摘要:

Results of experiments are reported for overventilated buoyancy-controlled flames of various fuel mixtures in normal atmospheric air. The fuels studied were C2H6, C2H4, C2H2and CH4, as well as fixed hydrogen-hydrocarbon mixtures of the first three, to give C2H6+H2, C2H4+H2, C2H2+H2and C2H2+2H2. The focus of the work was to test the concept of flame height correspondence between pure fuels and “synthetic” fuels, synthetic methane being C6vH+H2, synthetic ethylene C2H2+H2and synthetic ethane C2H4+H2and C2H2+2H2. Adiabatic flame temperatures Tafwere controlled by addition of N2to the fuels, and comparisons were made at fixed Taf,. In accordance with theory, excellent flame-height agreements were obtained for ethane and the two synthetic ethanes. Agreements were somewhat poorer for synthetic ethylene and especially poor for synthetic methane. The former discrepancy is associated with differing sooling tendencies of the different fuels, while the latter is readily attributable to influences of molecular diffusion coefficients. The reasons for these results and their relationships with previous flame-height and soot-height results are discussed.

ISSN:0010-2202    

DOI:10.1080/00102209908924179

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Combustion characteristics and related chemical processes were investigated for a HAN-based liquid propellant, XM46, and its ingredients, HAN and TEAN. Experiments were conducted over the pressure range of 0.1 to 1 atmosphere and at the heat fluxes from 50 to 400 W/cm2in air and inert gas environments. Flame behavior was observed using a high magnification video system. A triple quadruple mass spectrometer (TQMS) and micro-thermocouples were applied for the temporal measurements of gas-phase species and temperature profiles. Species in the XM46 residue left after burning were analyzed using a gas chromatograph/mass spectrometer (GC/MS). No visible flame was observed from XM46 or its ingredients at 1 ATM and 100 W/cm2. However, at 1 ATM and 400 W/cm2, HAN and TEAN showed distinctive flame behaviors, and XM46 exhibited three flames in sequence with the white HAN flame appearing first, followed by the blue and yellow TEAN flames. Gaseous products evolved from HAN and TEAN exhibited a distinctive set of species profiles for each ingredient, corresponding to its flame behavior. Species measurements of XM46 showed the same sequential characteristics as the flame behavior; however, a significant portion of the HAN and TEAN flames in XM46 was found to involve HAN+TEAN mixed reactions. The maximum temperatures for XM46 combustion in air were found to be approximately 1250 and 2050 K at 100 and 400 W/cm2, respectively. Species found in the residues of XM46 varied according to the stage where the residue was formed.

ISSN:0010-2202    

DOI:10.1080/00102209908924180

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The characteristics of attached non-premixed jet flames in mutual interaction are studied experimentally through the analysis of 1,3 and 5 propane flames with an individual Reynolds number of 20400. Laser Doppler velocimetry, fine-wire thermometry and chemical species concentration analysis were used to characterise the flame systems, as well as simultaneous acquisition techniques to obtain information on the scalar turbulent behaviour

ISSN:0010-2202    

DOI:10.1080/00102209908924181

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102209908924182

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This work investigates how radiation heat transfer influences downward flame spread by presenting a gas phase radiation model, described by a two dimensional P-1 approximation method, to incorporate with the combustion model of Duh and Chen (1991). The parametric study is based on the variation of gravity, which changes the Damkohler number (Da) and radiation to conduction parameter (I/N∞) simultaneously. Comparing the results with the previous studies of Duh and Chen (199l) and Chen and Cheng (1994). which only considered the radiation effect in cross stream direction, the role of stream-wise radiation was identified. The stream-wise radiation contributes to reinforce the forward heat transfer rate subsequently increasing the flame spread rate. However, this model also provides more directional radiation loss than that of Chen and Cheng (I994) and, in doing so, draws more energy out from the flame to further reduce its strength. The results indicates that the effect of heat loss is greater than that of enhancing the upstream heat transfer since the flame spread rate in the present model is always lower than the one predicted by Duh and Chen (1991), Finally, a contour of the Planck mean absorption coefficient distribution is illustrated to demonstrate the effectiveness of gas radiation distribution. It reveals that the strongest radiation occurs near the pyrolyzing surface and the other significant one is in the plume region. A comparisons with available experimental data also given to evaluate the ability of predict in the present combustion model.

ISSN:0010-2202    

DOI:10.1080/00102209908924183

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We show that identifying the intersection of a turbulent flame and a tomographic plane to a random self-avoiding planar walk yields dF= d-l + 1/3 for the fractal dimension (dF) of the front surface. This suggests that dF= 7/3 in 3-dimensional ambient space (d = 3) could have a geometrical origin, not directly related to the k−5/3Kolmogorov scaling law.

ISSN:0010-2202    

DOI:10.1080/00102209908924184

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Results are presented from a new mathematical model on the mixing of fuel and air. The model is derived from the ideal gas law and the equation of continuity. The equivalence ratio measured within an infinitesimal fluid element of mixture and the time rate of the equivalence ratio are used to quantify the degree and time rate of mixing. The model shows that in addition to the fuel molecular weight, the mixing rate depends on pressure, temperature, density, and their rates. The density rate depends on velocity gradients. The mixing between methane and air is described since the gaseous reactants delineate the droplet heat-up and evaporation for liquid fuels. Results presented here provide the isolated effect of each parameter involved in mixing. Implication of the results on mixing of other fuels and air is discussed. These results are intended to provide important design guidelines for developing high intensity and high efficiency combustors with special focus on low levels of pollutants emission.

ISSN:0010-2202    

DOI:10.1080/00102209908924185

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor