Large eddy simulation of radiation effects on pollutant emissions in diluted turbulent premixed flames

Radiation effects are examined in turbulent premixed flames using a detailed Large Eddy Simulation (LES) approach. The approach combines a tabulated premixed flamelet model (Flamelet Generated Manifolds) with an optically thin radiation model. Radiation heat loss is tracked using a heat loss parameter in the tabulation. Heat loss in the flamelets is calculated by varying a coefficient on the radiation source term, ranging from zero (adiabatic) to unity (full optically thin model). NO_x is also modeled using a transport equation, which accounts for both chemical generation and loss. The model is compared against experimental measurements of methane-air piloted turbulent premixed planar jet flames with increasing levels of water and carbon dioxide dilution but which maintains a constant adiabatic flame temperature. The effects of dilution on global flame structure and NO emissions resulting directly and indirectly from radiation are examined in detail.