Demonstration of Ceramic Design Methodology for a Ceramic Combustor Liner

Successful application of ceramics in the gas turbine environment involves brittle material design and analysis, unique material properties, and laboratory demonstration of components. Alternative ceramic structures for application in a hybrid ceramic-metal combustion system were considered. Thermal stresses and probabilities of failure were calculated for tube, ring, and stave designs. The stress levels are relatively low for axial and radial temperature gradients in all 6 in. (152 mm) diameter combustors. Scaling to larger sizes is also considered. A hot streak temperature distribution resulted in stresses in the stave and tube which were three times the stresses in the ring design. Bend specimens were cut from one end of a 6 in. (152 mm) diameter, 10 in. (254 mm) long REFEL silicon carbide tube to assure a representative flaw distribution. Strength, strength scatter, and strength degradation were evaluated at 2200°F (1200°C) and were incorporated in the stress analysis. A low probability of failure was predicted. The REFEL tube was tested in the hybrid ceramic-metal combustion system at gas temperatures in excess of 2660°F (1460°C), 16 atm pressure, and 6.9 lb/s (3.1 kg/s) mass flow while burning No. 2 fuel oil. Successful ceramic performance was demonstrated at 2000°F (1090°C) steady state and at 2000°F (1110°C) per minute shutdown cooling rate.