Radiation Characteristics and Turbulence-Radiation Interactions in Sooting Turbulent Jet Flames

The transported PDF method coupled with a detailed gas-phase chemistry, soot model and radiative transfer equation solver is applied to various turbulent jet flames with Reynolds numbers varying from ∼ 6700 to 15100. Two ethylene–air flames and four flames with a blend of methane–ethylene and enhanced oxygen concentration are simulated. A Lagrangian particle Monte Carlo method is used to solve the transported joint probability density function (PDF) equations, as it can accommodate the high dimensionality of the problem with relative ease. Detailed kinetics are used to accurately model the gas-phase chemistry coupled with a detailed soot model. Radiation is calculated using a particle-based photon Monte Carlo method, which is coupled with the PDF method and the soot model to accurately account for both emission and absorption turbulence–radiation interactions (TRI), using line-by-line databases for radiative properties of CO₂ and H₂O; soot radiative properties are also modeled as nongray. Turbulence–radiation interactions can have a strong effect on the net radiative heat loss from sooting flames. For a given temperature, species and soot distribution, TRI increases emission from the flames by 30–60%. Absorption also increases, but primarily due to the increase in emission. The net heat loss from the flame increases by 45–90% when accounting for TRI. This ixs much higher than the corresponding increase due to TRI in nonsooting flames. Absorption TRI was found to be negligible in the laboratory scale sooting flames with soot levels on the order of a few ppm, but may be important in larger industrial scale flames.