima gives clear evidence for the increase of the superhump period with dPsh/dt=0.000089.

I. Semeniuk; A. Olech; T. Kwast; M. Nalezyty

1997-04-22

310

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

311

Distance to NGC 1569 via Deep HST\\/ACS Photometry  

Microsoft Academic Search

The dwarf irregular galaxy NGC 1569 is the closest and strongest starburst galaxy to the Milky Way, and contains three of the most massive super star clusters ever discovered. Using the ACS\\/WFC on the Hubble Space Telescope we have obtained the deepest optical photometry of this galaxy to date, yielding a V,I color-magnitude diagram (CMD) with some 450,000 stars. These

Aaron J. Grocholski; A. Aloisi; R. P. van der Marel; J. Mack; F. Annibali; M. Sirianni; L. Angeretti; D. Romano; M. Tosi; L. Greggio; E. V. Held

2008-01-01

312

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

313

A Computational Investigation of Sooting Limits of Spherical Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

314

Identifying Contaminated K-Band Globular Cluster RR Lyrae Photometry  

NASA Astrophysics Data System (ADS)

Acquiring near-infrared K-band (2.2 ?m) photometry for RR Lyrae variables in globular clusters and nearby galaxies is advantageous, since the resulting distances are less impacted by reddening and metallicity. However, K-band photometry for RR Lyrae variables in M5, Reticulum, M92, ? Cen, and M15 display clustercentric trends. The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) data imply that multiple stars in close proximity to RR Lyrae variables located near the cluster core, where the stellar density increases markedly, are generally unresolved in ground-based images. RR Lyrae variables near the cluster core appear to suffer from photometric contamination, thereby yielding underestimated cluster distances and biased ages. The impact is particularly pernicious, since the contamination propagates a systematic uncertainty into the distance scale, and hinders the quest for precision cosmology. The clustercentric trends are probably unassociated with variations in chemical composition, since an empirical K-band period-magnitude relation inferred from Araucaria/VLT (Very Large Telescope) data for RR Lyrae variables in the Sculptor dSph exhibits a negligible metallicity dependence: (0.059 ± 0.095) × [Fe/H]ZW, a finding that supports prior observational results. A future multiepoch, high-resolution near-infrared survey, analogous to the optical HST ACS Galactic Globular Cluster Survey, may be employed to establish K-band photometry for the contaminating stars discussed here.

Majaess, D.; Turner, D.; Gieren, W.

2012-10-01

315

M2K Planet Search: Spectroscopic Screening and Transit Photometry  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

316

The Effects of Gravity on Wrinkled Laminar Flames  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

317

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

318

Characteristics of Non-Premixed Turbulent Flames in Microgravity  

NASA Technical Reports Server (NTRS)

This project is concerned with the characteristics of turbulent hydrocarbon (primarily propane) gas-jet diffusion flames in microgravity. A microgravity environment provides the opportunity to study the structure of turbulent diffusion flames under momentum-dominated conditions (large Froude number) at moderate Reynolds number which is a combination not achievable in normal gravity. This paper summarizes progress made since the last workshop. Primarily, the features of flame radiation from microgravity turbulent jet diffusion flames in a reduced gravity environment are described. Tests were conducted for non-premixed, nitrogen diluted propane flames burning in quiescent air in the NASA Glenn 5.18 Second Zero Gravity Facility. Measured flame radiation from wedge-shaped, axial slices of the flame are compared for microgravity and normal gravity flames. Results from numerical computations of the flame using a k-e model for the turbulence are also presented to show the effects of flame radiation on the thermal field. Flame radiation is an important quantity that is impacted by buoyancy as has been shown in previous studies by the authors and also by Urban et al. It was found that jet diffusion flames burning under microgravity conditions have significantly higher radiative loss (about five to seven times higher) compared to their normal gravity counterparts because of larger flame size in microgravity and larger convective heat loss fraction from the flame in normal gravity. These studies, however, were confined to laminar flames. For the case of turbulent flames, the flame radiation is a function of time and both the time-averaged and time-dependent components are of interest. In this paper, attention is focused primarily on the time-averaged level of the radiation but the turbulent structure of the flame is also assessed from considerations of the radiation power spectra.

Hegde, U.; Yuan, Z. G.; Stocker, D. P.; Bahadori, M. Y.

2001-01-01

319

Flame stabilization in the far field of a laminar round jet diffusion flame  

Microsoft Academic Search

A lifted flame stabilized in the far field of a round laminar jet is considered. Using recent developments in the theory of triple flames, and, the Landau-Squire solution for a nonreacting laminar round jet, a transcendental equation is derived for the lift-off height. This equation is shown to have stable solutions if the Schmidt number is greater than unity but

Sandip Ghosal

1999-01-01

320

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

321

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

322

Modeling Candle Flame Behavior In Variable Gravity  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

323

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.

324

Improving Kepler Pipeline Sensitivity with Pixel Response Function Photometry.  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

325

Flame Propagation in Low-Intensity Turbulence under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

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

Aldredge, R. C.

2001-01-01

326

Structure of Flame Balls at Low Lewis-Number  

NASA Technical Reports Server (NTRS)

The Structure of Flame Balls at Low Lewis-Number (SOFBALL) experiment explored the behavior of a newly discovered flame phenomena called "flame balls." These spherical, stable, stationary flame structures, observed only in microgravity, provide a unique opportunity to study the interactions of the two most important processes necessary for combustion (chemical reaction and heat and mass transport) in the simplest possible configuration. The previously unobtainable experimental data provided a comparison with models of flame stability and flame propagation limits that are crucial both in assessing fire safety and in designing efficient, clean-burning combustion engines.

Weiland, Karen J.; Ronney, Paul

1998-01-01

327

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

328

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

329

Turbulent Premixed Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

Menon, Suresh

1996-01-01

330

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

331

Gravity Effects Observed In Partially Premixed Flames  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

332

Sooting turbulent jet flame: characterization and quantitative soot measurements  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

333

A high-pressure premixed flat-flame burner for chemical process studies. [of pollutant formation in hydrocarbon flames  

NASA Technical Reports Server (NTRS)

A premixed flat-flame burner was designed and tested with methane-air mixtures at pressures from 1.1 to 20 atm and equivalence ratios from 0.7 to 1.1. Reactant velocity in the burner mixing chamber was used to characterize the range of stable flames at each pressure-equivalence-ratio condition. Color photographs of the flames were used to determine flame zone thickness and flame height. The results show that this burner can be used for chemical process studies in premixed high pressure methane-air flames up to 20 atm.

Miller, I. M.

