Efficient Lifetime Prediction of High Pressure Turbine Blades in Real Life Conditions

Abstract

Jet engines of airplanes are designed such that in some components damage occurs and grows in service without being critical up to a certain level. Since maintenance, repair and component exchange are cost-intensive and limit the operating life of the engine, it is necessary to predict the component lifetime using an acceptable computational effort. To efficiently calculate the lifetime consumption of turbine components with sufficient accuracy under operational conditions, we developed a hybrid approach, which is based on the following three steps: First, the possible operation space is analyzed and reduced to define a manageable Design-of-Experiments (DoE) space. Subsequently, precise aerodynamic and structural mechanic simulations of the component are performed at each DoE support point and the results are stored in a database. Next, the lifetime consumption of the component for the operation profile of interest is calculated based on interpolated stress and temperature fields using suitable lifetime prediction models. The implemented lifetime models are based on accepted lifetime prediction models for creep, fatigue and combined loading, which were extended to incorporate the loading situation on a high pressure turbine (HPT) blade. Due to efficient data management, the computational time for calculating the lifetime consumption of a whole HPT blade is approximately four seconds for one take-off. Consequently, a full three dimensional lifetime consumption analysis of the lifespan of a HPT blade is possible within a few hours. Using the developed approach, it is now possible to predict the lifetime of a HPT blade for different operators with the necessary precision in an acceptable time. To demonstrate the developed approach, a HPT blade of an exemplarily chosen jet engine with known flight history and documented borescope inspections will be used. Comparing the calculated lifetime of the HPT blade with the documented findings from shop visits reveals that the simulation is in good agreement for the investigated flight mission of the chosen engine.