Requirements for increased power density, improved fuel economy, and rapid start demand higher turbine inlet temperatures and turbine wheel tip speeds, resulting in the need for materials with high strength to weight ratio at temperatures in excess of 2000°F. High performance ceramics appear to be the most promising substitutes for the current cobalt-nickel based superalloys.
The numerous advantages of ceramics are coupled with several unfavorable properties, such as the brittleness, the low reliability of the ceramic pans, and the lack of established design, manufacturing and inspection techniques. The development of reliable components requires a close cooperation between the user and the manufacturer of the high performance ceramics.
Sundstrand Power Systems has been involved with the development of ceramic gas turbine components since 1972. The current Research and Development effort involves the demonstration of ceramic turbine components operating at 2200°F turbine inlet temperature.
Silicon nitride turbine wheel and stationary components were designed and subjected to a series of tests in the Gemini small gas turbine modified for this purpose. Engine start to full speed in 2.5 seconds and continuous operation at 2300°F was demonstrated.
The successful testing of the ceramic turbine components demonstrated the feasibility of the currently available structural ceramic materials for non-flight-critical and unmanned turbine applications.
