Turbulent heat transfer and large coherent structures in trailing-edge cutback film cooling

Hayder Schneider, Dominic Von Terzi, Hans Jörg Bauer

Research output: Contribution to journalArticleScientificpeer-review

31 Citations (Scopus)

Abstract

Film cooling is a key technology for improving the thermal efficiency and power output of gas turbines. The trailing-edge section of high-pressure turbine blades can be efficiently cooled by ejecting a film over a cutback on the pressure side of the blade. In this paper, results of Large-Eddy Simulations (LES) are presented that match an existing experimental setup. Altogether, eight simulations with the blowing ratio M varying as the only parameter were performed over a range from M = 0.35 to 1.4. Reasonably good agreement between LES and experiments were obtained for flow field statistics and adiabatic film-cooling effectiveness η aw. Within a limited range of blowing ratios, an increase in the blowing ratio results in a counter-intuitive decrease of the cooling effectiveness. The present work suggests a mechanism that can explain this behavior. The visualization and analysis of large coherent structures showed that there exists dominant clockwise-rotating structures that can give rise to a combined upstream- and wall-directed turbulent heat flux. This turbulent heat flux represents the main contribution of the total heat flux and causes a significantly intensified thermal mixing process, which in turn results in the counter-intuitive decrease of the cooling effectiveness.

Original languageEnglish
Pages (from-to)101-120
Number of pages20
JournalFlow, Turbulence and Combustion
Volume88
Issue number1-2
DOIs
Publication statusPublished - 2012
Externally publishedYes

Keywords

  • Film cooling
  • Heat transfer
  • Large coherent structures
  • Large-Eddy simulation
  • Turbulent mixing

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