Description: As the power density of advanced engines increases, the need for new materials that are capable of higher operating temperatures, such as ceramic matrix composites (CMCs), is critical for turbine hot-section static and rotating components. Such advanced materials have demonstrated the promise to significantly increase the engine temperature capability relative to conventional super alloy metallic blades. They also show the potential to enable longer life, reduced emissions, growth margin, reduced weight and increased performance relative to super alloy blade materials. MR&D is proposing to perform a combined analytical and experimental program to develop a durability model for CMC Environmental Barrier Coatings (EBC). EBCs are required for CMCs in turbine exhaust environments because of the presence of high temperature water. The EBC protects the CMC and significantly slows recession. However, the durability of these materials is not well understood making life prediction very challenging. This program will be the first step in developing a tool to accurately evaluate the life of the EBC for a CMC turbine blade helping to facilitate their inclusion in future engine designs. This will be done by developing a custom, user defined element formulation for finite element modeling to simulate the kinetic reactions of the EBC with the turbine exhaust. It will be built on the back of earlier work developing such an element to model the oxidation of carbon fiber in reentry environments.

Benefits: NASA Glenn has been directly involved in the effort to bring these materials to turbine hot section components. The NASA Ultra Efficient Engine Technology program (UEET) is focused on driving the next generation of turbine engine technology. One of the major thrusts is the development and demonstration of advanced high temperature materials which are capable of surviving the extreme environments of turbine combustion and exhaust.

In the commercial sector, the Rolls Royce Trent 1000 and Trent XWB engines are being developed for the Boeing 787 and Airbus A350 XWB aircraft, respectively. There are currently 1030 Boeing 787s on order or flying and 814 Airbus A350 XWBs on order. The Trent 1000 was the launch engine for the Boeing 787. These are large markets where the benefit of this technology will have a lasting impact in efficiency and cost. By working closely with Rolls Royce during the early stages of this development program, MR&D has ensured that the resulting products will meet the requirements of future customers. Rolls Royce has expressed a serious interest in this technology and, as demonstrated above, has a sizable market for its application. The aerospace industry is not the only potential beneficiary of this technology. The Department of Energy (DOE) is working hard to improve the efficiency of power generators. Just as with aircraft engines, power turbines' efficiency improves with higher operating temperatures. As an example, current turbines operate at 2600F, which provided a large improvement in efficiency over earlier models operating at 2300F. CMC turbine blades and stators will allow even higher temperature operation and is a topic which the DOE is currently investigating.