Effects of adiabatic flame temperature on flames’ characteristics in a gas-turbine combustor

In this study a comparison between the premixed methane oxygen-enriched-air (CH4/O2/N2) and oxy-methane (CH4/O2/CO2) in a gas-turbine model combustor that imitates pre-mixers in operational air-fuel dry low emissions gas turbines is presented. The comparison and analyses that follow in this study are based on the results of experiments conducted. The combustion stability maps were obtained through the estimation of acoustic limits and measurement of blowout limits within the space of equivalence ratio (φ) – oxygen fraction (OF). The stability maps obtained were superimposed on the contour plots of constant adiabatic temperature (Tad), Reynolds number (Re), and power density (PD) of the combustor. Effects of Tad on flame macrostructure, flame stability, flame speed, and blowout mechanism were investigated. The temperature distributions were also measured. The study results indicated that blowout of CO2 as well as N2 flames occur at constant Tad. These results are more pronounced in the case of the multi-hole burner because, such burner is not characterized with sporadic nature of flame lifting and reattachment that dominate the occurrence of a blowout in swirl burner; for a given OF, φ at which CO2 flames blowout is higher than that of N2 flames due to the poorer resistance of oxy-flames to blowout as compared to air flames; the stable combustion zone of CO2 flames is larger than that of N2 flames. •Blowout of CO2 and N2 flames occur at constant adiabatic temperature (Tad).•For a given oxygen fraction, CO2 flames blowout at higher equivalence ratio.•CO2 flames show a larger stability region.•Design and operation of combustors of oxyfuel gas-turbine should be based on Tad rather than dilution ratio.