Flow Check and Adiabatic Effectiveness Measurements on Traditionally Versus Additively Manufactured Film-Cooling Holes

In the recent years Additive Manufacturing (AM) methods, such as the Direct Metal Laser Melting (DMLM) technology, are getting more and more attractive and feasible for the realization of components and subcomponents of gas turbines. In particular, they are receiving much attention since, on the one hand, the manufacturing of complex 3D geometries is allowed and, on the other, manufacturing and delivery times can be cut down. Lately, Baker Hughes is studying the possibility to manufacture film-cooling holes via the DMLM technology in order to exploit the flexibility of such innovative manufacturing method and hence eliminate additional processes and lead time. From the open literature, it is known that additively manufactured holes can have a more irregular shape and higher roughness than traditional ones, which may lead not only to a reduction in coolant flow but more importantly to decay of the film-cooling adiabatic effectiveness. For this reason, a test campaign has been conducted in collaboration with the University of Florence (Italy) with the objective of characterizing the performance (minimum passage diameter, flow check, and adiabatic effectiveness) of AM versus traditional cylindrical holes on simple-geometry coupons built upon different construction angles. Ultimately, the dependency of AM holes performance on print angles is sought with the purpose of characterizing the impact of such manufacturing technology on film-cooling holes design.