1978-01-01

334

Cars temperature measurements in sooting, laminar diffusion flames  

NASA Astrophysics Data System (ADS)

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

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

1984-07-01

335

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

336

Color context analysis based efficient real-time flame detection algorithm  

Microsoft Academic Search

In this study, we propose a novel color context analysis based efficient real-time flame detection algorithm (CCAFDA). To measure the relevance of color context of every two adjacent flames in flame image sequences, two new flame feature vectors are defined: one is the flame detection context based dynamic feature row vector and the other is the optimal flame feature area

Huan. Li; Shan. Chang; Zhe. Li; Lipng Shao

2008-01-01

337

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

Microsoft Academic Search

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

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

2012-01-01

338

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

339

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

SciTech Connect

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

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

2009-12-15

340

EFFECT OF ORGANOPHOSPHORUS FLAME RETARDANTS ON NEURONAL DEVELOPMENT IN VITRO  

EPA Science Inventory

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

341

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

342

Development of video processing based on coal flame detector system  

SciTech Connect

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

He Wanqing; Yu Yuefeng; Xu Weiyong; Ma Liqun

1999-07-01

343

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

NASA Technical Reports Server (NTRS)

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

Mantel, Thierry

1994-01-01

344

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

NASA Technical Reports Server (NTRS)

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

Driscoll, James F.; Feikema, Douglas A.

2003-01-01

345

Investigating the Flame Microstructure in Type Ia Supernovae  

E-print Network

We present a numerical model to study the behavior of thermonuclear flames in the discontinuity approximation. This model is applied to investigate the Landau-Darrieus instability under conditions found in Type Ia supernova explosions of Chandrasekhar mass white dwarfs. This is a first step to explore the flame microstructure in these events. The model reproduces Landau's linearized stability analysis in early stages of the flame evolution and the stabilization in a cellular flame structure in the nonlinear stage.

F. K. Roepke; W. Hillebrandt; J. C. Niemeyer

2002-04-02

346

Studies of Premixed Laminar and Turbulent Flames at Microgravity  

NASA Technical Reports Server (NTRS)

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

Ronney, Paul D.

1993-01-01

347

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

348

Simulations of multidimensional burner-stabilized flames  

NASA Technical Reports Server (NTRS)

Detailed numerical simulations have been performed to study the structure and dynamics of downward propagating burner-stabilized flames in lean hydrogen-air mixtures. These simulations include the effects of fluid convection, detailed hydrogen-oxygen chemistry, multispecies diffusion, thermal conduction, viscosity, and heat losses to the burner. One-dimensional calculations have been carried out to investigate burner boundary conditions. Well known features of a burner-stabilized flame have been reproduced. Two-dimensional calculations show the presence of cellular structures at the burner surface. At low inlet velocities, these cellular structures are suppressed by the increased heat loss to the burner. These simulations have been examined in detail to gain understanding of the similarities and differences in structure and stability of freely propagating and burner-stabilized flames.

Patnaik, G.; Kailasanath, K.

1993-01-01

349

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

350

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

351

Photometry and spectroscopy in the open cluster alpha Persei, 2.  

NASA Technical Reports Server (NTRS)

Results from a combination of new spectroscopic and photometric observations in the lower main sequence and pre-main sequence of the open cluster alpha Persei are presented. New echelle spectroscopy has provided radial and rotational velocity information for thirteen candidate members, three of which are nonmembers based on radial velocity, absence of a Li 6707 A feature, and absence of H alpha emission. A set of revised rotational velocity estimates for several slowly rotating candidates identified earlier is given, yielding rotational velocities as low as 7 km/s for two apparent cluster members. VI photometry for several pre-main-sequence members is given; the new (V, V-I(sub K) photometry yields a more clearly defined pre-main sequence. A list of approximately 30 new faint candidate members based on the (V, V-I(sub K)), charge coupled device (CCD) photometry is presented in an effort to identify additional cluster members at very low masses. Low-dispersion spectra obtained for several of these candidates provide in some cases supporting evidence for cluster membership. The single brown dwarf candidate in this cluster is for the first time placed in a color-magnitude diagram with other cluster members, providing a better means for establishing its true status. Stars from among the list of new photometric candidates may provide the means for establishing a sequence of cluster members down to very faint magnitudes (V approximately 21) and consequently very low masses. New coordinate determinations for previous candidate members and finding charts for the new photometric candidates are provided in Appendices.

Prosser, Charles F.

1994-01-01

352

MOST photometry of the enigmatic PMS pulsator HD 142666  

NASA Astrophysics Data System (ADS)

Context: Modeling of pre-main sequence (PMS) stars through asteroseismology of PMS p-mode pulsators has only recently become possible, and spacebased photometry is one of the important sources of data for these efforts. We present precise photometry of the pulsating Herbig Ae star HD 142666 obtained in two consecutive years with the MOST (Microvariability & Oscilations of STars) satellite. Aims: Previously, only a single pulsation period was known for HD 142666. The MOST photometry reveals that HD 142666 is multi-periodic. However, the unique identification of pulsation frequencies is complicated by the presence of irregular variability caused by the star's circumstellar dust disk. The two light curves obtained with MOST in 2006 and 2007 provided data of unprecedented quality to study the pulsations in HD 142666 and also to monitor the circumstellar variability. Methods: Frequency analysis was performed using the routine sigspec and the results from the 2006 and 2007 campaigns were then compared to each other with the software cinderella to identify frequencies common to both light curves. The correlated frequencies were then submitted to an asteroseismic analysis. Results: We attribute 12 frequencies to pulsation. Model fits to the three frequencies with the highest amplitudes lie well outside the uncertainty box for the star's position in the HR diagram based on published values. Some of the frequencies appear to be rotationally split modes. Conclusions: The models suggest that either (1) the published estimate of the luminosity of HD 142666, based on a relation between circumstellar disk radius and stellar luminosity, is too high and/or (2) additional physics such as mass accretion may be needed in our models to accurately fit both the observed frequencies and HD 142666's position in the HR diagram. Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia with the assistance of the University of Vienna.

Zwintz, K.; Kallinger, T.; Guenther, D. B.; Gruberbauer, M.; Huber, D.; Rowe, J.; Kuschnig, R.; Weiss, W. W.; Matthews, J. M.; Moffat, A. F. J.; Rucinski, S. M.; Sasselov, D.; Walker, G. A. H.; Casey, M. P.

