SAMTECH PowerPoint Presentation

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MATCHING EXPERIMENTAL AND NUMERICAL DATA OF
DYNAMIC WIND TURBINE LOADS BY MODELLING OF
DEFECTS
A. Heege1, J. Hemmelmann2, L. Bastard1, L. Lens1,
J.L. Sanchez1 1 SAMTECH Iberica, 08007 Barcelona,
Spain 2GE Global Research, 85748 Garching b.
München, Germany
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Scope of the presentation

• Experimental measurements sensor locations
• Identification of alignment defects
• Aero-elastic mechanical modeling approach
• Coupling FEM, MBS BEM
• Dynamic behavior of large wind turbines
• Assement of numerical results by comparison to
  experimental measurements
• Time domain comparison of transients
• Frequency domain comparison of frequency
  content
• Impact of modeling approach on dynamic load
  spectra
• Conclusions

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Sensor locationsof experimental measurements

• Power train sensors
• Gearbox sensors

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Experimental measurements power train alignement
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Experimental measurements gearbox dynamics
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Aero-elastic mechanical modeling approach

• Dynamic behavior of large wind turbines
• Modeling of defects

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Coupled aero-elastic mechanical wind turbine
model by coupling FEM, MBS analysis BEM theory
Dynamic forces can only be evaluated, if the
complete wind turbine is modeled!
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Dynamic behaviour of large wind turbines
flexible system dynamics with coupled Eigen-Modes
Modes involve generally several components
simultaneously
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Assement of numerical results by comparison to
experimental measurements
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Comparison of measurement and SAMCEF
results global dynamic behaviour during E-stop
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Axial main bearing deformation gearbox
mouvements during Emergency Stop
! Relative mouvement of gearbox w.r.t. to main
bearing/rotorshaft !
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Deformations of torque arm couplings
gt ? non-symetric pre-tension of left and right
torque arm ? lt
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High speed shaft at gearbox exit bending moment
and axial mouvement during E-stop
! Measurements reveal systematically frequencies
of P_HSS !
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• Frequency fingerprint of wind turbines
• Power train and gearbox misalignments
• Impact of modelling degree on load spectra

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Gearbox movement at torque arm bushings in
vertical and longitudinal directions

• Torque arm displacements show
• 3P_rotor tower shadow, wind shear, rotor tilt
  angle
• 2P_rotor ??
• 1P_rotor misalignment, pitch error

1 P_rotor 0.275Hz 3 P_rotor 0.825 Hz
Pitch error and misalignment produces torque arm
displacement of frequency P_rotor
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Gearbox rear orbital movement
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Frequencies measured during production FFT of
rotor shaft torque
Transients are transformed from time domain s
to frequency domain by of FFT spectra

• 0.25 0.4Hz first tower bending modes
• 0.25 - 0.3 Hz ? 1P_rotor unbalance,
  misalignment, pitch error ?
• 0.5Hz 2 Hz first blade bending modes,
  torsional drive train modes
• 0.5 - 0.6 Hz ? 2P_rotor pitch error ?
• 0.8 1 Hz ? 3P_rotor tower shadow, wind
  shear, nacelle tilt angle
• 20 - 600 Hz gear mesh frequencies, structural
  components
• 30Hz ? P_HSS misalignment of high speed
  shaft, generator ?

!! Some frequencies can only be explained by
defects !!
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Impact of Mechanical Blade Model on Fatigue
Loads Blade Model a.) Super-Element/FEM - b.)
Beam Elements
RFC cycles of Lateral Nacelle Acceleration
Production with 10 TI
Blade models a.) Beam elements without
bending-torsional coupling b.) Super Elements
including bending-torsional coupling
! Coupling of bending-torsion mechanics should
be accounted in fatigue computations !
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Conclusion orbit analysis of power train
components

• Orbit analysis of power train reveal cyclic yaw
  and tilt motions.
• Misalignment of gearbox is periodic with
  frequency corresponding to rotor speed
• Root causes for yaw and tilt motions and/or
  general misalignments might be
• Misalignment of rotor shaft and gearbox at PLC
  coupling
• Individual blade pitch errors
• Defects of gearbox torque arm silent block
  couplings
• non-uniform pre-tensions and/or stiffness
  properties
• mechanical coupling of bending and translational
  stiffness (anisotropic off-diagonal stiffness
  terms)

   
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Thank you very much for your attention