Experimental field study of floater motion effects on a main bearing in a full-scale spar floating wind turbine (original) (raw)
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Assessing the dynamics of turbine components using advanced fluid-structure interaction
In order to assess the dynamic behavior and dynamic stresses of submerged components of hydro turbines, the effect of surrounding water flow must not be neglected. Hence, fluid-structure interaction (FSI) may play an important role during design optimizations if dynamic properties of the structural parts are critical. Examples of essential FSI phenomena are added-mass and flow induced damping effects, lock-in of vortex induced vibrations at natural frequencies, or hydroelastic instabilities of flows in deformable gaps like labyrinth seals, journal bearings, and valves. In contrast to aeroelasticity, hydroelastic systems require iteratively coupled or even monolithic (matrix-coupled) solution procedures, since the fluid mass which is moving with the structure (added-mass effect) is quite high and may change the dynamic behavior of submerged structures considerably. Depending on the mode shape, natural frequencies of a turbine runner in water may be reduced to less than 50% of corresp...
Marine Structures, 2015
This paper deals with the feasibility of using a 5 MW drivetrain which is designed for a land-based turbine, on floating wind turbines. Four types of floating support structures are investigated: spar, TLP and two semi-submersibles. The fatigue damage of mechanical components inside the gearbox and main bearings is compared for different environmental conditions, ranging from cut-in to cutout wind speeds. For floating wind turbines, representative wave conditions are also considered. All wind turbines are ensured to follow similar power curves, but differences in the control system (integral to different concepts) are allowed. A de-coupled analysis approach is employed for the drivetrain response analysis. First, an aero-hydro-servo-elastic code is employed for the global analysis. Next, motions, moments and forces from the global analysis are applied on the gearbox multi body model and the loads on gears and bearings are obtained. The results suggest that the main bearings sustain more damage in floating wind turbines than on land-based. The highest main bearing damage is observed for the spar floating wind turbine. The large wave induced axial load on the main shaft is found to be the primary reason of this high damage in the spar wind turbine. Apart from the main bearings-which are located on the main shaft outside the gearbox-other bearings and gears inside the gearbox hold damages in floating wind turbines equal or even less than in the land-based turbine. It is emphasized that the results presented in this study are based on a drivetrain with two main bearings, which considerably reduces the non-torque loads on
An Overview of the\ NREL/SNL Flexible Turbine Characterization Pttgject
There has been a desire to increase the generating capacity of the latest generation of wind turbine designs. In order to achieve these larger capacities, the dimensions of the turbine rotors are also increasing significantly. These larger structures are often much more flexible than their smaller predecessors. This higher degree of structural flexibility has placed increased demands on available analytical models to accurately predict the dynamic response to turbulence excitation. In this paper we present an overview and our progress to date of a joint effort of the National Renewable Energy Laboratory (NREL) and the Sandia National Laboratory (SNL). In this paper we present an overview and status of an ongoing program to characterize and analytically model the dynamics associated with the operation of one of the most flexible turbine designs currently available, the Cannon Wind Eagle 300 (CWE-300). The effort includes extensive measurements involving a detailed inventory of the turbine's physical properties, establishing the turbine component and full-system vibrational modes, and documenting the dynamic deformations of the rotor system and support tower while in operation.
An overview of the NREL/SNL flexible turbine characterization project
1998
There has been a desire to increase the generating capacity of the latest generation of wind turbine designs. In order to achieve these larger capacities, the dimensions of the turbine rotors are also increasing significantly. These larger structures are often much more flexible than their smaller predecessors. This higher degree of structural flexibility has placed increased demands on available analytical models to accurately predict the dynamic response to turbulence excitation. In this paper we present an overview and our progress to date of a joint effort of the National Renewable Energy Laboratory (NREL) and the Sandia National Laboratory (SNL). In this paper we present an overview and status of an ongoing program to characterize and analytically model the dynamics associated with the operation of one of the most flexible turbine designs currently available, the Cannon Wind Eagle 300 (CWE-300). The effort includes extensive measurements involving a detailed inventory of the turbine's physical properties, establishing the turbine component and full-system vibrational modes, and documenting the dynamic deformations of the rotor system and support tower while in operation.
Dynamic Analysis of Offshore Wind Turbine Structures
Modeling and Simulation Techniques in Structural Engineering
Wind turbines are slender flexible structures susceptible to strong wind fluctuations. The flexible wind turbine structure, when subjected to strong dynamic forces, it leads to an ideal condition for induced vibrations and resonance problems. Hence studying the dynamic response of these critical structures using the computational and experimental procedures becomes of utmost importance. This chapter reviews the theories used for the dynamic analysis of a modern day offshore wind turbine structure and applies these theories in analyzing realistic situations for offshore turbines under wave and wind action. The first half of the chapter gives a broad overview on the concepts of structural dynamics of wind turbine structures with illustrative examples that will enable the user to understand the methodology used to analyze these structures. The latter half of the chapter deals with the computational aspect of the analysis and focuses on the use of finite element software ANSYS 14 to model these critical structures.