2009-02-01

353

Cool White Dwarfs Revisited -- New Spectroscopy and Photometry  

E-print Network

In this paper we present new and improved data on 38 cool white dwarfs identified by Oppenheimer et al. 2001 (OHDHS) as candidate dark halo objects. Using the high-res spectra obtained with LRIS, we measure radial velocities for 13 WDs that show an H alpha line. We show that the knowledge of RVs decreases the UV-plane velocities by only 6%. The radial velocity sample has a W-velocity dispersion of sig_W = 59 km/s--in between the values associated with the thick disk and the stellar halo. We also see indications for the presence of two populations by analyzing the velocities in the UV plane. In addition, we present CCD photometry for half of the sample, and with it recalibrate the photographic photometry of the remaining WDs. Using the new photometry in standard bands, and by applying the appropriate color-magnitude relations for H and He atmospheres, we obtain new distance estimates. New distances of the WDs that were not originally selected as halo candidates yield 13 new candidates. On average, new distances produce velocities in the UV plane that are larger by 10%, with already fast objects gaining more. Using the new data, while applying the same UV-velocity cut (94 km/s) as in OHDHS, we find a density of cool WDs of 1.7e-4 pc^-3, confirming the value of OHDHS. In addition, we derive the density as a function of the UV-velocity cutoff. The density (corrected for losses due to higher UV cuts) starts to flatten out at 150 km/s (0.4e-4 pc^-3), and is minimized (thus minimizing a possible non-halo contamination) at 190 km/s (0.3e-4 pc^-3). These densities are in a rough agreement with the estimates for the stellar halo WDs, corresponding to a factor of 1.9 and 1.4 higher values.

Samir Salim; R. Michael Rich; Brad M. Hansen; L. V. E. Koopmans; Ben R. Oppenheimer; Roger D. Blandford

2003-08-07

354

Photometry and spectroscopy in the open cluster Alpha Persei, 2  

NASA Technical Reports Server (NTRS)

Results from a combination of new spectroscopic and photometric observations in the lower main-sequence and pre-main sequence of the open cluster alpha Persei are presented. New echelle spectroscopy has provided radial and rotational velocity information for thirteen candidate members, three of which are nonmembers based on radial velocity, absence of a Li 6707A feature, and absence of H-alpha emission. A set of revised rotational velocity estimates for several slowly rotating candidates identified earlier is given, yielding rotational velocities as low as 7 km/s for two apparent cluster members. VRI photometry for several pre-main sequence members is given; the new (V,V-I(sub K)) photometry yields a more clearly defined pre-main sequence. A list of approximately 43 new faint candidate members based on the (V,V-I(sub K)) CCD photometry is presented in an effort to identify additional cluster members at very low masses. Low-dispersion spectra obtained for several of these candidates provide in some cases supporting evidence for cluster membership. The single brown dwarf candidate in this cluster is for the first time placed in a color-magnitude diagram with other cluster members, providing a better means for establishing its true status. Stars from among the list of new photometric candidates may provide the means for establishing a sequence of cluster members down to very faint magnitudes (V approximately 21) and consequently very low masses. New coordinate determinations for previous candidate members and finding charts for the new photometric candidates are provided in appendices.

Prosser, Charles F.

1993-01-01

355

A digital imaging photometry system for cometary data acquisition  

NASA Technical Reports Server (NTRS)

This report describes a digital imaging photometry system developed in the Space Science Laboratory at the Marshall Space Flight center. The photometric system used for cometary data acquisition is based on an intensified secondary electron conduction (ISEC) vidicon coupled to a versatile data acquisition system which allows real-time interactive operation. Field tests on the Orion and Rosette nebulas indicate a limiting magnitude of approximately m sub v = 14 over the 40 arcmin field-of-view. Observations were conducted of Comet Giacobini-Zinner in August 1985. The resulting data are discussed in relation to the capabilities of the digital analysis system. The development program concluded on August 31, 1985.

Clifton, K. S.; Benson, C. M.; Gary, G. A.

1986-01-01

356

UBVRI photometry of the FK5 Extension Catalogue Stars  

NASA Astrophysics Data System (ADS)

UBVRI photometry in the Kron-Cousins system for 272 stars of the Extension Catalogue of the Fifth Fundamental Star Catalogue (FK5 stars) in the declination zone +7 deg to -90 deg is presented. Tables 1-2 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Based on observations made at the European Southern Observatory, La Silla, Chile.

Carrasco, G.; Ledoux, C.; Loyola, P.

1997-12-01

357

Photometry and Modelling of Tidal Dwarfs around AM Galaxies  

NASA Astrophysics Data System (ADS)

Tidal dwarf galaxies (TDGs) are a class of objects born from preenriched material in the tails of interacting and merging galaxies. The recent study of a small number of TDGs showed common properties in metallicity, blue colors, and H i-gas content. This study aims to a larger statistics of TDGs. Therefore we present B, V, R photometry of TDG-candidates in a sample of objects from the AM catalog. The modelling of the resulting colors through evolutionary synthesis is used for the interpretation regarding burst age, metallicity, and relative proportions of the old and young starburst components.

Weilbacher, P. M.; Duc, P.-A.; Fritze-v. Alvensleben, U.; Fricke, K. J.

358

U-band photometry of 17 WINGS clusters  

NASA Astrophysics Data System (ADS)

Context. This paper belongs to a series presenting the WIde Field Nearby Galaxy-cluster Survey (WINGS). The WINGS project has collected wide-field, optical (B, V), and near-infrared (J, K) imaging as well as medium resolution spectroscopy of galaxies in a sample of 76 X-ray selected nearby clusters (0.04 photometry of galaxies and stars in the fields of 17 clusters of the WINGS sample. We also extend the original B- and V-band photometry (WINGS-OPT) for 9 and 6 WINGS clusters to a larger field of view. Methods: We used both the new and already existing B-band photometry to obtain reliable (U - B) colors of galaxies within three fixed apertures in kpc. To this aim, we took particular care with the astrometric precision in the reduction procedure. Since not all the observations were taken in good transparency conditions, the photometric calibration was partly obtained by relying on the SDSS and WINGS-OPT photometry for the U- and optical bands, respectively. Results: We provide U-band (also B- and V-band, where possible) total magnitudes of stars and galaxies in the fields of clusters. For galaxies only, the catalogs also provide geometrical parameters and carefully centered aperture magnitudes. The internal consistency of magnitudes was checked for clusters imaged with different cameras, while the external photometric consistency was obtained by comparison with the WINGS-OPT and SDSS surveys. Conclusions: The photometric catalogs presented here add the U-band information to the WINGS database for extending the spectral energy distribution of the galaxies, in particular in the ultraviolet wavelengths which are fundamental for deriving the star formation rate properties. Photometric catalogs are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A111

Omizzolo, A.; Fasano, G.; Reverte Paya, D.; De Santis, C.; Grado, A.; Bettoni, D.; Poggianti, B.; D'Onofrio, M.; Moretti, A.; Varela, J.; Fritz, J.; Gullieuszik, M.; Cava, A.; Grazian, A.; Moles, M.

2014-01-01

359

CCD Photometry of Dwarf Nova AL Com in Superoutburst  

E-print Network

We report a CCD optical photometry of a dwarf nova AL Com in superoutburst. Before superhumps occurred the light curve was highly variable with dominant periods about 41 minutes and 81.5 minutes for different nights. The period of observed superhumps is 82.5 minutes and seems to be stable. The first harmonic of the basic period is also present. We detected a weak signal corresponding to period 78.1 minutes. One of the periods 78.1 or 81.5 is suspected to be a possible signature of orbital motion in the system.

