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1

Iontophoresis and Flame Photometry: A Hybrid Interdisciplinary Experiment  

ERIC Educational Resources Information Center

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

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

2010-01-01

2

Serum Potassium by Internal Standard Flame Photometry  

Microsoft Academic Search

FLAME photometric analysis1 of cations in biological fluids and tissues is, because of its simplicity, rapidity and greater accuracy, replacing laborious chemical procedures. The vaporization of alkali metal solutions in constant amount per minute into a controlled low-temperature air-acetylene flame produces simple emission spectra, the light intensities of which, measured photo-electrically after slit isolation of the most sensitive line spectrum

Ralph E. Bernstein

1950-01-01

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

FLAME PHOTOMETRIC STUDIES. PART A: STUDIES OF THE EXTRACTION AND FLAME EMISSION OF YTTRIUM. PART B: DROPLET SIZE OF AEROSOLS IN FLAME PHOTOMETRY. PART C: STUDIES OF THE REACTION ZONE OF AN OXYGEN-ACETYLENE FLAME  

Microsoft Academic Search

The Beckman DU flame spectrophotometer was employed in a study of the ; emission characteristics in an oxygenacetylene flame of the yttrium oxide bands ; which crest at 597 and 613 m mu . A 400-fold enhancement in the emission ; sensitivity of yttrium was obtained when a 4-methyl pentan2-one solution of ; yttrium as the 2-thenoyltrifluoroacetone chelate was aspirated

Carnes

1962-01-01

6

Fast Photometry  

Microsoft Academic Search

Fast photometry is measuring changes in brightness in the range of several seconds down to a few milliseconds or faster. Increasingly, asteroid and lunar occultation measurements are carried out using camcorders or video cameras. These can be very inexpensive, and allow event timing to about 0.02 sec. GPS timing signals, good to a microsecond or better, can be combined with

J. Menke

2007-01-01

7

Spectroscopy in separated flames-III Use of the separated nitrous oxide-acetylene flame in thermal emission spectroscopy.  

PubMed

The separation of a premixed nitrous oxide-acetylene flame at a modified commercial burner is described. The reducing interconal zone of the fuel-rich separated flame exhibits low radiative background. The reducing atmosphere and high temperature of this flame result in an effective medium for the excitation of the atomic line spectra of the refractory elements. The use of the fuel-rich flame in the flame photometry of these elements has been investigated. PMID:18960318

Kirkbright, G F; Semb, A; West, T S

1968-05-01

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

Multicolor stellar photometry  

NASA Astrophysics Data System (ADS)

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

Straižys, Vytautas

11

Flame front geometry in premixed turbulent flames.  

National Technical Information Service (NTIS)

Experimental and numerical determinations of flame front curvature and orientation in premixed turbulent flames are presented. The experimental data is obtained from planar, cross sectional images of stagnation point flames at high Damkoehler number. A di...

I. G. Shepherd W. T. Ashurst

1991-01-01

12

Premixed Turbulent Flame Propagation.  

National Technical Information Service (NTIS)

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

D. A. Santavicca

1989-01-01

13

Flame retardants  

NASA Technical Reports Server (NTRS)

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

Troitzsch, J.

1988-01-01

14

Flame stabilization with a tubular flame  

Microsoft Academic Search

A new technique to stabilize a flame in a high-velocity stream with use of a tubular flame has been proposed. To elucidate the validity of this technique, an experiment has been conducted by mounting a tubular flame burner on the nozzle. Flame stability limits and temperature distributions around the burner port have been determined, and experiments have been extended to

Daisuke Shimokuri; Satoru Ishizuka

2005-01-01

15

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

16

Photometry with NICMOS  

NASA Astrophysics Data System (ADS)

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

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

1998-12-01

17

Traveling Flame  

NSDL National Science Digital Library

In this activity, relight a candle by touching an unused match to smoke rising from a blown out candle. Discover the three basic things that fires need. Then, investigate different types, brands, and sizes of candles. This activity guide includes a step-by-step instructional video. Safety note: this activity involves an open flame; adult supervision is required. This activity may work best as a demonstration.

Center, Saint L.

2013-02-25

18

Results in speckle photometry  

NASA Astrophysics Data System (ADS)

Algorithms for reconstruction of isoplanically blurred point source pairs are considerably simpler and faster than full-blown image reconstruction techniques. Traditional autocorrelation approaches suffer from a 180 degree ambiguity, however, and only yield order of magnitude estimates for brightness ratios. A new asymmetric algorithm is here presented: the "Directed Vector Autocorrelation" (DVA), which is a rapid alternative to vector autocorrelation. Together with the 'Fork algorithm", a directional filter for estimating brightness ratios, the DVA algorithm has been used to resolve ambiguous orbits and produce differential color photometry for several binary stars.

Bagnuolo, W. G., Jr.; Barry, D. J.; Mason, B.; Dombrowski, E. G.

1990-08-01

19

Floating Flame Balls  

NSDL National Science Digital Library

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

2011-04-08

20

Photometry and the Virtual Observatory  

NASA Astrophysics Data System (ADS)

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

Rodrigo, C.; Solano, E.

2013-05-01

21

Strip Photometry of Halley's Comet  

Microsoft Academic Search

Post-perihelical photometric observations of comet Halley were performed on 25 nights at the 50 cm reflector of UFRGS by the technique of strip photometry. A slit of dimensions 8arcmin×8arcsec scanned the comet image at a speed of 1arcsec.345 cos delta sec-1, in east-west direction or inversely. For photometry the authors used NASA interference filters C2, C3, CO+, H2O+, lambda4845 and

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

1986-01-01

22

SUSTAINABLE FLAME RETARDANT NANOCOMPOSITES  

Microsoft Academic Search

This paper examines the current state of research into sustainable flame retardants with the work on nanocomposites highlighted. The motivations to move away from halogen-based flame retardants are discussed and a number of life -cycle-assessments are mentioned which set the stage for a similar LCA study of nanocomposite flame retardant products. Additives, such as hydrotalcite and cellulose nanofibrils, are proposed

Jeffrey W. Gilman

23

Micromachined flame ionization detector and flame spectrometer  

NASA Astrophysics Data System (ADS)

In the course of a progressive miniaturization of complex measuring systems conventional flame ionization detectors and flame spectrometers are no longer competitive with the new generation of mobile analysis systems. This paper presents a micro flame ionization detector and flame spectrometer structured by methods of the microsystem technology. Main component is a micro burner unit with a reduced oxyhydrogen consumption to realize a stable miniature oxyhydrogen flame. The required oxyhydrogen is generated by electrolysis in a miniaturized electrolysis cell at low energy consumption. Thus the electrolyzer can be battery operated. Due to the reduced amount of explosive oxyhydrogen and the small dimensions of the gas supply micro flame analyzers have an unlimited mobility without safety restrictions and are easy to handle. Furthermore they have a high sensitivity and selectivity similar to conventional systems. Concentrations down to one ppm are detectable up to now with the micro flame ionization detector. The micro flame spectrometer is in its initial stage. First measurements to demonstrate the further possibilities of such a microsystem are presented.

Zimmermann, Stefan; Wischhusen, S.; Mueller, Joerg

1999-08-01

24

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

25

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

26

Prediction of flame velocities of hydrocarbon flames  

NASA Technical Reports Server (NTRS)

The laminar-flame-velocity data previously reported by the Lewis Laboratory are surveyed with respect to the correspondence between experimental flame velocities and values predicted by semitheoretical and empirical methods. The combustible mixture variables covered are hydrocarbon structure (56 hydrocarbons), equivalence ratio of fuel-air mixture, mole fraction of oxygen in the primary oxygen-nitrogen mixture (0.17 to 0.50), and initial mixture temperature (200 degrees to 615 degrees k). The semitheoretical method of prediction considered are based on three approximate theoretical equations for flame velocity: the Semenov equation, the Tanford-Pease equation, and the Manson equation.

Dugger, Gordon L; Simon, Dorothy M

1954-01-01

27

Visible emission of hydrogen flames  

Microsoft Academic Search

The common misconception that hydrogen flames are not visible is examined. Examples are presented of clearly visible emissions from typical hydrogen flames. It is shown that while visible emissions from these flames are considerably weaker than those from comparable hydrocarbon flames, they are indeed visible, albeit at reduced light levels in most cases. Detailed flame spectra are presented to characterize

R. W. Schefer; W. D. Kulatilaka; B. D. Patterson; T. B. Settersten

2009-01-01

28

Diffusion Flame Stabilization  

NASA Technical Reports Server (NTRS)

Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm). 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

29

Diffusion Flame Stabilization  

NASA Technical Reports Server (NTRS)

Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (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

30

Acoustic coupling of flames  

SciTech Connect

In the limits of large activation energy and small Mach number, the full equations of reactive gas dynamics are reduced to a simpler set which is appropriate for studying acoustic interaction with slender flames. The model is used to study the interaction of a plane, steady flame with a normally incident acoustic wave. Explicit analytical expressions are obtained for the reflection and transmission coefficients, and, in two limiting cases, for the acoustically induced disturbance in the flame speed. 6 references.

Van Harten, A.; Kapila, A.K.; Matkowsky, B.J.

1984-10-01

31

RICHFLD photometry of NGC 6723  

NASA Astrophysics Data System (ADS)

New photographic photometry data for the globular cluster NGC 6723 are presented, and the implications for the CM diagram of the cluster are considered. Revisions to the photometry of Menzies (1974) are suggested which lead to a new value of E(B-V) = 0.10 + or - 0.05 mag. From analysis of the CM diagram and cluster apparent brightness distribution functions, the presence of a gap in the subgiant branch at V = 15.9 is suggested. This implies an uneven rate of evolution along the subgiant branch, similar to gaps seen by other observers for different clusters. Examination of the red end of the right horizontal branch suggests that there may be an extension in the form of an upper horizontal branch. This extension is compared with theoretical models, and agrees with predictions using Y = 0.2-0.3 and Z = 10 to the -4th.

Martins, Donald H.; Fraquelli, Dorothy A.

1987-09-01

32

Flame-Test Chamber  

NASA Technical Reports Server (NTRS)

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

Bjorklund, R. A.

1984-01-01

33

The Flame Tree  

ERIC Educational Resources Information Center

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

Lewis, Richard

2004-01-01

34

SPA, "The Stellar Photometry Assistant"  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

35

Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

36

Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames. Appendix K  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

37

Aerodynamic features of turbulent flames  

Microsoft Academic Search

The paper provides an interpretation for a variety of turbulent flame phenomena relating them to the aerodynamic properties of the flow field. This includes the classical notion of the breakdown of laminar flames propagation in ducts, the characteristic features of turbulent flame-fronts recorded by schlieren photography, as well as flame instabilities leading to flashback occurring in a combustion chamber behind

A. K. Oppenheim; A. F. Ghoniem

1983-01-01

38

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

39

Asteroid Analysis Using Lightcurve Photometry  

NASA Astrophysics Data System (ADS)

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

Zimmerman, Jessica

2011-10-01

40

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

41

Physics of Flames.  

National Technical Information Service (NTIS)

Theoretical and experimental analyses of flame spreading across pools of liquid fuels and the ignitability of such pool under quiescent and flowing environments are presented. The fundamental concept is that, when the temperature of the liquid fuel is bel...

I. Glassman M. Summerfield W. A. Sirignano

1970-01-01

42

Microphysics of Astrophysical Flames  

NASA Astrophysics Data System (ADS)

Type Ia supernovae are thought to begin with a deflagration phase, where burning occurs as a subsonic flame which accelerates and possibly undergoes a transition to a supersonic detonation. Both the acceleration and possible transition will depend on the microphysics of astrophysical flames, and their interaction with a turbulent flow in degenerate material. Here we present recent progress in studying the interactions of astrophysical flames and curvature and strain at the FLASH center; in particular, we discuss quantitative measurements of the effects of strain on burning rate of these flames, and implications for instability growth and quenching. This work was supported by the DOE ASCI/Alliances program at the University of Chicago under grant No. B341495 and the Scientific through Advanced Computing (SciDAC) program of the DOE, grant number DE-FC02-01ER41176 to the Supernova Science Center/UCSC.

Dursi, L. J.; Zingale, M.; Caceres, A.; Calder, A. C.; Timmes, F. X.; Truran, J. W.; Rosner, R.; Lamb, D. Q.; Brown, E.; Ricker, P.; Fryxell, B.; Olson, K.; Riley, K.; Siegel, A.; Vladimirova, N.

2003-03-01

43

"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

44

Flame Retardant Blend Materials.  

National Technical Information Service (NTIS)

This patent application relates to organic fibrous materials, especially polyester/cellulosic, which are rendered flame resistant upon treatment with an emulsion containing (1) a tetrakis(hydroxymethyl)phosphonium salt, (2) an amide (3) a salt of a strong...

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

1975-01-01

45

Flame spread across liquids  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

46

Flame Retardant Elastomeric Compositions.  

National Technical Information Service (NTIS)

A patent application for an invention related to novel flame retardant compositions was presented. These elastomeric compositions are comprised of either spandex type polyurethane having incorporated into the polymer chain halogen containing polyols conve...

J. T. Howarth A. A. Massucco K. R. Sidman S. G. Sheth

1976-01-01

47

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

48

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

49

What's Next in Asteroid Photometry  

NASA Astrophysics Data System (ADS)

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

Vander Haagen, Gary A.

2009-05-01

50

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

51

Flame height measurement of laminar inverse diffusion flames  

SciTech Connect

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

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

2006-07-15

52

Flame height measurement of laminar inverse diffusion flames.  

SciTech Connect

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

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

2005-09-01

53

Observations on Lifted Flame Oscillations and Flame Stability Near Blowout  

NASA Astrophysics Data System (ADS)

Studies are presented that examine the fluctuations in liftoff height of lifted flames in the presence of air co-flow. At a certain jet exit velocity, a flame will lift from the fuel nozzle and stabilize at some downstream position. The partially-premixed flame front of the lifted flame oscillates in the axial direction, with the oscillations becoming greater in flames stabilized further downstream. These oscillations are also observed in flames where blowout is imminent. This work attempts to determine the role of fuel velocity and air co-flow on flame oscillations in both stable and unstable regimes. The results of video imaging of a lifted methane-air diffusion flame are presented. Images are used to ascertain the changes in the reaction zone that influence these oscillations and relate the movement to blowout.

Moore, Nancy; Lyons, Kevin

2007-11-01

54

Illinois­—Where Astronomical Photometry Grew Up  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

55

Flame radiator structure  

SciTech Connect

This patent describes a combustion flame tempering device for a gas-fired furnace for inhibiting formation of oxides of nitrogen by a combustion system of the gas-fired furnace. The combustion system has at least one monoport inshot burner supplied with a gaseous fuel which is burned to produce the combustion flame which is projected through an inlet opening into an air heat exchanger for the gas-fired furnace. The combustion flame has a peripheral area of relatively high peak temperatures conductive to the formation of oxides of nitrogen. The combustion flame tempering device comprises: a perforated tubular main body section having open ends and side walls, having top and bottom edges, the sidewalls having longitudinal flanges at the top and bottom edges thereof. The flanges keep the tubular main body section rigid and stable, and ribs disposed on the sidewalls and being oriented generally perpendicular to the longitudinal flanges of the main body section. The ribs stiffen the sidewalls to prevent the main body section from bending relative to the combustion flame.

Pickering, M.A.

1986-10-28

56

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

57

A Dramatic Flame Test Demonstration.  

ERIC Educational Resources Information Center

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

Johnson, Kristin A.; Schreiner, Rodney

2001-01-01

58

Aerodynamic features of turbulent flames  

NASA Technical Reports Server (NTRS)

The paper provides an interpretation for a variety of turbulent flame phenomena relating them to the aerodynamic properties of the flow field. This includes the classical notion of the breakdown of laminar flames propagation in ducts, the characteristic features of turbulent flame-fronts recorded by schlieren photography, as well as flame instabilities leading to flashback occurring in a combustion chamber behind a bluff-body flame holder. The rudimentary nature of turbulent flame propagation is shown to be associated with (1) vortex motion of a large-scale turbulent eddy, combined with (2) self-advancement of the flame at the appropriate normal burning speed and (3) the concomitant action of distributed sources of specific volume. The results furnish an insight into the macroscopic properties of the mechanism of turbulent flame propagation, rationalizing in particular its capability to sustain high flow velocities at relatively low normal burning speeds.

Oppenheim, A. K.; Ghoniem, A. F.

1983-01-01

59

Flame propagation through periodic vortices  

SciTech Connect

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

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

1995-02-01

60

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

61

Flame retardant spandex type polyurethanes  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

62

CCD photometry of Comet P/Encke  

NASA Astrophysics Data System (ADS)

The authors present new photometry of Comet P/Encke taken near aphelion. Persistent cyclic variations in the brightness of the comet are attributed to rotation of the nucleus, with a most probable rotation period near 22.4 hr. The properties of the nucleus indicated by the new photometry do not compare favorably with the properties inferred from a model by Whipple and Sekanina (1979).

Jewitt, D.; Meech, K.

1987-06-01

63

Classification of stars with WBVR photometry  

NASA Astrophysics Data System (ADS)

We present a method of obtaining the most reliable stellar spectral type based on multi-color photometry. The method also allows us to estimate color excess EB-V and distance to the star. Approbation of the method using bright stars with known spectral classification and W BV R photometry permits to estimate its reliability. Stellar spectra models from Pickles (1998) library and Fluks et al. (1994) interstellar extinction law were used in the application of the method.

Sichevskiy, S. G.; Mironov, A. V.; Malkov, O. Yu.

2013-10-01

64

Flame resistant elastic elastomeric fiber  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

65

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

66

Flame Tests Performed Safely  

NSDL National Science Digital Library

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

Dogancay, Deborah

2005-09-01

67

Visible emission of hydrogen flames  

SciTech Connect

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

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

2009-06-15

68

"Magic Eraser" Flame Tests  

ERIC Educational Resources Information Center

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

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

2009-01-01

69

Modeling turbulent flame propagation  

SciTech Connect

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

Ashurst, W.T.

1994-08-01

70

Sounding and Sensitive Flames  

Microsoft Academic Search

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

A. S. Herschel

1874-01-01

71

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

72

Sky Survey and Photometry by the GAIA Satellite  

NASA Astrophysics Data System (ADS)

Gaia is designed as a scanning satellite to collect data for high-precision astrometry with standard errors of 10 microarcseconds of positions, parallaxes and annual proper motions for stars brighter than V = 15 mag and sub-milliarcsecond precision for all stars brighter than V = 20 mag. Multicolor photometry will be obtained for these about one billion stars. An overview of the Gaia mission with respect to multicolor photometry of stars is given. The detection of supernovae and solar system objects, and the possibility for surface photometry are discussed. An appendix on Gaia mapping and photometry contains the three sections: samples and patches, precision of aperture photometry, mapping and photometry.

Høg, E.; Fabricius, C.; Knude, J.; Makarov, V. V.

73

Improved Photometry for the DASCH Pipeline  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

74

Fuel control of a ducted bluffbody flame  

Microsoft Academic Search

In this paper, we consider the problem of controlling the flame dynamics of a ducted, premixed, bluffbody flameholder stabilized flame. The flame dynamics arise due to (complicated) interaction between the fluid dynamics and the inherent kinematical flame motion. For control oriented flame modelling, we make the simplifying assumption of ignoring the vortical component of the fluid dynamics in the problem,

Prashant G. Mehta; Marios C. Soteriou; Andrzej Banaszuk; Igor Mezic

2003-01-01

75

Candle Flames in Microgravity Video  

NASA Technical Reports Server (NTRS)

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

1997-01-01

76

Gaia photometry for white dwarfs  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

77

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

Microsoft Academic Search

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

A. P. Kelley; C. K. Law

2009-01-01

78

UBVRIJHK photometry of Dolidze 25 (Delgado+, 2010)  

NASA Astrophysics Data System (ADS)

Photometric color for 1673 stars in the direction of the young open cluster Dolidze 25. UBVRI CCD photometry, calibrated with previously published photoelectric values for some stars in the field, and the observations of standard fields. JHKs photometry, calibrated with matching to 2MASS data. The determination of cluster distance, reddening and age is carried out through comparison with ZAMS, post-MS and PMS isochrones. The reference lines used are obtained from theoretical post-MS and PMS isochrones from the Geneva and Yale groups, for metallicity Z=0.004, in agreement with the spectroscopic metallicity determination published for several cluster members. (1 data file).

Delgado, A. J.; Djupvik, A. A.; Alfaro, E. J.

