Improvement of the Outlet Temperature Distribution of a Dual-Fuel Gas Turbine Combustor by a Simplified CFD Model

The mixing process within the dilution zone noticeably affects the temperature field in the outlet section of a gas turbine combustor. In fact, dilution jets lower the temperature of the hot flow exiting the primary zone establishing suitable temperature profile and pattern factor at the combustor outlet. Thus, the dilution zone design has a significant impact on performance and durability of the turbine. In this study, a dual fuel gas turbine combustor is investigated by a commercial finite-volume CFD code. The computational domain extends from the compressor discharge to the gas turbine inlet and it is meshed with a coarse grid since it was originally conceived for thermoacoustic analysis. The model has been already validated throughout measurements acquired during full scale isothermal and reactive tests. On the basis of the results of reactive simulations, several solutions of the dilution zone are designed to improve the uniformity of radial and circumferential temperature at the turbine inlet. The designed configurations feature number, arrangement and diameter of dilution holes which differ from the commercial configuration providing four identical dilution holes equally spaced. Advantages and drawbacks of each dilution zone layout are supported by results of numerical calculations. The results suggest that the solutions featuring two dilution holes perform better than the actual layout.