W. Pych; A. Olech

1995-09-20

360

CCD-Delta a and BVR photometry of NGC 7296  

E-print Network

The first CCD photometric investigation of the open cluster NGC 7296 up to now was performed within the narrow band Delta a photometric system, which enables us to detect peculiar objects. A deeper investigation of that cluster followed, using the standard BVR-Bessel filter set. The age and E(B-V) was determined independently to log t= 8.0 and 0.15 respectively by using Delta a and broadband photometry. In total five Be/Ae objects and two metal-weak stars showing significant negative Delta a-values as well as one classical chemically peculiar star could be identified within that intermediate age open cluster.

M. Netopil; E. Paunzen; H. M. Maitzen; A. Claret; K. Pavlovski; E. Tamajo

2005-07-25

361

Photometry and polarimetry of pre-main sequence stars  

NASA Astrophysics Data System (ADS)

We present optical and infrared photometry, and optical polarimetry, of several pre-main sequence stars; much of the data were obtained quasi-simultaneously. Our data demonstrate that, while a simple occultation model for deep visual minima in pre-main sequence stars is consistent with the data in some cases, in others a major change in the outer dust shell is required to account for the optical-infrared behaviour. Apart from the marginal case of UX Ori, there is no significant correlation between polarization and photometric colours. We tentatively report the possible detection of circular polarization in AK Sco, RU Lup, HD97048 and HD144667.

Hutchinson, M. G.; Albinson, J. S.; Barrett, P.; Davies, J. K.; Evans, A.; Goldsmith, M. J.; Maddison, R. C.

1994-05-01

362

Broadband Photometry of the Potentially Hazardous Asteroid 2013 RH74  

NASA Astrophysics Data System (ADS)

The Near-Earth Asteroid (NEA) 2013 RH74 was discovered by the Catalina Sky Survey on September 15 2013 (MPEC 2013-S15) and has been designated as a Potentially Hazardous Asteroid (PHA) by the Minor Planet Center. We obtained six partial nights of broadband Bessel BVRI photometry at the JPL Table Mountain 0.6-m telescope (TMO), as summarized in Table 1. This object was detected by planetary radar soon after discovery (http://echo.jpl.nasa.gov/asteroids/index.html).

Hicks, M.; Ebelhar, S.

2013-11-01

363

Broadband Photometry of the Potentially Hazardous Asteroid 251346 (2007 SJ)  

NASA Astrophysics Data System (ADS)

The Near-Earth Asteroid (NEA) 251346 (2007 SJ) was discovered by the LINEAR Sky Survey on September 17, 2007 (MPEC 2007-S17). With a Minimum Orbit Intersection Distance (MOID) of 0.045 AU and an expected diameter between 1.3~2.8 km, this object has been designated as a Potentially Hazardous Asteroid (PHA) by the Minor Planet Center. We obtained two partial nights of broadband Bessel BVRI photometry (October 10 and December 11, 2013) and one night (December 13, 2013) at the JPL Table Mountain 0.6-m telescope (TMO), as summarized in Table 1.

Hicks, M.; Ebelhar, S.

2014-01-01

364

Large Scale Flame Spread Environmental Characterization Testing  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

365

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

366

30 CFR 56.7805 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

367

30 CFR 56.6904 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

368

30 CFR 57.7805 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

369

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

370

30 CFR 57.6904 - Smoking and open flames.  

... 1 2014-07-01 2014-07-01 false Smoking and open flames. 57.6904 Section 57.6904...Requirements-Surface and Underground § 57.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2014-07-01

371

30 CFR 56.7805 - Smoking and open flames.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Smoking and open flames. 56.7805 Section... Rotary Jet Piercing § 56.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2012-07-01

372

30 CFR 57.6904 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

373

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

374

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

375

30 CFR 56.7805 - Smoking and open flames.  

...2014-07-01 2014-07-01 false Smoking and open flames. 56.7805 Section... Rotary Jet Piercing § 56.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2014-07-01

376

30 CFR 57.7805 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

377

30 CFR 56.7805 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

378

30 CFR 56.6904 - Smoking and open flames.  

... 1 2014-07-01 2014-07-01 false Smoking and open flames. 56.6904 Section 56.6904...Explosives General Requirements § 56.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2014-07-01

379

30 CFR 57.6904 - Smoking and open flames.  

Code of Federal Regulations, 2012 CFR

... 1 2012-07-01 2012-07-01 false Smoking and open flames. 57.6904 Section 57.6904...Requirements-Surface and Underground § 57.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2012-07-01

380

30 CFR 57.7805 - Smoking and open flames.  

...2014-07-01 2014-07-01 false Smoking and open flames. 57.7805 Section...Piercing-Surface Only § 57.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2014-07-01

381

30 CFR 56.6904 - Smoking and open flames.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

382

30 CFR 57.7805 - Smoking and open flames.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Smoking and open flames. 57.7805 Section...Piercing-Surface Only § 57.7805 Smoking and open flames. Persons shall not...and supply lines. Signs warning against smoking and open flames shall be posted in...

2012-07-01

383

30 CFR 57.6904 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

384

30 CFR 56.6904 - Smoking and open flames.  

Code of Federal Regulations, 2012 CFR

... 1 2012-07-01 2012-07-01 false Smoking and open flames. 56.6904 Section 56.6904...Explosives General Requirements § 56.6904 Smoking and open flames. Smoking and use of open flames shall not be permitted...

2012-07-01

385

Heat transfer characteristics of an impinging premixed annular flame jet  

Microsoft Academic Search

The heat transfer behaviors of an annular jet flame impinging vertically normal to a flat surface were investigated experimentally. The relationship between the flow\\/flame structure of the annular jet flame and the local heat transfer behavior along the surface was analyzed. Further, the effects of Reynolds number (Re), equivalence ratio (?) and nozzle-to-plate distance (H) on the local and overall

H. S. Zhen; C. W. Leung; C. S. Cheung

386

Premixed flame impingement heat transfer with induced swirl  

Microsoft Academic Search

Experiments were performed to study the heat transfer characteristics of a swirling premixed flame impinging vertically normal to a horizontal plate. The effects of Reynolds number (Re), equivalence ratio (?) and nozzle-to-plate distance (H) on the heat flux were examined. Comparisons were also made between the heat transfer behaviors of the swirling premixed flame (SPF) with a non-swirling premixed flame

D. D. Luo; H. S. Zhen; C. W. Leung; C. S. Cheung

2010-01-01

387

Vortex phase-jitter in acoustically excited bluff body flames  

E-print Network

excitation on bluff body stabilized flames, specifically on the flow field characteristics. The Kelvin", manifested as cycle-to-cycle variation in flame and vorticity field at the same excitation phase. PhaseVortex phase-jitter in acoustically excited bluff body flames Santosh J. Shanbhogue, Michael

Lieuwen, Timothy C.

