Field Validation of the Stability Limit of a Multi MW Turbine

Kallesøe, Bjarne Skovmose; Kragh, Knud Abildgaard

doi:10.1088/1742-6596/753/4/042005

Cited by 14 publications

(8 citation statements)

References 1 publication

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“…In the work of Griffith and Chetan (2018), it was shown how larger blades tend to have a larger edgewise contribution to blade instability as blade structural designs at the 100 m scale are optimized for mass. These edgewise instabilities in large turbine blades have been observed experimentally and numerically by Kallesøe and Kragh (2016). The edgewise flutterlike instabilities were found to have a shallow crossover that is considered as "soft" crossover to an unstable mode due to higher structural damping.…”

Section: Introductionmentioning

confidence: 73%

Flutter behavior of highly flexible blades for two- and three-bladed wind turbines

2022

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Abstract. With the progression of novel design, material, and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the levelized cost of energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to aeroelastic instabilities due to their long, slender, highly flexible nature, and this effect is accentuated as rotors further grow in size. In addition to the trend of larger rotors, non-traditional rotor concepts are emerging including two-bladed rotors and downwind configurations. In this work, we introduce a comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two-bladed, downwind rotors. Flutter speed trends and characteristics for a series of both two- and three-bladed rotors are analyzed and compared in order to illustrate the flutter behavior of two-bladed rotors relative to more well-known flutter characteristics of three-bladed rotors. In addition, we examine the important problem of blade design to mitigate flutter and present a solution to mitigate flutter in the structural design process. A study is carried out evaluating the effect of leading edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass.

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Section: Introductionmentioning

confidence: 73%

Flutter behavior of highly flexible blades for two- and three-bladed wind turbines

2022

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“…However, as Griffith and Chetan have shown in their study, edgewise deformation of the blade may have a significant contribution to the flutter mode 25 . Moreover, inclusion of the finite blade deflections into the aeroelastic stability analysis of blades accounts for reduction in the flutter speed 26 . Since the main emphasis of the present study is to present a methodology to include compressibility into the aeroelastic stability analysis of wind turbine blades, structural model is simplified to include only the flapwise bending and the torsional deformations and their coupling using the geometrically linear formulation.…”

Section: Governing Equations Of the Rotating Beam‐blade Modelmentioning

confidence: 87%

“…25 Moreover, inclusion of the finite blade deflections into the aeroelastic stability analysis of blades accounts for reduction in the flutter speed. 26 Since the main emphasis of the present study is to present a methodology to include compressibility into the aeroelastic stability analysis of wind turbine blades, structural model is simplified to include only the flapwise bending and the torsional deformations and their coupling using the geometrically linear formulation. The extension of the present study to include edgewise deformation and associated couplings; and geometrically nonlinear TWB formulation is considered to be a future extension of the present study.…”

Section: Energy Expressionsmentioning

confidence: 99%

Classical flutter analysis of composite wind turbine blades including compressibility

Farsadi

Kayran

2020

Wind Energy

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For wind turbine blades with the increased slenderness ratio, flutter instability may occur at lower wind and rotational speeds. For long blades, at the flutter condition, relative velocities at blade sections away from the hub center are usually in the subsonic compressible range. In this study, for the first time for composite wind turbine blades, a frequency domain classical flutter analysis methodology has been presented including the compressibility effect only for the outboard blade sections, which are in the compressible flow regime exceeding Mach 0.3. Flutter analyses have been performed for the baseline blade designed for the 5-MW wind turbine of NREL. Beamblade model has been generated by making analogy with the structural model of the prewisted rotating thin-walled beam (TWB) and variational asymptotic beam section (VABS) method has been utilized for the calculation of the sectional properties of the blade. To investigate the compressibility effect on the flutter characteristics of the blade, frequency and time domain aeroelastic analyses have been conducted by utilizing unsteady aerodynamics via incompressible and compressible indicial functions. This study shows that with use of compressible indicial functions, the effect of compressibility can be taken into account effectively in the frequency domain aeroelastic stability analysis of long blades whose outboard sections are inevitably in the compressible flow regime at the onset of flutter.

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“…Results indicated that there is only a small quantitative difference between a full wind turbine model and a single-blade model in the predicted flutter speed. Kallesøe and Kragh (2016)’s research showed that the geometric non-linearities caused by steady state deflection of the blade for NREL 5-MW Reference Wind Turbine with 63-m blades may also influence the aeroelastic stability of wind turbines. Furthermore, Lobitz (2004) assessed the influence of different aerodynamic models on flutter speed for MW-sized wind turbines.…”

Section: Introductionmentioning

confidence: 99%

Structural damping sensitivity affecting the flutter performance of a 10-MW offshore wind turbine

Hua

Meng

Chen

et al. 2020

Advances in Structural Engineering

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Classical flutter of wind turbine blades is one of the most destructive instability phenomena of wind turbines especially for several-MW-scale turbines. In the present work, flutter performance of the DTU 10-MW offshore wind turbine is investigated using a 907-degree-of-freedom aero-hydro-servo-elastic wind turbine model. This model involves the couplings between tower, blades and drivetrain vibrations. Furthermore, the three-dimensional aerodynamic effects on wind turbine blade tip have also been considered through the blade element momentum theory with Bak’s stall delay model and Shen’s tip loss correction model. Numerical simulations have been carried out using data calibrated to the referential DTU 10-MW offshore wind turbine. Comparison of the aeroelastic responses between the onshore and offshore wind turbines is made. Effect of structural damping on the flutter speed of this 10-MW offshore wind turbine is investigated. Results show that the damping in the torsional mode has predominant impact on the flutter limits in comparison with that in the bending mode. Furthermore, for shallow water offshore wind turbines, hydrodynamic loads have small effects on its aeroelastic response.

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Field Validation of the Stability Limit of a Multi MW Turbine

Cited by 14 publications

References 1 publication

Flutter behavior of highly flexible blades for two- and three-bladed wind turbines

Flutter behavior of highly flexible blades for two- and three-bladed wind turbines

Classical flutter analysis of composite wind turbine blades including compressibility

Structural damping sensitivity affecting the flutter performance of a 10-MW offshore wind turbine

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