15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Authors
Abstract
Studies in turbine blade cooling have demonstrated the importance of surface porosity for high performing designs. As the development of homogenous, porous materials, fit for turbine blade usage is still far from maturity, the focus currently lies on closely packed arrays of smaller film cooling holes and slots. As manufacturing progress allows these discrete cooling features to be brought closer and closer together, the interactions between individual cooling features can no longer be ignored. This paper aims to demonstrate that these interactions can have significant implications on a film’s cooling effectiveness. Experiments at engine representative conditions on turbine blade geometries reveal that the difference between constructive and destructive interference between films can sway the overall film effectiveness by well over 20%. Combining both experimental and numerical results, this paper will then attempt to explain the nature of some of these interactions and how they can either benefit or hamper the effectiveness of cooling films. Through a combination of vortex interactions between films as well as an alteration of the near-wall boundary layer velocity field, films can be both encouraged to lift off at low blowing ratios or sucked back onto the blade surface at high blowing ratios. Beyond changing the blowing ratio at which lift off occurs, the appropriate use of interactions can help to push the hot mainstream gas away from the blade surface completely, resulting in film effectiveness of close to unity. In addition to dramatically improved film effectiveness levels, these results suggest that these new geometries should be modelled very differently to conventional films as few of the original assumptions are left standing.
ETC2023-298
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