Three-Dimensional Modeling of Creep Damage in Airfoils for Advanced Turbine Systems

Future oxy-fuel and hydrogen-fired turbines promise increased efficiency and low emissions. However, this comes at the expense of increased thermal load from higher inlet temperatures and a change in the working fluid in the gas path, leading to aero-thermal characteristics that are significantly different than those in traditional gas turbines. A computational methodology, based on three-dimensional finite element analysis (FEA) and damage mechanics is presented for predicting the evolution of creep in airfoils in these advanced turbine systems. Information revealed from three-dimensional computational fluid dynamics (CFD) simulations of external heat transfer and thermal loading over a generic airfoil provides detailed local distributions of pressure, surface temperature, and heat flux penetrating through the thermal barrier coated layer. There is an additional mechanical loading due to the centrifugal acceleration of the airfoil. Finite element analysis is then used to predict temperature and stress fields over the domain of the airfoil. The damage mechanics-based creep model uses a scalar damage parameter. This creep model is coupled with finite element analysis to predict the evolution of stress and creep damage over the entire airfoil. Visualization of the creep damage evolution over the airfoil shows the regions that are most susceptible to failure by creep.