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Analysis of Friction-Saturated Flutter Vibrations With a Fully Coupled Frequency Domain Method

Berthold, Christian and Gross, Johann and Krack, Malte and Frey, Christian (2020) Analysis of Friction-Saturated Flutter Vibrations With a Fully Coupled Frequency Domain Method. Journal of Engineering for Gas Turbines and Power, 142 (11). American Society of Mechanical Engineers (ASME). doi: 10.1115/1.4048650. ISSN 0742-4795.

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Official URL: https://asmedigitalcollection.asme.org/gasturbinespower/article/142/11/111007/1087610/Analysis-of-Friction-Saturated-Flutter-Vibrations


Flutter stability is a dominant design constraint of modern turbines. Thus, flutter-tolerant designs are currently explored, where the resulting vibrations remain within acceptable bounds. In particular, friction damping has the potential to yield limit cycle oscillations (LCOs) in the presence of a flutter instability. To predict such LCOs, it is the current practice to model the aerodynamic forces in terms of aerodynamic influence coefficients for a linearized structural model with fixed oscillation frequency. This approach neglects that both the nonlinear contact interactions and the aerodynamic stiffness cause a change in the deflection shape and the frequency of the LCO. This, in turn, may have a substantial effect on the aerodynamic damping. The goal of this paper is to assess the importance of these neglected interactions. To this end, a state-of-the-art aero-elastic model of a low pressure turbine blade row is considered, undergoing nonlinear frictional contact interactions in the tip shroud interfaces. The LCOs are computed with a fully coupled harmonic balance method, which iteratively computes the Fourier coefficients of structural deformation and conservative flow variables, as well as the a priori unknown frequency. The coupled algorithm was found to provide excellent computational robustness and efficiency. Moreover, a refinement of the conventional energy method is developed and assessed, which accounts for both the nonlinear contact boundary conditions and the linearized aerodynamic influence. It is found that the conventional energy method may not predict a limit cycle oscillation at all while the novel approach presented here can.

Item URL in elib:https://elib.dlr.de/138381/
Document Type:Article
Title:Analysis of Friction-Saturated Flutter Vibrations With a Fully Coupled Frequency Domain Method
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Berthold, ChristianChristian.Berthold (at) dlr.deUNSPECIFIED
Frey, ChristianChristian.Frey (at) dlr.deUNSPECIFIED
Date:November 2020
Journal or Publication Title:Journal of Engineering for Gas Turbines and Power
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1115/1.4048650
EditorsEmailEditor's ORCID iD
Sawicki, JerzyCleveland State UniversityUNSPECIFIED
Publisher:American Society of Mechanical Engineers (ASME)
Keywords:harmonic balance, fluid-structure interaction, aeroelasticity, limit cycle oscillations, turbine shroud
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:other
DLR - Research area:Aeronautics
DLR - Program:L - no assignment
DLR - Research theme (Project):L - no assignment
Location: Köln-Porz
Institutes and Institutions:Institute of Propulsion Technology > Numerical Methodes
Deposited By: Berthold, Christian
Deposited On:30 Nov 2020 09:27
Last Modified:30 Nov 2020 09:27

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