an efficient approach for determining the flutter characteristics of rotor blades for multi-megawatt...
TRANSCRIPT
An efficient Approach for Determining the
Flutter Characteristicsof Rotor Blades for
Multi-Megawatt Wind TurbinesEWEC 2006 - Presentation No. 627
CS4: Aerodynamics, Aeroelasticity and LoadsDipl.-Ing. Raphael Haas
EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH, Berlin
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Introduction – Problem definitionIntroduction – Problem definitionEUROS manufactures blades ranging from 10m to 56m for WEC from 100kW to 5.0MWTrend in development of large rotor blades:longer, lighter and narrower blades.Aeroelastically critical designs
Risk of flutter
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
What is flutter ?What is flutter ?
Flutter – an explanation:resonant (unstable) motion interaction of structural mass, stiffness, and aerodynamic forcesusually present above some limiting (rotor) speed.
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
OverviewOverviewSystem equation and structural modelUnsteady aerodynamics – GreenbergUnsteady aerodynamics – LoewyReduction of system sizeResults – Development of dampingResults – Influencing Factors
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
System equationSystem equation
Matrices:M: mass matrixD: damping matrixK: stiffness matrix
azgazgelaat pppxKKKKxDxMM
pxKxDxM
)()()(
Inidices:t: inertia mass termsa: aerodynamic termsel: elastic stiffness termsg: pretension stiffening termsz: centrifugal stiffening terms
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Structural model (1)Structural model (1)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Structural model (2)Structural model (2)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
)t(i0 exx
Unsteady Aerodynamics–Unsteady Aerodynamics–Greenberg(1)Greenberg(1)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Unsteady Aerodynamics–Unsteady Aerodynamics–Greenberg(2)Greenberg(2)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Unsteady Aerodynamics – Loewy Unsteady Aerodynamics – Loewy (1)(1)
Pict. source: Loewy: „A Two-Dimesional Approximation to the Unsteady Aerodynamics of Rotary Wings“Journal of the Aeronautical Sciences, Vol. 24, No. 2, pp. 81-92, Feb. 1957.
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Unsteady Aerodynamics – Loewy Unsteady Aerodynamics – Loewy (2)(2)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Static CondensationReduction of system size (1)Reduction of system size (1)
Pict. source: Gasch: „Strukturdynamik, Band 2: Kontinua und ihre Diskretisierung.“ Springer. Berlin. 1989.
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Modal CondensationReduction of system size (2)Reduction of system size (2)
Pict. source: Gasch: „Strukturdynamik, Band 2: Kontinua und ihre Diskretisierung.“ Springer. Berlin. 1989.
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Example blade EU80:Length: 39mWeight: 6.5 tons
DiagramsFirst order elastic beamHalf torsional stiffness (2nd o. beam)Full torsional stiffness (2nd o. beam)
Results-Trend of damping Results-Trend of damping coefficients(1)coefficients(1)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Damping coefficients vs. Rotor speed, first order elastic beam.
Results-Trend of damping Results-Trend of damping coefficients(2)coefficients(2)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Damping vs. rotor speed, 2nd order el. Beam, full torsional stiffness.
Results-Trend of damping Results-Trend of damping coefficients(3)coefficients(3)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Damping vs. rotor speed, 2nd order el. Beam, half torsional stiffness.
Results-Trend of damping Results-Trend of damping coefficients(4)coefficients(4)
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Results – Influencing FactorsResults – Influencing Factors
Higher torsional stiffness significantly shifts the flutter onset rotor speed
Usage of a second order FEM blade model is mandatory
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Present status and outlookPresent status and outlook
Natural frequencies and modeshapes evaluated for each blade
Fast and easy to use tool
Integration into an iterative design loop
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt An efficient Approach for Determining the Flutter Characteristics of Rotor Blades for Multi-Megawatt Wind TurbinesWind Turbines
Raphael Haas – EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH – Berlin – Germany
Natural frequ. vs. rotor speed, cons. system – no aerodynamic loads.Natural frequ. vs. rotor speed, 2nd order el. Beam, no returning wake.Damping vs. rotor speed, 2nd order el. Beam, no returning wake.
Results – No returning wakeResults – No returning wake
azgazgelaat pppxKKKKxDxMM
pxKxDxM
)()()(