ABSTRACT
This work presents a numerical study of radiation heat transfer and its interaction with gray and spectral radiation of combustion products and soot that are formed in a turbulent non-premixed combustion process. To this purpose, weighted sum of gray gases (WSGGM), Rayleigh, narrow-band model, and semi-empirical radiation properties models are considered. Two situations are studied −1-D radiation problem and non-premixed gaseous combustion process. The results demonstrate that the models exhibit discrepancies that are smaller than the available line-by-line or experimental data. A study of the factors that influence such a disagreement is presented, underscoring the role of the chemical kinetics of hydrocarbon species and soot oxidation.
Nomenclature
Latin letters | = | |
a | = | Global absorption coefficient of the medium |
aE | = | Mean absorption-emission coefficient |
ag | = | Gray absorption coefficient of the gaseous medium |
asoot | = | Gray absorption coefficient of soot |
aλ | = | Spectral absorption coefficient of the medium |
aλ,g | = | Spectral absorption coefficient of the gaseous medium |
aλ,soot | = | Spectral absorption coefficient of soot |
dP | = | Soot diameter |
fV | = | Soot volume fraction |
It | = | Turbulent intensity |
lt | = | Integral length-scale of turbulence |
m | = | Complex refractive index |
n | = | Refractive index |
pexit | = | Outlet pressure |
= | Vector of radiant heat flux | |
qR | = | Magnitude of radiant heat flux |
= | Vector position | |
= | Vector position | |
= | Vector position | |
= | Velocity fluctuation | |
Coxid | = | Oxidation scaling parameter of the Moss-Brookes soot model |
= | Equivalent soot volume fraction | |
G | = | Incident radiation |
I | = | Gray intensity of radiant energy |
Iλ | = | Spectral intensity of radiant energy |
Iλ, b | = | Spectral intensity of radiant energy emitted by a blackbody |
L | = | Separation between plates |
Lm | = | Mean path length |
= | Radiation heat transfer rate | |
= | Total heat transfer rate | |
Re | = | Reynolds number |
T | = | Temperature of the medium |
T0 | = | Inlet temperature |
Texit | = | Outlet temperature |
Tp | = | Wall temperature |
Uz, 0 | = | Inlet velocity at longitudinal direction |
XC3H8 | = | Propane molar fraction |
XO2 | = | Oxygen molar fraction |
XN2 | = | Nitrogen molar fraction |
= | Mean mixture fraction | |
= | Variance of the mixture fraction | |
Greek letters | = | |
ϵp | = | Wall emissivity |
λ | = | Wavelength |
σ | = | Stefan-Boltzman constant = 5.67 × 10−8 W/m2 K4 |
σs | = | Gray scattering coefficient of the medium |
σs,λ | = | Spectral scattering coefficient of the medium |
τλ | = | Spectral transmissivity |
Φ | = | Scattering phase function |
= | Solid angle |
Nomenclature
Latin letters | = | |
a | = | Global absorption coefficient of the medium |
aE | = | Mean absorption-emission coefficient |
ag | = | Gray absorption coefficient of the gaseous medium |
asoot | = | Gray absorption coefficient of soot |
aλ | = | Spectral absorption coefficient of the medium |
aλ,g | = | Spectral absorption coefficient of the gaseous medium |
aλ,soot | = | Spectral absorption coefficient of soot |
dP | = | Soot diameter |
fV | = | Soot volume fraction |
It | = | Turbulent intensity |
lt | = | Integral length-scale of turbulence |
m | = | Complex refractive index |
n | = | Refractive index |
pexit | = | Outlet pressure |
= | Vector of radiant heat flux | |
qR | = | Magnitude of radiant heat flux |
= | Vector position | |
= | Vector position | |
= | Vector position | |
= | Velocity fluctuation | |
Coxid | = | Oxidation scaling parameter of the Moss-Brookes soot model |
= | Equivalent soot volume fraction | |
G | = | Incident radiation |
I | = | Gray intensity of radiant energy |
Iλ | = | Spectral intensity of radiant energy |
Iλ, b | = | Spectral intensity of radiant energy emitted by a blackbody |
L | = | Separation between plates |
Lm | = | Mean path length |
= | Radiation heat transfer rate | |
= | Total heat transfer rate | |
Re | = | Reynolds number |
T | = | Temperature of the medium |
T0 | = | Inlet temperature |
Texit | = | Outlet temperature |
Tp | = | Wall temperature |
Uz, 0 | = | Inlet velocity at longitudinal direction |
XC3H8 | = | Propane molar fraction |
XO2 | = | Oxygen molar fraction |
XN2 | = | Nitrogen molar fraction |
= | Mean mixture fraction | |
= | Variance of the mixture fraction | |
Greek letters | = | |
ϵp | = | Wall emissivity |
λ | = | Wavelength |
σ | = | Stefan-Boltzman constant = 5.67 × 10−8 W/m2 K4 |
σs | = | Gray scattering coefficient of the medium |
σs,λ | = | Spectral scattering coefficient of the medium |
τλ | = | Spectral transmissivity |
Φ | = | Scattering phase function |
= | Solid angle |