Numerical Redesign of the Internal Cooling Geometry of a High-Pressure Turbine Blade

In this work, the cooled TG20 first rotor blade is numerically simulated using the commercial software StarCCM+. In the selected case study, the coolant enters the root of the blade in the radial direction through ellipse-shaped ducts characterized by a low aspect ratio. The flow enters a large plenum and then is fed to radial cylindrical channels, providing cooling to the blade. Eventually, the coolant is discharged into the main flow at the blade tip, contributing to the formation of the tip leakage vortex. Steady and unsteady RANS simulations of the rotor blade, along with hot gas and coolant flow were performed to describe the internal flow evolution and its interaction with the main flow, with particular focus on the internal and external heat transfer. It was noticed that vortical structures arise from both the sudden expansion occurring in the plenum and the improper guidance of the cooling flow towards the blade radial channels, which leads to stagnation regions at their inlet sections. The latter, along with the non-uniform flow in the plenum, produces non-homogeneous and unsteady inlet conditions to the radial channels, affecting the cooling performance of this solution. For those reasons, flow perturbators such as pin fins, aerodynamic profiles, and rib turbulators have been designed and analyzed to allow for a better mixing of the coolant and then reduce the impact of vortical structures on the cooling performance. It was found that flow perturbators can modify the flow pattern in the plenum, weakening the formation of vortical structures. This results into a smoother flow pattern over the inlet sections of the radial channels, retaining a significant impact on the temperature distribution over the blade profile.