Abstract
Wind turbines can exhibit flutter-like edgewise instabilities past a critical rotor speed. These edgewise instabilities are dominated by an edge-torsion coupling due to flapwise blade deflection. This paper experimentally validates the predicted stability limit of a 7 MW machine. State of the art simulation software is used to compare against recorded test data and characterize the observed flutter mechanism. The critical rotor speed at which the edgewise instabilities occur at in field measurements can be predicted by time domain simulations and stability analysis with very good agreement.
Highlights
The wind industry continues to push blade length limits in search of low-cost energy
Ref. [1] presents the results of a test validation campaign, where an edgewise instability was observed on a test turbine, demonstrating the existence of this phenomenon, and the need to consider it for safe turbine design and operation
There is generally excellent agreement between the operational deflection shapes observed in the HAWC2 time marching simulation and the blade-only mode shapes predicted by HAWCStab2, a frequency domain solution
Summary
The wind industry continues to push blade length limits in search of low-cost energy. [1] the authors conducted a test on a real turbine, that was brought to an rpm past the expected stability limit with the intent of observing an aeroelastic instability, and validating BHawC. Operational data and load values were recorded for all major turbine components, and a fiber Bragg optical strain gauge system was installed at 10 spanwise locations along the blade. At each of these locations 4 gauges are installed: a leading edge, trailing edge, pressure side, and suction side gauge; which enabling flapwise and edgewise bending moment estimation. Controller parameters changed: A) Rated rotor speed increased to value 10% above expected stability limit B) Fixed pitch of −2 deg requested in speed-power control region
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