A new method of determination of the angle of attack on rotating wind turbine blades

Wei Zhong, Wen Zhong Shen*, Tong Guang Wang, Wei Jun Zhu

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

The angle of attack (AoA) is the key parameter when extracting the aerodynamic polar from the rotating blade sections of a wind turbine. However, the determination of AoA is not straightforward using computational fluid dynamics (CFD) or measurement. Since the incoming streamlines are bent because of the complex inductions of the rotor, discrepancies exist between various existing determination methods, especially in the tip region. In the present study, flow characteristics in the region near wind turbine blades are analyzed in detail using CFD results of flows past the NREL UAE Phase VI rotor. It is found that the local flow determining AOA changes rapidly in the vicinity of the blade. Based on this finding, the concepts of effective AoA as well as nominal AoA are introduced, leading to a new method of AOA determination. The new method has 5 steps: (1) Find the distributed vortices on the blade surface; (2) select two monitoring points per cross-section close to the aerodynamic center on both pressure and suction sides with an equal distance from the rotor plane; (3) subtract the blade self-induction from the velocity at each monitoring point; (4) average the velocity of the two monitoring points obtained in Step 3; (5) determine the AoA using the velocity obtained in Step 4. Since the monitoring points for the first time can be set very close to the aerodynamic center, leading to an excellent estimation of AoA. The aerodynamic polar extracted through determination of the effective AoA exhibits a consistent regularity for both the mid-board and tip sections, which has never been obtained by the existing determination methods.
Original languageEnglish
Article number4012
JournalEnergies
Volume12
Issue number20
Number of pages19
ISSN1996-1073
DOIs
Publication statusPublished - 2019

Keywords

  • Wind turbine
  • Aerodynamics
  • Angle of attack
  • Blade element momentum
  • Downwash
  • Computational fluid dynamics

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