Development of Air-Cooled Ceramic Nozzles for a Power-Generating Gas Turbine

The development of air-cooled ceramic nozzle vanes for a power-generating gas turbine has been reported. To make up the limited temperature resistance of present ceramic materials, the utilization of a small amount of cooling air has been studied for the first-stage nozzle vanes of a 1500°C class gas turbine. A series of cascade tests were carried out for the designed air-cooled Si₃N₄ nozzle vanes under 6 atm and 1500°C conditions. It was confirmed that the maximum ceramic temperature can be maintained below 1300°C by a small amount of cooling air. In spite of the increased thermal stresses from local cooling, all Si₃N₄ nozzle vanes survived the cascade tests, including both steady-state and transients of emergency shutdown. The potential for an air-cooled ceramic nozzle was demonstrated for a 1500°C class gas turbine application.