Prediction of swirling combustion in high temperature and low oxygen condition

High temperature air combustion (HVAC) is effective to reduce NO emission from industrial furnace at preheated air and dilute oxygen conditions. Swirling burner with different swirling fin stretch length were designed for the HVAC application and its combustion performance was numerically modeled. The probability density function (PDF) combustion model, discrete ordinate (DO) radiation model and the Reynolds stress turbulent model (RM) were adopted for the modeling. Results showed that the swirling fin stretch factor influenced the local oxygen distribution and combustion process in the furnace which finally determined the thermal NO formation and burnout of the fuel. NO emission decreased with the swirling fin stretch factor first to the lowest value and then increased again as the swirling fin stretch factor increased further. Therefore, there was an optimal swirling fin stretch factor for minimum NO emission. The thermal NO emission decreased from 16.8 ppm to 12.3 ppm when the swirling fin stretch factor increased from 1 to 2.