Optimization and characterization of integrated cooling circuit for gas turbine cooling

The objective of this research was to optimize the integrated design of internal cooling and film cooling configuration for a gas turbine airfoil. Various film cooling hole geometries were tested with appropriate co-flow and counter-flow channel feed configurations in the wind tunnel facility. The results showed that X-AOpt hole, a shaped film cooling hole which had been previously developed in our laboratory using a computational adjoint optimization technique, outperformed all other geometries in adiabatic effectiveness. In terms of peak performance, X-AOpt hole was able to perform 70% better than the reference 7-7-7 hole. Thermal field measurements showed that the film cooling jets of the X-AOpt hole were better attached to the surface, showing little signs of separation. However, one drawback of the X-AOpt hole was that it showed significant hole-to-hole variation in co-flow and counter-flow tests. Next, computational simulations and experimental tests were run with serpentine channels. This part of the study investigated the optimum internal rib configuration to be used with a serpentine channel. Three rib configurations were considered: -60°, 90°, and +60° ribs. Computational simulations predicted that -60° ribs would reduce pressure drop compared to the smooth channel. Flow field visualization showed that large separation regions after each U-bend were responsible for increasing the pressure drop for the smooth serpentine channel, and the -60◦ ribs helped to redistribute the biased flow. Experiments showed that the pressure drop of the smooth serpentine channel was over-predicted, and the actual pressure drop between smooth and -60° rib case were similar. However, +60° ribs significantly increased the pressure drop, consistent with CFD predictions. In terms of heat transfer, both CFD predictions and experiments showed that there was no noticeable change in surface temperatures. Adiabatic effectiveness measurements with X-AOpt holes under cross-flow were also evaluated. The X-AOpt holes showed good hole-to-hole uniformity when operating in cross-flow. The spatially-averaged adiabatic effectiveness continued to increase with increasing film injection rates, eventually surpassing the performance of the same holes operating under co-flow and counter-flow at high injection rates. In terms of overall-effectiveness, the X-AOpt holes in serpentine channels showed 30% better effectiveness than co-flow channel tests.Mechanical Engineerin