388

Extinction of Flames in a Nonuniform Electric Field  

Microsoft Academic Search

The extinction of hydrocarbon flames which are subjected to a nonuniform electric field has been studied. The experimental system consists of a candle type burner having a hemispherical tip and a horizontal conducting plate situated above the flame. A direct current high voltage was applied between the burner head and the conducting plate. The voltage was gradually increased until flame

E. SHER; A. POKRYVAILO; E. JACOBSON; M. MOND

1993-01-01

389

Numerical simulation of diffusion flames with and without magnetic field  

Microsoft Academic Search

Numerical computations are made of axisymmetric laminar hydrogen diffusion flames, focusing on the unsteady behavior under microgravity and the effects of magnetic field. In the microgravity without magnetic field, it is revealed that combustion products remain around the diffusion flame because of the lack of convection, and the amount of O2 diffusion to the flame region becomes retarded. When a

Shinichi Kinoshita; Toshimi Takagi; Hideki Kotera; Nobuko I. Wakayama

2004-01-01

390

Flame Temperature Field Measurement Using Improved Generalized Cross Validation Method  

Microsoft Academic Search

The image quality is a crucial factor for calculating flame temperature field based on the color CCD method. However, much unknown noise in flame images would prevent from obtaining the temperature with accuracy. To eliminate noise, the wavelet denoising with soft-threshold is considered to be effective. An important parameter for this procedure is threshold. For flame images containing much unknown

Yinghui Zhou; Dezhong Zheng

2007-01-01

391

Investigations of swirl flames in a gas turbine model combustor  

SciTech Connect

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

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

2006-01-01

392

Sensitivity calculations in PDF modelling of turbulent flames  

E-print Network

are to certain parameters in the model formulation. In the fields of chemical kinet- ics and laminar flamesSensitivity calculations in PDF modelling of turbulent flames Zhuyin Ren *, Stephen B. Pope Sibley tabulation. In addition, PDF cal- culations with sensitivities of the Cabra H2/N2 jet flame are performed

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

27 CFR 555.212 - Smoking and open flames.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 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...

2012-04-01

395

49 CFR 392.25 - Flame producing devices.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

396

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

397

30 CFR 18.65 - Flame test of hose.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

398

30 CFR 7.26 - Flame test apparatus.  

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

2014-07-01

399

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

400

27 CFR 555.212 - Smoking and open flames.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false 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...

2010-04-01

401

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

402

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

403

49 CFR 392.24 - Emergency signals; flame-producing.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

404

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

405

30 CFR 18.65 - Flame test of hose.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Flame test of hose. 18.65 Section 18...ACCESSORIES Inspections and Tests § 18.65 Flame test of hose. (a) Size of test specimen...wide by thickness of the hose. (b) Flame-test apparatus. The principal...

2011-07-01

406

49 CFR 392.25 - Flame producing devices.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

407

27 CFR 555.212 - Smoking and open flames.  

...2014-04-01 2014-04-01 false 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...

2014-04-01

408

30 CFR 18.65 - Flame test of hose.  

Code of Federal Regulations, 2012 CFR

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

2012-07-01

409

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

410

49 CFR 392.24 - Emergency signals; flame-producing.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 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...

2013-10-01

411

27 CFR 555.212 - Smoking and open flames.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false 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...

2013-04-01

412

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

413

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

414

Detailed measurement and assessment of laminar hydrogen jet diffusion flames  

SciTech Connect

Time-averaged, spatially resolved point measurements of temperature, major species concentrations (O{sub 2}, N{sub 2}, H{sub 2}O, H{sub 2}), and hydroxyl radical concentration (OH) in laminar hydrogen jet diffusion flames (Re=30 and 330) are performed using nonintrusive UV Raman scattering coupled with the laser-induced predissociative fluorescence (LIPF) technique for assessment of combustion models. Effects of thermal diffusion and chemical kinetics on the flame structure are investigated by comparing computed results with experimental data. Comparisons of the computed temperature and species concentration profiles with experimental measurements are in good agreement for both flames. The numerical simulations, using the Miller and Bowman mechanism, indicate that thermal diffusion affects the flame structure for the Re=330 flame, whereas its influence becomes minor for the Re=30 flame. Effects of chemical kinetics on the flame structure are investigated in the Re=30 flame using five different H{sub 2}/air reaction mechanisms. Comparisons of the measured and calculated data reveal that this low stretched flame is not very sensitive to the mechanisms used and it may not be suitable for examining the effects of chemical kinetics on the flame structure. Effects of burner wall and coflow boundary conditions on the computed flame structures are also examined in detailed to clarify the importance of boundary conditions in simulating these flames. (author)

Cheng, T.S. [Department of Mechanical Engineering, Chung Hua University, 707, Sec. 2, Wufu Rd., Tungshiang, Hsinchu, Taiwan 300 (ROC); Wu, C.-Y.; Chen, C.-P.; Li, Y.-H.; Chao, Y.-C.; Yuan, T.; Leu, T.S. [Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan 701 (ROC)

2006-07-15

415

Modeling chemical flame structure and combustion dynamics in LES  

Microsoft Academic Search

In turbulent premixed combustion, the instantaneous flame thickness is typically thinner that the grid size usually retained in Large Eddy Simulations (LES), requiring adapted models. Two alternatives to couple chemical databases with LES balance equations, the Thickened Flame (TFLES) and the Filtered Tabulated Chemistry (F-TACLES) models, are investigated here and compared in terms of chemical flame structure and dynamics. To

P. Auzillon; B. Fiorina; R. Vicquelin; N. Darabiha; O. Gicquel; D. Veynante

2011-01-01

416

New optical observations of auroral flames  

NASA Astrophysics Data System (ADS)

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

Balcerak, Ernie

2013-12-01

417

Flame propagation in an electric field  

Microsoft Academic Search

Conclusions  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Under the influence of a transverse electric field the propagation velocity of the flame front up increases. The value of up has been found to depend on the potential difference between the capacitor plates.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a It has been shown that the increase in the flame propagation velocity in an electric field is due to the increase in the

G. D. Salamandra

1969-01-01

418

Velocity profiles in laminar diffusion flames  

NASA Technical Reports Server (NTRS)

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

Lyons, Valerie J.; Margle, Janice M.

1986-01-01

419

Computatonal and experimental study of laminar flames  

SciTech Connect

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

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

1993-12-01

420

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

NASA Technical Reports Server (NTRS)

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

Driscoll, James F.

