The effect of oxygen concentration on the structure of turbulent nonpremixed flames

Abstract

MILD combustion is a newly implemented and developed concept to achieve high thermal efficiency and fuel saving while maintaining emission of pollutants at very low levels. It utilizes the concept of heat and exhaust gas recirculation to achieve combustion at reduced temperature, with a flat thermal field and low turbulence fluctuations. An experimental burner is used in this study. Temporally, and spatially resolved measurements of reactive scalars are conducted on three different flames of H2/CH4 fuel mixture at fixed jet Reynolds number and different oxygen mass fractions in the hot oxidant stream. The results show substantial variation of the flame structure with the decrease of the oxygen level. The results also point towards a different chemical pathway for the reaction in this combustion regime, where the formation of the OH radical and NO is less dependent on temperature.