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Title:
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Bending-torsion coupling of a wind turbine rotor blade
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Author(s):
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Published by:
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Publication date:
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ECN
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1996
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ECN report number:
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Document type:
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ECN-I--96-060
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Other
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Number of pages:
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Full text:
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102
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Download PDF
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Abstract:
For a constant speed rotor an increase in energy yield of severalpercentages can be achieved when - with increasing wind speed - there is a
torsional deformation towards stall of the outer 60% of the blade span. The
required twist is about 0.4"o per meter span length. A spreadsheet programme
is used for calculation of the full stiffness matrix of a thin walled cross
section with webs, arbitrary shape and skin laminate. The theory for this is
formulated by Dr. N.M. Karaolis and the results have been validated with
those from other sources. It is feasible to realise the mentioned elastic
twist through bending-torsion coupling, preferably with a hybrid skin
laminate lay up. With torsion coupling towards stall aerodynamic damping is
increased and torsional stability is improved when compared to the uncoupled
situation. For flapwise bending however the stability is reduced due to a
reduction in aerodynamic stiffness. More research on dynamic stability is
recommended. Interesting alternatives for future research are a passive stall
design through bending-torsion coupling and to combine elastic twist to
improve blade stability with variable rotor speed for power optimization. 25
figs., 18 tabs., 15 appendices, 21 refs.
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