Advances In Wind Turbine Aerodynamics
Advances in Wind TurbineAerodynamicsJaikumar LoganathanAshok GopinathGE Global Research - BangaloreImagination at work.
Outline Introduction Wind turbine design process Wind turbine aerodynamics Airfoil and blade design Wind park as a product What next? Conclusion2
IntroductionSource :GWECExponential growthSource :EWEASource :EWEAContinuous technologyimprovementSource :NRELWind cost of energy is poised to overtake fossil fuel3
Steps Wind farm developmentSource : AWEA Understand Your Wind Resource Determine Proximity to Existing Transmission Lines Secure Access to Land Establish Access To Capital Identify Reliable Power Purchaser or Market Address Siting and Project Feasibility Considerations Understand Wind Energy's Economics Obtain Zoning and Permitting Expertise Establish Dialogue With Turbine Manufacturers and ProjectDevelopers Secure Agreement to Meet O&M Needs4
Wind Turbine Design ConceptsSavonius VAWTDanish HAWTDarrieus VAWT5
ComponentsWindSensors‘Top box’:low voltage,control 1.5 wind turbine52 metric ton nacelle35 metric ton rotorHigh-speed couplingMechanical brakeGearboxGeneratorPitch drivePitch bearingBed FrameYaw drivesYaw bearingHubRotor main shaft Main bearing6
Number of rotorsOneTwoThreeGearboxEfficiencyLoads7
Wind turbine designSource: DTU8
Wind turbine designSource: DTU9
Wind turbine AerodynamicsAirfoilBladeWind turbineWind Farm10
Airfoil designSource: TUDelftBlade geometryDesign goalsOperation11
Airfoil designWind turbine airfoilAirfoil polar - RoughAirfoil polar - CleanPressure distributionSource: TUDelft12
Airfoil design key parameters3211Design point (Max lift to drag ratio)2Stall point (Max CL)3Extreme load point (Max CD)13
Design pointDU96-W-180, A0A 6Re 4MM Max L/D - highest efficiency Transition location is critical Boundary layer is attachedXFOIL Panel method - Mark Drela, MIT Inviscid - linear-vorticity stream function Viscous - Integral BL formulation Transition - e n 53.25X-Tran Suction X-Tran Pressure3870407114
Design pointDU96-W-180, A0A 6Re 4MM Max L/D - highest efficiency Transition location is critical Boundary layer is attachedCFD (K SST)XFOIL Panel method - Mark Drela, MIT Inviscid - linear-vorticity stream function Viscous - Integral BL formulation Transition - e n criteria RANS – 2 eq turbulence model K SST (zonal model, limiter on eddy viscosity) -Re transition CL/CD150.26153.25115.00X-Tran Suction X-Tran 0.02CD0.0315
Stall pointDU96-W-180, A0A 14Re 4MM Max CL - high loads Boundary layer is partially separatedComparison with XFOIL & CFD2.001.60CL1.20EXPT0.80SST0.40XFOIL0.000246810 12 14 16 18 20AOA16
Delayed stall prediction Best practice K- SST predicts a delayed flow separation and stall Limitation of RANS modelsSpectral Gap Overlap of turbulent lengthscales with energycontaining scalesAnisotropyStress – Strain lag Turbulent velocitycomponents assumed to beequal in magnitude Stress and strain are directlyproportional Wind tip vortex flow by JimchowReynoldsshear stressMean strainrates17
Next gen airfoils- 2 dBAdd-Ons Serrations (noise) Vortex generators (flow separation)Flow control Flexible trailing edge Circulation controlNew architecture Flexible airfoils Sail wingLift destructionLow cost 0.5% CpLift AugmentationLow loads18
Betz Limit Wind turbine extracts power by slowing down incoming wind Betz limit is the measure of optimal slow downNo slow downFull slow downBetz Limit - 59.3%Optimal slow down19
Annual Energy Yield (AEP)t(bin) [h]c p (bin) [ ]Power [kW ]Energy Yield (bin) [kWh]5000.50700,00025004500.45400600,0000.40 3503002502002000electricaerodynamic"power curve"0.350.3015000.250.201500.151000.10500.051000 12141618202224002468101214v(bin) [m s] tWeibull( bin) v3( bin)161820220240246810121418v(bin) [m s]2022Portion [%]2,5007Power [kW ]portion of AEP6Wind ) [m s]1 c p elec.(bin) R 2 AEPactual2AEP increase strategies: (higher) Wind distribution Rotor growth (increase swept area) (turbine) efficiency increase Biggest portion of AEP generated near kneeof the power curve: 33% for 2 m/s windspeeds before rated16510152025v(bin) [m s]20
Blade aero designConceptual design Inputs Detailed designPrototype test Design pointBlade radiusPowerAirfoil selection EfficiencyStallRoughnessOff - designBlade design ChordTwistThicknessGeo smoothingObjectives Maximize Cp Minimize noiseConstraints Max chord Thickness and twistrate21
Conceptual design - BladeActuator disk modelBlade element momentum theory Blade element momentum theoryapplied to a rotor disk Propellerturbines Each annular ring is independent Does not account for wake expansion Applicable only to straight blades Fails at high blade loading and off designconditions Requires separate tip and root lossmodelHelicopterwindA powerful design toolForces acting on a blade element3 D Blades22
