Coarse grid CFD calculations of a dual-fuel gas turbine combustor flow field

The performance of a gas turbine is strongly dependent on the flow field inside the combustion system. In the primary zone, the air jets can improve the recirculation of hot products promoted by the break-down of the rotating fuel/air mixture exiting from the swirler. This recirculation stabilizes the flame and completes the fuel oxidation. Moreover, the mixing process in the dilution zone allows to obtain the outlet temperature profile maximizing turbine durability. This paper presents an experimental and computational fluid dynamics analysis of both the isothermal and the reactive flow field inside a heavy-duty gas turbine combustor designed to be fed with a mixture of hydrogen and natural gas (up to 100% of either one). The whole combustor domain comprising the air plenum, the annulus and the hot flow discharge is considered. The study aims at evaluating the capability of a coarse grid CFD model, already validated in previous full-load thermal calculations, in predicting the flow field. An experimental campaign was performed on an isothermal flow test rig to investigate combustion air splitting and the penetration of both primary and dilution air jets. The experimental data are compared with the results of the isothermal flow calculations to complete model validation. Then, reactive numerical simulations are carried out to evaluate the impact of combustion on the flow field and to discuss the influence of the air plenum on the features of the air jets.