Components and structures in power plants, especially in combined cycle power plants, or cogeneration installations are frequently subjected to severe thermal and mechanical stresses. Repeated loading due to startup and shutdown or normal operation cycles may lead to fatigue failure. Complex states of stress are common within these components. Different sources of cyclic loading may differ in phase and frequency. For example, a low-frequency thermal load from startup and shutdown may be combined with a high-frequency mechanical load due to flow-induced vibrations. In case of high operating temperatures creep may add to the complexity of the problem. Growing demands on safe, reliable and economic operation ask for a sufficient precaution against structural failure, especially fatigue failure. Advanced concepts of fatigue life prediction require detailed stress analysis amongst which the finite element method (FEM) has gained considerable importance. In the following article stress analyses utilizing FEM are termed CSM or computational structural mechanics. To account for the complex flow in the components in question a 3D computational fluid dynamics (CFD) analysis is necessary to determine appropriate boundary conditions. The following article presents the application of an integrated CFD-CSM analysis to predict the remaining life span of the exhaust gas duct of a gas turbine. Also, the analysis helps to evaluate different refurbishment concepts.
展开▼
