NONGRAY SOOT AND GAS-PHASE RADIATION MODELING IN LUMINOUS TURBULENT NONPREMIXED JET FLAMES

Abstract

Much progress has been made in radiative heat transfer modeling with respect to treatment of nongray radiation from both gas species and soot particles, while radiation modeling in turbulent ame simulations is still in its infancy. Aiming at reducing this gap, this paper introduces sophisticated models of soot and gas-phase radiation to turbulent ame simulations. The full-spectrum k-distribution method is implemented into a threedimensional unstructured CFD code for nongray radiation modeling. The mixture full-spectrum k-distributions including nongray absorbing soot particles are constructed from a narrow-band k-distribution database created for individual gas-phase species, and an efcient scheme is employed for the construction in complex CFD simulations. A detailed reaction mechanism including NOx and soot kinetics is used to predict ame structure. A detailed soot model with method of moments is employed to determine soot particle size distributions. An oxygen-enriched, turbulent, nonpremixed jet ame is simulated, which features large concentrations of gas-phase radiating species and soot particles. Nongray soot modeling is shown to be of greater importance than nongray gas modeling in sooty ame simulations, with gray soot models producing large errors. The nongray treatment of soot strongly inuences ame temperatures in the upstream and the ame tip region and is essential for accurate predictions of NO formation in sooty ames. The nongray treatment of gases, however, weakly inuences upstream ame temperatures and, therefore, has only a small effect on NOx predictions. The effect of nongray soot radiation on ame temperature is also substantial in downstream regions where the soot concentration is small.