Session: 12-09: Film Cooling Optimization and Novel Design

Paper Number: 153412

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

 

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. This is done by considering the Biot number of the vane wall and the temperature of the metal surface. Few studies in open literature have explored the overall cooling effectiveness of vanes utilizing thermal barrier coatings.  When utilizing TBC, the exterior surface on the vane is the TBC surface instead of the metal surface. Because of this, adiabatic effectiveness is not as useful of a design parameter as overall cooling effectiveness. TBC’s provide an immense improvement to the cooling performance of a vane. The results of this study indicate that at a constant coolant flow rate, the addition of a TBC that is 0.84D thick to a flat plate cooled internally by a serpentine channel yields a 33% improvement in the overall cooling effectiveness. This result along with increased reliability of TBC’s suggest that TBC’s should be considered when determining optimal film cooling configurations for an airfoil. In this study, 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. The parameters varied in the study included the internal cooling flowrate, film cooling hole geometry, film cooling hole exit through the TBC, and the lateral spacing between each film cooling hole. The goal of this optimization was to determine a film cooling configuration that provided 10% improvement in overall cooling effectiveness relative to the case without film cooling while using the least amount of coolant. The major findings of this study reveal that when in the presence of a TBC, a shaped hole and round hole perform similarly at equivalent velocity ratios. Additionally, it was found that in terms of overall cooling effectiveness, a trench is the highest performing hole exit for a film cooling with a round hole. It was also determined that to reach the desired overall cooling effectiveness level the lateral spacing of the film cooling holes is equal to the traditional spacing without TBC which is P/D = 3. Multirow simulations were also completed to explore the length of the bore cooling effects inside the film cooling hole. It was found that in terms of an allowable overall cooling effectiveness level, the bore cooling provided an additional 15D of spacing for a second row of holes. Finally, experiments of a select number of the single row configurations simulated were tested experimentally to compare to the RANS simulations. The results of these experiments were then used to determine an optimal multirow film cooling using the 1-D model for overall cooling effectiveness .

Presenting Author: Ameya Kulkarni The University of Texas at Austin

Presenting Author Biography: Ameya Kulkarni is a master's student at the University of Texas at Austin working in the Turbulence and Turbine Research Cooling Laboratory. He is advised by Professor David Bogard.

Authors:

Ameya Kulkarni The University of Texas at Austin
Joshua Lewis University of Texas at Austin
Emma Bond University of Texas at Austin
David Bogard University of Texas at Austin