Analysis of methane, propane, and syngas oxy-flames in a fuel-flex gas turbine combustor for carbon capture

Premixed oxy-combustion flames of methane, syngas (CH4:CO:H-2 with the molar ratio of 2:1:1), and propane in CO2-diluted environment (for carbon capture) are examined in a swirl-stabilized combustor using large eddy simulations (LES) in three-dimensional (3-D) domain. The flame and emission characteristics are examined for the different fuels over a range of equivalence ratios (phi: 0.34, 0.39, and 0.42), at 60% oxygen fraction (OF), and 2.5 m/s bulk inlet velocity under atmospheric conditions. The results indicate increments in several characteristic parameters that are of special importance for gas turbine combustion applications, including adiabatic flame temperature (T-ad), laminar flame speed (LFS), power density (PD), product formation rate (PFR), Damkohler number (Da), and CO emission, with the increase of phi whatever the type of fuel. Alternatively, flame thickness (delta) decreases with the increase in phi for the three fuels. Characteristic V shape with almost identical outer recirculation zone (ORZ) is also observed for the three fuels. Among the studied fuels, oxy-methane flames demonstrate highest flame thicknesses, least uniform temperature distribution (highest pattern factor) at combustor outlet, and lowest CO emission level. Oxy-syngas flames show more uniform temperature distribution (lowest pattern factor) at combustor outlet and highest CO emission as compared with the oxy-methane and oxy-propane flames. The oxy-propane flames have higher values of T-ad, LFS, PD, PFR, Da, and thermal power (TP) along with lowest flame thickness compared with methane and syngas counterparts. Increasing equivalence ratio improves the flame characteristics but increases CO emission. Fuel type has insignificant effects on shape/size of the outer recirculation zone (ORZ). Oxy-methane flames showed highest flame thicknesses and pattern factor and lowest CO. Oxy-syngas flames demonstrate highest CO emission and lowest pattern factor. Oxy-propane flames demonstrate higher values of temperature (T-ad), laminar flame speed (LFS), power density (PD), product formation rate (PFR), Damkohler number (Da), and thermal power (TP).

Automated summary

This study investigates the characteristics and emissions of premixed oxy-combustion flames in a combustor, comparing the effects of different fuels. The results show that increasing the equivalence ratio improves certain parameters important for gas turbine combustion, but also leads to higher CO emissions. Among the fuels studied, oxy-methane flames have the highest flame thicknesses and lowest CO emissions, while oxy-propane flames have higher values of temperature, flame speed, power density, and thermal power.