Radiative heat flux characteristics of methane flames in oxy-fuel atmospheres

Oxy-fuel combustion is a promising alternative for power generation with CO₂ capture, where the fuel is burned in an atmosphere enriched with oxygen and CO₂ is used as a diluent. This type of combustion is characterised by uncommon characteristics in terms of thermal heat transfer budget as compared to air supported systems. The study presents experimental results of radiative heat flux along the flame axis and radiant fractions of non-premixed jet methane flames developing in oxy-fuel environments with oxygen concentrations ranging from 35% to 70%, as well as in air. The flames investigated have inlet Reynolds numbers from 468 to 2340. The data collected have highlighted the effects of the flame structure and thermo-chemical properties of oxy-fuel combustion on the heat flux radiated by the flames. It was first observed that peak heat flux increases considerably with oxygen concentration. More generally the radiant fraction increases with both increasing Reynolds number in the laminar regime and oxygen concentration. It was found that despite a difference in flame temperature, the radiative characteristics of the flames (heat flux distributions and radiant fraction) in air were similar to those with 35% O₂ in CO₂. The radiative properties of flames in oxy-fuel atmosphere with CO₂ as diluents appear to be dominated by the flame temperature.