The experimental determination of rotor blade dynamic bending moments of a 10-kw wind turbine

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1991-05-05
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Virginia Tech
Abstract

A l0-kW horizontal axis wind turbine was studied to determine the effects of wind shear and gravity on rotor blade bending moments.

A drag sphere based wind measuring system was designed to measure rapid fluctuations in wind velocity at two different heights. However, severe power line noise problems with the low level signals forced the use of standard rotating cup anemometry.

Rotor blade bending moments were obtained with strain gages mounted on blade extenders near the root of the instrumented blade. Rotor angular position data were obtained with a photocell arrangement.

The one per revolution primary bending moment frequency was caused mostly by gravity-induced bending. Also present is the 6 Hz blade natural frequency. A logarithmic atmospheric boundary layer (ABL) profile was used to estimate wind conditions at the upper level. Examination of the bending moment data revealed good agreement with values predicted from the ABL profile (within 4% in the mean) indicating the profile was a good mean approximation.

A logarithmic atmospheric boundary layer (ABL) profile was used to estimate wind conditions at the upper level. Examination of the bending moment data revealed good agreement with values predicted from the ABL profile (within 4% in the mean) indicating the profile was a good mean approximation.

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