Reduced NOₓ emissions and enhanced large scale turbulence from a precessing jet burner

Abstract

The performance characteristics of a Precessing Jet (PJ) burner, developed at the University of Adelaide, have been investigated in Furnace No. 1 of the International Flame Research Foundation firing natural gas with air pre-heated to 320°C. Results showed that the PJ burner, operating without air swirl, fuel staging or FGR, produces NOₓ emissions of about 57 ppm (dry, 3% O₂) which is comparable to the performance of a swirled flame operated at optimised conditions with either flue gas recirculation, FGR, or fuel staging. The emissions are significantly lower than the 134 ppm measured for the base-line swirl burner, but greater than the 37 ppm measured for the swirl burner operated with both FGR and fuel staging. The flame was investigated by means of in-flame measurement of temperature and species concentration using suction probes and by laser sheet visualisation and subsequently derived probability density functions of jet fluid concentration. These techniques show that the mixing and combustion processes are dominated by the presence of large scale structures. It is anticipated that a more complete understanding of the interaction between the large scale turbulence and the combustion process will lead to further improvements in the performance of the burner.