The TMF Life Assessment of First-Stage W501F Turbine Blade Under Different Operating Temperatures

Abstract

Thermal Mechanical Fatigue (TMF) is emerging to be a major damage accumulation mode in the first-stage turbine blades of the F class industrial turbines. In this work, the effect of engine operating temperatures on the TMF life of the first-stage W501F turbine blade has been studied. The turbine inlet temperature (TIT) for the base load engine operation is predicted using thermodynamics based engine analysis. A computational fluid dynamics (CFD) based cascade analysis of the gas path was performed to predict the metal temperatures and temperature gradients. A higher average TIT with a sharper gradient compared to the TIT profile for the base load was also assumed to numerically represent a more severe engine operating test case. A material physics based TMF life prediction approach was adopted to identify the fracture critical locations (FCL). The cyclic life to crack nucleation under different engine operating conditions was also predicted. The predicted FCL and life matched with field experience. A FCL was also predicted inside the cooling channels of the blade, suggesting the need to develop suitable inspection techniques.