Numerical Investigation of Thermomechanical Fatigue Behavior in Aeroderivative Gas Turbine Blades

Abstract

The hot gas component of the gas turbine engine comprises the
burner, the turbine stages, and the exhaust nozzles/ducts. However,
the turbine blades experience high thermal and mechanical loading.
As a result, they suffer thermo-mechanical fatigue (TMF). The design
process usually involves the appropriate selection of the turbine
blade materials. Therefore, the need to carry out thermo-mechanical
fatigue studies on gas turbine blades to predict blade life. During
TMF loading, fatigue, oxidation, and creep damages are induced,
and the relative contributions of these damages vary with the
different materials and loading conditions. The study employed the
finite element method to examine the high temperature and stress
effects on the blades during TMF. The blade material considered in
this study is a nickel-based super-alloy, Inconel 738 Low Carbon
(IN738LC). The finite element method predicted the temperature and
stress distributions in the blade, illustrating the blade sections prone
to damage during thermomechanical fatigue. The equations from the
law of heat conduction of Fourier and the cooling law of Newton
predicted the heat transfer process of the interaction between the
blade, hot gases, and cooling air. Therefore, the finite element
method is suitable for studying the thermomechanical fatigue
behavior of turbine blade metals, which is a precursor to blade life
predictions.