Session: 12-13 Advanced film cooling enabled by additive manufacturing

Paper Number: 128010

128010 - Optimization of a Novel Design-For-Additive-Manufacturing Film Cooling Hole 

Additive Manufacturing has been proving a very interesting potential to produce objects having both tiny dimensions and complex and twisted shapes. For this reason, in the last years, many efforts have been done to employ AM techniques to film cooling technique in the turbine blade cooling field. The aim of the present work is to present a novel diffusive film cooling hole within the framework of Design-for-Additive-Manufacturing. First, starting from a set of fundamental parameters, the hole has been designed as a result of a numerical optimization in order to find out the best trade-off between different needs. Both the discharge coefficient and the adiabatic effectiveness have been evaluated and compared with the well-established 7-7-7 fan-shaped hole in order to quantify the potential of the novel geometry. Once the numerical procedure ended, two different shapes were selected as output to be printed by means of a Laser Powder Bed Fusion (LPBF) technique. Flow checks tests were performed on a row of 11 holes per shape and the measured discharge coefficient was found to be far lower than expected. A Computed Tomography analysis showed that the hole internal surfaces and entry/exit section collapsed in some areas. Hence, on the one hand, the numerical procedure and the outcoming shapes were validated over an up-scaled flat plate housing the novel holes. Pressure Sensitive Paints measurements were performed in an open-loop wind tunnel for a blowing ratio ranging between 0.25 and 2.00. The adiabatic effectiveness showed a good agreement with CFD data with the novel holes outperforming the 7-7-7 one. On the other hand, a compensation strategy was developed for one of the optimized geometries in order to overcome the difficulties encountered by the AM process due to the very tiny dimensions of the hole. After the critical features were identified and empirically fixed by a re-design of the optimized shape, a CFD validation showed a very similar performance than the original one. In the end, the re-designed hole was printed, and a flow check test confirmed a higher discharge coefficient than the original one.

Presenting Author: Niccolo' Castelli University of Florence

Presenting Author Biography: Ph.D. candidate at the University of Florence in Energetic Engineering. I'm currently working on gas turbine cooling systems.

Authors:

Niccolo' Castelli University of Florence
Alessio Picchi University of Florence
Bruno Facchini University of Florence
Lorenzo Winchler Baker Hughes
Francesco Morante Baker Hughes