Turbine film cooling flows typically are subject to jet detachment and reduced cooling effectiveness for high blowing rates. Current concepts to improve jet attachment involve impractical or overly complex hole designs due to manufacturing or durability constraints. Novel film cooling concepts from NASA’s Glenn Research Center involve creating a V-shaped recess on the flow surface of a turbine blade to induce fluid, temperature, or shedding effects; threading turbine film cooling holes with helical channels or grooves (much like the threads of a screw) for the purpose of producing a swirling flow of cooling fluid exiting the film cooling hole; and pairing the threaded holes with holes that have an opposite direction of swirl.
In order to mitigate failure of turbine blades due to excessive operating temperatures, film cooling holes are frequently incorporated into turbine blade designs. In film cooling, cool air is bled from the compressor, ducted to one or more internal chambers of the turbine blades, and discharged through one or more cooling holes to form cooling jets. As a result of the cooling jets, convective heat transfer to the surface of the turbine blade can be reduced. One of NASA Glenn’s innovative cooling designs involves creating a shaped recess on the blade surface. A variety of shaped recesses can be formed in order to create one or more desired cooling effects. Another innovative concept involves the threading of turbine film cooling holes with helical channels or grooves and then pairing those holes with holes that have a different helical direction and intersect with the first set of holes. In this way, the combined flow from these paired holes has a downward velocity component at the center, forcing the flow downward toward the wall and improving cooling effectiveness. Because film cooling is improved, the distance between holes can be increased, reducing the amount of cooling flow required and increasing efficiency.
This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities. Potential applications include use in gas turbines for ground power generation, combustion liners, and jet engines.