COUPLED SIMULATION OF A SHROUDED TURBINE BLADE ROW WITH CONTACT FRICTION INTERFACES - ANALYSIS OF A LIMIT TORUS OSCILLATION

In order to increase efficiency and achieve lighter engines,
turbine blades are currently developed with a higher aerodynamic
loading and tip Mach number which further increases
flutter probability. Thus, modern and innovative turbine concepts
include flutter-tolerant designs which limit the flutter induced
vibration amplitudes to an acceptable level due to intentional
friction in contact interfaces, which can lead to limit
state vibrations, where the dissipation due to friction balances
the aerodynamic excitation. Among several the possible limit
states, this work focuses on the analysis of a Limit Torus Oscillation
(LTO). Therefore, a fully coupled simulation of a turbine
blade row with nonlinear contact interactions in the shroud is
studied. An initial blade vibration evolves to an LTO. The harmonic
content of the converged LTO is studied and a certain
pattern of the participating harmonics is observed. Moreover
the aerodynamic forces are investigated with respect to the interaction
among the fluid waves of the quasi-periodic motion