2009-11-01

79

UBVJHKLM photometry of Nova Del 2013  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

80

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

81

Chemistry of flames  

SciTech Connect

Combustion scientists are primarily concerned with the fuels most often burned as energy sources (coal, petroleum products, and natural gas), with the goal of learning to burn them as efficiently, intensely, and cleanly as possible. Discovering those slight rearrangements of chemical bonds that together account for the net chemical transformation is the key to understanding how combustion proceeds. Once these reactions have been defined, the chemist can determine the rate coefficient of each reaction as a function of temperature and assemble the information into flame models. The computer programs that use these models to predict experimental results combine two sets of equations describing (1) the diffusive and reactive rates of change in concentration of all the molecules in the flame and (2) the flow of the reacting gases. Although the details of hydrocarbon-flame models are still disputed, many of their general features are clear and the basic reactions well-known; computer models for methane combustion already include over 100 elementary reactions. Experimental data on NO/sub x/ formation have led to ingenious methods for purifying postcombustion gases. Currently, the two most actively studied processes in combustion chemistry are the formation and oxidation of soot. The synthetic fuels most likely to replace fossil ones will probably contain less hydrogen, making them more prone to produce soot. How to understand and overcome this problem will be the next challenge for combustion chemists and engineers.

Gardiner, W.C. Jr.

1982-02-01

82

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

83

Flame radiation from polymer fires  

Microsoft Academic Search

Enclosure fires can be divided into two ventilation regimes: well-ventilated and under-ventilated combustion. The influence of fire ventilation on flame radiation is very important in enclosure fires especially for under-ventilated conditions. An approximate model for predicting flame radiation for both well- and under-ventilated fires is proposed on the basis of the ?-correlation, in which the role of flame sootiness and

Fenghui Jiang

1998-01-01

84

Flame Spectrometry: Atomic Fluorescence Vs. Atomic Absorption.  

National Technical Information Service (NTIS)

Atomic fluorescence flame spectrometry is compared with atomic absorption flame spectrometry with respect to: instrumentation, including the general systems, the sources of excitation, the entrance optics and monochromator, the flame cell-burner system, a...

J. D. Winefordner

1968-01-01

85

Radiation Properties of High-Temperature Flames.  

National Technical Information Service (NTIS)

A facility for generating high temperature flames at low pressures in a continuously flowing tube was constructed. Moderate-resolution flame emission spectra were collected, and we demonstrated that flames can be generated at temperatures in excess of app...

A. T. Pritt

1991-01-01

86

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

87

30 CFR 14.20 - Flame resistance.  

Code of Federal Regulations, 2010 CFR

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

2009-07-01

88

NCN detection in atmospheric flames  

SciTech Connect

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

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

2010-04-15

89

The ``turbulent flame speed'' of wrinkled premixed flames  

NASA Astrophysics Data System (ADS)

The determination of the turbulent flame speed is a central problem in combustion theory. Early studies by Damköhler and Shelkin resorted to geometrical and scaling arguments to deduce expressions for the turbulent flame speed and its dependence on turbulence intensity. A more rigorous approach was undertaken by Clavin and Williams who, based on a multi-scale asymptotic approach valid for weakly wrinkled flames, derived an expression that apart from a numerical factor recaptures the early result by Damköhler and Shelkin. The common denominator of the phenomenological and the more rigorous propositions is an increase in turbulent flame speed due solely to an increase in flame surface area. Various suggestions based on physical and/or experimental arguments have been also proposed, incorporating other functional parameters into the flame speed relation. The objective of this work is to extend the asymptotic results to a fully nonlinear regime that permits to systematically extract scaling laws for the turbulent flame speed that depend on turbulence intensity and scale, mixture composition and thermal expansion, flow conditions including effects of curvature and strain, and flame instabilities. To this end, we use a hybrid Navier-Stokes/front-capturing methodology, which consistently with the asymptotic model, treats the flame as a surface of density discontinuity separating burned and unburned gases. The present results are limited to positive Markstein length, corresponding to lean hydrocarbon-air or rich hydrogen-air mixtures, and to wrinkled flames of vanishingly small thickness, smaller that the smallest fluid scales. For simplicity we have considered here two-dimensional turbulence, which although lacks some features of real three-dimensional turbulence, is not detrimental when using the hydrodynamic model under consideration, because the turbulent flame retains its laminar structure and its interaction with turbulence is primarily advective/kinematic in nature.

Matalon, Moshe; Creta, Francesco

2012-11-01

90

Hipparcos photometry of CP stars (Adelman 1998)  

NASA Astrophysics Data System (ADS)

The Hipparcos photometry of the chemically peculiar main-sequence B, A and F stars are examined for variability. Some non-magnetic CP stars, Mercury-Manganese and metallic-line stars, which according to canonical wisdom should not be variable, may be variable and are identified for further study. Some potentially important magnetic CP stars are noted. (3 data files).

Adelman, S. J.

1998-06-01

91

HST BVI Photometry of Triton and Proteus.  

National Technical Information Service (NTIS)

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 gr...

A. D. Storrs D. Pascu E. N. Wells J. L. Hershey J. R. Rohde

2006-01-01

92

Photometry from online Digitized Sky Survey plates  

NASA Astrophysics Data System (ADS)

Online Digitized Sky Survey (DSS) material is often used to obtain information on newly discovered variable stars for older epochs (e.g. Nova progenitors, flare stars, etc.). We present here the results of an investigation of photometry on online DSS material in small fields calibrated by CCD sequences. We compared different source extraction mechanisms and found that even down near to the sensitivity limit, despite the H-compression used for the online material, photometry with an accuracy better than 0.1 mag rms is possible on DSS-II. Our investigation shows that the accuracy depends strongly on the source extraction method. The SuperCOSMOS scans, although retrieved with a higher spatial resolution, do not give us better results. The methods and parameters presented here allow the user to obtain good plate photometry in small fields down to the Schmidt plate survey limits with a few bright CCD calibrators, which may be calibrated with amateur-size telescopes. Especially for the events mentioned above, new field photometry for calibration purposes mostly exists, but the progenitors were not measured photometrically before. Also, the follow-up whether stellar concentrations are newly detected clusters or similar work may be done without using mid-size telescopes. The calibration presented here is a `local' one for small fields. We show that the method presented here gives higher accuracies than `global' calibrations of surveys (e.g. Guide Star Catalogue-II (GSC-II), SuperCOSMOS and the US Naval Observatory Astrometry Catalog B).

Bacher, A.; Kimeswenger, S.; Teutsch, P.

2005-09-01

93

Narrow Band Photometry of Selected Asteroids.  

National Technical Information Service (NTIS)

The CCD photometry of selected asteroids was carried out to check for possible cometary activity in them. To distinguish the asteroids with possible cometary activity from those of the main belt, each object of interest was observed in two filters; one ce...

R. Rajamohan S. G. Bhargavi

1992-01-01

94

Wise Observatory System of Fast CCD Photometry  

NASA Astrophysics Data System (ADS)

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

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

95

TERMS Photometry of Known Transiting Exoplanets  

Microsoft Academic Search

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

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

2011-01-01

96

Concurrent Flow Flame Spread Study.  

National Technical Information Service (NTIS)

An experimental study has been performed of the spread of flames over the surface of thick PMMA and thin filter paper sheets in a forced gaseous flow of varied oxygen concentration moving in the direction of flame spread. It is found that the rate of spre...

H. T. Loh

1992-01-01

97

Sound generation by ducted flames  

Microsoft Academic Search

The sound field established by a v-shaped flame confined in a rectangular duct is investigated both theoretically and experimentally. A theoretical model is developed to predict pressure spectra caused by the unsteady heat release from the flame. Comparisons between the theoretical and experimentally measured spectra confirm the validity of the model and are also reported. It is also found that

U. G. Hegde; D. Reuter; B. T. Zinn

1988-01-01

98

Statistics of premixed flame cells  

SciTech Connect

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

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

1991-07-15

99

Statistics of premixed flame cells  

NASA Technical Reports Server (NTRS)

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

Noever, David A.

1991-01-01

100

Not Just Another Old Flame  

NSDL National Science Digital Library

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

2007-07-03

101

Flame retarded asphalt blend composition  

SciTech Connect

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

Walters, R.B.

1987-04-21

102

Flame Resistant Foam  

NASA Technical Reports Server (NTRS)

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

1984-01-01

103

Infrared Photometry for Automated Telescopes: Passband Selection  

NASA Astrophysics Data System (ADS)

The high precision that photometry in the near and intermediate infrared region can provide has not been achieved, partly because of technical challenges (including cryogenics, which most IR detectors require), and partly because the filters in common use are not optimized to avoid water-vapor absorptions, which are the principal impediment to precise ground-based IR photometry. We review the IRWG filters that achieve this goal, and the trials that were undertaken to demonstrate their superiority. We focus especially on the near IR set and, for high elevation sites, the passbands in the N window. We also discuss the price to be paid for the improved precision, in the form of lower throughput, and why it should be paid: to achieve not only higher precision (i.e., improved signal-to-noise ratio), but also lower extinction, thus producing higher accuracy in extra-atmospheric magnitudes. The edges of the IRWG passbands are not defined by the edges of the atmospheric windows: therefore, they admit no flux from these (constantly varying) edges. The throughput cost and the lack of a large body of data already obtained in these passbands are principal reasons why the IRWG filters are not in wide use at observatories around the world that currently do IR work. Yet a measure of the signal-to-noise ratio varies inversely with both extinction and with a measure of the Forbes effect. So, the small loss of raw throughput is recouped in signal-to-noise gain. We illustrate these points with passbands of both near and intermediate IR passbands. There is also the matter of cost for small production runs of these filters; reduced costs can be realized through bulk orders with uniform filter specifications. As a consequence, the near-IR IRWG passbands offer the prospect of being able to do photometry in those passbands at both high and low elevation sites that are capable of supporting precise photometry, thereby freeing infrared photometry from the need to access exclusively high and dry elevation sites, although photometry done at those sites can also benefit from improved accuracy and transformability. We suggest that if the IRWG passbands are made available, they will be used! New automated systems making use of these passbands have the advantage of establishing the system more widely, creating a larger body of data to which future observations will be fully transformable, and will be cheaper to purchase. This work has been supported in part by grants to EFM by the Canadian Natural Sciences and Engineering Research Council.

Milone, Gene; Young, Andrew T.

2011-03-01

104

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

105

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

NASA Astrophysics Data System (ADS)

The flame base structures of laminar lifted flames are numerically investigated in order to develop a model of triple flame applicable to the flamelet model. The lifted flames formed in the downstream expanded duct developed by Kioni et al.are calculated systematically in terms of the fuel concentration gradient at the inlet using a variant of the HSMAC method, modified so as to deal with variations of density. The triple flame is formed at the flame base of lifted nonpremixed flame for every case, even the case which does not initially have partial mixing. The diffusion flame appears to be supported by the enhancement of the surrounding premixed flames, resulting in a temperature rise. All scalar quantities along the premixed flames of the triple flame decline along a similar profile in mixture fraction space, and scalar quantities in the region surrounded by the premixed flames are almost completely conserved. On the basis of the results, we developed a model of triple flame that is applicable to the flamelet model. In the model, the region without reaction upstream of the flame base is referred to as the unburned region (frozen flow structure region), followed by the transition region outside the premixed flames, in which the flame changes from the frozen structure to the fully burning diffusion structure. The region surrounded by the premixed flames is referred to as the triple flame structure region. The region following the triple flame structure region is the fully burning diffusion flame structure region.

Noda, Susumu; Yamamoto, Shuhei

106

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

107

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

108

2060 Chiron - CCD and electronographic photometry  

NASA Astrophysics Data System (ADS)

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

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

1989-02-01

109

2060 Chiron - CCD and electronographic photometry  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

110

CCD and photographic photometry of NGC 1904  

NASA Astrophysics Data System (ADS)

Combined CCD and photographic photometry of the globular cluster NGC 1904 are presented. The data reduction procedures for the CCD and digital iris photometry are presented. The cluster's C-M diagram is nearly identical in morphology to that of the nearby globular cluster M13, the only significant difference being the subgiant branch, where the NGC 1904 ridge line is flatter than in M13. If a cluster age of 16 Gyr, as suggested by theoretical models, is adopted, the turnoff and main-sequence region in the C-M diagram are fit by VandenBerg's (1983) isochrone for Y = 0.20 and Z = 0.001 for a distance modulus of 15.65 and a reddening of 0.01. If the cluster is more metal-poor, as suggested by Zinn and West (1984), then an older isochrone is required to match the observations.

Heasley, J. N.; Janes, K. A.; Christian, C. A.

1986-05-01

111

Introducing SPA, "The Stellar Photometry Assistant"  

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

112

Narrow band photometry of selected asteroids  

NASA Technical Reports Server (NTRS)

The CCD photometry of selected asteroids was carried out to check for possible cometary activity in them. To distinguish the asteroids with possible cometary activity from those of the main belt, each object of interest was observed in two filters; one centered on the C2 emission band at 5140A (90A bandpass) and the other centered on the nearby continuum at 4845A (65A bandpass). None of the observed asteroids appear to have any C2 emission.

Rajamohan, R.; Bhargavi, S. G.

1992-01-01

113

Infrared (JHK) photometry of asteroids. II  

NASA Technical Reports Server (NTRS)

JHK (1.2, 1.6, and 2.2 micron) photometry for 38 asteroids of various spectral classifications is reported. M asteroids tend to have infrared colors intermediate between the color domains of E and P asteroids. A few D asteroids have redder J - H colors than most C asteroids. The unusually red J - H color of 246 Asporina indicates it is a member of the A class.

Veeder, G. J.; Matson, D. L.; Hoover, G.; Kowal, C.

1983-01-01

114

Recalibrating SFD Using SDSS Spectroscopy And Photometry  

NASA Astrophysics Data System (ADS)

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

Schlafly, Eddie; Finkbeiner, D. P.

2011-05-01

115

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

116

Intraluminal flame spread in tracheal tubes.  

PubMed

Intraluminal combustion in polyvinyl chloride tracheal tubes was investigated. Two flame types were observed: intraluminal and downstream. The flame-spread velocity, burning rate, and equivalence ratio of the intraluminal flame were determined. The products of the intraluminal flame were analyzed, revealing compounds capable of further combustion. Below a certain oxidant flow rate, the tubes do not ignite. At low flow rates that support a flame, the burning rate is minimal and the equivalence ratio reveals no fuel available for the downstream flame, suggesting that ignition of tracheal tubes is least likely in the absence of intraluminal flow. We conclude that the downstream flame is the flame type that is most dangerous and that the intraluminal flame is the generator of fuel and ignition energy for the downstream flame. PMID:8022252

Wolf, G L; Sidebotham, G W; Stern, J B

1994-07-01

117

A kinematic model of a ducted flame  

Microsoft Academic Search

A premixed ducted flame, burning in the wake of a bluff-body flame-holder, is considered. For such a flame, interaction between acoustic waves and unsteady combustion can lead to self-excited oscillations. The concept of a time-invariant turbulent flame speed is used to develop a kinematic model of the response of the flame to flow disturbances. Variations in the oncoming flow velocity

A. P. Dowling

1999-01-01

118

Optogalvanic laser spectroscopy of flames  

SciTech Connect

The authors describe a technique for the laser spectroscopy of metal vapors which involves the evaporation, combustion, and ionization of a metal salt in a flame placed within the resonator of a dye laser spectrometer. The technique is based on the premise that at the moment that a laser pulse passes through the flame, the concentration of ions and electrons between the two electrodes placed in the flame changes, resulting in a current pulse in the measuring circuit. The technique is both mathematically and experimentally verified by testing for the detection limits of lithium, europium, and samarium.

Udartsev, A.M.; Kim, V.G.; Iordanidi, G.K.; Mashakova, S.M.; Ksandopulo, G.I.

1987-07-01

119

Flame combustion of carbonaceous fuels  

SciTech Connect

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

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

1984-05-08

120

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

121

Flame-flow structure in an acoustically driven jet flame  

Microsoft Academic Search

An investigation is presented of the interaction between the flowfield and the chemical reaction for non-premixed combustion in a flowfield dominated by large-scale vortical structures has been undertaken. The desired information on the flame-flow structure can be obtained from time-resolved field measurements of velocity and conserved and reactive scalars in a time-dependent laminar non-premixed hydrocarbon-air flame created by acoustic excitation

U. Vandsburger; G. Lewis; J. M. Seitzman; M. G. Allen; C. T. Bowman; R. K. Hanson

1986-01-01

122

Flame spraying of polymers  

SciTech Connect

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

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

1997-08-01

123

Radiation Measurements on Magnesium Flames.  

National Technical Information Service (NTIS)

The radiation of a diffusely radiating Mg0 flame is characterized by four parameters, which are initially unknown: temperature, optical thickness, and dispersion (wavelength dependence) of the absorption and scattering coefficients. The black body tempera...

F. Roessler

1968-01-01

124

Flame Retardant Organic Fibrous Materials.  

National Technical Information Service (NTIS)

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

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

1973-01-01

125

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...

126

Extracting Photometry Measurements from VizieR Catalogs  

NASA Astrophysics Data System (ADS)

Photometry measurements in astronomical catalogs cover a wide range of spectral bandpasses with many different photometric systems and units. The VizieR Catalog service has recently extended the standardized description of catalogs to include photometry . This includes the observed frequency and bandwidth in GHz and conversion of magnitudes and other units to flux densities in Jy. We present various prototype interfaces for extracting and combining photometry across multiple catalogs and discuss the uses and limitations of this service.

Allen, M. G.; Ochsenbein, F.; Derriere, S.; Boch, T.; Fernique, P.; Landais, G.

2014-05-01

127

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

128

Unreleased Energy in Flame Gases  

Microsoft Academic Search

WE recently reported1 the results of temperature measurements made by means of very fine quartz-coated platinum wires in the flame gases resulting from the combustion of hydrocarbon-air mixtures in a specially constructed burner. From these measurements estimates were made of the proportion of the heat of combustion which was unreleased in the flame gases for the purpose of increasing their

W. T. David; J. Mann

1944-01-01

129

Flame spread across liquid pools  

NASA Technical Reports Server (NTRS)

For flame spread over liquid fuel pools, the existing literature suggests three gravitational influences: (1) liquid phase buoyant convection, delaying ignition and assisting flame spread; (2) hydrostatic pressure variation, due to variation in the liquid pool height caused by thermocapillary-induced convection; and (3) gas-phase buoyant convection in the opposite direction to the liquid phase motion. No current model accounts for all three influences. In fact, prior to this work, there was no ability to determine whether ignition delay times and flame spread rates would be greater or lesser in low gravity. Flame spread over liquid fuel pools is most commonly characterized by the relationship of the initial pool temperature to the fuel's idealized flash point temperature, with four or five separate characteristic regimes having been identified. In the uniform spread regime, control has been attributed to: (1) gas-phase conduction and radiation; (2) gas-phase conduction only; (3) gas-phase convection and liquid conduction, and most recently (4) liquid convection ahead of the flame. Suggestions were made that the liquid convection was owed to both vuoyancy and thermocapillarity. Of special interest to this work is the determination of whether, and under what conditions, pulsating spread can and will occur in microgravity in the absence of buoyant flows in both phases. The approach we have taken to resolving the importance of buoyancy for these flames is: (1) normal gravity experiments and advanced diagnostics; (2) microgravity experiments; and (3) numerical modelling at arbitrary gravitational level.

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

1993-01-01

130

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

131

Experimental study of flame driving function in an acoustically excited duct with anchored flames  

NASA Astrophysics Data System (ADS)

This research experimentally investigates the flame driving function in an acoustically excited vertical duct with a laminar, premixed flame anchored on a grid. The flame driving function is determined from the measured acoustic intensity upstream and downstream of the flame zone, which relates both the acoustic velocities and pressures on either side of the flame zone. Results of this research reveal that the location of the flame zone on the acoustic field plays the main role in determining the sign and magnitude of the flame driving function. The flame equivalence ratio plays a role only in the magnitude of the flame driving function. This study also shows that the characteristics of the flame driving function can be qualitatively predicted by knowing the imaginary part of nonreactive acoustic admittance at the flame location.

Chen, Tzeng-Yuan; Chen, Chien-Pang

132

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

National Technical Information Service (NTIS)

Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion fl...

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

2000-01-01

133

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

Microsoft Academic Search

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

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

1990-01-01

134

BVRI photometry of HR 1105 (Adelman 1998)  

NASA Astrophysics Data System (ADS)

BVRI photometry of the extrinsic S star HR 1105 shows a stable periodic light variability with a period of 24.76 days superimposed upon long term changes presumably related to the orbital period. The variations are in phase for all four magnitudes with the amplitude of this variability being about the same for B and V, but smaller for R and even smaller for I. As the primary is a M3 III star, these brightness changes are mostly likely due to the pulsation of the primary star. (1 data file).

