Transient Stress Analysis and High Cycle Fatigue Life Estimation of a Gas Turbine Shrouded HP Compressor Blade

This work is focused on developing a technique to assess high cycle fatigue of shrouded HP compressor blades subjected to thermo-mechanical loads like centrifugal stresses, vibratory stresses and thermal stresses in a gas turbine rotor. In practice, the blades are also subjected to resonance condition during steady or transient conditions of operation when passing through critical speeds. Hence, shrouds are added initially at 3/4 length along blade height which helps in reducing vibration amplitude by providing suitable stiffness to the blade and hence better structural integrity. Industrial best practice like Campbell diagram is used for the above purpose. Two approaches employed here for fatigue analysis are linear Finite element analysis (FEA) and Elasto-Plastic FEA. Fictive elastic results are recalculated using Neuber’s Rule. Strain amplitude approach is followed and Coffin-Manson Equation is used to determine the number of start-up and shut-down cycles. Design and analysis is performed using ANSYS 14.5 tool for reliable fatigue life estimation and to predict catastrophic failure due to High Cycle Fatigue.