scholarly journals Structure and Radiation Properties of Luminous Turbulent Acetylene/Air Diffusion Flames

1988 ◽  
Vol 110 (1) ◽  
pp. 173-181 ◽  
Author(s):  
J. P. Gore ◽  
G. M. Faeth
Keyword(s):  
Radiative Heat ◽  
Diffusion Flames ◽  
Mixture Fraction ◽  
Heat Fluxes ◽  
Band Model ◽  
Spectral Radiation ◽  
Radiative Heat Loss ◽  
Radiation Properties ◽  
Air Diffusion ◽  
Laminar Flamelet

An experimental and theoretical study of the structure and radiation properties of luminous, round, turbulent acetylene/air diffusion flames is described. Measurements were made of mean and fluctuating velocities, mean concentrations, laser extinction (514 and 632.8 nm), spectral radiation intensities (1200–5500 nm), and radiative heat fluxes. The measurements were used to evaluate structure predictions based on the laminar flamelet concept, and radiation predictions based on a narrow-band model both ignoring and considering turbulence/radiation interactions. State relationships needed for the laminar flamelet concept were found from auxiliary measurements in laminar flames. Predictions were encouraging; however, quantitative accuracy was inferior to earlier findings for luminous flames. This is attributed to the large radiative heat loss fractions of acetylene/air flames (approaching 60 percent of the heat release rate); coupled structure and radiation analysis should be considered for improved results. The findings suggest significant turbulence/radiation interactions (increasing spectral intensities 40–100 percent from estimates based on mean properties); and that soot volume fractions may approximate universal fractions of mixture fraction in turbulent acetylene/air diffusion flames.

Spectral and Total Radiation Properties of Turbulent Hydrogen/Air Diffusion Flames

1987 ◽  
Vol 109 (1) ◽  
pp. 165-171 ◽  
Author(s):  
J. P. Gore ◽  
S.-M. Jeng ◽  
G. M. Faeth
Keyword(s):  
Diffusion Flames ◽  
Radiant Heat ◽  
Streamwise Velocity ◽  
Equilibrium Structure ◽  
Heat Fluxes ◽  
Laminar Flames ◽  
Spectral Radiation ◽  
Radiation Properties ◽  
Method Effects ◽  
Air Diffusion

A study of the structure and radiation properties of round turbulent hydrogen/air diffusion flames is described. Measurements were made of mean and fluctuating streamwise velocity, mean temperatures, species concentrations, spectral radiation intensities, and radiant heat fluxes. The measurements were used to evaluate predictions based on the laminar flamelet concept and narrow-band radiation models both ignoring (using mean properties) and considering (using a stochastic method) effects of turbulence/radiation interactions. State relationships found by correlating auxiliary measurements in laminar flames proved to be almost equivalent to conditions for local thermodynamic equilibrium. Structure and radiation predictions were reasonably good for present test conditions. Effects of turbulence/radiation interactions were significant for these flames, causing almost a 100 percent increase in spectral radiation intensities, in comparison to mean property predictions, upstream of the flame tip.

Radiation Properties of Oxygen-Enhanced Normal and Inverse Diffusion Flames

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
S. S. Krishnan ◽  
M. K. Saini ◽  
Y. Zheng ◽  
J. P. Gore
Keyword(s):  
Heat Flux ◽  
Heat Loss ◽  
Radiative Heat ◽  
Diffusion Flames ◽  
Release Rates ◽  
Spectral Radiation ◽  
Radiative Heat Loss ◽  
Radiation Spectra ◽  
Inverse Diffusion Flames ◽  
Inverse Diffusion

Radiative heat transfer in oxygen-enhanced inverse flame configurations is an important area of study for fundamental combustion research and for terrestrial and spacecraft fire safety. Motivated by this, heat flux distributions, total radiative heat loss and spectral radiation intensities were investigated experimentally for oxygen-enhanced normal and inverse laminar ethane diffusion flames with increasing heat release rates. The oxygen mole fraction in the oxidizer was varied as 21%, 30%, 50%, and 100% with coflowing normal and inverse flame burners used to stabilize the flames. The inverse diffusion flames were essentially nonluminous while the normal diffusion flames with identical heat release rates were highly luminous. Oxygen enhancement led to reduced flame lengths, increased luminosities and increased total radiative heat loss and spectral radiation intensities for both normal and inverse diffusion flames. Using flame length as the characteristic length parameter, the normalized radiative heat flux distributions for flames approximately collapsed together, further establishing the effectiveness of the single point radiant output measurement technique. Radiative heat loss fractions of normal and inverse diffusion flames with varying oxygen concentrations in the oxidizer are compared. The radiation spectra of all flames included significant contributions from gas radiation from carbon dioxide and water vapor and the radiation spectra of the high oxygen concentration flames included contributions from soot radiation.

