Validation of Numerical Methods for the Analysis of a Cooled Turbine Vane

Gas turbines operate under highly demanding thermal and aerodynamic conditions, particularly in the high-pressure turbine stages where the gas temperature can be significantly greater than the melting point of the components. Turbine vanes use modern cooling systems that include internal air passages and multi-row film cooling to protect the surface from severe heat loads. In this context, the current thesis investigates the aero-thermal behaviour of a high-pressure turbine vane through numerical analysis. To assess the reliability of the selected Computational Fluid Dynamics (CFD) approaches in predicting the flow field and heat-transfer processes in a cooled vane, this work focuses on both modelling boundary layer development and the identification of the most appropriate parameters to be used for performance evaluation. The numerical analysis was performed using Reynolds-Averaged Navier-Stokes (RANS) simulations with turbulence and transition models validated against the available experimental data. A grid dependence evaluation guaranteed the correctness of the result, and the use of transition modelling enabled the accurate prediction of boundary layer development and of mixing events between the coolant jets and main flow. Post-processing and data interpretation have been used to assess flow measures such as the isentropic Mach number and the Nusselt number. The validation phase consists of an extensive comparison with experimental measurements, aimed at evaluating the predictive accuracy of the numerical approach and identifying which turbulence model most faithfully reproduce the aerodynamic and thermal behaviour of the vane. The comparative study between the uncooled and cooled vane configurations provides valuable insight into how film cooling influences the development of the flow field, the heat transfer process, and the distribution of surface temperature. The findings confirm the ability of the cooling system to relieve the thermal load acting on the vane and, at the same time, show the complex physical interactions that take place where the coolant jets meet the high-temperature mainstream, giving rise to local variations in turbulence and noticeable changes in the aerodynamic behaviour of the flow. In a broader sense, the work defines a solid and experimentally validated numerical methodology for the detailed study of cooled turbine vanes. The methodology developed in this thesis contributes to a deeper comprehension of the mutual dependence between thermal protection and aerodynamic performance, while providing a reliable and well-validated reference framework to guide future research activities and design improvements in the field of high-temperature turbomachinery.