The study presents the results of experimental and numerical investigations of oxycombustion H-2-enriched-CH4 diffusion flames in an atmospheric pressure swirl stabilized gas turbine model combustor. The flames characteristics in terms of temperature and species distributions, structures and flow fields are studied experimentally and numerically over ranges of operating parameters. The effects of equivalence ratio, oxidizer composition, H-2-enrichment and swirl vane angle on flame stability, temperature distribution and flow field are studied in details. The swirl number considered in the experimental measurements is 1.10 with corresponding swirl vane angle of 55 degrees. ANSYS Fluent was used to perform the numerical study and the models adopted are; k-epsilon (standard), discrete ordinate (DO), eddy-dissipation-concept (EDC) for turbulence, radiation, and species transport. Combined modified Jones-Lindstedt reaction mechanism and Marinov reaction mechanism for H-2 were considered as reaction mechanism for the numerical study. The numerical results are in good agreement with their corresponding experimental data. It was observed that utilizing H-2-enriched-CH4 improves the flame stability. The numerical results showed that oxy-fuel combustion of H-2-enriched-CH4 is not achievable at an equivalence ratio of 0.95 and above due to stability issues. The stability is highly enhanced by the corresponding formation of inner recirculation zone. A swirler with swirl vane angle of 65 achieved better stability limits of the gas turbine combustor. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.