2001-01-01

421

Chemical flame inhibition using molecular beam mass spectrometry bromotrifluoromethane in low pressure methane--oxygen--argon flames  

Microsoft Academic Search

A molecular beam-mass spectrometer-low pressure flat flame apparatus has been constructed for the purpose of examining the chemical microstructure of normal methane-oxygen-argon flames and those inhibited with Halon extinguishants. Details of construction and performance of this apparatus and of related flame temperature measurements are given. Particular attention is paid to the empirical characterization of the perturbation to the flame caused

J. C. Biordi; C. P. Lazzara; J. F. Papp

1973-01-01

422

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

E-print Network

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

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

2014-01-01

423

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

SciTech Connect

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

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

2007-10-15

424

BVI CCD photometry of the globular cluster M4  

SciTech Connect

CCD BV1 main-sequence (MS) photometry of M4, the globular cluster closest to the sun, is presented. The photometry is matched to the BVI isochrones of VandenBerg and Bell (1985). The MS turnoffs are found to be at V = 16.90 + or - 0.05, B-V = 0.81 + or - 0.02, V-I = 0.96 + or - 0.02, and B - I = 1.77 + or - 0.02. The magnitude difference between the MS turnoff and the horizontal branch is Delta M(V) = 3.52 + or - 0.1 for all three color indices. Using Y = 0.2, (Fe/H) = - 1.27, and alpha = 1.65, with a distance modulus of (m-M)V = 12.7 and E(B-V) = 0.41, a consistent age for M4 is deduced in all three color indices of 17 + or - 1.5 Gyr. 34 references.

Alcaino, G.; Liller, W.; Alvarado, F.

1988-07-01

425

Macular Pigment Optical Density Measured by Heterochromatic Modulation Photometry  

PubMed Central

Purpose To psychophysically determine macular pigment optical density (MPOD) employing the heterochromatic modulation photometry (HMP) paradigm by estimating 460 nm absorption at central and peripheral retinal locations. Methods For the HMP measurements, two lights (B: 460 nm and R: 660 nm) were presented in a test field and were modulated in counterphase at medium or high frequencies. The contrasts of the two lights were varied in tandem to determine flicker detection thresholds. Detection thresholds were measured for different R:B modulation ratios. The modulation ratio with minimal sensitivity (maximal threshold) is the point of equiluminance. Measurements were performed in 25 normal subjects (11 male, 14 female; age: 30±11 years, mean ± sd) using an eight channel LED stimulator with Maxwellian view optics. The results were compared with those from two published techniques – one based on heterochromatic flicker photometry (Macular Densitometer) and the other on fundus reflectometry (MPR). Results We were able to estimate MPOD with HMP using a modified theoretical model that was fitted to the HMP data. The resultant MPODHMP values correlated significantly with the MPODMPR values and with the MPODHFP values obtained at 0.25° and 0.5° retinal eccentricity. Conclusions HMP is a flicker-based method with measurements taken at a constant mean chromaticity and luminance. The data can be well fit by a model that allows all data points to contribute to the photometric equality estimate. Therefore, we think that HMP may be a useful method for MPOD measurements, in basic and clinical vision experiments. PMID:25354049

Huchzermeyer, Cord; Schlomberg, Juliane; Welge-Lüssen, Ulrich; Berendschot, Tos T. J. M.; Pokorny, Joel; Kremers, Jan

2014-01-01

426

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

427

PHOTOMETRY OF VARIABLE STARS FROM DOME A, ANTARCTICA  

SciTech Connect

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 deg{sup 2} 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 {delta} Scuti, {gamma} Doradus, and RR Lyrae variables. One variable may be a transiting exoplanet.

Wang Lingzhi [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Macri, Lucas M.; Krisciunas, Kevin; Wang Lifan [Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel; Storey, John W. V. [School of Physics, University of New South Wales, NSW 2052 (Australia); Cui Xiangqun; Gong Xuefei; Yuan Xiangyan [Nanjing Institute of Astronomical Optics and Technology, Nanjing 210042 (China); Feng Longlong; Yang Ji; Zhu Zhenxi [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Liu Qiang; Zhou Xu [National Astronomical Observatory of China, Chinese Academy of Sciences, Beijing 100012 (China); Pennypacker, Carl R. [Center for Astrophysics, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Shang Zhaohui [Department of Physics, Tianjin Normal University, Tianjin 300074 (China); Yang Huigen [Polar Research Institute of China, Pudong, Shanghai 200136 (China); York, Donald G. [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

2011-11-15

428

Stellar Photometry and Astrometry with Discrete Point Spread Functions  

E-print Network

The key features of the MATPHOT algorithm for precise and accurate stellar photometry and astrometry using discrete Point Spread Functions are described. A discrete Point Spread Function (PSF) is a sampled version of a continuous PSF which describes the two-dimensional probability distribution of photons from a point source (star) just above the detector. The shape information about the photon scattering pattern of a discrete PSF is typically encoded using a numerical table (matrix) or a FITS image file. Discrete PSFs are shifted within an observational model using a 21-pixel-wide damped sinc function and position partial derivatives are computed using a five-point numerical differentiation formula. Precise and accurate stellar photometry and astrometry is achieved with undersampled CCD observations by using supersampled discrete PSFs that are sampled 2, 3, or more times more finely than the observational data. The precision and accuracy of the MATPHOT algorithm is demonstrated by using the C-language MPD code to analyze simulated CCD stellar observations; measured performance is compared with a theoretical performance model. Detailed analysis of simulated Next Generation Space Telescope observations demonstrate that millipixel relative astrometry and millimag photometric precision is achievable with complicated space-based discrete PSFs. For further information about MATPHOT and MPD, including source code and documentation, see http://www.noao.edu/staff/mighell/matphot

Kenneth J. Mighell

2005-05-20

429

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

430

Photometry of Variable Stars from Dome A, Antarctica  

E-print Network

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 square-degree 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 find 6 times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% are unclassified, 27% are likely binaries and 17% are likely pulsating stars. The latter category includes delta Scuti, gamma Doradus and RR Lyrae variables. One variable may be a transiting exoplanet.

Wang, Lingzhi; 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

2011-01-01

431

Infrared spectroscopy and photometry of Comet Austin 1990 V  

NASA Technical Reports Server (NTRS)

3-micron and 10-micron spectra and IR photometry of the dynamically new Comet Austin 1990 V were obtained for March-May 1990. An unusual 9-11 micron emission feature 15-20 percent above the continuum is evident at 0.78 AU postperihelion. The shape, in particular a peak at 11.06 micron, differs from that seen in Halley and several other comets, suggesting a difference in the mineralogy of the silicate grains. The 3.1-7.7 micron spectrum at 0.35 AU shows no obvious feature; feature/continuum contrast of the 3.36 micron emission feature is less than about 5 percent. Based on the IR photometry and a dust model weighted toward small grains, the dust production rate on 6 May at 0.78 AU was about 3 x 10 exp 5 g/s. The corresponding dust/gas mass ratio was about 0.1, classifying Austin as a dust-poor comet. This designation refers only to the relative dust cross section, not to the total mass.

Hanner, Martha S.; Russell, Ray W.; Lynch, David K.; Brooke, Timothy Y.