Adelman, S. J.

1998-02-01

135

uvby photometry in NGC 7419 (Marco+, 2013)  

NASA Astrophysics Data System (ADS)

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

Marco, A.; Negueruela, I.

2013-02-01

136

Differential photometry of FK Com (Korhonen+, 2007)  

NASA Astrophysics Data System (ADS)

In the present work we publish new photometric observations of the very active single giant, FK Com for the time period between the 1st of January 2002 and the 8th of July 2004. The observations have been carried out with three different automatic photometric telescopes: Phoenix 10, Wolfgang and Amadeus, all located in Arizona, USA. Observations contain measurements at the following bands: Johnson U, B and V, Cousins I and Stroemgren b and y. The observations are differential photometry in respect to the primary comparison star HD 117567. (3 data files).

Korhonen, H.; Berdyugina, S. V.; Hackman, T.; Ilyin, I. V.; Strassmeier, K. G.; Tuominen, I.

2007-10-01

137

Photometry of six radar target asteroids  

NASA Technical Reports Server (NTRS)

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

Wisniewski, W. Z.

1987-01-01

138

Effects of buoyancy on premixed flame stabilization  

SciTech Connect

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

Bedat, B.; Cheng, R.K.

1995-10-01

139

SPHOTOM - Package for an Automatic Multicolour Photometry  

NASA Astrophysics Data System (ADS)

We present basic information about package SPHOTOM for an automatic multicolour photometry. This package is in development for the creation of a photometric pipe-line, which we plan to use in the near future with our new instruments. It could operate in two independent modes, (i) GUI mode, in which the user can select images and control functions of package through interface and (ii) command line mode, in which all processes are controlled using a main parameter file. SPHOTOM is developed as a universal package for Linux based systems with easy implementation for different observatories. The photometric part of the package is based on the Sextractor code, which allows us to detect all objects on the images and perform their photometry with different apertures. We can also perform astrometric solutions for all images for a correct cross-identification of the stars on the images. The result is a catalogue of all objects with their instrumental photometric measurements which are consequently used for a differential magnitudes calculations with one or more comparison stars, transformations to an international system, and determinations of colour indices.

Parimucha, Š.; Va?ko, M.; Mikloš, P.

2012-04-01

140

IC 4651 uvby photometry (Meibom, 2000)  

NASA Astrophysics Data System (ADS)

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 contains information about the Date, Night, Filter, Exposure time, Airmass, CCD rotation angle, and RA- , DE-offsets for all 89 frames. Table 2 gives cross-references between the MEI-system (this paper) and the Lindoff (1972A&AS....7..231L, IC 4651 NNN), Eggen (1971ApJ...166...87E, Cl* IC 4651 Egg NN), Anthony-Twarog & Twarog (1987AJ.....94.1222A, Cl* IC 4651 AT 1-NNN, Cl* IC 4651 AT 2-NN), and Anthony-Twarog et al. (1988AJ.....95.1453A, Cl* IC 4651 AMC I-NNN, Cl* IC 4651 AMC NNNN) identification numbers. Table 3 is the final catalogue of the new Stroemgren uvby photometry, ordered by MEI identification number. For each star, it gives the MEI number, Global CCD x- and y-coordinates, J2000 coordinates , the new y, b, v, and u magnitudes on the standard system, number of detections of the individual stars, and their mean errors. (3 data files).

Meibom, S.

2000-08-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

142

CCD Flatfielding for Strömvil Photometry in M 67  

Microsoft Academic Search

How obtain in the Strömvil system CCD photometry of one percent quality needed for subsequent stellar classification in temperature, surface gravity, reddening and metallicity? At the Vatican 1.8-meter telescope on Mt. Graham we always observe M 67 as a standard field. Laugalys et al. (Baltic Astronomy, 13, 1, 2004) demonstrate the quality of their CCD photometry in M 67 as

R. P. Boyle; R. Janusz; A. G. D. Philip; V. Laugalys; A. Kazlauskas

2005-01-01

143

DOPHOT, a CCD photometry program: Description and tests  

Microsoft Academic Search

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

Paul L. Schechter; Mario Mateo; Abhijit Saha

1993-01-01

144

UBVRI photometry of southern T Tauri stars (Batalha+ 1998)  

NASA Astrophysics Data System (ADS)

We present full tables of the photoelectric photometry of T Tauri Stars observed in the 0.5m telescope at Laboratorio Nacional de Astronomia (Brazil). The photometry was performed with the instrument FOTRAP (Jablonski et al., 1994PASP..106.1172J, see text). For a description of the UBVRI photometric system, see e.g. (2 data files).

Batalha, C. C.; Quast, G. R.; Torres, C. A. O.; Pereira, P. C. R.; Terra, M. A. O.; Jablonski, F.; Schiavon, R. P.; Sartori, M. J.

1997-11-01

145

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

Microsoft Academic Search

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

M. Thuillard

2002-01-01

146

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

Microsoft Academic Search

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

Susumu Noda; Shuhei Yamamoto

2006-01-01

147

A visual study on flame behavior in tone-excited non-premixed jet flames  

Microsoft Academic Search

A visualization study on the effect of forcing amplitude in tone-excited jet diffusion flames has been conducted. Visualization techniques are employed using optical schemes, which are a light scattering photography. Flame stability curve is attained according to Reynolds number and forcing amplitude at a fuel tube resonant frequency. Flame behavior is globally grouped into two from attached flame to blown-out

Kee Man Lee; Tae Kwon Kim; Won Jin Kim; Seung Gon Kim; Jeong Park; Sang In Keel

2002-01-01

148

Interaction Between Flames and Electric Fields Studied.  

National Technical Information Service (NTIS)

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 io...

Z. G. Yuan U. Hegde

2003-01-01

149

Transitional Gas Jet Diffusion Flames in Microgravity.  

National Technical Information Service (NTIS)

Drop tower experiments were performed to identify buoyancy effects in transitional hydrogen gas jet diffusion flames. Quantitative rainbow schlieren deflectometry was utilized to optically visualize the flame and to measure oxygen concentration in the lam...

A. K. Agrawal K. Alammar S. R. Gollahalli

2000-01-01

150

A kinematic model of a ducted flame  

NASA Astrophysics Data System (ADS)

A premixed ducted flame, burning in the wake of a bluff-body flame-holder, is considered. For such a flame, interaction between acoustic waves and unsteady combustion can lead to self-excited oscillations. The concept of a time-invariant turbulent flame speed is used to develop a kinematic model of the response of the flame to flow disturbances. Variations in the oncoming flow velocity at the flame-holder drive perturbations in the flame initiation surface and hence in the instantaneous rate of heat release. For linear fluctuations, the transfer function between heat release and velocity can be determined analytically from the model and is in good agreement with experiment across a wide frequency range. For nonlinear fluctuations, the model reproduces the flame surface distortions seen in schlieren films.

Dowling, A. P.

1999-09-01

151

Studies in Flame Propagation and Blowout.  

National Technical Information Service (NTIS)

This report outlines our most recent research work on the topic of upstream flame propagation and blowout in hydrocarbon jet flames. Outlined specifically are the recent elements of the research for the study of fundamental structural characteristics of j...

K. M. Lyons

2006-01-01

152

Flame Resistant Insulation Materials, Composition and Method.  

National Technical Information Service (NTIS)

This patent application concerns flame retardancy of loosefill insulation materials, especially cellulosic insulation materials. More particularly, the invention relates to flame resistant insulation materials, methods of treating insulation materials to ...

R. J. McCarter

1980-01-01

153

Flame-Sprayed Polymeric Protective Coatings.  

National Technical Information Service (NTIS)

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

R. J. Janowieck M. C. Willson

1966-01-01

154

Flame Propagation under Partially-Premixed Conditions.  

National Technical Information Service (NTIS)

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

G. R. Ruetsch

1994-01-01

155

Interface Scheme for Turbulent Flame Propagation.  

National Technical Information Service (NTIS)

Turbulent flame propagation in a premixed combustible gas is studied by replacing the flame structure with an idealized reaction front of zero thickness. The flow is computed with an algorithm designed to track an interface between two fluids. The interfa...

P. K. Barr W. T. Ashurst

1984-01-01

156

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

157

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

158

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

159

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

160

Lifted Partially Premixed Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

161

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

162

Sound generation by ducted flames  

SciTech Connect

The sound field established by a v-shaped flame confined in a rectangular duct is investigated both theoretically and experimentally. A theoretical model is developed to predict pressure spectra caused by the unsteady heat release from the flame. Comparisons between the theoretical and experimentally measured spectra confirm the validity of the model and are also reported. It is also found that changes in the flowfield in the flame zone can significantly modify combustion rates. These modifications, in turn, affect the generated sound field and are important in determining the pressure levels in the duct. The results of this investigation are applicable to combustion noise and instability studies in a variety of burner and propulsion system configurations. 15 references.

Hegde, U.G.; Reuter, D.; Zinn, B.T.

1988-05-01

163

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

NASA Technical Reports Server (NTRS)

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

Buchanan, Thomas; Wang, Hai

2005-01-01

164

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

165

Burner Stabilities of Jet Diffusion Flames.  

National Technical Information Service (NTIS)

The near field lift-off phenomena associated with jet diffusion flames were investigated. Lift-off is defined as the instant when the luminous flame zone detaches from the burner exit, stabilizing itself downstream. The lift-off of the jet diffusion flame...

J. P. Seaba

1990-01-01

166

Flame Propagation Along a Fine Vortex Tube  

Microsoft Academic Search

Interaction between a premixed flame and a fine vortex tube perpendicular to the flame is simulated numerically in order to study the effects of the rotating velocity and tube diameter on flame propagation along the vortex tube. The vortex tube has an initial circumferential velocity ranging from 1.8 to 36 times the laminar burning velocity and an initial core diameter

T. HASEGAWA; K. NISHIKADO; J. CHOMIAK

1995-01-01

167

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

168

Combustion dynamics of an acoustically forced flame  

Microsoft Academic Search

A technique has been devised that can provide information about the local dynamic response of a flame to an acoustic field. In the experiments, a flame in an acoustic chamber is subjected to pressure oscillations by a pair of low-frequency drivers. The response of the flame is visualized by planar laser-induced fluorescence of the hydroxyl radical, which is used as

W. Pun; S. L. Palm; F. E. C. Culick

2003-01-01

169

Dynamics of flame\\/vortex interactions  

Microsoft Academic Search

Vortex interactions with flames play a key role in many practical combustion applications. Such interactions drive a large class of combustion instabilities, they control to a great extent the structure of turbulent flames and the corresponding rates of reaction, they occur under transient operations or when flames travel in ducts containing obstacles. Vortices of various types are often used to

P.-H. Renard; D. Thévenin; J. C. Rolon; S. Candel

2000-01-01

170

Experimental study of flame driving function in an acoustically excited duct with anchored flames  

Microsoft Academic Search

This research experimentally investigates the flame driving function in an acoustically excited vertical duct with a laminar,\\u000a premixed flame anchored on a grid. The flame driving function is determined from the measured acoustic intensity upstream\\u000a and downstream of the flame zone, which relates both the acoustic velocities and pressures on either side of the flame zone.\\u000a Results of this research

Tzeng-Yuan Chen; Chien-Pang Chen

2001-01-01

171

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

172

CCD photometry of Abell clusters. II - Surface photometry of 249 cluster galaxies  

NASA Technical Reports Server (NTRS)

The luminosity of the brightest cluster galaxies remains the best standard candle for observational cosmology. Studies of over 250 relatively nearby clusters show that the luminosity of these objects within an aperture of constant metric diameter has a dispersion of only 0.35 mag. The observations considered by Schneider et al. (1983) were acquired to measure the aperture luminosities of the brightest cluster galaxies. However, the data base, because of its high signal-to-noise ratio and large spatial coverage, allows several other investigations to be performed. In the present investigation, surface photometry of the brightness three galaxies within approximately 250 kpc of the cluster center is presented, taking into account the cores of 83 Abell clusters. The relevance of the photometry to cosmological studies is also discussed. It is found that dynamical friction does play an extremely important role in determining properties of brightest cluster galaxies and cluster morphology.

Schneider, D. P.; Hoessel, J. G.; Schneider, D. P.

1983-01-01

173

Perchloric Acid Flames. Part VII. Mixed Fuel-Rich Flames.  

National Technical Information Service (NTIS)

Fuel-rich perchloric acid flames containing binary mixtures of hydrocarbons (methane-ethane, methane-ethylene and ethane-ethylene) as fuels were studied by sampling the burnt gas products for a range of mixtures of each pair of fuels. It was shown that th...

G. S. Pearson

1967-01-01

174

Photometry of small asteroids and cometary cores  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

175

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

176

UBVIc photometry of NGC 4852 (Carraro+, 2005)  

NASA Astrophysics Data System (ADS)

We present wide-field deep UBVIc photometry for the previously unstudied open cluster NGC 4852 down to a limiting magnitude Ic~24, obtained from observations taken with the Wide Field Imager camera on-board the MPG/ESO 2.2m telescope at La Silla (ESO, Chile), in the photometric night of July 7, 2002. These data are used to obtain the first estimate of the cluster basic parameters, to study the cluster spatial extension by means of star counts, and to derive the Luminosity (LF) and Mass Functions (MF). The cluster radius turns out to be 5.0+/-1.0arcmin. The cluster emerges clearly from the field down to V=20mag. At fainter magnitudes, it is completely confused with the general Galactic disk field. The stars inside this region define a young open cluster (200 million years old) 1.1kpc far from the Sun (m-M=11.60, E(B-V)=0.45). The Present Day Mass Functions (PDMF) from the V photometry is one of the most extended in mass obtained to date, and can be represented as a power-law with a slope alpha=2.3+/-0.3 and (the Salpeter MF in this notation has a slope alpha=2.35), in the mass range 3.2<=m/m?<=0.6. Below this mass, the MF cannot be considered as representative of the cluster MF, as the cluster merges with the field and therefore the MF is the result of the combined effect of strong irregularities in the stellar background and interaction of the cluster with the dense Galactic field. The cluster total mass at the limiting magnitude results to be 2570+/-210M?. (1 data file).

Carraro, G.; Baume, G.; Piotto, G.; Mendez, R. A.; Schrnidtobreik, L.

2005-03-01

177

Forced Flow Flame-Spreading Test (FFFT)  

NASA Technical Reports Server (NTRS)

The Forced Flow Flame-Spreading Test was designed to study flame spreading over solid fuels when air is flowing at a low speed in the same direction as the flame spread. Previous research has shown that in low-speed concurrent airflows, some materials are more flammable in microgravity than earth. This image shows a 10-cm flame in microgravity that burns almost entirely blue on both sides of a thin sheet of paper. The glowing thermocouple in the lower half of the flame provides temperature measurements.

1997-01-01

178

KSC Launch Pad Flame Trench Environment Assessment  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

179

Pulsed Turbulent Diffusion Flames in a Coflow  

NASA Astrophysics Data System (ADS)

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

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

2000-11-01

180

Imaging Invisible Flames Without Additives  

NASA Technical Reports Server (NTRS)

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

Weiland, Karen J.

1996-01-01

181

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

182

Instability of buoyant diffusion flames  

NASA Astrophysics Data System (ADS)

Buoyant jet diffusion flames are known to exhibit large scale vortical flow structures strongly interacting with flame structures. In the present work, the formation and evolution of coherent flow structures is studied in a methane/ air coflow arrangement. This is accomplished by utilizing visualization techniques (planar laser induced hydroxyl fluorescence and Mie-scattering) and Laser Doppler Velocimetry. A striking repeatability and correlation of evolving coherent structures of the air co-flow and the reaction zone is observed. In the transitional region, flow and flame structures oscillate at very pure frequencies ranging from 10 15 Hz. A local absolutely unstable velocity profile close to the burner rim seems to be responsible. Self-excited axisymmetric wavelike structures propagate up- and downstream of this location. We study the influence of the exit velocities and the type of coflowing oxidizer (air or oxygen) on the location of transition to periodic flow structures and related frequencies. Conditional averages of image and velocity data are employed to describe the evolution of coherent flow structures and their interaction with flame structures.

Lingens, A.; Reeker, M.; Schreiber, M.

1996-02-01

183

Radiation from jet combustor flames  

Microsoft Academic Search

Radiant energy from aircraft gas turbine type combustion processes was investigated using a laboratory scale combustor in which two paraffinic and two aromatic test fuels were burned at combustor pressures from one to fifteen atmospheres. Infrared flame emission and absorption spectra from 0.5 to 15 microns in wavelength were obtained. The average transverse emissivity of the infrared spectral region ranged

R. M. Schirmer; E. C. Miller

1958-01-01

184

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

185

Fuel Burner with Flame Holder.  

National Technical Information Service (NTIS)

The bi-propellant combustion chamber is cone-shaped and has a central oxidizer and surrounding fuel injection elements in its small end and a combustion discharge tube in its larger end. There is a conical flame holder baffle in the smaller end for mainta...

A. B. Vanoni

1965-01-01

186

Flex-flame burner and combustion method  

DOEpatents

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

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

2010-08-24

187

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

SciTech Connect

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

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

2004-03-01

188

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

NASA Astrophysics Data System (ADS)

The nonlinear equation for curved stationary flames of realistic expansion coefficients is solved numerically for the problem of flame propagation in cylindrical tubes. Two different configurations of a flame front corresponding to convex and concave flames are obtained. The convex and concave flames propagate with different velocities that depend on the tube radius and on the expansion coefficient of the burning matter. For tubes of a moderate radius the velocity amplification for convex flames exceeds the respective velocity amplification of two-dimensional flames almost twice. For tubes of a large radius unlimited increase of the curved flame velocity with increase of the tube width takes place. The obtained theoretical results are in good quantitative agreement with the results of numerical experiments on flame dynamics in cylindrical tubes.

Bychkov, Vitaliy; Kleev, Andrey

1999-07-01

189

Automated surface photometry for the Coma Cluster galaxies: The catalog  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

190

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

191

Long-term photometry of Variables IV (Sterken+, 1995)  

NASA Astrophysics Data System (ADS)

This is the fourth catalogue of photometric data in the Stroemgren system obtained during the period June 18, 1992 - August 23, 1994 in the framework of the Long-Term Photometry of Variables (LTPV) program at the European Southern Observatory. Since our goal is not absolute (all-sky) photometry, the observations should be used for differential photometry only. The mean values of the r.m.s. deviations of the differential measurements of comparison stars are around (from Table 3 of paper) ------------------------------ y b-y m1 c1 ------------------------------ 0.005 0.002 0.004 0.007 ------------------------------ (2 data files).

Sterken, C.; Manfroid, J.; Beele, D.; de Koff, S.; Eggenkamp, I. M. M. G.; Goecking, K.; Jorissen, A.; Kaufer, A.; Kuss, C.; Schoenmakers, A. P.; Still, J. M.; van Loon, J.; Vink, J.; Vrielmann, S.; Waelde, E.

1996-10-01

192

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

193

Radiant extinction of gaseous diffusion flames  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

194

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

SciTech Connect

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

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

2004-03-01

195

CCD Photometry of Seven Asteroids at the Belgrade Astronomical Observatory  

NASA Astrophysics Data System (ADS)

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

Benishek, Vladimir

2008-03-01

196

CCD-Photometry of Comets at Large Heliocentric Distances.  

National Technical Information Service (NTIS)

CCD imaging and time series photometry are used to determine the state of activity, nuclear properties and eventually the rotational motion of cometary nuclei. Cometary activity at large heliocentric distances and mantle evolution are not yet fully unders...

