Characterization of pollutant emissions in diffusion and premixed natural gas burners

This paper describes the measurement of pollutant emissions (nitric oxides and carbon monoxide) in different natural gas burners: particularly, a swirl burner with different fuel injection typologies (co-axial and radial injection, with respect to the rotating air stream) and a premixed burner have been taken into account. As for the premixed burner, pollutant emissions have been related with thermal characterization of the reactant zone performed by thin thermocouples. In this case, a strong correlation with temperature and equivalence ratio has been observed. At the contrary, the swirl burner presents a strict dependence from the value of the air stream swirl number, which plays an important role for flame stabilization and fluid dynamic mixing process in the primary flame zone. Moreover, the radial injector in the swirl burner contributes to a general decrease of pollutant emissions, behaving similarly to the premixed burner, also as for the trend of CO and NOx emissions versus the equivalence ratio.