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 language | English |
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Pages (from-to) | 101-120 |
Number of pages | 20 |
Journal | Flow, Turbulence and Combustion |
Volume | 88 |
Issue number | 1-2 |
DOIs | |
Publication status | Published - 2012 |
Externally published | Yes |
Keywords
- Film cooling
- Heat transfer
- Large coherent structures
- Large-Eddy simulation
- Turbulent mixing