Turbine D, thank you for your answer. I understand perfectly and will share your illuminating response with our engineer. He's an amiable type and won't mind a differing perspective on things theoretical.
Riff Raff, thanks for your ongoing discussion and research. It is an interesting development to be sure and likely something similar will be used by all manufacturers in the future.
On our divergent understanding of CMC turbine blades and cooling, it could be I may be reading the optimistic news, while you are getting conservative input from your sources. GE Aviation claims a no-bleed cooling requirement for the 2nd stage turbine blades made of CMC.
With a 27:1 pressure ratio, 20% higher than that in the GENx (in turn 20% higher than in the GE90), the HPC is one of the key changes being introduced in the GE9X, which will exclusively power the 777X.
Others are a “fourth-generation” composite fan with wider, thinner (and fewer) blades, and lightweight, uncooled ceramic matrix composites (CMC) for high-pressure turbine (HPT) nozzles, shrouds and blades.
Dan McCormick (GE head military division)
“The CMC low-pressure turbine blade is about one-third the weight of the metal blade it replaces, and at the second stage, the CMC doesn’t have to be air-cooled. The airfoil can now be more aerodynamically efficient because it does not need all that cooling air pumping through the middle of it.”
I agree commercial aviation is a conservative business and new materials are often introduced incrementally with a great deal of time and effort spent on proving their suitability for in-service operation.