The role of large scale mixing and radiation in the scaling of NOx emissions from unconfined flames

Abstract

Measurements of global emissions, flame radiation and flame dimensions are presented for unconfirmed turbulent-jet and precessing-jet diffusion flames. Precessing jet flames are characterised by increases in global flame radiation and global flame residence time for methane and propane fuels, however a strong dependency of the NOx emission indices on the fuel type exists. The fuel type dependence is considered to be because soot radiation is more effective than gas-radiation at reducing global flame temperatures relative to adiabatic flame temperatures and reducing the NO production rate.