scholarly journals High fidelity radiative heat transfer models for high-pressure laminar hydrogen–air diffusion flames

2014 ◽  
Vol 18 (6) ◽  
pp. 607-626 ◽  
Author(s):  
Jian Cai ◽  
Shenghui Lei ◽  
Adhiraj Dasgupta ◽  
Michael F. Modest ◽  
Daniel C. Haworth
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Diffusion Flames ◽  
High Fidelity ◽  
Air Diffusion ◽  
Transfer Models

Nongray Radiative Gas Analyses Using the S-N Discrete Ordinates Method

1991 ◽  
Vol 113 (4) ◽  
pp. 946-952 ◽  
Author(s):  
T. K. Kim ◽  
J. A. Menart ◽  
H. S. Lee
Keyword(s):  
Radiative Heat ◽  
Narrow Band ◽  
Wide Band ◽  
Heat Fluxes ◽  
Discrete Ordinates ◽  
Band Model ◽  
Spectral Correlation ◽  
Discrete Ordinates Method ◽  
Computational Speed ◽  
Wide Band Model

The S-N discrete ordinates method is applied to analyze radiative heat transfer in nongray gases. Spectral correlation between the terms in the equation of transfer is considered for black or nearly nonreflecting walls. Formulations to apply the S-N method using a narrow-band or the exponential wide-band model are presented. The net radiative wall heat fluxes and the radiative source distributions are obtained for uniform, parabolic, and boundary layer type temperature profiles, as well as for a parabolic concentration profile. The narrow- and wide-band nongray solutions are compared with gray-band approximations using the same band models. The computational speed of the gray-band approximation is obtained at the expense of accuracy in the internal fluxes and radiative source distributions. The wall radiative flux predictions by the gray-band approximation are satisfactory.

scholarly journals Numerical investigation of the effect of the insulation thickness on the degree of nonuniformity of the billet temperature

2015 ◽  
Vol 19 (3) ◽  
pp. 1097-1105
Author(s):  
Eakarach Somriewwongkul ◽  
Chittin Tangthieng
Keyword(s):  
Heat Loss ◽  
Radiative Heat ◽  
Measurement Data ◽  
Heat Fluxes ◽  
Radiative Heat Loss ◽  
Billet Temperature ◽  
Numerical Result ◽  
Finite Volume Discretization ◽  
Insulation Thickness ◽  
Steady State Heat

The degree of nonuniformity of the billet temperature subjected to the radiative heat loss to the discharge door with different insulation thicknesses is investigated in this present study. The 2-D steady-state heat conduction for the billet subjected to different heat fluxes is solved by being transformed into a dimensionless form. The Gauss-Seidel iterative method for a finite volume discretization of the billet is employed to obtain the temperature distribution of the billet. The numerical result is validated by comparing with the field measurement data. A qualitative agreement between these two is observed. An effect of different insulation thicknesses on the heat-transfer characteristics and the degree of nonuniformity of the billet temperature is examined. In case of the replaced 50-mm thick insulation of the discharge door, the radiative heat loss to the discharge door is reduced by 49% with the replaced insulation, and the degree of nonuniformity of the billet temperature is decreased by 23?C.

Flamelet Studies of Reduced and Detailed Kinetic Mechanisms for Methane/Air Diffusion Flames

2000 ◽  
Author(s):  
Foluso Ladeinde ◽  
Xiaodan Cai ◽  
Balu Sekar
Keyword(s):  
Dissipation Rate ◽  
Diffusion Flames ◽  
Mixture Fraction ◽  
Intermediate Species ◽  
Flamelet Model ◽  
Mass Fractions ◽  
Kinetic Mechanisms ◽  
Moderate Effect ◽  
Extinction Strain Rate ◽  
Air Diffusion

We adopt a steady-state flamelet model in this paper to study the performance of reduced and detailed kinetic mechanisms for methane/air diffusion flames. Through the numerical calculations, we investigate the sensitivity of the main and intermediate species mass fractions to the mixture fraction dissipation rate, χ. Our results seem to suggest a weak to moderate effect of χ on the calculated species mass fraction. It has also been shown in this paper that the current flamelet calculations fail to predict the extinction strain rate.

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