Ceramic Combustor Research Articles

Combustor Development for Automotive Gas Turbines

This paper describes the development of a combustion system for the AGT 100 automotive gas turbine engine. The AGT 100 is a 100 hp engine being developed by Detroit Diesel Allison Division of General Motors Corporation. To achieve optimum fuel economy, the AGT 100 engine operates on a regenerative cycle. A maximum turbine inlet temperature of 1288/sup 0/C (2350/sup 0/F) is reached, and air is supplied to the inlet of the combustor at temperatures as high as 1024/sup 0/C (1875/sup 0/F). To meet the low-emission and high-durability requirements at these conditions, a premix/prevaporization ceramic combustor employing variable geometry to control the temperature in the burning zone has been developed. A test section capable of handling 1024/sup 0/C (1875/sup 0/F) inlet air was designed and fabricated to evaluate this combustor. Testing of both metal (transpiration cooled) and ceramic combustors was conducted. Emissions were measured and found to be a function of burner inlet temperature. At 999/sup 0/C (1830/sup 0/F) burner inlet temperature, NO /SUB x/ emissions were two orders of magnitude below the program goals. At the same temperature but at a different variable-geometry position, the CO was 30 times below the program goal. Considerable testing was conducted to evaluate themore » behavior of the ceramic materials used in the combustor. No failures occurred during steady-state operation; however, some cracks developed in the dome during extended transient operation.« less

Preliminary Design Analysis of a Catalytic Ceramic Structure in a Turbine Combustor

Analysis and design of a catalytic ceramic element and its support structure in a turbine combustor for low emission application have been performed. Preliminary analysis including a survey of literature has helped identify certain design considerations and conceptual designs of the catalytic ceramic element. A thermo-mechanical analysis of the major components in these conceptual designs has been performed for both steady-state and transient (shut-down) situations. Consequently, an arrangement to build a viable catalytic ceramic combustor element has been identified which is expected to perform its mechanical functions.

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.