Aerodynamical and Structural Analysis of Operationally Used Turbine Blades

Abstract

This paper presents an integrated methodology for the analysis of operationally-used turbine blades, incorporating aerodynamic and multiple structural simulations. In jet engines, blade rubbing and erosion lead to deviations of the blade geometry. The presented functional simulations are conducted in order to predict the influence of wear on the performance of turbine blades based on these geometric variations. A numerical simulation of the investigated turbine blades using CFD show the change of aerodynamic performance and the flow field due to wear. Additionally, the deviations of the blade geometry lead to a different pressure and temperature distribution on the blade surface, which is used as input for the structural simulations. The change in geometry, surface pressure and temperature lead to a change in vibration behavior of the blade. Particularly the eigenfrequencies and excitation are affected. This is incorporated into the analysis by performing a structural vibration simulation of a complete bladed disk, using component mode synthesis and wave base substructuring. The mistuning effects are analyzed statistically using the Monte Carlo method. The change in vibration amplitudes influences crack opening and closing for a single blade under thermo-mechanical load. These processes, including thermal expansion, are investigated using the extended finite element method. Two real turbine blades are used to compare the characteristics of a new and a used blade.