Diluted combustion in a aerodynamically staged swirled burner fueled by Diesel oil

Among new combustion technologies, MILD (Moderate and Intense Low Oxygen Diluted) combustion is particularly attractive since it is characterized by: flame temperature peaks lower than registered in conventional systems, reducing NOx formation; a stable oxidation without a flame front even with lean fuels, limiting vibrations and noise due to flame front; an increase in combustion efficiency, and a lower sensitivity to fuel characteristics. Such a kind of combustion mode can be obtained by means of the dilution of reactants with inert gas and the increase of their temperature. For this reason, an aerodynamically staged swirled burner fuelled by diesel oil has been experimentally tested and numerically simulated under diluted and highly preheated inlet flow conditions. The staging is obtained through a double coaxial air inlet with the same swirl orientation. The diesel oil is injected through a central atomizing nozzle characterized by a very high rangeability. The numerical results, in agreement with experiments, confirm that the burner, under properly operating conditions, is able to completely burn the fuel without a flame front and with a very uniform temperature field.