On the Effect of Air Temperature on Mild Flameless Combustion Regime of High Temperature Furnace

This paper presents an experimental study of the effect of air preheating temperature on the main features of mild flameless combustion obtained in a laboratory-scale furnace. Mild flameless combustion regime is conserved whatever the air temperature varying from 838 K to ambient value. No visible flame is observed. Main aerodynamic features of the flow at the exit of the burner are similar with and without air preheating. Large momentum of methane and air turbulent jets favours the entrainment of recirculating flue gas and then the progressive dilution of reactant by flue gas. Main difference comes from the structures of the reaction zone which are more and more lifted and NOx emissions which decrease progressively with air temperature, down to a very low value (4 pp