Investigation of Innovative Trailing Edge Cooling Configurations With Enlarged Pedestals and Square or Semicircular Ribs: Part II—Numerical Results

Abstract

Trailing edge is a critical region for turbine airfoils since this part of the blade has to match aerodynamic, cooling and structural requirements at the same time. In fact aerodynamic losses are strictly related to trailing edge thickness which, on the contrary, tends to be increased to implement an internal cooling system, in order to face high thermal loads. At the moment the most employed devices consist of pin fins of various shapes, which contribute to both heat transfer enhancement and structural resistance improvement. Enlarged pedestals decrease pressure losses in comparison with multirow pin fins, even if the heat transfer increase is limited. This work deals with the investigation of the usage of enlarged pedestals, inserted in a wedge shaped duct, in conjunction with square or semicircular rib turbulators. The aim of the analysis is the evaluation of the convective Heat Transfer Coefficient (HTC) distribution over the endwall surface and the pressure drop of the converging duct. Numerical analysis used 3D RANS calculations. An in-house modified object-oriented CFD code and a commercial one were used. Several turbulence models and mesh types were tested. Numerical calculations were compared with experimental results obtained on the same geometries using a transient Thermochromic Liquid Crystals (TLC) based technique. Goals of this comparison are both the evaluation of the accuracy of CFD packages with standard two equation turbulence models in heat transfer problems with complex geometries and the analysis of flow details to complete and support experimental activity.