Life Time Prediction for Ceramic Gas Turbine Components

Stürmer, G.; Schulz, Achmed; Wittig, Sigmar

doi:10.1115/91-gt-096

Cited by 9 publications

(4 citation statements)

References 12 publications

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“…The maximum tensile stresses remain below 75MPa and 135MPa for continuous operation and trip respectively. Failure probability calculations (CFRITS [6]) demonstrate sufficient reliability for engine operation. The time dependent (slow crack growth) failure probability determination led to P r = 0.84x104 considering 10,000 hours of continous operation.…”

Section: Presented At the International Gas Turbine And Aeroengine Congmentioning

confidence: 99%

“…A finite element analysis shows that the load remains far below the characteristic fracture strength of the considered SSIC-material for continuous engine operation as well as for emergency shutdown. At the same' time the reliability has been raised substantially, so that even under severe transient thermal boundary conditions (trip) a satisfactory failure probability is to be obtained (ITS fracture statistics code CERITS) [6].…”

Section: Introductionmentioning

confidence: 99%

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Testing of a Low Cooled Ceramic Nozzle Vane Under Transient Conditions

Dilzer

Gutmann

Schulz

et al. 1998

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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At the Institut für Thermische Strömungsrnaschinen, University of Karlsruhe (ITS) a design technology has been introduced to reduce the mechanically and especially the thermally induced stresses in ceramic components. The concept is based on a three-layered construction (outer ceramic shell - heat insulating layer - metallic core) and an optimization of the thicknesses of the single layers, in order to obtain a homogenous temperature distribution in the ceramic structure. The optimization is performed by finite element analyses in combination with failure probability calculations. This methodology has been applied to increase the reliability of a first stage Sintered Silicon Carbide (SSiC) ceramic nozzle vane of a stationary gas turbine (70MW/1400°C). As a result it was found that the mechanically and thermally induced loads have been reduced considerably and do not exceed 100MPa, thus achieving adequate life based upon failure probability calculations. Even in a trip situation (fuel cutoff), when the highest loads do occur, the calculations demonstrate a significantly reduced failure probability. The results of the finite element analyses were verified by simulating the typical operating conditions after fuel cutoff in a test rig.

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Section: Presented At the International Gas Turbine And Aeroengine Congmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Testing of a Low Cooled Ceramic Nozzle Vane Under Transient Conditions

Dilzer

Gutmann

Schulz

et al. 1998

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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“…The goals (homogeneous temperatures and low thermal stresses respectively) are verified by finite element analyses of a first stage ceramic nozzle vane for a 70MW stationary gas turbine. Finally the results are evaluated by failure probability calculations taking into account fast fracture mode calculations for tripping conditions and slow-crack-growing effects for continuous operation [5].…”

mentioning

confidence: 99%

Systematic Reduction of Stress Levels for a Thermally High Loaded Ceramic Nozzle Vane With Trailing Edge Ejection

Dilzer

Schulz

Wittig

1999

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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This paper presents a design concept for thermally high loaded ceramic shell components, that is developed at the Institute for Thermal Turbomachinery (ITS, University of Karlsruhe). The aim is to obtain homogenous temperature distribution in the ceramic structure for the whole operating cycle of the engine. Based on simple flat wall considerations design guidelines are introduced to reduce the dominant thermally induced stresses in ceramic components. The concept includes a systematic adjustment of the local cooling configuration and the local wall thicknesses according to the local thermal boundary conditions. The concept is applied to increase the reliability of a directly cooled Sintered Silicon Carbide first stage nozzle vane with trailing edge ejection for a 70MW stationary gas turbine. Finite element analyses demonstrate that the application of this methodology leads to a rather uniform temperature distribution in the ceramic structure and therefore to low stress levels for steady state and for tripping conditions. A transformation of the theoretically derived optimum cooling configuration to a technically feasible cooling setup is performed in the purpose of real engine application. It is found that some differences between optimum and technically feasible cooling configuration (mainly located at the trailing edge region) are of minor importance. The results of failure probability calculations (ITS fracture statistics code CERITS) confirm significantly improved reliability of the ceramic nozzle vane.

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“…This includes finite element analyses to calculate temperature and stress distributions in complex shaped structures as well as failure probability calculations using the computer code CERITS. Taking into account subcritical crack growth the time dependent failure probability can be determined (see Stiirmer et al 1991).…”

mentioning

confidence: 99%