Numerical study of igniting counterflow diffusion flames with diluted and preheated air and/or fuel streams for MILD combustion

The main characteristics of MILD combustion have been studied in cases where the fuel and/or oxidizer streams were diluted with various amounts of products. Igniting one-dimensional counterflow diffusion flames are simulated using detailed chemistry and transport models. Special attention is given to the definition of initial and boundary conditions. The role of molecular transport and chemistry has been analyzed. The results confirm the low NO emissions of MILD combustion. Ignition delays have been studied for different situations with the same overall dilution level. The ignition delay is much shorter when both streams are diluted instead of only one.