The goal of the Ceramic Stationary Gas Turbine (CSGT) Development Program, under the sponsorship of the United States Department of Energy (DOE), Office of Industrial Technologies (OIT), is to improve the performance (fuel efficiency, output power, exhaust emissions) of stationary gas turbines in cogeneration through the selective replacement of hot section components with ceramic parts. The program, currently in Phase II focuses on detailed engine and component design, ceramic component fabrication and testing, establishment of a long term materials property data base, the development of supporting nondestructive evaluation (NDE) technologies, and the application of ceramic component life prediction. A 4000 hr engine field test is planned for Phase III of the program. This paper summarizes progress from January 1995 through January 1996.
First generation designs of the primary ceramic components (first stage blades and nozzles, combustor liners) for the program engine, the Solar Centaur 50S, and of the secondary metallic components interfacing with the ceramic parts were completed. The fabrication of several components has been completed as well. These components were evaluated in rigs and the Centaur 50S test engine. NTI64 (Norton Advanced Ceramics) and GN-10 (AlliedSignal Ceramic Components) silicon nitride dovetail blades were cold and hot spin tested and engine tested at the baseline nominal turbine rotor inlet temperature (TRIT) of 1010°C. Full scale SiC/SiC continuous fiber-reinforced ceramic matrix composite (CFCC) liners (B.F. Goodrich Aerospace) were also rig tested and engine tested at the nominal baseline TRIT of 1010°C. One of the engine tests, incorporating both the GN-10 blades and the full scale SiC/SiC CFCC liners, was performed for 21.5 hrs (16 hrs at 100% load) with six start/stop cycles. A cumulative 24.5 hrs of engine testing was performed at the end of January, 1996. The ceramic components were in good condition following completion of the testing.
Subscale Hexoloy® SA silicon carbide (Carborundum) and enhanced SiC/SiC CFCC (DuPont Lanxide Composites) and Al2O3/Al2O3 CFCC (Babcock & Wilcox) combustor liners were tested to evaluate mechanical attachment, durability and/or emissions reduction potential. The enhanced SiC/SiC CFCC of DuPont Lanxide Composites demonstrated superior durability in subscale combustor testing and this material was subsequently selected for the fabrication of full scale combustor liners for final engine rig testing in Phase II and field testing in Phase III of the program. Enhanced SiC/SiC CFCC liners also showed significantly reduced emissions of NOx and CO when compared with conventionally cooled subscale metallic liners. This observation is believed to apply generally to “hot wall” combustor substrates. The emissions results for the enhanced SiC/SiC CFCC liners were paralleled by similar emissions levels of NOx and CO monitored during engine testing with B.F. Goodrich Aerospace SiC/SiC CFCC combustor liners. NOx levels below 25 ppmv and CO levels below 10 ppmv were measured during the engine testing.
Short term (1,000 hrs) creep testing of candidate ceramic materials under approximate nozzle “hot spot” conditions was completed and long term (5000–10,000 hrs) creep testing is in progress. The selected nozzle material, SN-88 silicon nitride, has survived over 5,500 hrs at 1288°C and 186 MPa stress at the end of January, 1996.