The Manufacturing and Experimental Validation of a Nickel Superalloy Double-Wall, Effusion Test Specimen

With the hot stage of a modern aeroengine operating with combustor firing temperatures well beyond the melting point of the nickel superalloys from which the turbine blades are manufactured, developments to the methods of cooling of these components are required to advance performance. Double-wall, effusion systems exhibit a quasi-transpiration like cooling effect with recent work demonstrating their exceptional cooling performance. Such systems are characterised by two walls, one with impingement holes and the other with film cooling holes, that are mechanically and thermally connected via pedestals. However, manufacturing such geometries from single crystal nickel superalloys remains a significant barrier to entry into service.

This paper presents a method of manufacturing double-wall effusion specimens from a nickel superalloy commonly used in modern commercial high pressure turbine components. The method maintains the mechanical integrity associated with nickel superalloys. Details of the method are presented alongside x-ray and GOM laser scan data of a flat-plate test article that demonstrates the success of the manufacturing process. Aerothermal testing of the specimen in a bespoke recirculating wind-tunnel facility was undertaken in which the overall cooling effectiveness of the system is obtained. The results reaffirm the excellent cooling performance of double-wall, effusion systems and further validate the manufacturing methodology as a method by which to realise enhanced cooling effectiveness in service.