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Title:
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Aeroelastic Analysis of the LMH64-5 Blade
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Author(s):
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Published by:
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Publication date:
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ECN
Wind Energy
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1-6-2003
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ECN report number:
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Document type:
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ECN-C--03-020
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ECN publication
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Number of pages:
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Full text:
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51
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Download PDF
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Abstract:
Within the DOWEC project, investigations were performed into the developmentof large size wind turbines for offshore applications. Many of the studies
in this project were performed for a 6MW concept of which the turbine
was designed by NEG-Micon Holland
and the LMH64-5 blade by LM Glasfiber Holland. One of the tasks within
this project was to investigate the aeroelastic stability problems for
large size wind turbines which was performed for this 6MW concept. These
analyses were done with the program BLADMODE.
This document starts with a description of the modelling of the blade
in basis of a set of 51 files with the cross sectional layout. For the
first bending modes the direction of blade motion 'theta' was calculated
for the rotating and non-rotating state, which can
be used as input for hinge-spring-damper analysis tools. The operational
conditions as function of wind speed for which the aeroelastic stability
was investigated, were calculated
with the program PHATAS.
The aerodynamic damping was calculated for the original LMH64-5 blade
concept, and also for some parameter variations on structural and aerodynamic
modelling aspects and on the so-called 'Structural Pitch'. Finally a
comparison was made of the aeroelastic damping calculated with the original
LMH64-5 geometry and a tapered variant.
It was concluded that for pitch-to-vane controlled wind turbines the
flapwise blade vibrations have a positive aerodynamic damping. In general
the aerodynamic damping for the edgewise modes is positive for most
of the operational conditions. For the 6MW concept the aerodynamic damping
of the edgewise blade motions can be improved with a small increase
of the partial-load pitch angle, and with 'Structural Pitch' modifications
of the blade structure. It was also concluded that increasing the torsional
stiffness of
the rotor shaft with a factor 1.7 avoids 6P resonance problems for the
collective edgewise mode and reduces the negative contribution of the
generator characterist.
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