Conceptual design - BladeVortex lifting line modelBlade representation Blade modeled as a set of lifting lines Vorticity shed from the trailing edgeis modeled as vortex filamentsWake representation Induced velocities on blade andwake is computed using Biot-savartlaw23
Detailed design - CFD A powerful tool to understanddetailed flow structure RANS - K SST 6 million cells for a single bladeanalysis Rotational effects Flow separation prediction ? Modelling transition – exorbitantlyexpensive Highly dissipative – smeared wake24
Detailed design – Hybrid CFD Elegant combination of near wallNavier-Stokes and helicoidalvortex method Preservers wake structuresSmall NavierStokes domainModeled wake shape(function of computedcirculation from NSdomain) Improved computational efficiency(1/8) Flow transition Unsteady, multi-blade analysisSource: UC Davis25
Improving Blade PerformanceAero Related Energy Losses for Wind Turbines Tip Loss: Entitlement 1.5% AEP Main Blade Loss: Entitlement 1.5% AEP Root Loss: Entitlement 3.5% AEP *) Operation Loss: Entitlement 2.0% AEPCFD wind velocity contoursdepicting high velocities inroot region due to ‘slippage’through the root ‘hole’Root enhancementTip enhancement26
Industry trendsCarbon Enhanced stiffness while managing weight 32% mass reduction, 15% reduction in tip deflection Costly (10X time glass fibers)Segmented blade Potential benefit in transportation & erection cost 9% increase in blade massActive devices Morphing trailing edge 2% rotor growth – loads neutral Controlled with compressed air or piezo electricsPassive – Material tailoring Bend- Twist coupling 53m vs 49m Blade – less 500kg/5% more AEP Exploring natural fibersTip rotationunder loadsUndeformed blade27
Wind farm as a product Wakes behind the rotor cause losses Coordinated control reduce these losses Around 1-2% of farm AEP is gained28
Wake structureSource : SNL29
Wake modelingobjectives Predict the wake strength and behavior(stability, shear, veer & turbulence intensity) Determine sensitivity of wake development to rotor loading Micro siting Quantify effect of ambient flow conditions and terrainBEM Free vortexRANS Actuator diskLES Actuator line30
Summary Wind turbine aerodynamics - maximize power output Airfoils – high L/D – Stall prediction Blade – Maximize Cp – computational efficiency Wake – understand, minimize & optimize Big data31
Thank you32
Advances in Wind Turbine Aerodynamics . Blank 2 Outline Introduction Wind turbine design process Wind turbine aerodynamics Airfoil and blade design . Propeller Helicopter wind turbines Each annular ring is independent Does not account for wake expansion Applicable only to straight blades .
WE Handbook- 2- Aerodynamics and Loads Wind Turbine Blade Aerodynamics Wind turbine blades are shaped to generate the maximum power from the wind at the minimum cost. Primarily the design is driven by the aerodynamic requirements, but economics mean that the blade shape is a compromise to keep the cost of con-struction reasonable.
2. Brief Wind Turbine Description The wind turbine under study belongs to an onshore wind park located in Poland. It has a power of 2300 kW and a diameter of 101 m. Figure 1 shows its major components. A summary of the wind turbine technical specifications is Fig. 1. Main components of the wind turbine [16]. given in Table I. The wind farm .
Chapter 13: Aerodynamics of Wind Turbines. Chapter 13: Aerodynamics of Wind Turbines. Chapter 13: Aerodynamics of Wind Turbines. Time accurate predictions for a 2-bladed HAWT are shown in the next figure (13.22) At high tip speed ratio (low wind speeds) vortex ring state (part a)
Aerodynamics of Wind Turbines Emrah Kulunk New Mexico Institute of Mining and Technology USA 1. Introduction A wind turbine is a device that extracts kine tic energy from the wind and converts it into mechanical energy. Therefore wind turbine power production depends on the interaction between the rotor and the wind.
Aerodynamics is the study of the dynamics of gases, or the interaction between moving object and atmosphere causing an airflow around a body. As first a movement of a body (ship) in a water was studies, it is not a surprise that some aviation terms are the same as naval ones rudder, water line, –File Size: 942KBPage Count: 16Explore furtherIntroduction to Aerodynamics - Aerospace Lectures for .www.aerospacelectures.comBeginner's Guide to Aerodynamicswww.grc.nasa.govA basic introduction to aerodynamics - SlideSharewww.slideshare.netBASIC AERODYNAMICS - MilitaryNewbie.comwww.militarynewbie.comBasic aerodynamics - [PPT Powerpoint] - VDOCUMENTSvdocuments.netRecommended to you b
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Aerodynamics of wind turbines is a classic concept and is the key for wind energy development as all other parts rely on the accuracy of its aerodynamic models. There are numerous books and articles dealing with wind turbine aerodynamic problems and models. As a good example, the wind
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