The Effect of Blade Geometry on Blade Stall Characteristics

[+] Author and Article Information
R. P. van Rooij

 Delft University of Technology, Faculty of Aerospace Engineering, Wind Energy Group, Kluyverweg 1, 2629 HS, Delft, The Netherlandsr.vanrooij@lr.tudelft.nl

J. G. Schepers

 Energy Research Center of the Netherlands, ECN, P.O. Box 1, 1755 ZG, Petten, The Netherlandsschepers@ecn.nl

J. Sol. Energy Eng 127(4), 496-502 (Jul 12, 2005) (7 pages) doi:10.1115/1.2037090 History: Received February 04, 2005; Revised July 11, 2005; Accepted July 12, 2005

The effect of rotation has been investigated with emphasis on the impact of blade geometry on the “correction factor” in stall models. The data used came from field tests and wind tunnel experiments performed by the National Renewable Energy Laboratory and were restricted to the steady-state nonyawed conditions. Three blade layouts were available; a blade with constant chord without twist (phase II), a blade with constant chord and twist (phases III and IV), and a tapered blade with twist (phase VI). Effects due to twist and taper were determined from comparison ofcnbetween the different blade layouts. The formulation of the stall model was rewritten so that the measuredcnvalues could be used without reference to 2D airfoil performance. This enabled a direct comparison of the normal force characteristics between the four blade stations of the selected blade configurations. In particular, the correction termfused in stall models for rotational effects was analyzed. The comparison between the test results with a straight and a twisted blade showed that a relation for twist+pitch is required inf. In addition, a dependency offon the angle-of-attack was identified in the measurements and it is recommended that this dependency be incorporated in the stall models.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 5

The trend lines for cn for 30% and 47% span locations

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Figure 7

The difference in 3D correction factor, Delta_fII−III, as a function of the angle of attack

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Figure 9

The measured Delta_f compared with the results of two stall models

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Figure 8

The difference in 3D correction factor, Delta_fVI−III, as a function of the angle of attack

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Figure 6

The trend lines for cn for 67% and 80% span locations

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Figure 4

Cn augmentation for the three span sections

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Figure 3

The impact of blade configuration at the 80% span on the 1/denominator term in f of Eq. 7

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Figure 2

Comparison of the 2D wind tunnel data and 3D 80% blade span performance data. The denominator is of Eqs. 5,7.

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Figure 1

The difference between the measured data points and the 2D characteristics for hub wind speeds between 9.4 and 10.6m∕s (phase II)




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