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.