B. E. A. Mueller

1992-01-01

197

Nanoparticle synthesis in low pressure flames  

NASA Astrophysics Data System (ADS)

The results of an experimental and computational study of nanoparticle synthesis in low pressure flames are presented. In a stagnation point flow configuration, hydrogen/oxygen low pressure flat flames were supplied with metalorganic vapor precursors and the flame conditions were identified for nanoparticle formation and growth, followed by deposition on a cooled substrate. The effects of pressure, burner to substrate distance, stoichiometry and flowrate on the particle size, morphology and phase were examined. Titania, alumina and zirconia non-agglomerated nanopowders were synthesized and analyzed using X-ray diffraction, BET gas absorption and TEM. A flame model with complex chemistry is used for the prediction of the temperature and flow fields. Thermophoretic effects upon the particle dynamics are estimated and the time/temperature profiles for several flames are predicted. A collision/coalescence mechanism growth model based on the predicted time/temperature is employed for computation of the deposited particle size. Laser induced fluorescence is used for determination of temperature and monoxide concentration profiles in the flame. Temperature measurements using two line fluorescence thermometry in an nitric oxide seeded flame indicate that the flame model predicts temperatures to within 200 K for simple flames. The temperatures of the precursor fed flames exceed the simple flame temperatures by as much as 600 K, showing that precursor decomposition/pyrolysls highly affects the thermochemistry of the flame. Radical concentration measurements in flames synthesizing titania, alumina and zirconia indicate that try monitoring the respective metal monoxides, the location of precursor decomposition and monomer formation in the flame can be inferred. A parametric study of the zirconia synthesis flame showed a certain degree of control on the particle size, agglomeration and crystallinity. Flames hotter than 1700 K and with high quenching rates produced a mixture of monoclinic and cubic zirconia, whereas moderate temperature flames (1400--1700 K) combined with lower quenching rates favored cubic zirconia synthesis. Cubic phase zirconia nanopowder was produced for the first time, demonstrating that lour pressure flames have the potential for developing new materials.

Colibaba-Evulet, Andrei

198

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

199

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

200

L' AND M' Photometry Of Ultracool Dwarfs  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

201

Experimental investigation of local displacement speeds of wrinkled unsteady flames  

Microsoft Academic Search

Local flame displacement speeds were measured along the flame front of laminar unsteady premixed flames wrinkled by laminar toroidal vortices. The displacement speed is argued to be the most important and sensitive parameter that must be simulated correctly in numerical simulation of turbulent flames. An axisymetric flame wrinkle is created in order to measure all components of the normal velocity

Jose Oscar Sinibaldi

1999-01-01

202

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

203

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

204

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

205

FIXING THE U-BAND PHOTOMETRY OF TYPE Ia SUPERNOVAE  

SciTech Connect

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

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

2013-01-01

206

Optical R band photometry of selected HBLs  

NASA Astrophysics Data System (ADS)

This paper presents the highlights of optical R band photometry of high-energy selected BL Lacertae objects performed at 70 cm meniscus type telescope of Abastumani Astrophysical Observatory, Georgia. Most of the targets exhibit long-term variability with 1-5 yr timescales and overall brightness variations with up to 2.4 stellar magnitudes. 1ES 0229+200 do not show clear long-term variability despite the removal the host galaxy contribution but some short-term bursts. The later are found at all brightness states of the targets, giving rise to an idea that the variety of hypothetic mechanisms should be responsible for such variations but the interactions between shock waves and jet inhomogeneities. No periodical variations are found. 1ES 1028+511 changes nearly periodically but there are no enough data points in order to consider this result as a credible one. Two-peak maxima in the historical light curves, indicating the existence of reverse shock waves along with the forward ones, are detected for several sources. The fact that no intra-night variations are found for the sample, is in agreement with the conclusions of some authors that high energy selected BL Lacs are intrinsically less variable than low-energy selected ones. The targets show intra-day changes being mainly in association with short-term bursts.

Kapanadze, B.

207

BVRI Photometry of 53 Unusual Asteroids  

NASA Astrophysics Data System (ADS)

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

Ye, Q.-z.

2011-02-01

208

BV photometry of quadrupole system ET Bootis  

NASA Astrophysics Data System (ADS)

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

Özdarcan, O.; Evren, S.

2012-10-01

209

Surface photometry of comet P/Encke  

NASA Astrophysics Data System (ADS)

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

Djorgovski, S.; Spinrad, H.

1985-05-01

210

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

211

Superoutburst Photometry of AL Comae Berenices  

NASA Astrophysics Data System (ADS)

Photometric observations obtained during the 1995 April - May superoutburst of the dwarf nova AL Comae Berenices are presented. This star shows rare, large-amplitude outbursts, the last definitely seen in 1975. During the 1995 outburst, as with that of 1961, there was a sharp, two-magnitude temporary minimum in the outburst light curve at about 28 days after maximum tight. We offer an explanation for such temporary minima involving the migration of a cooling wave within the accretion disk. V and I band CCD time-series photometry taken throughout the two-month-tong event, reveal a complex period structure with two dominant periods, one near 82 min and one near 41 min. Early in the outburst, photometric modulations of 81 and 86 min were seen and are likely to be related to superorbital modulations seen in other large outburst amplitude dwarf novae. Superhumps developed after ˜10 days and show a quasi-stable, nonphase coherent period of 82.5 min. A low-amplitude 41 min period was present throughout, also appearing not to be phase coherent. We conclude that the two dominant periods seen are of related origin and we list several possible mechanisms for their cause. Previous quiescence observations of AL Com have shown periods near 87 and 41 min.

Howell, Steve B.; De Young, James; Mattei, Janet A.; Foster, Grant; Szkody, Paula; Cannizzo, John K.; Walker, Gary; Fierce, Erik

1996-06-01

212

Measurement of laminar flame speeds and flame stability analysis of tert-butanol–air mixtures at elevated pressures  

Microsoft Academic Search

Laminar flame speeds and Markstein lengths of tert-butanol–air premixed mixtures were measured over a wide range of equivalence ratios at different initial temperatures and pressures by using the spherically propagating flame in a constant volume combustion chamber. Effects of Markstein number, flame thickness and density ratio at two sides of flame front on flame instability were analyzed combined with the

Xiaolei Gu; Qianqian Li; Zuohua Huang; Ni Zhang

2011-01-01

213

FLIC (FLame with Implicit Convection)-A Detailed, Two-Dimensional Flame Model.  

National Technical Information Service (NTIS)

The report describes the new computer code FLame with Implicit Convection (FLIC), a two-dimensional time-dependent program developed specifically to compute and study the behavior of flames and other subsonic chemically reactive flows. In order to describ...

E. Oran G. Patnaik K. Kailasanath K. J. Laskey T. Burn

1989-01-01

214

Transitional Gas Jet Diffusion Flames in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

215

The VLT FLAMES Tarantula Survey  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

216

Determination of particle temperatures in a silica-generating counterflow flame via flame emission measurements  

Microsoft Academic Search

We propose a simple technique to measure particle temperatures in a particle generating counterflow flame. The silica particle temperature was derived from flame light emission measurements. This technique allows the non-intrusive measurement of particle temperatures over 2000K. In addition, the OH concentration distribution in the hydrogen–oxygen flame was estimated from flame emission spectra in the ultraviolet region. A numerical model

Jeonghoon Lee; Jason Olfert; Igor S. Altman; Mansoo Choi

2010-01-01

217

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

SciTech Connect

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

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

2010-11-15

218

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

219

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

220

Transient response of premixed methane flames  

SciTech Connect

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

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

2006-08-15

221

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

222

Emission characteristics of hydrogen-oxygen flames  

NASA Astrophysics Data System (ADS)

The emission spectra of hydrogen-oxygen flames are discussed. High temperature measurements of the radiative characteristics of the OH group in flames are described. The spectral absorption coefficients and the integral intensities of the hydroxyl bands are analyzed. A method for determining the nonequilibrium radiative cooling of hydrogen-oxygen flames using experimental data, their temperatures, and nonequilibrium coefficients is described and the results are examined.

Moskalenko, N. I.; Zaripov, A. V.; Loktev, N. F.; Ilyin, Y. A.

2010-07-01

223

Effect of turbulence on flame radiative emission  

Microsoft Academic Search

A collection of radiative emissions by several flames is analyzed. Such flames have been obtained in a number of burners,\\u000a either premixed or not, fed with different fuels, while radiative emission is collected by means of a photo-diode, whose sampled\\u000a signal is able to carry a large quantity of information about chemistry of flames and its interaction with turbulence. All

E. Giacomazzi; G. Troiani; E. Giulietti; R. Bruschi

2008-01-01

224

Computational and experimental study of laminar flames  

SciTech Connect

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

Smooke, M.; Long, M.

1991-01-01

225

Flow/Soot-Formation Interactions in Nonbuoyant Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

226

The Coherent Flame Model for Turbulent Chemical Reactions.  

National Technical Information Service (NTIS)

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

F. E. Marble J. E. Broadwell

1977-01-01

227

Extinction Characteristics of Cup-Burner Flame in Microgravity.  

National Technical Information Service (NTIS)

Carbon dioxide extinguishes flames through dilution process. The extinction characteristics of CO2 were previously studied using a cup-burner flame under normal-gravity conditions. As the diffusion flames behave differently in microgravity compared to tho...

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

2003-01-01

228

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

Microsoft Academic Search

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

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

2011-01-01

229

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

Microsoft Academic Search

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

J.-M. Samaniego; T. Mantel

1999-01-01

230

Flame Hysteresis Effects in Methane Jet Flames in Air-Coflow  

Microsoft Academic Search

Typically, a jet flame that is lifted off of the burner and stabilized at some downstream location corresponds to a pair of fuel and co-flow velocities that is unique to a flame at that position. However, there exists a hysteretic region near the nozzle in which a jet flame can be attached or lifted given the same conditions. In either

Nancy Moore; Kevin Lyons

231

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

Microsoft Academic Search

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

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

2004-01-01

232

Rich methane premixed laminar flames doped with light unsaturated hydrocarbons  

Microsoft Academic Search

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

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

2006-01-01

233

Rich methane premixed laminar flames doped with light unsaturated hydrocarbons  

Microsoft Academic Search

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

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

2006-01-01

234

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

235

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

NASA Astrophysics Data System (ADS)

This experimental study is performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition (u'/SL0=1.4), in order to clarify basically the influence of the addition of hydrogen to lean and rich methane or propane mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen ?H are prepared. A two-dimensional sequential laser tomography technique is used to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. Some of the key parameters of local flame properties quantitatively measured are the local flame displacement velocity SF, curvature and stretch of turbulent flames. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the trends of the mean values of measured SF with respect to ?H, the total equivalence ratio ? and fuel types corresponded well its turbulent burning velocity. The trend of the obtained Ma could explain the SF of turbulent flames only qualitatively. The local burning velocity at the part of turbulent flames with positive stretch and curvature using this Ma, SLt, attempted to be estimated quantitatively. As a result, a quantitative relationship between the estimated SLt and the SF at positive stretch and curvature of turbulent flames could be observed only for mixtures with Le > 1 or Ma >0.

Nakahara, Masaya; Shirasuna, Takamori; Hashimoto, Jun

236

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

237

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

PubMed Central

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

Pearce, E M; Liepins, R

1975-01-01

238

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

239

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

240

Counterflow Control of a Premixed Jet Flame  

Microsoft Academic Search

Most industrial applications involving combustion through jet flames aim for high jet velocities at the lowest possible fuel to air ratio. Various techniques such as swirl, acoustic excitation etc., have been introduced in order to stabilize the flame from lifting and blowing-off at higher velocities. In the present study counter current shear layer control technique is used to control the

Esin Koc-Alkislar; Ramasamy Elavarasan; Luiz Lourenco

1998-01-01

241

Radiation from Buoyant Turbulent Diffusion Flames  

Microsoft Academic Search

The relationship between the radiant fraction, X R, of the total heat release rate from buoyant turbulent diffusion flames and a fuel's laminar flame smoke point is refined and extended to include: additional hydrocarbon fuels, fuel dilution with nitrogen and a range of oxygen\\/nitrogen ambient environments. Correlation of the data allows one to predict X R in terms of the:

L. Orloff; J. DE RIS; M. A. DELICHATSIOS

1992-01-01

242

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

243

Medical Hazards of Flame-Suppressant Atmospheres.  

National Technical Information Service (NTIS)

Flames are a potential hazard to the occupants of sealed chambers. This report describes four modifications of air that will suppress or extinguish flames. They are: (1) SUPPLEMENTATION - the addition of an appropriate foreign gas to air. (2) N2 PRESSURIZ...

D. R. Knight

1991-01-01

244

Dynamics of premixed confined swirling flames  

NASA Astrophysics Data System (ADS)

Considerable effort is currently being extended to examine the fundamental mechanisms of combustion instabilities and develop methods allowing predictions of these phenomena. One central aspect of this problem is the dynamical response of the flame to incoming perturbations. This question is examined in the present article, which specifically considers the response of premixed swirling flames to perturbations imposed on the upstream side of the flame in the feeding manifold. The flame response is characterized by measuring the unsteady heat release induced by imposed velocity perturbations. A flame describing function is defined by taking the ratio of the relative heat release rate fluctuation to the relative velocity fluctuation. This quantity is determined for a range of frequencies and for different levels of incoming velocity perturbations. The flame dynamics is also documented by calculating conditional phase averages of the light emission from the flame and taking the Abel transform of these average images to obtain the flame geometry at various instants during the cycle of oscillation. These data can be useful to the determination of possible regimes of instability. To cite this article: P. Palies et al., C. R. Mecanique 337 (2009).

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

2009-06-01

245

Dynamics of premixed confined swirling flames  

Microsoft Academic Search

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

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

2009-01-01

246

Flame aerosol synthesis of ceramic powders  

Microsoft Academic Search

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

Sotiris E. Pratsinis

1998-01-01

247

The Mechanics of Vibrating Flames in Tubes  

Microsoft Academic Search

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

H. Jones

1977-01-01

248

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

SciTech Connect

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

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

1997-11-01

249

Uranian Satellites and Triton: JHK Photometry  

NASA Astrophysics Data System (ADS)

We report photometric measurements of Uranian satellites Miranda, Ariel, Umbriel, and Titania (10.4 Aug. 1995), and Neptune's satellite Triton (21.2 Sept. 1995) with the infrared camera (IRCAM) and standard J (1.13-1.42 mu m), H (1.53-1.81 mu m), and K (2.00-2.41 mu m) filters at the 3.8-m UKIRT telescope on Mauna Kea. The individual image frames are 256 x 256 pixels with an image scale of 0.286 arcsec/pixel, resulting in a 1.22 arcmin field of view. The standard star used for airmass correction and flux calibration was UKIRT FS 34 (EG141). The photometric information for the Uranian satellites was derived from 5-image mosaics created after dark frame and flat-field corrections; a circular aperture approximation based on DAOPHOT/aper-irtf (P. B. Stetson, PASP 99, 191, 1987) was used except in the case of Miranda, in which a linear fit to the strong background light gradient from the nearby image of Uranus was applied. The center of Uranus was 9.7 arcsec (measured on the images) from Miranda. Triton data were extracted from individual images (not mosaics) with an 8-arcsec aperture and a sky anulus 10-15 arcsec. The phase angle of the Uranian satellites was alpha =1.0(o) , and that of Triton was alpha =1.7(o) . The resulting magnitudes are as follows: Miranda J = 15.30 +/-.05, H = 15.14 +/-.05, K = 15.40 +/-.06; Ariel J = 12.96 +/-.04, H = 12.86 +/-.04, K = 13.04 +/-.04; Umbriel J = 13.60 +/-.04, H = 13.37 +/-.04, K = 13.44 +/-.04; Titania J = 12.58 +/-.04, H = 12.44 +/-.04, K = 12.60 +/-.04; Triton J = 12.26 +/-.04, H = 12.14 +/-.04, K = 12.31 +/-.04. Other reports of Uranian satellite photometry are: P. D. Nicholson and T. J. Jones (Icarus 42, 54, 1980), D. P. Cruikshank (Icarus 41, 246, 1980), and K. H. Baines et al. (Icarus 132, 266, 1998).

Kesten, P. R.; Davies, J. K.; Cruikshank, D. P.; Roush, T. L.

1998-09-01

250

uvby photometry of 4 CP stars (Adelman, 1997)  

NASA Astrophysics Data System (ADS)

Differential Stroemgren uvby photometric observations from the Four College Automated Photoelectric Telescope are presented for four magnetic chemically peculiar stars. Comparison with uvby photometry of Pedersen & Thomsen for HD 37776 yields an improved period of 1.538675 days. New periods of 15.0305 days and 18.065 days are found for the sharp-lined stars HR 2258 and HR 6958, respectively, rather than one of their aliases. For HR 6958 each color shows a slightly different time of maximum. Comparison of the four color photometry of 108 Aqr taken during the fall of 1995 which well covers the period shows the presence of a secondary minimum near primary maximum in u, v, and b. Comparison with published photometry indicates indicates that subtle changes in the shapes of the light curves have occurred suggesting that this star might be precessing. (5 data files).

Adelman, S. J.

1996-11-01

251

New MOST Photometry of the 55 Cancri System  

NASA Astrophysics Data System (ADS)

Since the discovery of its transiting nature, the super-Earth 55 Cnc e has become one of the most enthusiastically studied exoplanets, having been observed spectroscopically and photometrically, in the ultraviolet, optical and infrared regimes. To this rapidly growing data set, we contribute 42 days of new, nearly continuous MOST photometry of the 55 Cnc system. Our analysis of these observations together with the discovery photometry obtained in 2011 allows us to determine the planetary radius (1.990+0.084 -0.080) and orbital period (0.7365417+0.0000025 -0.0000028) of 55 Cnc e with unprecedented precision. We also followed up on the out-of-transit phase variation first observed in the 2011 photometry, and set an upper limit on the depth of the planet's secondary eclipse, leading to an upper limit on its geometric albedo of 0.6.

Dragomir, Diana; Matthews, Jaymie M.; Winn, Joshua N.; Rowe, Jason F.

2014-04-01

252

High-resolution surface photometry of elliptical galaxies  

NASA Technical Reports Server (NTRS)

High-resolution CCD surface photometry profiles have been obtained for a sample of 42 nearby elliptical and SO galaxies as a first step in a program to investigate their central structure and core properties. A comparison of the present profiles to those of other observers shows that the accuracy of the central surface brightnesses is to better than 0.02 mag rms. Central resolution is limited by the atmospheric seeing PSF which is measured for each profile. A hybrid Fourier deconvolution procedure has been developed to correct the surface photometry for seeing in a model-independent way. Tests of the procedure on simulated galaxy images show that intrinsic core radii equal to the seeing FWHM or larger can be recovered from the observations. Application of the deconvolution procedure to the observed galaxies yields surface photometry profiles of slightly sub-arc second resolution.

Lauer, T. R.

1985-01-01

253

CCD Photometry of Bright Stars Using Objective Wire Mesh  

NASA Astrophysics Data System (ADS)

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

Kami?ski, Krzysztof; Schwarzenberg-Czerny, Aleksander; Zgórz, Marika

2014-06-01

254

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

255

Aerodynamic features of flames in premixed gases  

NASA Technical Reports Server (NTRS)

A variety of experimentally established flame phenomena in premixed gases are interpreted by relating them to basic aerodynamic properties of the flow field. On this basis the essential mechanism of some well known characteristic features of flames stabilized in the wake of a bluff-body or propagating in ducts are revealed. Elementary components of the flame propagation process are shown to be: rotary motion, self-advancement, and expansion. Their consequences are analyzed under a most strict set of idealizations that permit the flow field to be treated as potential in character, while the flame is modelled as a Stefan-like interface capable of exerting a feed-back effect upon the flow field. The results provide an insight into the fundamental fluid-mechanical reasons for the experimentally observed distortions of the flame front, rationalizing in particular its ability to sustain relatively high flow velocities at amazingly low normal burning speeds.

Oppenheim, A. K.

1984-01-01

256

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

257

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

258

Laminar flame propagation in a stratified charge  

NASA Astrophysics Data System (ADS)

The propagation of laminar flame from a rich or stoichiometric mixture to a lean mixture in a stratified methane-air charge was investigated experimentally and numerically. Emphasis was on the understanding of the flame behavior in the transition region; in particular, on the mechanism of burning velocity enhancement in this region. In the experimental setup, mixtures of two different equivalence ratios were separated by a soap bubble in a spherical constant volume combustion vessel. The richer mixture inside the bubble was ignited by a focused laser beam. The flame development was observed by Schlieren technique and flame speeds were measured by heat release analysis of the pressure data. An one-dimensional, time- dependant numerical simulation of the flame propagation in a charge with step-stratification was used to interpret the experimental results. Both the experimental and numerical studies showed that the instantaneous flame speed depended on the previous flame history. Thus a `strong' (with mixture equivalence ratio close to stoichiometric) flame can sustain propagation into finite regions of substantially lean equivalence ratio. Both thermal and chemical effects were crucial for explaining the mechanism of the flame speed enhancement in the transition period. Because of the presence of this `back- support' effect, the usual concept of specifying the burning velocity as a function of the end gas state is inadequate for a stratified charge. A simple correlation for instantaneous flame velocity based on the local burned gas temperature is developed. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

Ra, Youngchul

259

Identification and Removal of Noise Modes in Kepler Photometry  

NASA Astrophysics Data System (ADS)

We present the transiting exoearth robust reduction algorithm (TERRA) - a novel framework for identifying and removing instrumental noise in Kepler photometry. We identify instrumental noise modes by finding common trends in a large ensemble of light curves drawn from the entire Kepler field of view. Strategically, these noise modes can be optimized to reveal transits having a specified range of timescales. For Kepler target stars of low photometric noise, TERRA produces ensemble-calibrated photometry having 33 ppm rms scatter in 12 hr bins, rendering individual transits of Earth-size planets around Sun-like stars detectable as ˜3? signals.