Tidal turbine blade load experiments for oscillatory motion
2011
This paper presents blade root bending moment measurements of a horizontal-axis tidal turbine for planar oscillatory motion, conducted in a stationary water towing tank. By comparing the measurements with quasi-steady reconstructions for both single and multiple frequency oscillatory motion, the bending moment was shown to be sensitive to both frequency and amplitude, as well as to the mean tip-speed ratio. The unsteady loads associated with the separation of the flow and dynamic stall are shown to be of considerably greater importance than those which are already present for attached flow, such as added mass and dynamic inflow. A linear model fit to the unsteady bending moment also indicates that the inertia contribution is relatively small. For cases where attached flow exists over the majority of the load cycle, these reconstruction methods are likely to be sufficient to obtain a reasonable prediction of the root out-of-plane bending moment. However, turbines whose blades are likely to...
Renewable Energy, 2020
This paper deals with the effect of bedplate flexibility on drivetrain dynamics of a 10 MW spar type floating wind turbine. The 10 MW drivetrain bedplate is designed based on extreme design loads and ultimate limit state (ULS) design criteria. A decoupled analysis approach is employed. Global dynamic analysis of the 10 MW floating turbine is firstly conducted using an aero-hydro-servo-elastic code, then the global response is used as input to the drivetrain dynamic analysis. Load effects and fatigue damage of gears and bearings in the rigid and flexible bedplate models in different environmental conditions are compared. In addition, sensitivity of the drivetrain fatigue damage to varying fidelity in the bedplate modelling is studied. The results indicate that the bedplate flexibility would increase the load effects on bearings inside the gearbox, while it would reduce the load effects on the main bearings. Reasonable bedplate modelling fidelity is of great importance, because it could save a great deal of computational costs without loss of the drivetrain dynamic response accuracy. The present work provides a reference for a proper drivetrain design and dynamic analysis in the future, by accounting for bedplate flexibility.
Fluid-structure interaction in the case of a wind turbine rotor
Proc. 18éme Congrès Français de Mécanique, …, 2007
A fluid-structure coupling method is developed for calculation of unsteady forces applied to the blades of wind turbine. This method combines fluid simulation with structure dynamic analysis. Aerodynamic modelling is quasi-3D. Here the velocity induced by the rotor is calculated by means of a hybrid model which replaces the blades by lifting surfaces. The pressure distribution applied to these surfaces is obtained using 2D calculations around the blade airfoils. To take into account structure deformations, here blade flapping and blade section pitching are calculated by means of structure dynamics solver and thus the mesh is adapted at each time step. The suggested method is validated in the case of NREL VI wind turbine in yaw and the results of comparison concerning the blade flapping are satisfactory. Résumé : Une méthode de couplage aéroélastique est développée pour le calcul des forces instationnaires appliquées sur les pales d'une éolienne. Cette méthode combine la simulation de l'écoulement avec le calcul de la dynamique de structure. La modélisation aérodynamique est quasi-3D. Les vitesses induites par le rotor sont calculées à l'aide d'un model hybride, qui remplace les pales par des surfaces portantes. La distribution de pression appliquée sur ces surfaces est obtenue à l'aide des calculs 2D autour des profils de la pale. Pour prendre en compte l'élasticité de structure; ici, le battement de la pale et les oscillations des profils sont évaluées à l'aide d'un code de dynamique de structure et ainsi le maillage des profils est adapté à chaque pas de temps. La méthode proposée est validée dans le cas de l'éolienne NREL VI en dérapage où les résultats de comparaison obtenus pour le moment de flexion de la pale sont satisfaisants.
Strain gauge measurements on a full scale tidal turbine blade
Renewable Energy, 2021
The development of tidal energy converters, and particularly floating tidal energy converters, is an area of increased development in recent years. Testing of a floating tidal energy device over winter 2017/18 led to an opportunity to record and examine strain of a full scale composite turbine blade under operational conditions, with comparison of generating and parked behaviours. Comparison of the recorded data shows that blade strain correlates well with both torque and thrust over the averaging periods specified in IEC62600-200, although examination of frequency spectra generated from the strain data show that higher frequency fluctuations in strain are not necessarily detectable in the larger scale thrust and torque recordings with this particular measurement arrangement. The need for well synchronised clocks on recording systems is also highlighted, along with a cross-correlation method used to recover the alignment of data from different systems to allow comparison between them over periods of a similar order of magnitude to the clock skew between the systems.