ECN publication
Bending-torsion coupling of a wind turbine rotor blade
Published by: Publication date:
ECN 1996
ECN report number: Document type:
ECN-I--96-060 Other
Number of pages: Full text:
102 Download PDF  

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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