1993-01-01

432

Macho Proper Motions From Optical/Infrared Photometry  

E-print Network

Optical/infrared photometry can double the number of proper motion measurements of Massive Compact Objects (MACHOs) relative to single band photometry. The proper motion of a MACHO can be measured by finding the ratio $q$ of the (known) radius of the source star to the Einstein radius of the MACHO, $q=\\theta_s/\\theta_e$. A classic method for doing this is to look for the effect on the light curve of the finite size of the source. A modification of this method proposed by Witt (1995) is to look for color changes in the light curve due to the fact that the limb darkening of the source is different in different bands. We demonstrate that the ``classical'' method is not feasible unless the MACHO actually transits the source: if the MACHO passes at say 1.5 source radii, there is still a sizable $\\sim 5\\%$ effect, but the light curve cannot be distinguished from point-source light curves with different parameters. However, color measurements in $V$ $(0.55\\,\\mu$m) and $H$ $(1.65\\,\\mu$m) reduce the errors by a factor $\\sim 120$ and permit proper motion measurements at impact parameters of up to 2 source radii. Color maps in $V-H$ are also useful in the detection of planetary systems. Giant stars have a ``red ring'' in such maps. A planet which transits this ring gives rise to a distinctive signature which can help in the measurement of the planetary system's proper motion.

Andrew Gould; Douglas L. Welch

1995-06-07

433

Improving the Photometry of the Pi of the Sky System  

NASA Astrophysics Data System (ADS)

The "Pi of the Sky" robotic telescope was designed to monitor a significant fraction of the sky with good time resolution and range. The main goal of the "Pi of the Sky" detector is to look for short timescale optical transients arising from various astrophysical phenomena, mainly for the optical counterparts of Gamma Ray Bursts (GRB). The system design, the observation methodology and the algorithms that have been developed make this detector a sophisticated instrument for looking for novae and supernovae stars and for monitoring blasars and AGNs activity. The final detector will consist of two sets of 12 cameras, one camera covering a field of view of 20° × 20°. For data taken with the prototype detector at the Las Campanas Observatory, Chile, photometry uncertainty of 0.018-0.024 magnitudo for stars 7-10m was obtained. With a new calibration algorithm taking into account the spectral type of reference stars, the stability of the photometry algorithm can be significantly improved. Preliminary results from the BGInd variable are presented, showing that uncertainty of the order of 0.013 can be obtained.

?arnecki, A. F.; Ma?ek, K.; Soko?owski, M.

434

From Spitzer Galaxy photometry to Tully-Fisher distances  

NASA Astrophysics Data System (ADS)

This paper involves a data release of the observational campaign: Cosmicflows with Spitzer (CFS). Surface photometry of the 1270 galaxies constituting the survey is presented. An additional ˜400 galaxies from various other Spitzer surveys are also analysed. CFS complements the Spitzer Survey of Stellar Structure in Galaxies, that provides photometry for an additional 2352 galaxies, by extending observations to low galactic latitudes (|b| < 30°). Among these galaxies are calibrators, selected in the K band, of the Tully-Fisher relation. The addition of new calibrators demonstrates the robustness of the previously released calibration. Our estimate of the Hubble constant using supernova host galaxies is unchanged, H0 = 75.2 ± 3.3 km s-1 Mpc-1. Distance-derived radial peculiar velocities, for the 1935 galaxies with all the available parameters, will be incorporated into a new data release of the Cosmicflows project. The size of the previous catalogue will be increased by 20 per cent, including spatial regions close to the Zone of Avoidance.

Sorce, J. G.; Tully, R. B.; Courtois, H. M.; Jarrett, T. H.; Neill, J. D.; Shaya, E. J.

2014-10-01

435

Optimal Addition of Images for Detection and Photometry  

E-print Network

In this paper we describe weighting techniques used for the optimal coaddition of CCD frames with differing characteristics. Optimal means maximum signal-to-noise (s/n) for stellar objects. We derive formulae for four applications: 1) object detection via matched filter, 2) object detection identical to DAOFIND, 3) aperture photometry, and 4) ALLSTAR profile-fitting photometry. We have included examples involving 21 frames for which either the sky brightness or image resolution varied by a factor of three. The gains in s/n were modest for most of the examples, except for DAOFIND detection with varying image resolution which exhibited a substantial s/n increase. Even though the only consideration was maximizing s/n, the image resolution was seen to improve for most of the variable resolution examples. Also discussed are empirical fits for the weighting and the availability of the program, WEIGHT, used to generate the weighting for the individual frames. Finally, we include appendices describing the effects of clipping algorithms and a scheme for star/galaxy and cosmic ray/star discrimination.

Philippe Fischer; Greg P. Kochanski

1993-10-14

436

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

437

Flame Structure and Soot Formation in Inverse Diffusion Flames (Ph.D. Dissertation)  

E-print Network

fuel additives that either suppress soot formation, such as sulfur dioxide (SO 2 ), carbon dioxide (CO 2 ), water (fuel side of the flame in very small concentrations [5,9,29,49]. Peak water and carbon dioxide (

Mikofski, Mark A

2005-01-01

438

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.

439

Report on the ESO Workshop Six Years of FLAMES Operations  

NASA Astrophysics Data System (ADS)

A significant fraction of the community of users of the VLT multi-fibre spectrograph facility, FLAMES, gathered at ESO Headquarters in December 2008 to present scientific highlights, after six years of FLAMES operations. This proved to be a great opportunity to review the scientific impact that FLAMES has had on different fields of astrophysical research and for ESO to assess the current and future needs of FLAMES users. We report on the two and a half day meeting, during which all participants openly discussed their experience with FLAMES and shared their expertise.

Melo, Claudio; Primas, Francesca; Pasquini, Luca; Patat, Ferdinando; Smoker, Jonathan

2009-03-01

440

Analytical Study of Gravity Effects on Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

441

An experimental study of air-assist atomizer spray flames  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

442

Radiative Structures of Lycopodium-Air Flames in Low Gravity  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

443

Flame Structure and Scalar Properties in Microgravity Laminar Fires  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

444

Structure of Flame Balls at Low Lewis Number (SOFBALL) Video  

NASA Technical Reports Server (NTRS)

The Structure of Flame Balls at Low Lewis (SOFBALL) experiment, was run on Space Shuttle Columbia in 2003 for STS-107. The experiment tested various fuel-oxygen-inert gas mixtures in microgravity to produce flame balls, which are spherical steady flames that reveal combustion processes hidden by the volatile effects of gravity on Earth. In this video, a hydrogen-oxygen-sulfur hexafluoride gas mixture produced nine flame balls, the most ever created at once, one of which lasted 81 minutes making it the longest lasting flame ball ever burned in space.

2003-01-01

445

VizieR Online Data Catalog: CU Vir Stroemgren differential photometry (Pyper+, 2013)  

NASA Astrophysics Data System (ADS)

Our data are from two sources: Stroemgren differential uvby photometry obtained using the Four College Automated Photometric Telescope (FCAPT) originally on Mt. Hopkins, AZ, and later at Fairborn Observatory, Washington Camp, AZ, and photometry from the Solar Mass Ejection Imager (SMEI). (1 data file).

