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Title:
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Smart rotor: feasibility study for a passive pitch regulation of a windturbine 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--96-011
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Other
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Number of pages:
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Full text:
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65
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Download PDF
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Abstract:
In October 1995 the section Wind Energy of the Netherlands EnergyResearch Foundation ECN initiated a study on the feasibility of a passive
pitch regulation on a wind turbine rotor blade; a so called 'Smart Rotor'. By
means of an isotropic tailoring (choosing specific fiber orientations in the
rotor blade root) a defined coupling is created between strains and torsional
deformation. Chapter 2 describes the basic principles of power control for
wind turbines and limitations of this study. Chapter 3 outlines the computer
model of the applied rotor test facility of ECN: the 25m HAWT with AERPAC
25WPX blades. Also the possible improvements in the power curve by altering
the pitch angle are discussed. In chapter 4 the loads in the rotor blade are
calculated. In chapter 5 the qualitative deformation of the pitch bearing is
defined by combining the required pitch angles with the calculated loads. The
anisotropic mechanical behaviour of fibre reinforced plastic laminae can be
used to give structural members a coupling between longitudinal strain and
shear deformation (aero-elastic tailoring). Specific tailoring of the wind
turbine rotor blades, couples flap bending with torsional or pitch
deformation as a power regulating principle. This study investigates the
possibility to use a relatively small part of the rotor (only the shanks
between rotor centre and largest chord) to function as a passive pitch
bearing. Main conclusions are that: a continuous relation between wind speed
and pitch angle is feasible; torsional deformation due to normal force and
flap bending moment can be designed independently, without coupling lag
bending; there is a quasi linear relation between flap bending moment and
required pitch angle variation to stall above rated wind speed; a passive
pitch bearing has considerable lower inspection and maintenance costs.
Further research should be carried out on a more realistic rotor, designed
with pitch angle variation. Also the required material properties to reach
the amount of coupling within the constraints for fatigue resistance, should
be further investigated. 21 figs., 4 tabs., 10 refs., 3 appendices
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