On Remaining Life Analysis of Turbine Disks Subjected to High Thermal Stresses

Abstract

Disk failures can be caused by a number of mechanisms under the turbine operating conditions of high rotational speed at elevated temperatures. It is not uncommon for highly stressed turbine blades and disks to operate at temperatures in excess of 1,000°F, where increased exposure can affect their life. In the past, it has been adequate to analyze the life of these high temperature components using methods which calculate creep life and low cycle fatigue life independently in predicting service hours. More often than not, the parameters included in the creep life model are based on empirical data. Here, a practical methodology is presented to predict the remaining life of a turbine disk that utilizes a combination of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and a creep model. A full three-dimensional CFD analysis is performed on the turbine disks at design and off-design conditions, in order to accurately capture the thermal loads. A detailed FEA is performed on the turbine disk. The stress inputs for the creep life model are based on the stresses obtained from the FEA. A case study is presented that utilizes the proposed methodology. It is found that the methodology is beneficial for the remaining life analysis on highly loaded turbine disks. The accuracy of the methodology is somewhat dictated by the amount of historical operating data that is available.