Petigura, Erik A.; Marcy, Geoffrey W.

2012-10-01

260

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

261

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

NASA Astrophysics Data System (ADS)

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

Liao, Ying-Hao

262

Turbulent jet flames into a vitiated coflow  

NASA Astrophysics Data System (ADS)

Examined is the vitiated coflow flame, an experimental condition that decouples the combustion processes of flows found in practical combustors from the associated recirculating fluid mechanics. The configuration consists of a 4.57 mm diameter fuel jet into a coaxial flow of hot combustion products from a lean premixed flame. The 210 mm diameter coflow isolates the jet flame from the cool ambient, providing a hot environment similar to the operating conditions of advanced combustors; this important high temperature element is lacking in the traditional laboratory experiments of jet flames into cool (room) air. A family of flows of increasing complexity is presented: (1) nonreacting flow, (2) all hydrogen flame (fuel jet and premixed coflow), and (3) set of methane flames. This sequence of experiments provides a convenient ordering of validation data for combustion models. Laser Raman-Rayleigh-LIF diagnostics at the Turbulent Diffusion Flame laboratory of Sandia National Laboratories produced instantaneous multiscalar point measurements. These results attest to the attractive features of the vitiated coflow burner and the well-defined boundary conditions provided by the coflow. The coflow is uniform and steady, isolating the jet flame from the laboratory air for a downstream distance ranging from z/d = 50--70. The statistical results show that differential diffusion effects in this highly turbulent flow are negligible. Complementing the comprehensive set of multiscalar measurements is a parametric study of lifted methane flames that was conducted to analyze flame sensitivity to jet and coflow velocity, as well as coflow temperature. The linear relationship found between the lift-off height and the jet velocity is consistent with previous experiments. New linear sensitivities were found correlating the lift-off height to coflow velocity temperature. A blow-off study revealed that the methane flame blows off at a common coflow temperature (1260 K), regardless of coflow or jet velocity. An explanation for this phenomenon is that entrainment of ambient air at the high lift-off heights prevents autoignition. Analysis of the results suggests that flame stabilization occurs through a combination of flame propagation, autoignition, and localized extinction processes. Proposed is an expanded view of distributed reaction combustion based on analysis of the distributions of probe volume conditions at the stabilization region of the lifted hydrogen and methane flames. Turbulent eddies the size of the flame thickness mix fuel and hot coflow across the flame front, thereby enhancing the reaction zone with autoignition of reactants at elevated temperatures; this is the reverse effect of turbulent flames in ambient air, where intense turbulence in cool mixtures result in localized extinction. Each of the three processes (i.e., flame propagation, autoignition and localized extinction) contributes to flame stabilization in varying degrees, depending on flow conditions.

Cabra, Ricardo

263

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

264

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

265

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

266

Excitation of thermoacoustic oscillations by small premixed flames  

Microsoft Academic Search

Experiments have been carried out in which very small lean premixed flames closely representative of those formed by modern multiport domestic gas burners have been subjected to controlled acoustic perturbation. PLIF from CH has been used to visualise the flame response and the heat-release-rate fluctuations have been evaluated directly from the flame images. It is shown that small laminar flames

C. M. Coats; Z. Chang; P. D. Williams

2010-01-01

267

A Study of Radiant Tube Flame Structure and NOx Emissions  

Microsoft Academic Search

The structure and NOx behavior of turbulent natural gas\\/air flames, confined in a quartz radiant tube, are experimentally studied. The configuration features initially unmixed reactants with fuel admitted through multiple holes and air admitted through mild swirl slots. Visible flame heights and colors demonstrate that two burning modes exist, one involving long, orange flames and another involving short, blue flames.

L. G. BLEVINS; J. P. GORE

1995-01-01

268

Particle image velocimetry (PIV) analysis of flame structure  

Microsoft Academic Search

An experimental study of methane–air flame propagation in a duct is reported. A flat duct was chosen to allow optical visualization and flame propagation measurements. The duct was equipped with optical-quality windows to allow Schlieren visualization and particle image velocimetry (PIV) velocity measurements. The flame propagation velocity, flow structure, and velocity distribution in the flame for a different air excess

Teruhito Otsuka; Piotr Wolanski

2001-01-01

269

Control of confined nonpremixed flames using a microjet  

Microsoft Academic Search

Industrial burners, such as those used in materials processing furnaces, require precise control over the flame length, width, overall shape and other physical flame attributes. The mechanism used to control the flame topology should be relatively simple, safe, and devoid of an emissions penalty. We have explored the feasibility of hydrodynamic control of confined nonpremixed flames by injecting air through

Ashok Sinha; Ranjan Ganguly; Ishwar K. Puri

2005-01-01

270

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

271

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

272

Role of compressibility in moderating flame acceleration in tubes  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

273

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

274

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

275

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

276

Velocity statistics in premixed turbulent flames  

SciTech Connect

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

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

1983-01-01

277

Laminar Premixed and Diffusion Flames (Ground-Based Study)  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

278

Turbulent premixed combustion in V-shaped flames: Characteristics of flame front  

NASA Astrophysics Data System (ADS)

Flame front characteristics of turbulent premixed V-shaped flames were investigated experimentally using the Mie scattering and the particle image velocimetry techniques. The experiments were performed at mean streamwise exit velocities of 4.0, 6.2, and 8.6 m/s, along with fuel-air equivalence ratios of 0.7, 0.8, and 0.9. Effects of vertical distance from the flame-holder, mean streamwise exit velocity, and fuel-air equivalence ratio on statistics of the distance between the flame front and the vertical axis, flame brush thickness, flame front curvature, and angle between tangent to the flame front and the horizontal axis were studied. The results show that increasing the vertical distance from the flame-holder and the fuel-air equivalence ratio increase the mean and root-mean-square (RMS) of the distance between the flame front and the vertical axis; however, increasing the mean streamwise exit velocity decreases these statistics. Spectral analysis of the fluctuations of the flame front position depicts that the normalized and averaged power-spectrum-densities collapse and show a power-law relation with the normalized wave number. The flame brush thickness is linearly correlated with RMS of the distance between the flame front and the vertical axis. Analysis of the curvature of the flame front data shows that the mean curvature is independent of the experimental conditions tested and equals to zero. Values of the inverse of the RMS of flame front curvature are similar to those of the integral length scale, suggesting that the large eddies in the flow make a significant contribution in wrinkling of the flame front. Spectral analyses of the flame front curvature as well as the angle between tangent to the flame front and the horizontal axis show that the power-spectrum-densities feature a peak. Value of the inverse of the wave number pertaining to the peak is larger than that of the integral length scale.

Kheirkhah, S.; Gülder, Ö. L.

2013-05-01

279

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

280

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

281

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

Microsoft Academic Search

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

Munki Kim; Youngil Choi; Jeongseog Oh; Youngbin Yoon

2009-01-01

282

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

Microsoft Academic Search

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

Munki Kim; Youngil Choi; Jeongseog Oh; Youngbin Yoon

2009-01-01

283

Photometry requested for three "Vestoid" Near-Earth Objects  

NASA Astrophysics Data System (ADS)

Dr. Michael David Hicks (Jet Propulsion Laboratory) contacted the AAVSO requesting precision photometry of three solar system objects in support of NASA's DAWN mission to Vesta. These "Vestoids" are near-Earth objects with reflectance spectra similar to Vesta itself, suggesting they may be fragments of that larger body. Broad-band photometry may help constrain object sizes and compositions. The objects are 1981 Midas (1973 EA), 4688 (1980 WF), and 137052 (1998 VO33). Hicks and collaborators are hoping to obtain photometry at the 0.1-magnitude level or better of all three objects during some or all of the first four months of 2011. All are fainter than 16th magnitude throughout their apparitions during this time frame. Multiple exposures will likely be required to reach the required signal to noise for most observers, and 4688 (1980 WF) will likely be beyond the capabilities of most telescopes by early March 2011. The Alert Notice includes ephemerides computed from known orbital parameters computed in intervals of five days beginning 2011 January 07 (JD 2455568). Magnitudes in the tables are V. Observations are requested using Rc filter if possible; V filter observations are also acceptable. We note that since these are solar system objects, they are not included in the AAVSO International Database. Observers are asked to communicate their photometry directly to the PI, and to email Elizabeth Waagen at AAVSO Headquarters so we know that you have participated.

Templeton, Matthew R.

2011-01-01

284

Photometry of the lunar surface during lunar eclipses  

Microsoft Academic Search

The photometric observations of the lunar surface during lunar eclipses were carried out on four nights between 1972 to 1978, using the 91 cm reflector of the Dodaira Station of the Tokyo Astronomical Observatory. The photometry was performed in B-, V-, and R-colours, and arranged in accordance with the angular distance from the centre of the Earth's shadow. The results

Naosuke Sekiguchi

1980-01-01

285

Adaptive Filter Applications in Surface Photometry of Galaxies  

Microsoft Academic Search

We consider the smoothing application of the adaptive filter, juxtaposed to the other most commonly used filters, in the surface photometry of galaxies. We point out the adaptive filter advantages and illustrate them with the azimuthally shrunk luminosity profiles of the Seyfert galaxy NGC 5548.

L. S. Slavcheva-Mihova; B. M. Mihov; G. T. Petrov

2006-01-01

286

Spitzer-IRAC Photometry of M, L, and T Dwarfs  

Microsoft Academic Search

In the first year of Spitzer science operations, we have carried out a program to acquire photometry for some 80 late-M, L, and T dwarfs using the Infrared Array Camera (IRAC). We find it is the T dwarfs which stand out in IRAC colors and provide the most insight into the nature of brown dwarf atmospheres. For the T dwarfs

B. M. Patten; T. J. Henry; A. Burrows; J. R. Stauffer; D. Ragavan; J. Liebert; K. L. Luhman; J. L. Hora; T. Megeath; M. Marengo; G. G. Fazio

2004-01-01

287

Airborne Photometry of Comet Halley from 40 to 160 Microns.  

National Technical Information Service (NTIS)

Far infrared photometry of comet Halley was obtained from NASA's Kuiper Airborne Observatory. The brightness of the comet decreases by nearly a factor of two on the second day in phase with the variability observed in blue light by IUE during the same tim...

H. Campins M. Joy P. M. Harvey D. F. Lester H. B. Ellis

1986-01-01

288

BVI photometry of young stars in 10 clusters (Mayne+, 2007)  

Microsoft Academic Search

We present photometry in V, V-I and in some cases B-V for a range of star forming regions. NGC2547, NGC7160, NGC2264, Cepheus OB3b, Sigma Orionis, IC348 and h and chi Per. A full description of the data can be found at: http:\\/\\/www.astro.ex.ac.uk\\/people\\/timn\\/Catalogues (8 data files).

N. J. Mayne; T. Naylor; S. P. Littlefair; E. S. Saunders; R. D. Jeffries

2007-01-01

289

Comet Kohoutek. [proceedings - astronomical photometry/astronomical spectroscopy  

NASA Technical Reports Server (NTRS)

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

Gary, G. A. (editor)

1975-01-01

290

Far-Infrared and 'uvby' Photometry of V 1057 Cygni.  

National Technical Information Service (NTIS)

Four-color (uvby) photometry and broadband observations at 5 micrometers, 11 micrometers, and 20 micrometers are reported for V1057 Cyg (LkH alpha 190). The observations reveal a large flux excess superposed on the stellar continuum in the infrared. The c...

T. Simon N. D. Morrison S. C. Wolff D. Morrison

1972-01-01

291

Combined Photometry and Spectroscopy of Globular Cluster Tidal Streams  

Microsoft Academic Search

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

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

2005-01-01

292

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

NASA Technical Reports Server (NTRS)

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

Walker, E. N.

1976-01-01

293

BVRI CCD Photometry of the Open Cluster IC 4996  

NASA Astrophysics Data System (ADS)

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.

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

294

1961-1999 UBV photometry of 14 variables (Oja, 2011)  

NASA Astrophysics Data System (ADS)

Photoelectric UBV photometry of the variable stars V636 Cas, alpha UMi, V440 Per, zeta Gem, UU Cnc, TYC2-880-515-1, V473 Lyr, chi Cyg, V1794 Cyg, DT Cyg, V1334 Cyg, V532 Cyg, pi Aqr, and DY Peg is reported. (15 data files).

Oja, T.

2011-11-01

295

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

296

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

297

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

298

The behavior of partially premixed flames  

NASA Astrophysics Data System (ADS)

In this investigation, we have characterized the structure of two-dimensional partially-premixed slot burner flames through the measurement of the heat release topography, and the temperature and velocity distribution. The measurements were used to infer the flame stretch and the response of the local propagation speed of the inner rich premixed reaction zone in these flames to stretch rate variations due to hydrodynamic and curvature effects. The inner premixed reaction zone of the PPFs exhibits a highly curved portion near its tip and planar topography along its lower portion. An "effective flame speed" was characterized for two flames beyond the rich flammability limit that can only burn in a partially-premixed mode due to the synergy between the inner premixed and outer nonpremixed reaction zones. The reaction zone speed in the curved region increases significantly during the transition from a planar to curved topology due to curvature effects. The Markstein relation must be suitably modified to account for the curvature of the reaction zones for flame with negative curvature. Negative curvature increases the local value of the flame speed above the unstretched flame speed Su o while positive curvature decreases it below that value. Although curvature effects are included in the definition of stretch, they are not fully accounted for by the Su(kappa) Markstein linear relation. This implies that the curvature has an influence on Su through kappa and another more explicit effect. The propagation of triple flames in premixed and nonpremixed jet modes was investigated. The response of flame speed at the triple point to stretch has a turning behavior due to the variation of the radius of curvature while the flame is propagating downward. In normal gravity, the buoyant gases accelerate the flow in a direction opposite to the gravity vector, causing air entrainment, which enhances the mixing of the reactants with ambient laboratory air and consequently, influences the flame structure. Therefore, a multipurpose experimental drop rig was built at NASA Glenn research center to microgravity experiments.

Choi, Chun Wai

299

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

Microsoft Academic Search

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

H. Pitsch; H. Steiner

2000-01-01

300

Turbulent transport in premixed flames  

NASA Technical Reports Server (NTRS)

Simulations of planar, premixed turbulent flames with heat release were used to study turbulent transport. Reynolds stress and Reynolds flux budgets were obtained and used to guide the investigation of important physical effects. Essentially all pressure terms in the transport equations were found to be significant. In the Reynolds flux equations, these terms are the major source of counter-gradient transport. Viscous and molecular terms were also found to be significant, with both dilatational and solenoidal terms contributing to the Reynolds stress dissipation. The BML theory of premixed turbulent combustion was critically examined in detail. The BML bimodal pdf was found to agree well with the DNS data. All BML decompositions, through the third moments, show very good agreement with the DNS results. Several BML models for conditional terms were checked using the DNS data and were found to require more extensive development.

Rutland, C. J.; Cant, R. S.

1994-01-01

301

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

302

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

303

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

304

Photometry of southern globular clusters. V - Photographic photometry of faint stars in Omega Centauri  

NASA Astrophysics Data System (ADS)

Photographic photometry obtained by the 3.9-m Anglo-Australian Telescope of approximately 300 faint stars in the globular cluster Omega Centauri is presented. The color-magnitude diagram was obtained from prime-focus plates measured with an iris photometer and calibrated by a faint photoelectric sequence. The main sequence turn-off point on the diagram is found to lie significantly below a V magnitude of 18, which is about 3.8 mag below the horizontal branch, however the value probably does not imply an exceptionally large age for the cluster. The spread in color observed at the top of the main sequence is noted to be compatible with the spread in heavy element abundance deduced from previous studies of the evolved stars, however does not establish the existence of a primordial abundance spread and is also compatible with a negligible intrinsic scatter in color. Future studies capable of resolving the problem of primordial abundance variations and the age of the cluster are indicated.

Cannon, R. D.; Stewart, N. J.

1981-04-01

305

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

307

Don`t detonate -- Arrest that flame  

SciTech Connect

Flame arrestors are essential safety devices. The prime applications are to protect people and equipment in refineries, gas plants, storage terminals and offshore rigs from backflashes, fires and catastrophic explosions. Detonation and deflagration arrestors serve in the pulp and paper, chemical, petrochemical, power generation, pharmaceutical, energy transportation and other related process industries. A flame arrestor is a special type of heat exchanger. It cools the flame so combustion is not sustained. It needs time to dissipate heat. That`s why the design and construction of the quenching media is of paramount importance. The paper discusses their operation, equations for gas fuels, varieties of flame arrestors, and a case history of an explosion in a crude oil tank at a gas plant.

Mendoza, V.A.; Smolensky, V.G.; Straitz, J.F. III [NAO Inc., Philadelphia, PA (United States)

1996-05-01

308

Exploratory Studies of Flame and Explosion Quenching.  

National Technical Information Service (NTIS)

These studies were aimed at the development of improved agents to suppress coal dust-air explosions. The approach employed was to sample both gaseous species and particles from uninhibited and inhibited flames, to obtain basic information about the mechan...

F. T. Greene J. Beachey T. A. Milne

1973-01-01

309

Flame Retardant Homopolymer and Polymer Blend Composites  

NASA Astrophysics Data System (ADS)

We investigated the flame retardant performance of homopolymer, EVA, PMMA, PP, and PS, and polymer blends, PS/PMMA, PC/SAN, with organoclay and conventional flame retardant agents such as decabromodiphenyl ether (DB) and phosphorus compounds. These materials were characterized by TEM, STXM, LOI and UL 94 V-0. TEM and STXM photographs show that the addition of organoclays into polymer blends drastically slows down the phase separation and accelerates the decompose of bromine compounds during the combustion. Further, UL 94 V-0 results indicate that PS/PMMA blend with DB can not achieve self-extinguishing in the absence of clay. The amounts of flame retardants and clay used were varied to try to achieve the optimal formula to pass UL 94 V-0. The synergism of clay and flame retardant agents were completely studied by various measurements, time dependence burning (TEM, Ion Chromatography), GC-MS, and cone calorimeter.

Rafailovich, Miriam; Si, Mayu; Sokolov, Jonathan; Araki, Tohru; Ade, Harald; Hefter, Daniel; Sokolov, Aryeh

2006-03-01

310

Shatter-Resistant, Flame-Resistant Window  

NASA Technical Reports Server (NTRS)

Combustion-chamber window combines properties of polycarbonate and sapphire. Inner layer of sapphire, withstands flame in chamber. Outer layer of polycarbonate tough but susceptible to weakening by flame and protected from flame by sapphire layer. Resists flames, shattering, and high pressure. Windows withstand 60 lb/in. to second power (414 kPa) in hydrostatic pressure vessel. Also survives leak test under internal pressure of 2 atm (0.2 MPa) of helium and external pressure of 10 to negative fifth power torr (1.3 mPa). Has transmission density of 0.08 to 0.11 in visible light. In contrast, unbonded layers have transmission density of 0.13 to 0.16.

Richardson, William R.; Walker, Ernie D.

1989-01-01

311

Turbulent Jet Flames Into a Vitiated Coflow.  

National Technical Information Service (NTIS)

Examined is the vitiated coflow flame, an experimental condition that decouples the combustion processes of flows found in practical combustors from the associated recirculating fluid mechanics. The configuration consists of a 4.57 mm diameter fuel jet in...

J. D. Holdeman R. Cabra

2004-01-01

312

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...

