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A CFD Investigation of the Near-Blade 3D Flow for a Complete Wind Turbine. Sugoi Gomez-Iradi & Xabier Munduate (CENER) George N. Barakos (Liverpool University). OUTLINE. 01 & 02. Introduction: Background and CFD method NREL blade Validation cases (isolated rotor) Cp
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A CFD Investigation of the Near-Blade 3D Flow for a Complete Wind Turbine Sugoi Gomez-Iradi & Xabier Munduate (CENER) George N. Barakos (Liverpool University)
OUTLINE 01 & 02 Introduction: Background and CFD method NREL blade Validation cases (isolated rotor) Cp Integrated loads Local Flow Angles Isolated rotor Yawed flow Full wind turbine Summary & Future steps 03 04 05 to 06 07 08 09 to 10 11 12 to 16 17
01/17 INTRODUCTION: BACKGROUND + The design of large-diameter wind turbines is outsidethe knowledge envelope of wind turbine manufacturers (Larger diameters wind turbines) • Flow compressibility • Stalled flow • Blade deflection + CFD base WT design + The objectives are to take into account compressibility effects, aeroelastic influence and to analyze the computation of HAWT http://www.supergen-wind.org.uk/images/blade_transport_reducedsize.jpg From SUPERGEN WIND http://ec.europa.eu/research/energy/pdf/renews5.pdf From EWEA
02/17 INTRODUCTION: CFD METHOD + PDE solver (WMB) + Implicit time marching + Osher's scheme for convective fluxes + MUSCL scheme for formally 3rd order accuracy + Central differences for viscous fluxes + Multi-block capability + Paralleled using the SPMD paradigm (just requires MPI) + Flow Physics: Euler, RANS, URANS, DES + Aeroelastic analysis based on modal representation of structures + Moving, deforming and sliding grids + Documentation (validated for wind turbine flows) + Developed and used by academics and engineers
03/17 NREL UAE Phase VI Experiments Twist M.M. Hand, D.A. Simms, L.J. Fingersh, D.W. Jager, J.R. Cotrell, S. Schreck and S.M. Larwood, Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns, Technical Report TP-500-29955, NREL, December 2001.
04/17 NREL UAE Phase VI Experiments S. Gómez-Iradi and G. Barakos, Computational Fluid Dynamics Investigation of Some Wind Turbine Rotor Design Parameters, Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 222(5):455–470, 2008. DOI:10.1243/09576509JPE526.
05/17 Isolated Rotor - 30%R, 46.6%R & 63.3%R 30%R 46.6%R 63.3%R 5m/s 7m/s10m/s 13m/s 20m/s
06/17 Isolated Rotor - 80%R & 95%R 80%R 95%R 5m/s 7m/s10m/s 13m/s 20m/s
07/17 INTEGRATED LOADS Averaged Thrust Averaged Torque Averaged: Azimuth angles between 120o and 240o excluded (tower influence)
08/17 2D / 3D COMPARISON
09/17 ISOLATED ROTOR – LOCAL FLOW ANGLE
10/17 2D / 3D COMPARISON Down-wash = LFA3D -LFA2D + Compute 3D flow + Extract LFA and CN (3D) + Compute 2D at same Relocal and match Cn to CN varying AoA + Extract 2D LFA + Down-wash: the influence of the induction
11/17 YAWED FLOW
12/17 FULL WIND TURBINE Approximate Nacelle geometry Sliding Grid Location Hub CFD ≉ experimental Tower S. Gómez-Iradi, R. Steijl and G.N. Barakos, Development and Validation of a CFD Technique for the Aerodynamic Analysis of HAWT, Journal of Solar Energy Engineering-Transactions of the ASME, 131(3):031009, 2009. DOI: 10.1115/1.3139144.
13/17 FULL WIND TURBINE - CP Rotor/Tower Grid 7 million cells 198 chord-wise 95 span-wise Wilcox k-ω 3 Revolutions 0.25o time step
14/17 FULL WIND TURBINE - INTEGRATED LOADS Full surface integration 22 P.T. integration Nacelle Tower Rotor Total Thrust (N) 31.6 127.5 1,233.7 1,392.8 (2.3%) (9.2%) (88.5%) Torque (Nm) 0.5 -41.8 810.2 768.9 (0.1%) (-5.4%) (105.3%) ROTOR: Isolated/ Tower Thrust (N) 1,280.0 / 1,233.7 Torque (Nm) 823.2 / 810.2 1.6% Reduction due to the tower
15/17 FULL WIND TURBINE - LFA ΔLFA⋍ -1o ΔLFA⋍ -3o ΔLFA⋍ -1o ΔLFA⋍ 0o ΔLFA⋍ 0.5o
16/17 FULL WIND TURBINE - λ2 Tip vortex Root vortex Vortices shed from tower Wake expansion
17/17 CONCLUSIONS & FUTURE WORK + CFD solver was validated for working conditions. Stalled flow needs further investigation. + LFA comparisons show good agreement in the outer half span of the blade. + The relation between 2D & 3D LFA has been studied. This could be useful for more engineering methods. + LFA associated to Yawed flow were studied. Further research is needed (varying the grid). + Tower / blade interaction was correctly predicted. Important for design purposes since the blade tower pass interaction is one of the relevant issues on the blade and tower fatigue. LFA prediction comparison agrees well with the experiments regarding the shape and the deviation in angle for the outer stations is minimal. + Work more with structural model coupling (CFD/modal). To take into account blade deflections and torsion during the computations.
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