COMPUTATIONAL STUDY OF ADDITIVELY MANUFACTURED INTERNALLY COOLED AIRFOILS FOR INDUSTRIAL GAS TURBINE APPLICATIONS

Internal cooling features such as pin-fins, impingement jets, and rib-turbulators are necessary to keep turbine components cool, but if sufficiently advanced can potentially also eliminate the need for film cooling on turbine blades particularly in industrial gas turbines where temperatures are not extreme. Furthermore, by leveraging additive manufacturing (AM), other advanced designs such as lattice and incremental impingement configurations are possible and have recently been experimentally tested. While the performance of such configurations has been quantified recently through means of overall cooling effectiveness, it is not as clear why certain designs were better than others, or what the mechanisms were behind the observed external cooling patterns. The purpose of this study was to computationally analyze different advanced turbine blade internal cooling designs previously tested by the National Energy Technology Laboratory. Conjugate steady Reynolds Averaged Navier Stokes (RANS) simulations were performed on three symmetric blades with different internal cooling configurations: a baseline cooling design with pin-fin arrays, a double wall design with impingement jets and serpentine channels, and an incremental impingement design. The computational results were compared to previously obtained experimental data and were further studied to understand the advantages and disadvantages of different cooling configurations. This study found that the double wall design had better overall cooling than the baseline design, as found in the experiment, because of increased convective heat transfer in the double-wall region. However, the computational model based on design-intent geometry indicated a higher rate of coolant flow in the trailing edge as compared to the experiment resulting in an overprediction of cooling. Additionally, the incremental impingement design had the highest overall cooling effectiveness of the various designs. This was attributed to the impingement jets in the incremental impingement design that produced relatively uniformly distributed high internal heat transfer coefficients.