摘要:

To estimate the inhibition effect of several bromine-free polyfluoroalkylamines such as (CF3CF2)N, (CF3)2NCF2CF3, (CF3)2NCF2,CHF2and (CF3)2NCF=CF2on flame propagation, the laminar burning velocity was measured for a mixture of 9.5% methane, 90.0% air, and 0.5% inhibitor, at an initial temperature of 298 ± 2 K. and a pressure of 1 atm. All of the polyfluoroalkylamines inhibited flame propagation less than CF3Br(Halon 1301), but more than CH3CHFCF3(FM200). Calculations showed that the inhibition effect of polyfluoroalkylamines was caused not only by physical factors, but also by a chemical process in which fluoric species capture chain carriers (H, O, and OH) ofcombustion reactions to form stable HF molecules. The inhibition efficiencies of polyfluoroalkylamines were found to be higher than those of polyfluoroalkanes because of polyfluoroalkylamines decomposition to reactive polyfluoroalkyl radicals in the lower temperature region of each flame. The application of polyfluoralkylamines to fire-extinguishers was also discussed

ISSN:0010-2202    

DOI:10.1080/00102209408935477

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The role of streamwise-spanwise vorticity interactions that occur in turbulent shear flows on flame/vortex interactions is examined by means of asymptotic analysis and numerical simulation in the limit of small Mach number. An idealized model is employed to describe the interaction process. The model consists of a one-step, irreversible Arrhenius reaction between initially unmixed species occupying adjacent half-planes which are then allowed to mix and react in the presence of a streamwise vortex embedded in a shear flow. It is found that the interaction of the streamwise vortex with shear gives rise to small-scale velocity oscillations which increase in magnitude with shear strength. These oscillations give rise to regions of strong temperature gradients via viscous heating, which can lead to multiple ignition points and substantially decrease ignition times. The evolution in time of the temperature and mass-fraction fields is followed, and emphasis is placed on the ignition time and structure as a function of vortex and shear strength.

ISSN:0010-2202    

DOI:10.1080/00102209408935478

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Tunable excimer lasers are used to obtain 2-D images to analyse spatial distributions of different species in a liquid fuelled flame of a single burner model combustor with optical access from all sides at ambient pressure and a maximum air inlet temperature of 600 K. The flame is stabilised by a turbulent structure generated by air mixing jets in combination with the axial swirls of an air spoke injector

ISSN:0010-2202    

DOI:10.1080/00102209408935479

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Measurements are reported of the specific heat of 5 U.S. Army solid gun propellants over the temperature range — 40°C to 75°C at atmospheric pressure. The propellants are members of the BRL Research Series propellants that have been widely distributed to research laboratories in the U.S. These propellants include representative types from each class of materials that are either in the fielded inventory or experimental (“X” prefix), i.e., a single base (M10), a double base (M9), a homogeneous triple base (JA2), a composite triple base (M30), and a composite nitramine (XM39). The measurements were performed with a commercial differential scanning calorimeter (DSC) which was calibrated to the propellant heat-flow range using two sapphire standards of different masses. Corrections were made for temperature lags in both the standard and propellant specimens. The average values are estimated to be accurate to within ±5%, and polynomial fits over the stated temperature range are provided for convenient use in calculations

ISSN:0010-2202    

DOI:10.1080/00102209408935480

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A qualitative physical characterization of particulates emitted in undiluted exhaust of single cylinder direct injection (D. I.) diesel engine was performed. In the experiments, an optical technique based on a Xenon lamp was used to measure scattering and extinction coefficients in the spectral range of 0.2 to 0.6 nm at the exhaust of an engine operating under steady-state conditions. The spectral nature of the data was first compared against the theoretical predictions performed for spherical particles and clusters, using the complex index of refraction data for glassy carbon. Additional calculations were performed after determining the spectral refractive index of exhaust soot directly from experiments, which yielded better comparisons with the measured scattering efficiency spectra. The discrete dipole approximation was employed to predict radiative properties of 16, 32, and 64-sphere random-shaped clusters. Based on these comparisons, the effective size of exhaust soot particles was estimated qualitatively for different experimental conditions

ISSN:0010-2202    

DOI:10.1080/00102209408935481

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Scaling relations for flame stretch profiles (i.e. spatial distribution of flame stretch) induced by a vortex are provided in that the magnitude of the flame stretch profiles is found to scale with the maximum flame stretch (K*) determined by both the characteristic flow strain and flame curvature contribution, while the spatial extent of the flame stretch profiles scales as (r2K*/SL) where rmand SLare the vortex radius and laminar flame speed, respectively. In addition, temporal variations in flame stretch profiles can be approximated by assigning a parabolic function for the time-dependent peak flame stretch and appropriately scaling the magnitude and spatial extent of flame stretch profiles.

ISSN:0010-2202    

DOI:10.1080/00102209408935482

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Results of measured adiabatic burning velocities of methane- and propane-air premixed laminar flames are presented, as obtained by the Heat Flux method. A comparison is made with results of the Counterflow method. The effect on the Counterflow method results of a non-linear instead of a linear correction for stretch is estimated. With a non-linear correction the agreement between both methods is good. It can be concluded that non-linear correction for stretch on the results of the Counterflow method is necessary in general. However, its effect may vary with varying fuel gas.

ISSN:0010-2202    

DOI:10.1080/00102209408935483

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor