Development of transpiration cooling film effectiveness correlations from PSP data taken from turbine blade geometries

Authors

Augustin Wambersie  - University of Oxford Thermofluids Institute, United Kingdom
Peter Ireland - University of Oxford Thermofluids Institute, United Kingdom

Abstract

Film effectiveness levels measured downstream of high porosity cooling features, have demonstrated exceptionally high levels of performance. Conventional film cooling models remain very limited in their ability to predict such films, particularly on the suction surface where films significantly exceed expectations. CFD models are equally limited with turbulent mixing models over predicting film decay. A novel approach to describing and these films has been attempted using the similarities between tangential slot cooling and the experimental data. Based on these assumptions, a model developed by combining two separate interpretations of film cooling was established: that of superposition as well as tangential slot decay.   The success of this model reinforces both the idea that tangential slots and transpiration cooling share similar film distributions, as well as the idea that the high porosity geometries proposed in fact mimic transpiration cooling. The final section of this research paper uses the model to explore the likelihood of laminar-like film cooling on the suction surface. By comparing the suction surface to the pressure surface and a baseline flat plate, the model is seen to be completely consistent between all three scenarios once the suction surface is considered to be laminar.