Analysis of nonlinear aeroelastic interactions during forced response of coupled turbine blades

• Applicants: Dr. Christian Frey; Professor Dr.-Ing. Malte Krack
• Subject Area: Hydraulic and Turbo Engines and Piston Engines
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 382141955

• Final Report Year: 2023

Final Report Abstract

The project was dedicated to extending the understanding and improving the prediction quality of aeroelastic blade vibrations. Both flutter vibrations and forced vibrations due to speed-synchronous excitation were considered. The prevailing practice in blade vibration analysis is to model the flow as an imposed force and as a single influence coefficient of the dominant mode. In particular, for blades coupled via shrouds, the nonlinear friction leads to an amplitude-dependent mode shape that significantly alters the aerodynamic damping. To capture this effect, a full matrix of modal influence coefficients can be used. The fully coupled harmonic-balance method developed in this project inherently accounts for the amplitude-dependent deflection mode shape, reducing the computational cost. More importantly, this method is able to model the aerodynamic coupling between the structural harmonics and even the amplitude dependence of the aerodynamic forces. The numerical results show that the conventional methods lead to large quantitative and qualitative errors in the prediction of the forced response and flutter.

Publications

• Effect of creep on the nonlinear vibration characteristics of blades with interlocked shrouds. International Journal of Non-Linear Mechanics, 99, 240-246.
  Gross, Johann; Buhl, Patrick; Weber, Ulrich; Schuler, Xaver & Krack, Malte
  
• Rig and Engine Validation of the Nonlinear Forced Response Analysis Performed by the Tool OrAgL. Journal of Engineering for Gas Turbines and Power, 141(2).
  Hartung, Andreas; Hackenberg, Hans-Peter; Krack, Malte; Gross, Johann; Heinze, Torsten & Panning-von, Scheidt Lars
  
• Harmonic Balance for Nonlinear Vibration Problems. Mathematical Engineering. Springer International Publishing.
  Krack, Malte & Gross, Johann
  
• Analysis of Friction-Saturated Flutter Vibrations With a Fully Coupled Frequency Domain Method. Journal of Engineering for Gas Turbines and Power, 142(11).
  Berthold, Christian; Gross, Johann; Frey, Christian & Krack, Malte
  
• Effect of Modal Interactions on Friction-Damped Self-Excited Vibrations. Journal of Vibration and Acoustics, 143(3).
  Woiwode, Lukas; Gross, Johann & Krack, Malte
  
• Multi-Wave Vibration Caused by Flutter Instability and Nonlinear Tip-Shroud Friction. Journal of Engineering for Gas Turbines and Power, 142(2).
  Gross, Johann & Krack, Malte
  
• Development of a fully-coupled harmonic balance method and a refined energy method for the computation of flutter-induced Limit Cycle Oscillations of bladed disks with nonlinear friction contacts. Journal of Fluids and Structures, 102, 103233.
  Berthold, Christian; Gross, Johann; Frey, Christian & Krack, Malte
  
• Multiwave Vibrations in Mistuned Cascades With Tip-Shroud Friction. Journal of Engineering for Gas Turbines and Power, 143(5).
  Johann, Gross & Malte, Krack
  
• Fully Coupled Analysis of Flutter Induced Limit Cycles: Frequency Versus Time Domain Methods. Journal of Engineering for Gas Turbines and Power, 145(7).
  Berthold, Christian; Gross, Johann; Frey, Christian & Krack, Malte