313

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

314

Inhibition of coal dust--air flames  

Microsoft Academic Search

Nine dust and gaseous inhibitors of propagating coal dust-air flames (lean, stoichiometric, and rich) were evaluated in a newly developed 15-cm-id, 3.6-meter long instrumented flame duct, under conditions such that wall quenching was virtually absent and the dust concentration was temporally and spacially uniform to within about +- 5 percent. Listed roughly in order of increasing efficiency, the inhibitors evaluated

J. Grumer; A. E. Bruszak

1971-01-01

315

Structure of a Controlled Ducted Flame  

Microsoft Academic Search

The structure of self-excited and controlled ducted flames was studied by imaging the CH emission and analyzing the pressure and CH intensity time variation.Self-excited combustion oscillations occur when the flame interacts with the large-scale vortices which are excited in the shear layer by the acoustic forcing at the duct resonance modes. The periodic heat release produced by the combustion inside

E. GUTMARK; T. P. PARR; D. M. HANSON-PARR; K. C. SCHADOW

1993-01-01

316

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

317

Flame retardants for polypropylene based on lignin  

Microsoft Academic Search

Lignin has been investigated as flame retardant for isotactic polypropylene (PP) by means of thermogravimetric analysis in nitrogen and cone calorimetry with incident heat flux exposure at 25 kW\\/m2. Lignin has been used in synergism with aluminium hydroxide, poly(vinyl alcohol), melamine phosphate, monoammonium phosphate and ammonium polyphosphate. These flame retardants, based on lignin, increase the thermal degradation temperature, the combustion

A De Chirico; M Armanini; P Chini; G Cioccolo; F Provasoli; G Audisio

2003-01-01

318

Analytical Coordination Chemistry: Titrimetry, Gravimetry, Flame Photometry, Spectrometry, Gas Evolution and Isotopic Preparations, July 1965 to June 1966.  

National Technical Information Service (NTIS)

Contents Include: Titrimetry (spectrophotometric titrations, controlled potential coulometric titration - molybdenum, pyrohydrolytic separations); Gravimetry (analysis of standard reference materials, studies and application of homogeneous precipitations,...

O. Menis

1966-01-01

319

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

SciTech Connect

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

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

2003-12-19

320

Quantitative Species Measurements In Microgravity Combustion Flames  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

321

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

322

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

323

Laminar and Turbulent Gaseous Diffusion Flames. Appendix C  

NASA Technical Reports Server (NTRS)

Recent measurements and predictions of the properties of homogeneous (gaseous) laminar and turbulent non-premixed (diffusion) flames are discussed, emphasizing results from both ground- and space-based studies at microgravity conditions. Initial considerations show that effects of buoyancy not only complicate the interpretation of observations of diffusion flames but at times mislead when such results are applied to the non-buoyant diffusion flame conditions of greatest practical interest. This behavior motivates consideration of experiments where effects of buoyancy are minimized; therefore, methods of controlling the intrusion of buoyancy during observations of non-premixed flames are described, considering approaches suitable for both normal laboratory conditions as well as classical microgravity techniques. Studies of laminar flames at low-gravity and microgravity conditions are emphasized in view of the computational tractability of such flames for developing methods of predicting flame structure as well as the relevance of such flames to more practical turbulent flames by exploiting laminar flamelet concepts.

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

2001-01-01

324

Use of a Continuous Source of Excitation, an Argon-Hydrogen-Air Flame, and an Extended Flame Cell for Atomic Absorption Flame Spectrophotometry.  

National Technical Information Service (NTIS)

A continuous source of excitation in conjunction with an argon-hydrogen-entrained air flame, an extended flame cell, a medium-dispersion monochromator and a typical detection system is shown to give good sensitivities for the atomic absorption flame spect...

W. W. McGee J. D. Winefordner

1966-01-01

325

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

326

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

327

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

Microsoft Academic Search

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

Jianjun Wang; Li Wang; Anguo Xiao

2009-01-01

328

Infrared photometry and spectrometry of Nova Aquilae 1982  

NASA Astrophysics Data System (ADS)

Photometry and 2-4 and 8-13 micron spectrometry of Nova Aquilae 1982, obtained during its dust shell phase are presented. The photometry indicates that, if dust formation ocurred in the outburst ejecta, it did so at an anomalously early stage of the outburst; alternatively the dust shell may have predated the eruption. Spectrometry at the shorter wavelengths suggests the presence of broad, weak features, whilst that in the 8-13 micron window shows strong emission from siicate grains. This indicates that, unlike the situation in previous dusty novae, the grains around Nova Aquilae formed in an oxygen-rich environment. The difference between this nova and others observed in the infrared to date may thus provide clues to differing elemental abundances in classical nova progenitors. On the other hand, this object may not have undergone a normal classical nova outburst.

Bode, M. F.; Evans, A.; Whittet, D. C. B.; Aitken, D. K.; Roche, P. F.; Whitmore, B.

1984-04-01

329

Galaxy Photometry Science Verification Tests for the Dark Energy Survey  

NASA Astrophysics Data System (ADS)

The Dark Energy Survey (DES) is an optical imaging survey that will use a new 570-megapixel camera, the Dark Energy Camera (DECam), to image 5000 square degrees of the Southern Galactic Cap in the 5 filters grizY. The primary DES science goal is to constrain dark energy cosmological parameters using the 4 complementary science probes of galaxy clusters, weak lensing, large scale structure, and supernove. Commissioning of DECam has begun Sept. 2012, and DES science verification and the beginning of first season of operations are scheduled for late 2012. Here we report on tests of galaxy photometry undertaken as part of DES science verification. In particular, we will describe the results of measurements of galaxy detection completess and purity, checks of the fidelity of estimated photometric errors, and tests of the homogeneity of photometry across the very large, 2-degree diameter DECam focal plane.

Lin, Huan; Soares-Santos, M.; Diehl, H.; Dark Energy Survey Collaboration

2013-01-01

330

UBVRI photometry of the recurrent nova T coronae borealis  

NASA Astrophysics Data System (ADS)

Differential UBVRI photometry of this bright recurrent nova at three different observatories in 1981, 1982, and 1983 reveals variability on three different timescales. By Fourier analysis the amplitude of the ellipticity effect at UBVRI is determined and used to find the prolateness coefficient z = 0.14 + or - 0.01. Times of minimum light equated with times of conjunction and combined with previously published times yield 227.67 d + or - 0.02 d for a refined orbital period. Continuous photometry on one night confirms short-term variability reported earlier. Residuals from the Fourier fits reveal an additional variability with a period of about 55 days and an amplitude that in 1983 was 0.35 mag in V, 0.5 mag in B, and 0.8 mag in U. It is concluded that the gM3 primary is probably a semiregular red variable.

Lines, Helen C.; Lines, Richard D.; McFaul, Thomas G.

1988-05-01

331

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

332

Galaxy photometry at faint light levels - Interaction with the environment  

NASA Astrophysics Data System (ADS)

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

Carter, D.

333

BV photometry of two evolved variables in NGC 188  

NASA Astrophysics Data System (ADS)

CCD BV photometry, is presented of two NGC 188 variables located on the cluster color-magnitude diagram between red-giant-branch and blue stragglers region. Variable V8 has a sine-like light curve with an amplitude of variations about 0.15 mag. The period of variation is 4.03 d or 8.06 d. Different sets of photometry collected between 1985 and 1989 are compared. There is no evidence for changes of the mean brightness level or amplitude of light variations. Variable V11, probably being an eclipsing binary, exhibited small (total range about 0.03 mag), but clearly real, changes of brightness during 13 consecutive nights. V11 belongs to RS CVn-type variables.

Mazur, Beata; Kaluzny, Janusz

334

Long-term photometry of Variables I. (Manfroid+ 1991)  

NASA Astrophysics Data System (ADS)

This is the first catalogue of photometric data in the Stroemgren system obtained during the period October 1982 - September 1986. Full description can be found in ESO report SP 8. Since our goal is not absolute (all-sky) photometry, the observations should be used for differential photometry only. The mean values of the r.m.s. deviations of the differential measurements of comparison stars are around (from Table 5 of paper) ------------------------------------ System y b-y m1 c1 ------------------------------------ 1 0.0109 0.0088 0.0133 0.0136 4 0.0068 0.0057 0.0079 0.0118 5 0.0087 0.0070 0.0114 0.0114 6 0.0090 0.0078 0.0126 0.0132 7 0.0071 0.0033 0.0041 0.0065 ------------------------------------ (2 data files).

Manfroid, J.; Sterken, C.; Bruch, A.; Burger, M.; de Groot, M.; Duerbeck, H. W.; Duemmler, R.; Figer, A.; Hageman, T.; Hensberge, H.; Jorissen, A.; Madejsky, R.; Mandel, H.; Ott, H. A.; Reitermann, A.; Schulte-Ladbeck, R. E.; Stahl, O.; Steenman, H.; Vander Linden, D.; Zickgraf, F. J.

1995-11-01

335

Time-resolved CCD photometry of an ensemble of stars  

NASA Astrophysics Data System (ADS)

A technique for obtaining CCD photometry of a large ensemble of stars, with precision limited by atmospheric scintillation and photon statistics is presented. Under bright-sky conditions with a 0.9-m telescope, a precision of about 0.0015 mag relative to an ensemble average standard was obtained for 12th-13th mag stars in M 67 with exposure times of 1 min. The increase in noise level due to variable cirrus clouds is minimal. Effective noise levels for the detection of coherent oscillations with periods of 5-20 min could thus be reduced to about 30 micromag over ten nights of observing for stars of this brightness. A much larger ensemble of faint stars could be followed at lower precision with sky background and photon statistics as dominant error sources. Four probable-cluster DA white dwarfs were detected in the old galactic cluster M 67, using B, V calibration photometry.

Gilliland, Ronald L.; Brown, Timothy M.

1988-06-01

336

High-speed multicolour photometry with CMOS cameras  

NASA Astrophysics Data System (ADS)

We present the results of testing the commercial digital camera Nikon D90 with a CMOS sensor for high-speed photometry with a small telescope Celestron 11'' at the Peak Terskol Observatory. CMOS sensor allows to perform photometry in 3 filters simultaneously that gives a great advantage compared with monochrome CCD detectors. The Bayer BGR colour system of CMOS sensors is close to the Johnson BVR system. The results of testing show that one can carry out photometric measurements with CMOS cameras for stars with the V-magnitude up to ?14^{m} with the precision of 0.01^{m}. Stars with the V-magnitude up to ˜10 can be shot at 24 frames per second in the video mode.

Pokhvala, S. M.; Zhilyaev, B. E.; Reshetnyk, V. M.

2012-11-01

337

16 and 24-Micron Photometry of Transiting Extrasolar Planets  

NASA Astrophysics Data System (ADS)

We have recently used Spitzer MIPS-24 to detect light from the transiting extrasolar planet HD 209458b during its secondary eclipse. Previously, there had been no direct detection of light from an extrasolar planet. Our calculated brightness temperature constrains models of this planet's thermal emission. We now propose additional eclipse photometry of HD 209458b using the IRS blue peak-up array and MIPS-24 to provide a brightness temperature at 16 microns, reduce the errors on our 24-micron measurement, search for variability due to atmospheric dynamics, investigate the puzzlingly large radius of this planet, and possibly derive the day/night temperature contrast. We also propose eclipse photometry of the second-brightest transiting planet, TrES-1b, in the IRS blue peak-up array, with similar goals. These pioneering measurements of extrasolar planetary fluxes will constrain the many competing radiative, chemical, and dynamical models of these planets' atmospheres.

Harrington, Joseph; Cho, James; Deming, Drake; Hansen, Brad; Menou, Kristen; Richardson, Jeremy; Seager, Sara

2005-06-01

338

BV photographic and CCD photometry of IC 4651  

NASA Astrophysics Data System (ADS)

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 distance modulus and reddening derived from uvby photometry in Anthony-Twarog and Twarog (1987) are employed. While evidence is found of a hook in the upper main sequence, no evidence is found of a significantly bifurcated main sequence for this cluster, although it is similar in age to NGC 752 and NGC 3680, where this phenomenon has been noted. Finally, the survey has not resolved the apparent deficit of main-sequence stars fainter than V = 14.5 noted in Anthony-Twarog and Twarog (1987).

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

1988-05-01

339

Ultraviolet photometry of OB associations in M31  

NASA Technical Reports Server (NTRS)

The study obtains near-UV and FUV magnitudes for 76 massive stars in 24 OB associations in the central and southern portions of M31 from images obtained by the Ultraviolet Imaging Telescope (UIT) during the Astro 1 spacelab mission. A comparison is made with the previous UIT photometry of 30 stars in the giant association NGC 206. Extinctions are estimated from the relation between E(B - V) and the distance from the center of M31 derived by Hodge and Lee (1988) from topical CCD stellar photometry. From evolutionary models, lower limits to the maximum stellar mass are estimated at about 60-100 solar masses in NGC 206, A29, A61, A63, A130, and A132. For other associations, the limits are in the range of about 20-55 solar masses.

Hill, Jesse K.; Isensee, Joan E.; Bohlin, Ralph C.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

1993-01-01

340

T1C photometry of NGC7507 (Caso+, 2013)  

NASA Astrophysics Data System (ADS)

We present a catalog of point-like sources around NGC 7507, which forms the photometric database for our paper. The sources were obtained from the PSF photometry of MOSAIC images in filters R and C. The catalog contains coordinates, T1 magnitudes with uncertainties, and C-T1 colors and their uncertainties. Magnitudes and colour are corrected by absorption and reddening. (1 data file).

Caso, J. P.; Richtler, T.; Bassino, L. P.; Salinas, R.; Lane, R. R.; Romanowsky, A.

2013-07-01

341

The lenticular NGC 3115 - A standard for galaxy photometry  

NASA Astrophysics Data System (ADS)

NGC 3115, a lenticular galaxy that is seen edge-on, is an ideal candidate for surface photometry in virtue of its proximity and absence of close prominent companions. An independent two-dimensional study of NGC 3115 has been made using the high resolution CFH telescope, as well as the ESO and UK Schmidt telescopes (for the outer regions). Light profiles along both main axes were produced for each intensity frame; the results obtained are presented in graphical form.

Capaccioli, M.; Held, E. V.; Nieto, J.-L.

342

CCD BVI photometry of 3 open clusters (Pietrukowicz+, 2006)  

NASA Astrophysics Data System (ADS)

Photometry of two fields which include three open clusters: NGC 2425, Haffner 10 and Czernik 29. For each star of the clusters: equatorial coordinates, Johnson-Cousins system magnitudes and colours with uncertainties. Instrumentation: 1.02-m f/10.0 Ritchey-Chretien + 1024x1024 CCD with a scale 0.695 arcsec/pixel at Las Campanas Observatory. Date of observations: Feb 20/21 and Feb 21/22, 1995. (2 data files).

Pietrukowicz, P.; Kaluzny, J.; Krzeminski, W.

2005-10-01

343

Spitzer IRAC Photometry of M, L, and T Dwarfs  

Microsoft Academic Search

We present the results of a program to acquire photometry for 86 late M, L, and T dwarfs using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We examine the behavior of these cool dwarfs in various color-color and color-magnitude diagrams composed of near-IR and IRAC data. The T dwarfs exhibit the most distinctive positions in these diagrams.

Brian M. Patten; John R. Stauffer; Adam Burrows; Massimo Marengo; Joseph L. Hora; Kevin L. Luhman; Sarah M. Sonnett; Todd J. Henry; Deepak Raghavan; S. Thomas Megeath; James Liebert; Giovanni G. Fazio

2006-01-01

344

Infrared Photometry of Late-M, L, and T Dwarfs  

Microsoft Academic Search

We present ZJHKL'M' photometry of a sample of 58 late M, L, and T dwarfs, most of which are identified from the Sloan Digital Sky Survey and the Two Micron All-Sky Survey. Near-infrared spectra and spectral classifications for most of this sample are presented in a companion paper by Geballe et al. We derive the luminosities of 18 dwarfs in

David A. Golimowski; Xiaohui Fan; T. R. Geballe; G. R. Knapp; J. Brinkmann; István Csabai; James E. Gunn; Suzanne L. Hawley; Todd J. Henry; Robert Hindsley; Zeljko Ivezic; Robert H. Lupton; Jeffrey R. Pier; Donald P. Schneider; J. Allyn Smith; Alan Uomoto; D. G. York

2002-01-01

345

Reconstructing Galaxy Spectral Energy Distributions from Broadband Photometry  

Microsoft Academic Search

We present a novel approach to photometric redshifts, one that merges the\\u000aadvantages of both the template fitting and empirical fitting algorithms,\\u000awithout any of their disadvantages. This technique derives a set of templates,\\u000adescribing the spectral energy distributions of galaxies, from a catalog with\\u000aboth multicolor photometry and spectroscopic redshifts. The algorithm is\\u000aessentially using the shapes of the

I. Csabai; A. J. Connolly; A. S. Szalay; T. Budavari

1999-01-01

346

High precision differential photometry of planet transits with the MMTF  

Microsoft Academic Search

We propose to use Magellan+MMTF(IMACS) to achieve some of the very highest precision ground-based, time-differential, narrow-band photometry to date on selected favorable transiting planet host stars. The proposed observations are expected to provide precise measurements of the time, duration, shape, and color of an exoplanet transit. Our primary target, CoRoT-7, is an active star hosting the first transiting super-Earth transiting

Brian L. Lee; Knicole D. Colon; Eric B. Ford; Cullen H. Blake; Suvrath Mahadevan

2010-01-01

347

High Speed Optical Photometry of LMXBs and CVs  

NASA Astrophysics Data System (ADS)

High speed photometry of several accreting binaries was obtained using the McDonald Observatory 2.1m telescope and ARGOS CCD photometer. A broad-band filter (BVR) was used in order to maximize flux and maintain a short (1-10s) integration time on faint targets. Such observations obtained over several years allow for variability study over time scales covering many orders of magnitude. Observations and analysis for several binaries are summarized.

Mason, Paul A.; Robinson, Edward L.; Gomez, Sebastian; Gonzalez, Emmanuel; Lopez, Isaac D.; Monroy, Lorena; Price, Alex

2013-02-01

348

IR photometry of ESO calibration stars (van der Bliek+ 1996)  

NASA Astrophysics Data System (ADS)

We describe the infrared (IR) photometric system for the single channel photometers at ESO, which have been used from 1983 until 1994. In addition to the broadband near infrared (NIR, 1-5?m) photometric system presented in 1991 by Bouchet et al. and Bersanelli et al., we describe a narrow-band NIR photometric system and a mid infrared (MIR, 7-20?m) photometric system. We also extend the set of NIR standard stars by Bouchet et al. towards fainter objects (K=~9). The photometric data of the standard stars in these systems were extracted from the complete IR photometric data archive of ESO, covering 10 years. The zeropoints of the NIR photometry are set by assuming that HR 3314 has a V-magnitude of 3.89, and that V-K=-0.05, J-K=-0.01, H-K=-0.01, K-L'=0.00, K-M=0.00. The zeropoints of the MIR photometry are set by assuming that the colours of? Hyi (HR 0098) and ? CenA (HR 5459) are equal to the colours of the Sun. We adopt the absolute calibration of Megessier (1995A&A...296..771M) for the NIR and we argue that this calibration can be extrapolated to 20?m, using the MIR calibrations by Rieke et al. (1985AJ.....90..900R) and Cohen et al. (1992AJ....104.1650C). The definition of the zeropoints is consistent with the absolute calibration. We obtained accurate (?=~0.02mag.) NIR photometry of about 240 standard stars and MIR photometry of about 40 standard stars (?=~0.04mag). Comparison of our NIR photometric system with other well established systems shows that there are some small colour dependencies and zeropoint offsets which are always smaller than about 0.02mag. except for the L' band. (3 data files).

van der Bliek, N. S.; Manfroid, J.; Bouchet, P.

1996-04-01

349

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

350

BVRI photometry of the type Ic Hypernova SN 2002ap  

Microsoft Academic Search

The BVRI photometric observations of type-Ic SN 2002ap at maximum and during the fast-decline phase after maximum are presented. We used our BVRI photometry and published data in order to compute the magnitudes and dates of peak brightness. The absolute magnitude at maximum brightness of SN 2002ap shows that it was fainter than SN 1998bw, but similar to SN 1997ef.

L. M. Cook; E. V. Katkova; N. A. Sokolov; I. S. Guseva

2002-01-01

351

Blue-light imagery and photometry of sprites  

Microsoft Academic Search

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

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

1998-01-01

352

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

353

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

354

Can we characterize turbulence in premixed flames?  

