Analysis on gas turbine blade cooling by compressed air channels using CFD simulation

Enhancement of gas turbine performance can be achieved by increasing the working fluid temperature. On other hand, the level and variation in the temperature within the blade material which causes thermal stresses, must be limited to achieve reasonable durability goals. Therefore, there is a critical need to cool the blades for safe operation by internal air flow passages. In this study, CFD technique was employed to investigate the temperature distribution at different operational conditions. The blade was digitized to get the exact dimensions in the form of AutoCad drawing which was then exported to GAMBIT for discretization and to FLUENT for simulation. Flowing into a rectangular 9×18 mm channel, 400 K compressed air is used to cool the blade while the blade is spinning in hot gas of 1700 K. The temperature distribution was compared with the results previously obtained by using analytical-finite difference coupled method. The results show that the temperature difference is less than 5% at the root of the blade and 15.9% at the channel of height 157.7 mm. Further simulation and analysis of a ribbed channel with rib angle, α = 60° and rib blockage ratio, e/Dh = 0.078 have been carried out and compared with previous analytical results. Ribbed channel was compared with smooth channel cooling. The results showed that there is a decrease in the blade material temperature which improves the efficiency by 8.68% when using two-opposite rib walls on the 18 mm wide side of the channel.