Investigation Into the Optimal Gas Turbine Film Cooling Configuration With the Use of a Thermal Barrier Coating

Abstract The overall cooling effectiveness of a gas turbine airfoil characterizes the conjugate effect of both film cooling and internal cooling on an airfoil in one parameter. Few studies in open literature have explored the overall cooling effectiveness of airfoils utilizing thermal barrier coatings. In this study it was found that the addition of a 0.84D thick TBC to an internally cooled flat plate yields a 130% improvement in the overall cooling effectiveness. This result along with increased reliability of TBCs suggests that TBCs should be considered when determining optimal integrated cooling configurations for an airfoil. RANS computational simulations were used to determine the optimal cooling configuration for a flat plate with a single row of film cooling holes and TBC. A variety of parameters were iterated upon to determine a film cooling configuration that provided a 14% improvement in overall cooling effectiveness relative to the case without film cooling while using the least amount of coolant. Multi-row simulations were also performed in order to determine an optimal streamwise spacing. The major findings of this study reveal that when in the presence of a TBC, a round hole in a trench is the highest performing film cooling configuration. It was also determined that to reach a 14% improvement, the lateral spacing of the film cooling holes must still be the traditional spacing of P/D = 3. Finally, experiments of a select number of the single row configurations simulated were tested experimentally to compare to the RANS simulations.