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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 |