Effect of Nitrogen Dilution on the Lean Blowout Limit and Emissions of Premixed Propane/Air Swirl Flame

The effects of nitrogen dilution on propane/air flame and emissions was investigated using a model gas turbine type swirl flame burner. The burner consists of a six-vane axial swirler and a combustor wall made from quartz tube. Nitrogen was diluted at 5%, 10% and 15% by volume of the total main air flow rate with propane/air mixture at the burner plenum prior to combustion at atmospheric condition. Direct flame imaging was performed using a digital camera to observe the flame shape, intensity and lean blowout phenomenon of premixed nitrogen-diluted propane/air flames. The result shows that nitrogen addition to propane/air flame reduces flame intensity and lean blowout limit, making the nitrogen-diluted flames more susceptible to blowout. Emissions results show that NOx reduce with the increase of nitrogen dilution rate, while the effect on carbon monoxides and unburned hydrocarbons are insignificant.