SciTech Connect

Modeling of premixed turbulent combustion involves averaging reaction rates in turbulent flows. The focus of most approaches to resolving this problem has been placed on determining the dependence of the mean rate w of product creation on the laminar flame speed S{sub L}, the rms turbulence velocity u', etc. The goal of the present work is to draw attention to another issue: May the input quantity u{sup '} for a model of w= w(u'/S{sub L},..) be considered to be known? The point is that heat release substantially affects turbulence and, hence, turbulence characteristics in premixed flames should be modeled. However, standard moment methods for numerically simulating turbulent flows do not allow us to evaluate the true turbulence characteristics in a flame. For instance, the Reynolds stresses in premixed flames are affected not only by turbulence itself, but also by velocity jump across flamelets. A common way to resolving this problem consists of considering the Reynolds stresses conditioned on unburned (or burned) mixture to be the true turbulence characteristics. In the present paper, this widely accepted but never proved hypothesis is put into question, first, by considering simple model constant-density problems (flame motion in an oscillating one-dimensional laminar flow; flame stabilized in a periodic shear, one-dimensional, laminar flow; turbulent mixing). In all the cases, the magnitude of velocity fluctuations, calculated using the conditioned Reynolds stresses, is affected by the intermittency of reactants and products and, hence, is not the true rms velocity. Second, the above claim is further supported by comparing balance equations for the mean and conditioned Reynolds stresses. The conditioned Reynolds stresses do not characterize the true turbulence in flames, because conditional averaging cuts off flow regions characterized by either high or low velocities. (author)

Lipatnikov, A.N. [Department of Applied Mechanics, Chalmers University of Technology, Gothenburg, 412 96 (Sweden)

2009-06-15

355

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

356

Engineering Flame Retardant Biodegradable Nanocomposites  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

357

Theory of wide-angle photometry from standard stars  

NASA Technical Reports Server (NTRS)

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

Usher, Peter D.

1989-01-01

358

MATPHOT algorithm for digital point spread function CCD stellar photometry  

NASA Astrophysics Data System (ADS)

The MATPHOT algorithm for digital Point Spread Function (PSF) CCD stellar photometry is described. A theoretical photometric and astrometric performance model is presented for PSF-fitting stellar photometry. MATPHOT uses a digital representation of the sampled PSF consisting of a numerical table (e.g., a matrix or a FITS image) instead of an analytical function. MATPHOT achieves accurate stellar photometry with under-sampled CCD observations with super-sampled PSFs. MATPHOT currently locates a PSF within the observational model using a 21-pixel-wide damped sinc interpolation function. Position partial derivatives of the observational model are determined using numerical differentiation techniques. Results of MATPHOT-based design studies of the optical performance of the Next Generation Space Telescope are presented; observations of bright stars analyzed with the MATPHOT algorithm can yield millimag photometric errors with millipixel relative astrometric errors -- or better -- if observed with a perfect detector. Plans for the future development of a parallel-processing version of the MATPHOT algorithm using Beowulf clusters are described. All of the C source code and documentation for MATPHOT is freely available as part of the MXTOOLS package for IRAF (http://www.noao.edu/staff/mighell/mxtools). This work is supported by a grant from NASA's Office of Space Science.

Mighell, Kenneth J.

2002-12-01

359

Spitzer photometry of globulars in 2 galaxies (Spitler+, 2008)  

NASA Astrophysics Data System (ADS)

Catalogues are described in Spitler et al. (2008MNRAS.389.1150S) All photometry is corrected for Galactic dust extinction and are on the Vega photometric system. NGC 5128 optical photometry is from Peng et al. (2004ApJS..150..367P), as compiled in Woodley et al. (2007AJ....134..494W). Globular cluster identification numbers are from Woodley et al. (2007, Cat. J/AJ/134/494). NGC 4594 optical photometry is from Spitler et al. (2006AJ....132.1593S) updated with new aperture corrections as described in Harris et al. (2010MNRAS.401.1965H). Identification number, globular cluster half-light radii and the assumed distance modulus for the half-light radii are from Spitler et al. (2006, Cat. J/AJ/132/1593). A ultra-compact dwarf galaxy is included in this catalogue with ID="ucd" (see also Hau et al. 2009MNRAS.394L..97H). (2 data files).

Spitler, L. R.; Forbes, D. A.; Beasley, M. A.

2010-06-01

360

Transformed photometry of young stars in Cha requested  

NASA Astrophysics Data System (ADS)

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

Waagen, Elizabeth O.

2013-01-01

361

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

362

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

363

Experimental study of premixed flames in intense isotropic turbulence  

SciTech Connect

A methodology for investigating premixed turbulent flames propagating in intense isotropic turbulence has been developed. The burner uses a turbulence generator developed by Videto and Santavicca and the flame is stabilized by weak-swirl generated by air injectors. This set-up produces stable premixed turbulent flames under a wide range of mixture conditions and turbulence intensities. The experiments are designed to investigate systematically the changes in flame structures for conditions which can be classified as wrinkled laminar flames, corrugated flames and flames with distributed reaction zones. Laser Doppler anemometry and Rayleigh scattering techniques are used to determine the turbulence and scalar statistics. In the intense turbulence, the flames are found to produce very little changes in the mean and rams velocities. Their flame speed increase linearly with turbulence intensity as for wrinkled laminar flames. The Rayleigh scattering pdfs for flames within the distributed reaction zone regime are distinctly bimodal. The probabilities of the reacting states (i.e. contributions from within the reaction zone) is not higher than those of wrinkled laminar flame. These results show that there is no drastic changes in flame structures at Karlovitz number close to unity. This suggest that the Klimov-Williams criterion under-predicts the resilience of wrinkled flamelets to intense turbulence.

Bedat, B.; Cheng, R.K.

1994-04-01

364

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

365

A Theory of Oscillating Edge Flames  

NASA Technical Reports Server (NTRS)

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

Buckmaster, J.; Zhang, Yi

1999-01-01

366

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.

367

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

368

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

369

Chaotic radiation/turbulence interactions in flames  

SciTech Connect

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

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

1998-11-01

370

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

371

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

372

An Improved Method for Students' Flame Tests in Qualitative Analysis  

NASA Astrophysics Data System (ADS)

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

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

1998-04-01

373

On the theoretical analysis of vibratory flame propagation  

Microsoft Academic Search

The condition is established under which the mutual effect between wave generation at a flame surface and periodic accelerations in the surrounding medium may become an essential feedback mechanism in the vibratory propagation of the flame along ducts.

I. A. Chuchkalov; S. A. Abrukov

1970-01-01

374

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...

375

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

376

Prediction of laminar flame properties of propane-air mixtures  

Microsoft Academic Search

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

C. K. Westbrook; W. J. Pitz

1985-01-01

377

Prediction of laminar flame properties of propane-air mixtures  

Microsoft Academic Search

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

C. K. Westbrook; W. J. Pitz

1983-01-01

378

ACOUSTIC NEARFIELD CHARACTERISTICS OF A WRINKLED PREMIXED FLAME  

Microsoft Academic Search

Nearly all combustion systems are prone to exhibit self-excited oscillations. These oscillations are driven by means of acoustic interactions between the flame and it's acoustic near-field. This acoustic nearfield is sensitive to the shape of the flame surface. This paper analyzes the near-field acoustic characteristics of premixed wrinkled, flame fronts subjected to acoustic excitation. The flame thickness is assumed to

H. SANTOSH; R. I. SUJITH

2006-01-01

379

Stable cyclonic flames of natural gas and air  

Microsoft Academic Search

Gases flowing cyclonically from a nozzle burned stably at velocities up to 100 ft\\/sec. Flame temperatures were higher than 2400°F Stable flames were obtained in cyclonic flow in ducts of 1\\/2 in. inside diameter, 4 to 20 in. long. Flames burned inside ducts but did not touch or heat walls, although flame temperatures of over 2600°F and velocities of 700

L. F. Albright; L. G. Alexander

1956-01-01

380

Flame photometric detector for thin-layer chromatography  

Microsoft Academic Search

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

Minoru Ogasawara; Kyoko Tsuruta; Shinsuke Arao

2002-01-01

381

On stability of premixed flames in stagnation - Point flow  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

382

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

383

Flame Tests Using Improvised Alcohol Burners  

NASA Astrophysics Data System (ADS)

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

Dragojlovic, Veljko

1999-07-01

384

Properties of flame synthesized germanium oxide nanoparticles.  

PubMed

Germanium oxide (GeOx) nanoparticles in the size range from 1.5 to 10 nm were synthesized in a low-pressure premixed H2/O2/Ar flame in the pressure range 25-55 mbar. The flame was doped with different amounts of tetramethylgermanium (Ge(CH3)4) ranging from 500 to 2000 ppm. The influence of process parameters such as pressure, flame coordinate, and cold gas flow velocity with respect to growth of germanium oxide particles were investigated. The formed particles were analyzed in-situ according to their mass and charge by means of a particle mass spectrometer (PMS). The specific surface area was determined ex-situ by the BET method. The crystal structure and chemical composition of the produced nanopowder was characterized by EDX and XRD measurements. Additionally, the particles were analyzed by means of FT-IR spectroscopy. PMID:15913252

Simanzhenkov, Vasily; Wiggers, Hartmut; Roth, Paul

2005-03-01

385

Interaction of pulsating and spinning waves in nonadiabatic flame propagation  

Microsoft Academic Search

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

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

1987-01-01

386

Calculations of premixed turbulent flames by pdf methods  

Microsoft Academic Search

Idealized premixed turbulent flames are studied using probability density function (pdf) methods. A modeled transport equation for the joint pdf of velocity and the reaction progress variable is solved by a Monte Carlo method. Detailed calculations of flame properties and flow statistics, including the flame speed, the scalar flux, the turbulence intensities, the kinetic energy budget and conditional statistics are

M. S. Anand; S. B. Pope

1987-01-01

387

Swirl effects on harmonically excited, premixed flame kinematics  

Microsoft Academic Search

This paper describes the response of a swirling premixed flame with constant burning velocity to non-axisymmetric harmonic excitation. This work extends prior studies of axisymmetric forcing, which have shown that wrinkles are excited on the flame that propagate downstream along the mean flame surface at a speed given by Uocos?, where Uo is the mean flow velocity and ? is

Vishal Acharya; Shreekrishna; Dong-Hyuk Shin; Tim Lieuwen

388

Vortex phase-jitter in acoustically excited bluff body flames  

Microsoft Academic Search

This paper describes an experimental study of the effect of acoustic excitation on bluff body stabilized flames, specifically on the flow field characteristics. The Kelvin-Helmholtz (KH) instability of the shear layer is excited due to the incident acoustics. In turn, the KH instability imposes a convecting, harmonic excitation on the flame, which leads to spatially periodic flame wrinkling and heat-release

Santosh J. Shanbhogue; Michael Seelhorst; Tim Lieuwen

2009-01-01

389

Acoustic near-field characteristics of a conical, premixed flame  

Microsoft Academic Search

The occurrence of self-excited pressure oscillations routinely plagues the development of combustion systems. These oscillations are often driven by interactions between the flame and acoustic perturbations. This study was performed to characterize the structure of the acoustic field in the near field of the flame and the manner in which it is influenced by oscillation frequency, combustor geometry, flame length

Doh-Hyoung Lee; Tim C. Lieuwen

2003-01-01

390

Structure And Dynamics Of Modulated Traveling Waves In Cellular Flames  

Microsoft Academic Search

We describe spatial and temporal patterns in cylindrical premixed flames in the cellular regime, $Le < 1$, where the Lewis number $Le$ is the ratio of thermal to mass diffusivity of a deficient component of the combustible mixture. A transition from stationary, axisymmetric flames to stationary cellular flames is predicted analytically if $Le$ is decreased below a critical value. We

A. Bayliss; B. J. Matkowsky; H. Riecke

1994-01-01

391

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

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

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

392

The Forced Flow Flame-Spreading Test (FFFT)  

NASA Technical Reports Server (NTRS)

The Forced Flow Flame-Spreading Test was designed to study flame spreading over solid fuels when air is flowing at a low speed concurrent airflows, some materials are more flammable in microgravity than earth. 1.5 cm flame in microgravity that melts a polyethylene cylinder into a liquid ball.

1997-01-01

393

Sensitivity analysis of transfer functions of laminar flames  

Microsoft Academic Search

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

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

394

Experimental and numerical study of premixed flame flashback  

Microsoft Academic Search

The flashback of premixed flames in ducts is investigated both experimentally and theoretically. New experimental results, compatible with classical results on the subject, are presented. A minimal model for premixed flame propagation in a boundary layer is presented. The scales of the problem are derived from asymptotic considerations. Numerical results for the flame propagation velocity are given; in particular we

V. Kurdyumov; E. Fernández-Tarrazo; J.-M. Truffaut; J. Quinard; A. Wangher; G. Searby

2007-01-01

395

30 CFR 7.26 - Flame test apparatus.  

Code of Federal Regulations, 2013 CFR

...Ventilation Tubing § 7.26 Flame test apparatus. The...apparatus used to test for flame-resistance of brattice...16-gauge stainless steel duct section tapering from...connected to the tapered duct section; (e) A...other in pairs and the flame from these pairs...

2013-07-01

396

The Asymmetric Behavior of Steady Laminar Flame Propagation in Ducts  

Microsoft Academic Search

The steady propagation of a premixed flame in an isothermal duct subject to the Poiseuille flow is numerically investigated in the present study. The complete Navier-Stokes equations are used in the mathematical formulation and the flame chemistry is modeled by an one-step overall reaction. The numerical results show that the flame propagating steadily in ducts opposed to the Poiseuille flow

Chien-Hsiung Tsai

2008-01-01

397

Gaseous Premixed Flames in Non-Uniform Flows.  

National Technical Information Service (NTIS)

A theoretical analysis led to an evolution law for a flame front propagating in a nonuniform flow when the scales of the nonuniformity of the flow are much larger than the flame thickness. This law gives the local burning velocity of the flame front as a ...

P. Cambray B. Deshales G. Joulin

1988-01-01

398

Flame Measurement and Combustion Diagnoses with Spectrum Analysis  

Microsoft Academic Search

With the spectroscopic technique presented in this paper, a CCD spectrometer is employed to acquire flame emission spectra, from which both the temperature and emissivity of flames can be obtained as well as some characteristic spectral lines correlated with the fuel type and the combustion state. As shown by the experiment results, the shape of flame emission spectrum curve varies

Xiaoshu Cai; Zhihai Cheng; Shimin Wang

2007-01-01

399

Thermoplastic Polyurethane-Encapsulated Melamine Phosphate Flame Retardant Polyoxymethylene  

Microsoft Academic Search

Due to its “unzipping” degradation mode and poor compatibility with most other flame retardants, polyoxymethylene (POM) is the most difficult flame-retarded polymer among macromolecular materials. In this project, we took advantage of thermoplastic polyurethane (TPU) resin, which possesses good compatibility with POM, serving as an encapsulation layer, and the carrier resin of the nitrogen-phosphorus composite flame retardant melamine phosphate to

Yuan Liu; MeiFang Liu; Daiyi Xie; Qi Wang

2008-01-01

400

Reduced Kinetic Mechanisms for Propane Diffusion Flames  

NASA Astrophysics Data System (ADS)

Propane is an important practical fuel and its high temperature combustion is characterised by the rapid decomposition into smaller C1-C3 intermediates [15.1]. This behaviour is similar to the combustion of more complex hydrocarbon fuels. From a modelling perspective, a propane combustion mechanism, compared to that of other higher hydrocarbons, requires the smallest number of species and reactions that are necessary for a thorough kinetic study of the C1-C3 species. Previous modelling studies of propane combustion with detailed [15.1,15.2] and simplified [15.3] chemistry have mainly focused on premixed flames with little attention given to non-premixed conditions [15.4]-[15.5]. There is also a lack of simplified mechanisms based on the systematic reduction of complex chemical mechanisms for non-premixed propane flames. The purpose of the present study is to formulate reduced reaction mechanisms based on the systematic theoretical investigation of propane-air diffusion flames using a planar counterflow geometry and the detailed chemistry defined in Chap. 1. Propane flames are here computed using rates of strain from 10/s to extinction at pressures ranging from 1 to 10 bar. The deduced mechanisms are also validated against the experimental results obtained by Tsuji and Yamaoka [15.6] for counterflow propane-air flames at strain rates of 150/s and 350/s. Using the results of the above computations the behaviour of non-premixed propane flames is analysed and the most important reaction paths indentified as functions of rate of strain and pressure.

Leung, K. M.; Lindstedt, R. P.; Jones, W. P.

401

Photographic surface photometry of the Milky Way. III - Photometry of the central area of the Galaxy in the ultraviolet  

NASA Astrophysics Data System (ADS)

6 photographic plates, taken at La Silla, Chile, with the spherical mirror super-wide-angle camera of the Astronomisches Institut der Ruhr Universität Bochum (see paper I: Schmidt-Kaler, Th. et al., 1982) were measured to study the surface brightness distribution in the area around the centre of the Milky Way, between galactic longitudes 297° and 27°, and latitudes - 30° to + 30°, with an angular resolution of 0.°3 × 0.°3 (Fig. 5). In section 2 the plate material and details of the reductions are presented, so far as not already given in paper I. During the photometric scanning of the plates all stars brighter than a limiting magnitude mlim were marked by hand, and the corresponding data points were replaced by an average from neighbouring points (section 3). Defined at the level of 50% elimination, mlim ? 8.m0 (in U). Figure 4 shows the effect of various methods of eliminating bright stars. The errors of the surface photometry are discussed in section 4. The internal mean error of the intensity of one data point, as determined from the scatter from the 6 plates, is ± 9.4%. This error is split into an additive component ± 8 S10U (S10 = intensity of a star of 10m), mostly due to the contributions of airglow and scattered light, and a multiplicative component of ± 7.5%, mostly due to the uncertainty of the photographic characteristic curve. Possible systematic errors are estimated and upper limits for these are given in table II. Section 5 presents the results of the photometry. For the sake of clear representation in the isophote map (Fig 5) data with intermediate intensities 110 < Igal ? 250 S10U were smoothed over 0.°9 × 0.°9, data with Igal ? 110 S10U were smoothed over 1.°2 × 1.°2. The mean error of the isophotes is about ± 6%. We then compare our photometry with existing ultraviolet surface photometries. Apart from the area l = 320° to 330°, b = -25° to -20° where our intensities are probably vitiated by some remaining airglow influence, there is generally very good agreement with the results of Seidensticker, Schinidt-Kaler and Schlosser (= paper II), their values being smaller by a statistically insignificant additive difference of -14(± 15) S10U. The comparison (Fig 6) with the photoelectric surface photometry of Pfleiderer and Mayer (1971) shows a negligible additive difference of -8 (± 12) S10U, but a large scale difference of 24(± 9)%, the Bochum values being larger. The comparison with the measurements of Leinert and Richter (1981), obtained by the satellite Helios, shows very good agreement in the run of the intensities (Fig. 7). Computation of a point by point correlation reveals their values being smaller by an additive difference of -5 (± 2) S10U and a scale difference of 17(± 2)%. As obvious from figure 7 the main difference in the two photometry results from the finer structures in our data, due to different resolution and different completeness in eliminating background stars. Thus we constructed a lower envelope to our data. This reveals an additive difference of 0 (± 0.3) S10U and a scale difference of 2.4 (± 9)% in the same sense as above. In the last paragraph we discuss the structure of the Milky Way central region in U, in particular those spiral filaments which appear inclined to the galactic equator (shingles, corrugations). The three shingles discovered by Schmidt-Kaler and Schlosser (1973) in the next-inner spiral arm-I and an additional feature appear if the data-field of the UV photometry is spatially differentiated (Fig. 8).

Proell, H. J.; Schmidt-Kaler, T.; Schlosser, W.

1983-01-01

402

Edge-Flames in Von Karman Swirling Flows  

NASA Technical Reports Server (NTRS)

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

Nayagam, Vedha; Williams, Forman A.

1999-01-01

403

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

404

A numerical study on the formation of diffusion flame islands in a turbulent hydrogen jet lifted flame  

Microsoft Academic Search

This paper presents a numerical study on the formation of diffusion flame islands in a hydrogen jet lifted flame. A real size hydrogen jet lifted flame is numerically simulated by the DNS approach over a period of about 0.5ms. The diameter of hydrogen injector is 2mm, and the injection velocity is 680m\\/s. The lifted flame is composed of a stable

Yasuhiro Mizobuchi; Junji Shinjo; Satoru Ogawa; Tadao Takeno

2005-01-01

405

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

406

Pdf prediction of supersonic hydrogen flames  

NASA Technical Reports Server (NTRS)

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

Eifler, P.; Kollmann, W.

1993-01-01

407

Pregel Aggregate Structure in A Sooty Flame  

NASA Astrophysics Data System (ADS)

Optical structure factor and fast microphotography have been used to study large gel-like soot aggregates in acetylene diffusion flames. We find that submicron, D_f~= 1.8 soot fractal aggregate form early in the flames or when the carbon concentration is low. Otherwise soot clusters with diameters as large as 100? and fractal dimension approaching D_f~= 2.5 are obtained. One scenario to explain these observations, consistent with simulations we have performed, is that the smaller D_f~= 1.8 aggregates ``raft'' together to form percolated superclusters. This occurs after the normalized free volume becomes significantly less than one.

