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LES OF FILM COOLING EFFICIENCY FOR DIFFERENT HOLE SHAPES

Peter Renze
Aerodynamisches Institut Rheinisch Westfälische Technische Hochschule Aachen Wüllnerstr. zw. 5 u. 7, D-52062 Aachen, Germany

Wolfgang Schroder
Institute of Aerodynamics RWTH Aachen University Wullnerstr. 5a, 52062 Aachen, Germany

Matthias Meinke
Aerodynamisches Institut, RWTH Aachen, Wullnerstrasse zw. 5 und 7, D-52062 Aachen, Germany

Abstrakt

Large-eddy simulations (LES) of film cooling flows are carried out at different hole shape geometries. The main thrust of this study is to contribute to the understanding of the impact of the hole shape on the mixing process of film cooling flows. A cooling fluid is injected from inclined drilling holes α = 30° into a turbulent boundary layer. Two different hole shapes are considered, a cylindrical geometry and a fan-shaped geometry that includes both a diffusor-like exit and a laidback expansion. The turbulent transport of heat and momentum has been investigated for the case of a cylindrical and a fan-shaped film cooling hole at a temperature gradient of TR = 2.26. The maxima of the turbulent shear stress and turbulent thermal transport of the jet-crossflow interaction are clearly reduced by the shaped jet hole. The instantaneous data show local ingestion of boundary layer fluid into the fan-shaped jet hole at the flow parameters considered in this study. The vortical structures inside the flow field and the driving mechanism of the momentum and heat exchange between the jet and the crossflow are identified and discussed.