Modeling Of Creep In The Nickel Based Single-Crystal Super-Alloys Gas Turbine Airfoils

The modern gas turbine system promises increased efficiency and low emissions by increasing the thermal load from higher inlet temperature. The turbine inlet temperature of future gas turbines is expected to exceed 1700K. None of the traditional metal could work in this condition. Single-crystal super-alloys are chose as the material of turbine blade because of their excellent high-temperature fatigue and creep resistance properties, with appropriate thermal protection. Thereby, it is a key tool to predict and increase the life of Single-crystal super-alloys for gas turbine blade design and improvement.A computational methodology, based on three-dimensional computational fluid dynamics analysis (CFD), finite element analysis (FEA) and damage mechanics is presented for predicting the evolution of creep in gas turbine airfoil working at 1700K.A three-dimensional gas turbine blade model is developed based on the NASA E 3 (Energy Efficient Engine) high-pressure turbine blade airfoil data. Information revealed from three-dimensional computational fluid dynamics (CFD) simulations of external heat transfer over the airfoil model provides detailed local distributions of pressure, surface temperature, and heat flux penetrating through the thermal barrier coated layer.The detailed temperature distribution over the domain of the airfoil is calculated by using CFD coupled with FEA. And the stress filed is determined over the gas turbine model, considering the centrifugal velocity mechanical loading.A creep model for CMSX-4 based on damage mechanics is used to predict the evolution of creep in the blade model. A scalar damage parameter is used in the damage mechanics-based creep model. A formulation for damage equivalent stress for material with cubic symmetry is performed to relate the multi-axial state of stress in the component to the one-dimensional stress in the damage mechanics formulation and experimental data. The creep model for CMSX-4 is implemented as a user-modified creep routine in the ANSYS. The creep damage evolution over gas turbine blade model is visualized with contour, showing the regions that are most susceptible to failure by creep.