Three-dimensional numerical study of the impact of the cooling nozzle shape on the cooling film for a gas turbine blade

Abstract

• A 3D CFD simulation was conducted to study how various cooling nozzle shapes influence film cooling in gas turbine blades. • Three nozzle designs—cylindrical, rectangular, and crescent—were examined using the RANS equations with the k-ω SST turbulence model. • The crescent-shaped nozzle showed the highest cooling efficiency, especially at a blowing ratio of 2. • A 30° inclination angle consistently enhanced film coverage and uniformity across all nozzle types. This study presents a three-dimensional numerical investigation to evaluate how different cooling nozzle shapes impact film cooling (FC) performance on gas turbine blades (GTBs). Adequate cooling is essential for maintaining blade durability in extreme temperatures, and the proper design of coolant nozzles plays a key role in optimizing heat transfer while minimizing thermal stress. Using Computational Fluid Dynamics, various nozzle shapes were modeled to assess heat transfer between hot gases and coolants. The analysis used the Reynolds-averaged Navier-Stokes equations and the k-ω shear stress transport turbulence model to capture detailed flow around the nozzles. Results indicate that nozzle geometry significantly affects FC performance. Among the configurations tested, cylindrical, rectangular, and crescent-shaped nozzles achieved the highest efficiency at a blowing ratio of 2, creating a more uniform and protective cooling film. Additionally, an inclination angle of 30° consistently improved cooling effectiveness across all nozzle types. The study also examines the effects of two incidence angles, 30° and 60°, on FC efficiency. At 30°, flow pathlines stabilized after cooling injection, with the cooling jet lifting high-temperature mainstream air, enhancing the cooling flow and distancing the jet from the wall. Counter-rotating vortex pairs further promoted lateral spreading of the jet. At a 60° incidence angle, the vortex pairs increased the jet's upward velocity, preventing film adherence. Overall, the findings emphasize the importance of nozzle shape and injection angle in enhancing cooling efficiency for GTBs, providing valuable insights for designing advanced cooling systems.