Pyper, D. M.; Stevens, I. R.; Adelman, S. J.

2014-06-01

446

Achieving high-precision ground-based photometry for transiting exoplanets  

E-print Network

Achieving high-precision ground-based photometry for transiting exoplanets Olivier Guyona, USA ABSTRACT Detection of transiting exoplanets requires high precision photometry, at the percent opportunity for exoplanet transit detection. We have recently assembled a prototype DSLR-based robotic imaging

Guyon, Olivier

447

VizieR Online Data Catalog: Metallicity calibrations for UBV photometry (Karatas+, 2006)  

NASA Astrophysics Data System (ADS)

UBV photometry [V, (B-V), (U-B)] has been collected from large data bases in conjunction with the derivation of intrinsic-colour, metallicity and absolute magnitude calibrations of F-, G- and early-K-type stars for uvby-beta photometry being derived by Karata & Schuster (in preparation). (2 data files).

Karatas, Y.; Schuster, W. J.

2007-05-01

448

VizieR Online Data Catalog: [Fe/H] & VMAG calibrations for UBV photometry (Karatas+, 2006)  

NASA Astrophysics Data System (ADS)

UBV photometry [V, (B-V), (U-B)] has been collected from large data bases in conjunction with the derivation of intrinsic-colour, metallicity and absolute magnitude calibrations of F-, G- and early-K-type stars for uvby-beta photometry being derived by Karata & Schuster (in preparation). (2 data files).

Karatas, Y.; Schuster, W. J.

2007-05-01

449

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...

450

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

451

Magnetic field controls carbon arc tail flame  

NASA Technical Reports Server (NTRS)

Polarity of two electromagnets placed near the exhaust flue cancels out a high carbon-arc field. The arc tail flame is correctly drawn to the exhaust flue and contamination is diverted. This device should reduce maintenance cycles on any arc-powered illuminator.

1965-01-01

452

NO formation in counterflow partially premixed flames  

SciTech Connect

An experimental and computational study of NO formation in low-strain-rate partially premixed methane counterflow flames is reported. For progressive fuel-side partial premixing the peak NO concentration increased and the NO distribution along the stagnation streamline broadened. New temperature-dependent emissivity data for a SiO{sub 2}-coated Pt thermocouple was used to estimate the radiation correction for the thermocouple, thus improving the accuracy of the reported flame temperature. Flame structure computations with GRIMech 3.00 showed good agreement between measured and computed concentration distributions of NO and OH radical. With progressive partial premixing the contribution of the thermal NO pathway to NO formation increases. The emission index of NO (EINO) first increased and then decreased, reaching its peak value for the level of partial premixing that corresponds to location of the nonpremixed reaction zone at the stagnation plane. The observation of a maximum in EINO at a level of partial premixing corresponding to the nonpremixed reaction zone at the stagnation plane seems to be a consistent feature of low (<20 s{sup -1})-strain-rate counterflow flames. (author)

Mungekar, Hemant; Atreya, Arvind [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

2007-02-15

453

Soret and Dilution Effects on Premixed Flames  

Microsoft Academic Search

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

PEDRO GARCÍA-YBARRA; COLETTE NICOLI; PAUL CLAVIN

1984-01-01

454

HEALTH ASPECTS OF BROMINATED FLAME RETARDANTS (BFRS)  

EPA Science Inventory

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

455

BROMINATED FLAME RETARDANTS: WHY DO WE CARE?  

EPA Science Inventory

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

456

Quenching of flames by magnetic fields (abstract)  

Microsoft Academic Search

The effects of magnetic fields on combustion of alcohol with the aid of platinum catalysis have been studied to simulate in part the oxidation of organic matter in the living body, and it has been found that the combustion reactions are influenced by magnetic fields. It has also been observed that candle flames are pressed down by magnetic fields of

S. Ueno

1988-01-01

457

Modeling extinction and reignition in turbulent flames  

SciTech Connect

The conditional moment closure method (CMC) has been extended to improve reactive species predictions in flames with significant local extinction and reignition. Simple first-order closure of the conditionally averaged reaction rate term does not give satisfactory results due to large fluctuations around the conditional mean and an alternative closure is suggested here. The new closure is based on a precomputed parameterized reference field that maps reactive species mass fractions as functions of mixture fraction and sensible enthalpy. During the computations, the reference field is continuously adjusted to ensure consistency with the CMC solution and doubly conditioned chemical source terms that are functions of time, space, mixture fraction, and sensible enthalpy can thus be obtained. Integration over sensible enthalpy space yields the improved singly conditioned chemical source term that can be used for the solution of the CMC equations. Full closure can be achieved by assuming a {beta}-PDF for the probability distribution in sensible enthalpy space and an additional conditional variance equation needs to be solved. The overall agreement between the measured and the computed variance is satisfactory and the extended CMC model is applied to Sandia Flames D, E, and F. Excellent predictions of temperature, major species, intermediates, and NO are obtained in Flames D and E while temperature predictions can be significantly improved in Sandia Flame F.

Kronenburg, A.; Kostka, M. [Department of Mechanical Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ (United Kingdom)

2005-12-01

458

Are brominated flame retardants endocrine disruptors?  

Microsoft Academic Search

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

Juliette Legler; Abraham Brouwer

2003-01-01

459

Flame in methane jet after spark ignition  

E-print Network

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

Ahmed, Samer F; Mastorakos, Epaminondas

2009-05-21

460

Ignition of spray flame with multiple spark  

E-print Network

. The main flow is from top to botton and the swirling flow from right to left (evident in the front view movies). The flame ignites a long time after the spark sequence has begun. The work is described in: T. Marchione, S.F. Ahmed, E. Mastorakos, "Ignition...

Marchione, Teresa; Ahmed, Samer F; Mastorakos, Epaminondas

2009-05-25

461

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

462

Ignition of bluff-body methane flames  

E-print Network

The movies show the ignition process following a spark in a bluff-body stabilised methane non-premixed flame. The flow is described in: S.F. Ahmed, R. Balachandran, T. Marchione, E. Mastorakos, Spark ignition of turbulent nonpremixed bluff...

Ahmed, Samer F; Marchione, Teresa; Balachandran, R; Mastorakos, Epaminondas; Triantafyllidis, A

2009-05-21

463

Development Of Holographic PIV For Flame Studies  

Microsoft Academic Search

Current combustion diagnostic techniques are sufficiently sophisticated to permit quantitative measurements, although limited to single-point or planar. However, even the simplest jet diffusion flame involves highly transient turbulent flow structures. To measure the instantaneous 3D flow velocity field, a diagnostic technique such as HPIV is needed. HPIV has been demonstrated for simple water and air flows by a fe