Sorensen, C. M.; Shi, D.; Kim, W.; Fry, D.; Chakrabarti, A.

2002-03-01

408

Flame synthesis of high Tc superconductors  

NASA Astrophysics Data System (ADS)

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

Zachariah, Michael R.; Huzarewicz, Serge

1991-10-01

409

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

Microsoft Academic Search

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

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

2004-01-01

410

Suppression of Low Strain Rate Nonpremixed Flames by an Agent  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

411

Turbulent Flame Speed and the Deflagration-to-Detonation Transition  

NASA Astrophysics Data System (ADS)

Turbulent thermonuclear burning fronts are presently believed to be the key component of the explosion mechanism powering type Ia supernovae (SNIa). Rapid increase in intensity of turbulent motions inside the white dwarf in the course of the explosion causes wrinkling of the flame, which significantly increases its surface area and, thus, accelerates the flame. This creates tightly packed flame configurations with high local flame curvature. Furthermore, small-scale turbulence begins to penetrate the flame, thus modifying its structure and altering its properties. Even in the thin reaction zone regime, i.e., when turbulence has disrupted only the preheat zone of the flame, the turbulent flame may be significantly different locally from a planar laminar burning front. Large-scale numerical modeling of SNIa requires the use of subgrid-scale models which accurately reproduce local properties, and in particular the local speed, of the turbulent flame formed in the presence of intense turbulence. We present results of the direct numerical simulations aimed at studying the mechanisms which control the turbulent flame speed in the thin reaction zone regime. Simulations were performed using the massively parallel reactive-flow code Athena-RFX. The increase of the flame surface area is the primary process responsible for accelerating the flame. We find, however, a significant additional increase in flame speed at high turbulent intensities. Such accelerated burning is the result of flame collisions in a tightly packed turbulent flame. Failure to account for this process in subgrid models can lead to the underestimation of the turbulent flame speed by as much as 30-50%. Finally, we discuss the implications of these results for the process of the deflagration-to-detonation transition. This work was supported in part by the Naval Research Laboratory, the Office of Naval Research, the Air Force Office of Scientific Research, and by the National Science Foundation through the TeraGrid resources.

Poludnenko, Alexei Y.; Oran, E. S.

2011-01-01

412

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

413

Theory of Flame-Acoustic Interaction for Flame Propagation in Spherical Chamber.  

National Technical Information Service (NTIS)

A simplified model describing acoustically-generated parametric instability in a spherical chamber is developed for quasi-one-dimensional, low-Mach flames. We demonstrate how sound waves generated by a centrally-ignited, outwardly-propagating accelerating...

C. K. Law V. Akkerman

2011-01-01

414

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

415

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

416

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

417

Measurement of flame temperature distribution by IR emission computed tomography  

SciTech Connect

Noncontact and nondestructive measurements for determining flame temperature distribution are under investigation. This paper proposes a new method we have called infrared emission computed tomography to measure the temperature distribution in arbitrary transaxial layers of the flame by calculating the infrared radiation intensity emitted from a flame as the projection data. The authors developed an experimental system using an infrared sensor as the detector and applied our method to a laminar flame. They obtained good images of the temperature distribution in a flame. In addition, temperature profiles obtained by this method were in good agreement with the results of the thermocouple probe measurement.

Uchiyama, H.; Nakajima, M.; Yuta, S.

1985-12-01

418

UBV photometry of 56 Ari: 1990-1994  

NASA Astrophysics Data System (ADS)

We report on five seasons of UBV photometry of 56 Ari obtained with the 0.4-m telescope of the Braeside Observatory starting in the fall of 1990. These observations were part of the data used by Adelman et al. (2001) to find the very slow decrease in the main period of this magnetic CP star and the secondary period of approximately 5 years. Comparison of the light curves obtained in different seasons even with the same telescope tend to show slight discrepancies.

Fried, R. E.; Adelman, S. J.

2003-01-01

419

Io hot spots - Infrared photometry of satellite occultations  

NASA Technical Reports Server (NTRS)

Io's active hot spots, which are presently mapped on the basis of IR photometry of this moon's occultation by other Gallilean satellites, are obtained with greatest spatial resolution near the sub-earth point. A model is developed for the occultation lightcurves, and its fitting to the data defines the apparent path of the occulting satellite relative to Io; the mean error in apparent relative position of occulting satellites is of the order of 178 km. A heretofore unknown, 20-km diameter hot spot is noted on Io's leading hemisphere.

Goguen, J. D.; Matson, D. L.; Sinton, W. M.; Howell, R. R.; Dyck, H. M.

1988-01-01

420

Spitzer\\/IRAC Photometry of the Eta Chameleontis Association  

Microsoft Academic Search

We present IRAC 3.6, 4.5, 5.8 and 8 micron photometry for the 17 A, K and M\\u000atype members of the Eta Chameleontis association. These data show infrared\\u000aexcesses toward six of the 15 K and M stars, indicating the presence of\\u000acircumstellar disks around 40% of the stars with masses of 0.1-1 solar mass.\\u000aThe two A-stars show no

S. T. Megeath; L. Hartmann; K. L. Luhman; G. G. Fazio

2005-01-01

421

uvby photometry in McCormick proper motion fields  

NASA Technical Reports Server (NTRS)

The Danish 50 cm telescope at the European Southern Observatory was used to obtain high-precision uvby photometry for 50 F2 to G2 stars, with V values in the 9.4-12.3 mag range, which were selected in the southern galactic polar regions of the McCormick proper motion fields and measured on six different nights. The brighter stars are found to systematically exhibit smaller m(1) indices, of about 0.02 mag, upon comparison with the earlier data of Blaauw et al (1976). Single measurements are given for 98 stars in eight McCormick fields at intermediate southern galactic latitudes.

Degewij, J.

1982-01-01

422

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

423

Long-term photometry of Variables III (Manfroid+, 1995)  

NASA Astrophysics Data System (ADS)

This is the third catalogue of photometric data in the Stroemgren system obtained during the period October 1990-January 1992 in the framework of the Long-Term Photometry of Variables (LTPV) program at the European Southern Observatory. All data have been obtained with the Danish 50-cm telescope. The mean values of the r.m.s. deviations of the differential measurements of comparison stars are around (from Table 4 of paper) ------------------------------ y b-y m1 c1 ------------------------------ 0.005 0.002 0.004 0.006 ------------------------------ (2 data files).

Manfroid, J.; Sterken, C.; Cunow, B.; de Groot, M.; Jorissen, A.; Kneer, R.; Krenzin, R.; Kruijswijk, M.; Naumann, M.; Niehues, M.; Schoeneich, W.; Sevenster, M.; Vos, N.; Vogt, N.

1995-11-01

424

Multicolour time series photometry of three periodic ultracool dwarfs  

NASA Astrophysics Data System (ADS)

Photometry in I, or contemporaneously in I and R, of the known variable ultracool dwarfs Kelu-1 and 2MASS J11553952-3727350 is presented. The nature of the variability of Kelu-1 appears to evolve on time-scales of a day or less. Both the period and amplitude of the variability of 2MASS J11553952-3727350 have changed substantially since publication of earlier observations of the object. DENIS 1454-6604 is a new variable ultracool dwarf, with persistent and prominent brightness modulations at a period of 2.6 h.

Koen, Chris

2013-02-01

425

Limits to CCD ensemble photometry precision, and prospects for asteroseismology  

NASA Astrophysics Data System (ADS)

Results are reported of CCD-ensemble time-resolved photometry with the KPNO 2.1-m telescope yielding precision of 400 micromag per minute of integration. Detailed stellar-evolution modeling and eigenfrequency-analysis results are given for the stars of the old open cluster M67. Using observed amplitudes of solar p-mode oscillations, and published scaling laws with spectral type, direct detection of solar-analog oscillations on 13th-magnitude M67 stars is possible with a several-night 4-m network campaign. Asteroseismology on a substantial ensemble of cluster stars promises to allow fundamental tests of stellar structure and evolution theory.

Gilliland, Ronald L.; Brown, Timothy M.

1992-07-01

426

Vilnius Photometry in two Nebulae (Straizys et al., 1993)  

NASA Astrophysics Data System (ADS)

The results of photoelectric photometry of 564 stars in the Vilnius seven-color system in three areas near the North America and Pelican nebulae are given. Photometric spectral types, absolute magnitudes, colour excesses, interstellar extinctions and distances of the stars are determined. We find that the dark cloud separating both nebulae is at 580pc distance. A number of stars immersed into the dark cloud have been found. It seems that the dark cloud extends to south down to 40deg declination. The area southwest of ? Cyg in the declination zones 42 and 43deg is comparatively transparent at least up to 1kpc. (6 data files).

Straizys, V.; Kazlauskas, A.; Cernis, K.; Vansevicius, V.

1994-11-01

427

Eos, Koronis, and Maria Family Asteroids: Infrared (JHK) Photometry  

NASA Technical Reports Server (NTRS)

Infrared photometry at 1.2, 1.6, and 2.2 micrometer (JHK) is reported for 56 asteroids in the Eos, Koronis and, Maria dynamical families. These data are consistent with similar surface composition for all of the asteroids of each family. The infrared colors within each family cluster in the region observed for the S taxonomic class, but Eos asteroids may belong to a separable K class. Asteroid 243 Ida, which was observed by the Galileo spacecraft, is a typical member of the Koronis family. The average infrared colors of the Maria family are slightly redder than those of the Eos and Koronis families.

Veeder, Glenn J.; Matson, Dennis L.; Owensby, Pamela D.; Gradie, Jonathan C.; Bell, Jeffrey F.; Tedesco, Edward F.

1995-01-01

428

Photometric redshifts determinations for galaxies by means of multicolor photometry  

NASA Astrophysics Data System (ADS)

Multicolor photometry is increasingly used for galaxies redshifts estimations. Using optical and NIR photometrical data and HST/WFPC2 morphological data we analyze the environments of radio galaxies 3C 184 (z = 0.996, 35 galaxies in a 6.2 arcmin2 field) and 3C 210 (z = 1.169, 57 galaxies in a 6.2 arcmin2 field). Color - color diagrams, red sequence technique and template fitting technique are used in order to determine the photometric redshifts of galaxies and to analyze the clustering of galaxies and ERGs (extremely red galaxies) in the environment of these two radio galaxies at z ~ 1.

Popescu, Nedelia A.

2007-03-01

429

ZJ VISTA photometry in NGC253 stellar halo (Greggio+, 2014)  

NASA Astrophysics Data System (ADS)

This catalogue lists position, magnitude and photometric error of stellar sources identified on the VISTA Z and J images of the NGC 253 spiral galaxy. The data were analyzed with the VISTA data flow system at the Cambridge University Astronomy Survey Unit, and photometry carried out with the imcore package, which provides a morphological classification for each detection. The catalogue presented here is referred to as Catalogue B in the paper, and includes sources classified as stellar or likely stellar in both filter (Type=1), plus sources classified as stellar on the J and extended on the Z tile (Type=4). The last column of the catalogue reports this classification. (1 data file).

Greggio, L.; Rejkuba, M.; Gonzales, O. A.; Arnaboldi, M.; Iodice, E.; Irwin, M.; Neeser, M. J.; Emerson, J.

2014-02-01

430

Hardness Ratio Estimation in Low Counting X-Ray Photometry  

NASA Astrophysics Data System (ADS)

Hardness ratios are commonly used in X-ray photometry to roughly indicate spectral properties. They are usually defined as the ratio of counts in two different wave bands. This definition, however, is problematic when the counts are very limited. Here we instead define the hardness ratio using the ?-parameter of Poisson processes and develop an estimation method via Bayesian statistics. Our Monte Carlo simulations show the validity of our method. Based on this new definition we can estimate the hydrogen column density for the photoelectric absorption of X-ray spectra in the case of low counting statistics.

Jin, Y. K.; Zhang, S. N.; Wu, J. F.

2006-12-01

431

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

Microsoft Academic Search

An open-open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane-air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re = 1780-4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube

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

2009-01-01

432

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

Microsoft Academic Search

An open–open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane–air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re=1780–4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube combustor. This

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

2009-01-01

433

Fundamental mechanisms in premixed turbulent flame propagation via flame-vortex interactions. Part I: Experiment  

SciTech Connect

A combined experimental and numerical study of the interaction of a two-dimensional vortex with planar laminar premixed flames has been carried out. In such a flow, the flame is subjected to time-varying strain and curvature and, hence, the interaction may be viewed as a model of fundamental processes occurring in premixed turbulent flames. Part I of the paper describes the experimental facility and diagnostics employed and presents results from the experimental investigation of effects of Lewis number, radiative heat losses, and unsteadiness on the interaction. A two-dimensional V-shaped laminar premixed flame is stabilized on a heated wire in a constant-area square duct. A two-dimensional vortex pair, generated from a slot in the duct wall, eventually interacts with one of the flame fronts. Schlieren and smoke flow visualization indicate that the flow field remains two-dimensional over a significant part of the flame-vortex interaction. This feature allows use of line-of-sight diagnostics, and, in particular, a CO{sub 2}* emission m=imaging technique for determination of quantitative heat release rates. Several fuel and oxidizer mixtures are employed in order to vary the Lewis number from 0.8 to 1.6 and to increase the heat loss parameter by a factor of 2.6. For the conditions investigated, the Lewis and Damkoehler numbers are important controlling parameters in the evolution of the heat release rate and radiative losses may be neglected. In Part II of the paper, results from direct numerical simulations of a flame-vortex pair interaction are presented. The simulations were performed using a two-dimensional Navier-Stokes solver in which variable density and temperature-dependent transport coefficients are considered. The simulations utilize the initial conditions of the experiment and were used to investigate the role of multistep chemistry in the flame-vortex interaction.

Samaniego, J.M.; Mantel, T.

1999-09-01

434

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

Microsoft Academic Search

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

Biao Zhou; Andrzej Sobiesiak; Peng Quan

2006-01-01

435

Study on intumescent flame retarded polystyrene composites with improved flame retardancy  

Microsoft Academic Search

The flame retardancy and thermal stability of ammonium polyphosphate\\/tripentaerythritol (APP\\/TPE) intumescent flame retarded polystyrene composites (PS\\/IFR) combined with organically-modified layered inorganic materials (montmorillonite clay and zirconium phosphate), nanofiber (multiwall carbon nanotubs), nanoparticle (Fe2O3) and nickel catalyst were evaluated by cone calorimetry, microscale combustion calorimetry (MCC) and thermogravimetric analysis (TGA). Cone calorimetry revealed that a small substitution of IFR by most

Hongdian Lu; Charles A. Wilkie

2010-01-01

436

Study of Microwave Plasma Enhanced Methane Flame at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

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

Srivastava, Nimisha; Wang, Chuji

2011-11-01

437

The Interaction of High-Speed Turbulence with Flames  

NASA Astrophysics Data System (ADS)

Interaction of flames with turbulence occurs in systems ranging from chemical flames on Earth to thermonuclear burning fronts in supernovae. We present results of a systematic study of the dynamics and properties of turbulent flames formed under the action of high-speed turbulence in stoichiometric hydrogen-air mixture. Numerical simulations were performed using the massively parallel reactive-flow code Athena-RFX. Here we discuss (1) global properties of the turbulent flame in this regime (flame width, speed, etc.); (2) the internal structure of the flame brush; and (3) the internal structure of the flamelets folded inside the flame brush. We demonstrate that, in the case of hydrogen, turbulence does not affect the internal flame structure essentially for all subsonic turbulent intensities. We address the relative role of large-scale and small-scale motions on global and local properties of the turbulent flame. We also consider the processes that determine the turbulent burning velocity and identify two distinct regimes of flame evolution. Finally, we discuss the effects of non-equilibrium non-Kolmogorov turbulence on the turbulent flame properties.

Poludnenko, Alexei; Oran, Elaine

2009-11-01

438

Laser-saturated fluorescence measurements in laminar sooting diffusion flames  

NASA Technical Reports Server (NTRS)

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

Wey, Changlie

1993-01-01

439

The structure of cyanogen-nitrogen dioxide premixed flames  

SciTech Connect

This paper presents the results for two cyanogen - nitrogen dioxide flames. The most striking feature of these flames is their intense visible emission and large heat release. CN, major stable species and temperature profiles have been measured and are compared to the results of flame structure calculations in order to develop a combustion mechanism. The richer of the two flames studied is more stable than the leaner flame. This is because oxygen atoms in the leaner flame react with NO/sub 2/ to give NO and O/sub 2/, thereby depleting the ''reactive'' free radical pool. In the richer flame, the major route for NO/sub 2/ loss is thermal decomposition to give NO+O. This adds oxygen atoms to the ''reactive'' radical pool and stabilizes the flame. The major loss mechanisms for CN in these flames led to the formation of NCO which is depleted primarily by reacting with NO and disproportionation. Both reactions serve to stabilize the flame, the former reaction releases a substantial amount of heat and the second is a major channel for N production. The largest differences between the observed and calculated profiles occur for NO far down stream and CN in the richer flame. These discrepancies are probably due to the lack of additional sink reactions for C and CN in the model.

Smith, O.I.; Thorne, L.R.

1986-01-01

440

The effects of gravity on wrinkled laminar flames  

SciTech Connect

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

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

1992-09-01

441

The effects of gravity on wrinkled laminar flames  

SciTech Connect

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

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

1992-09-01

442

Flame propagation in a dusty gas  

Microsoft Academic Search

The phlegmatizing (heat absorbing) properties of powders used for extinguishing fires were considered. An indicator of the effectiveness of fire extinguishing media is the sensitivity of combustion rate to concentration of the phlegmatizer. In this connection the change in flame velocity was studied as a function of the dispersed material parameters. The effect of the powder on combustion was evaluated

E. I. Gubin; I. G. Dik

1988-01-01

443

FLAME Test Vehicle 1976 Flight Test Series.  

National Technical Information Service (NTIS)

The FLAME vehicle was designed as an inexpensive test vehicle to subject various reentry nosetip experiments to ICBM-type reentry environments. The vehicle is a two-stage solid rocket that is dropped from an F-4 aircraft, allowed to coast for a predetermi...

J. R. Fryer

1977-01-01

444

Characterization of acoustically forced swirl flame dynamics  

Microsoft Academic Search

Lean premixed combustors are highly susceptible to combustion instabilities, caused by the coupling between heat release fluctuations and combustor acoustics. In order to predict the conditions under which these instabilities occur and their limit cycle amplitudes, understanding of the amplitude dependent response of the flame to acoustic excitation is required. This study presents an analysis of phase-locked OH PLIF images

Sai Kumar Thumuluru; Tim Lieuwen

2009-01-01

445

Flaming Gorge Unit: Colorado River Storage Project.  

National Technical Information Service (NTIS)

One of the first sights John Wesley Powell encountered on his journey down the Colorado and Green Rivers in 1869 was a beautiful canyon which he christened Flaming Gorge Canyon because of its fiery colors. Today the canyon retains its fiery colors, undimi...

T. R. Linenberger

1998-01-01

446

Sound Emission of Ducted Premixed Flames  

NASA Astrophysics Data System (ADS)

Sound emissions of laminar premixed flames stabilized on the outlet plane of a burner located at one end of a rectangular duct were experimentally investigated. Specifically, this research applied the approach of direct acoustic admittance measurement to investigate and elucidate the close relations between sound emission, non-reactive burner acoustic admittance, flame equivalence ratio and combustor length. The admittance data were obtained by directly measuring the amplitudes of velocity and pressure oscillations, and the phase relations between the oscillatory velocity and pressure. Results of this research reveal that flames would hardly induce sound emissions without the “right” acoustic property of the non-reactive burner system. Also, the reactive burner acoustic admittance is dominated by the non-reactive burner acoustic admittance. The flame is important in determining the strength of possible sound emissions. This study also shows that the fundamental frequency of the combustor system should be within the range of critical frequencies of the non-reactive burner system to sustain possible sound emissions. The critical frequencies, the frequencies for possible sound emissions and the “right” acoustic property of the burner system could be approximately predicted by knowing the distribution of the imaginary parts of non-reactive burner acoustic admittance.

Chen, Tzeng-Yuan; Chen, Man-Ge

1999-03-01

447

The Structure of a Premixed Turbulent Flame  

Microsoft Academic Search

An experimental study of the structure of a premixed turbulent flame propagating in a duct-confined, stoichiometric propane-air mixture has been carried ou