Experimental and Numerical Investigations of Structure and Stability of Premixed Swirl-Stabilized CH4/O2/CO2 Flames in a Model Gas Turbine Combustor

Abstract

Premixed CH4/O2/CO2 flames were studied experimentally and numerically in a swirl-stabilized combustor. The bulk throat velocity of the incoming combustible mixture was maintained constant at 5.2 m/s. The oxygen fraction of the O2/CO2 oxidizer was kept constant at 60 vol %, while the effect of the equivalence ratio was examined from the blowout limit to the flashback one. The LES computational model was successfully validated through comparisons with experimental data in terms of axial and radial temperature profiles, as well as predicted OH* concentration maps versus visual flame appearance. Three different flame structures were observed while varying the equivalence ratio, namely, (I) double conical flame, (II) corner-stabilized flame, and (III) swirl-stabilized (V-shaped) flame. The double conical flame is observed at low equivalence ratios near the blowout limit. This flame stabilizes within both the inner and outer shear layers and has two distinct reaction zones with two inner recirculation zones (I...