1 / 15

Experimental and numerical investigations of 3D airfoil characteristics on a MW wind turbine

Experimental and numerical investigations of 3D airfoil characteristics on a MW wind turbine. Niels Troldborg, Christian Bak, Niels N. Sørensen, Frederik Zahle, Helge Aa. Madsen, Srinivas Guntur, Pierre-Elouan Réthoré Wind Energy Department, DTU Wind Energy, DK-4000 Roskilde, Denmark.

kirsi
Download Presentation

Experimental and numerical investigations of 3D airfoil characteristics on a MW wind turbine

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Experimental and numerical investigations of 3D airfoil characteristics on a MW wind turbine Niels Troldborg, Christian Bak, Niels N. Sørensen, Frederik Zahle, Helge Aa. Madsen, Srinivas Guntur, Pierre-Elouan Réthoré Wind Energy Department, DTU Wind Energy, DK-4000 Roskilde, Denmark

  2. Background • Aeroelastic models typically use airfoil data (CL, CD) to predict aerodynamic forces

  3. Background • Airfoil data commonly obtained from wind tunnel measurements in 2D steady flow Test section Inflow

  4. Background • However, airfoil characteristics on a wind turbine can be quite different from wind tunnel measurements: • CL(α) varies with spanwise position • 3D effects are important! 3D airfoil charcteristics from the NREL/NASA Ames test. (From: Bak et al. Three-Dimensional Corrections of Airfoil Characteristics Based on Pressure distributions. EWEC 2006.)

  5. Objectives • Study 3D aerofoil characteristics on a modern MW wind turbine vs. 2D aerofoil characteristics using • Wind tunnel tests • Full scale field experiment • 2D airfoil computations (CFD) • 3D rotor computations (CFD) • Evaluate quality of measurements and computations for studying 3D effects • Validate measurements and CFD • Verify that the datasets are suitable for future development/improvements of 3D airfoil correction models.

  6. Experimental approach: The DANAERO MW project The Tjæreborg field experiment on the 2.3 MW NM80 turbine: • Four blade sections with 64 pressure taps: • Section 1: r/R=33%, NACA63-433 • Section 2: r/R=48%, NACA63-424 • Section 3: r/R=75%, NACA63-421 • Section 4: r/R=93%, NACA63-418 • Five-hole Pitot tubes at r/R=36%, 51%, 78% and 90%, respectively • High frequency measurements of wind speed and direction from nearby met mast Wind tunnel tests in the LM Wind Power tunnel: • Measurements on four aerofoils with the same shape as the instrumented sections on the LM38.8 blade of the NM80 turbine, i.e. sections 1, 2, 3 and 4.

  7. Computational approach: EllipSys2D/3D 3D rotor computations on the NM80 turbine • 256x128x128 grid points on blade • Total mesh 432x32^3 • k-ω SST turbulence model • Correlation based transition model • Steady uniform inflow • 21 computations with varying wind speed and pitch angle 2D airfoil computations blade sections 1, 2, 3 and 4 of the NM80 turbine • 256x128 grid points • k-ω SST turbulence model • Correlation based transition model • Steady uniform inflow

  8. Wind tunnel measurements vs 2D airfoil CFD Section 1 (NACA63-433) Section 2 (NACA63-424) Section 3 (NACA63-421) Section 4 (NACA63-418)

  9. Wall effects in a wind tunnel Differences between measurements and CFD may be due to wall effects which are significant for thick aifoils FFA airfoil 30% thickness at AoA = 3°

  10. Wall effects in a wind tunnel Differences between measurements and CFD may be due to wall effects which are significant for thick aifoils and airfoils at high AOA FFA airfoil 30% thickness at AoA = 3° NACA63-418 at AoA = 15°

  11. Measurements on NM80 turbine vs 3D rotor CFD Section 1 NACA63-433 r/R=33% Section 2 NACA63-424 r/R=48% Section 3 NACA63-421 r/R=75% Section 4 NACA63-418 r/R=93% Comparison of Cp distributions at V∞=6.1 and RPM=12.1

  12. Determining the angle of attack from 3D CFD • Azimuthal averaging technique (AAT) • Extract velocities in annular rings up and downstream of the rotor. • Compute azimuthal average for each ring • Interpolate average velocities from up and downstream to the rotor plane.

  13. Determining the angle of attack from measurements • Extract 1-minute averages of measured distributions • Bin average on flow angle measured by Pitot tube at r/R=0.78, i.e. establish • From the rotor computations determine the AoA for each blade section using the AAT and establish • Estimate the measured AoA by minimizing • where n=64 is the number of pressure taps around the airfoil.

  14. Comparison of 2D and 3D airfoil characteristics Section 1 (NACA63-433) Section 2 (NACA63-424) Section 3 (NACA63-421) Section 4 (NACA63-418)

  15. Conclusions • Unique dataset for studying 3D airfoil characteristics in comparison with 2D characteristics on a modern MW wind turbine is established. • Suitable as a basis for future development/improvements of 3D correction models • 3D effects known from smaller turbines are documented • Increased in-board lift at high AOA • Decreased lift slope at in-board/out-board sections • Comparison between measured and computed airfoil characteristics on the NM80 rotor generally reveals good agreement • Large differences between 2D airfoil CFD and wind tunnel measurements for thick airfoils and for airfoils at high AOA. • Likely to be due to wall effects in the wind tunnel

More Related