Effects of emergency and fired shut down on transient thermal fatigue life of a gas turbine casing

Abstract

The study aims to establish the transient thermal fatigue life of detected crack on the edge of eccentric pin hole of a gas turbine casing under the terms of linear elastic and elastic-perfectly plastic material behavior, in accord to engine work cycle to fired and emergency shut down. Using non-destructive tests, the crack position and direction were determined. The distribution of inner surface temperature was measured using ten thermocouples that were installed inside the casing's wall. In finite element simulation, the temperature data were applied as a boundary condition. Through the use of Abaqus software and Zencrack fracture mechanics code, the transient thermal stress and thermal fatigue crack growth were predicted. The analysis showed that the stress distribution is same for two terms of material behavior while crack propagation is different. The analyses also showed that the most important factor in thermal fatigue crack growth is the rate of cooling the turbine casing.