Effects of CO2 and N2 Dilution on the Combustion Characteristics of H2/CO Mixture in a Turbulent, Partially Premixed Burner

Herein, the influences of CO2 dilution, N-2 dilution, and CO2/N-2 (in which half of the N-2 is replaced by CO2) dilution on the combustion characteristics of a turbulent, partially premixed CO/H-2-air flame were experimentally investigated in terms of the flame structure, flame temperature, and CO and CO2 concentrations in flames. TDLAS (tunable diode laser absorption spectroscopy) technique and an infrared gas analyzer were used for such purposes. CO2 dilution not only increases more momentum but also reduces the reaction rate. This results in a much longer flame length than that under N-2 dilution. Compared with N-2 dilution, the LH (axial length of the high-temperature reaction zone) values for the same levels of CO2 dilution and CO2/N-2 dilution are much longer. The highest CO concentration in the CO2 diluted flame is higher than that in the CO/H-2 flame and that in the CO2 /N-2 diluted flame is higher than in that the N-2 diluted flame. The sizes of the main chemical reaction zone in CO2 and CO2/N-2 diluted flames are larger than that in the N-2 diluted flame. The inflection points in the rates of variation of the flame temperature and the CO and CO2 concentrations verify that CO2 dilution creates lower intensities and lower rates of chemical reactions, compared with N-2 dilution.