Impact assessment of a wind turbine blade root during an offshore mating process (original) (raw)
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Volume 10: Ocean Renewable Energy, 2018
Structural analysis of floating wind turbines is normally carried out with the hull considered as a rigid body. This paper explores the consequences of modeling the pontoons of a tension leg platform (TLP) wind turbine as flexible structures. The analysis is based on numerical simulations of free decays, structural response to wave excitation and short-term fatigue damage accumulation at chosen points of the platform. In addition, the importance of considering hydroelasticity effects is evaluated. It is observed that pontoon flexibility can change the platform natural periods significantly, as well as the intensity and peak frequencies of internal structural loads. The adoption of a fully rigid-body is shown to be non-conservative for the fatigue damage analysis. Loads due to hydroelasticity have order of magnitude comparable to those related to rigid-body motions, but still lower enough to be considered of secondary importance.
2019
In 2022 the first 12 MW offshore wind turbines are expected to be installed. Due to the continuous upscaling of wind turbine generators new problems are expected to arise during the installation of the turbines. Especially the workability of the installation of larger wind turbine blades, which are already causing problems during the installation of 8.4 MW turbine blades, are questioned by Van Oord. This research focuses on the alignment process of the blade with the hub, which is considered to be the limiting factor in installing wind turbine blades. The ultimate goal is to reduce single blade installation times by facilitating the alignment process To investigate how different environmental conditions influence the dynamic behavior of the blade in the alignment process, a numerical model is developed. The motions of the blade, forces in the taglines and aerodynamic forces on the blade are evaluated for different environmental conditions during 30-minute simulations in the time dom...
Structural analysis of offshore wind turbine blades using finite element method
Wind Engineering, 2019
Wind energy is one among the most promising renewable energy sources, and hence there is fast growth of wind energy farm implantation over the last decade, which is expected to be even faster in the coming years. Wind turbine blades are complex structures considering the different scientific fields involved in their study. Indeed, the study of blade performance involves fluid mechanics (aerodynamic study), solids mechanics (the nature of materials, the type of solicitations …), and the fluid coupling structure (IFS). The scope of the present work is to investigate the mechanical performances and structural integrity of a large offshore wind turbine blade under critical loads using blade element momentum. The resulting pressure was applied to the blade by the use of a user subroutine “DLOAD” implemented in ABAQUS finite element analysis software. The main objective is to identify and predict the zones which are sensitive to damage and failure as well as to evaluate the potential of c...
Applied Sciences, 2020
The importance of a reliable blade root connection has grown due to the higher-gravity-induced edgewise loads on the blade root that resulted from the recent increased size and weight of a wind turbine rotor blade. To avoid the loosening of a bolt joint connection or even consecutive blade failures, the stress concentration factor (SCF) at the bolt thread root that is sensitive to fatigue should be understood comprehensively. In this work, two-dimensional and three-dimensional finite element (FE) analysis methods were used to determine the SCF at the bolt threads both between an insert and a M42 bolt used for a large offshore blade, and between a M42 bolt and a nut. The effect of various geometric parameters on the SCF were also investigated, which included shank diameter, nut height, nut type, and relief cone. Results showed that the decreased diameter of a M42 bolt shank diameter was the dominant design driver in reducing the stress concentration factor by 40%, from 3.94 to 2.32. ...
Parametric Study of Accidental Impacts on an Offshore Wind Turbine Composite Blade
Wind turbine blades are the key components that allow the extraction of energy from the wind; these blades are often subjected to accidental impacts which usually occurs on moving blades with maintenance tools, hail, or flying birds, resulting in a significant degradation of the structural integrity of the blade. In this paper, a numerical simulation is adopted using finite element method (FEM) with ABAQUS software to investigate the mechanical behavior of a GRP composite wind turbine blade under low-velocity impact in operating conditions. On the other hand, damage modeling was formulated based on Hashin criteria for intra-laminar damage to detect failure modes in large wind turbine blade, the sensitive zones, and the size of damaged areas. To investigate this situation, a comparative evaluation was carried out considering many impact scenarios and the main parameters such as the impactor geometry, velocity, and weight. The results are then examined and analyzed, which show that major damage appeared at the tip of the blade and on trailing edge. Furthermore, the impactor geometry affects the type of damage, the weight affects the size of the damaged area, while the impact velocity influences the mechanical response of the composite wind turbine blade.
Structural Integrity Evaluation of Offshore Wind Turbines
Earth and Space 2010, 2010
Wind turbines are complex structures that should deal with adverse weather conditions, are exposed to impacts or ship collisions and, due to the strategic roles in the energetic supplying, can be the goal of military or malevolent attacks. Even if a structure cannot be design to resist any unforeseeable critical event or arbitrarily high accidental action, this kind of systems should be able to maintain integrity and a certain level of functionality also under accidental circumstances, which are not contemplated or cannot be considered in the usual design verification. According to a performance-based design view, the entity of actions to be resisted and the services levels to be maintained are the design objectives, which should be defined by the stakeholders and by the designer in respect of the regulation in force. For what said above, the structural integrity of wind turbines is a central issue in the framework of a safe design: it depends on different factors, like exposure, vulnerability and robustness. Particularly, the requirement of structural vulnerability and robustness are discussed in this paper and a numerical application is presented, in order to evaluate the effects of a ship collision on the structural system of an offshore wind turbine. The investigation resorts nonlinear dynamic analyses performed on the finite element model of the turbine and considers three different scenarios for the ship collision. The review of the investigation results allows for an evaluation of the turbine structural integrity after the impact and permits to identify some characteristics of the system, which are intrinsic to the chosen organization of the elements within the structure.
Structural engineering & mechanics, 2010
Offshore wind turbines are relatively complex structural and mechanical systems located in a highly demanding environment. In the present paper the fundamental aspects and the major issues related to the design of these special structures are outlined. Particularly, a systemic approach is proposed for a global design of such structures, in order to handle coherently their different parts: the decomposition of these structural systems, the required performance and the acting loads are all considered under this philosophy. According to this strategy, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessments in various sub-problems, which can be solved by means of sub-models at different levels of detail, for both structural behavior and loads simulation. Specifically, numerical models are developed to assess the safety performances under aerodynamic and hydrodynamic actions. In order to face the problems of the actual design of a wind farm in the Mediterranean Sea, in this paper, three schemes of turbines support structures have been considered and compared: the mono pile, the tripod and the jacket support structure typologies.
Development and application of a simulator for offshore wind turbine blades installation
Ocean Engineering, 2018
In an offshore environment, offshore wind energy resources are more available and stable, but the investment cost is much higher than that of onshore wind. The installation cost is a crucial factor of the investment. With the increasing number of planned and approved offshore wind farms, offshore wind turbine installation and relevant operations have received tremendous attention. Therefore, expediting the turbine-structure mating operations through a higher level of automation in offshore wind turbine installations may provide important economic benefits. To achieve a higher automation level and reduce the weather waiting time during the installation of offshore wind turbines, a flexible simulation-verification framework with high fidelity is needed. However, state-of-the-art wind turbine numerical analysis code is neither convenient nor open enough for applications concerning the design and verification of control algorithms. MATLAB/Simulink is among the most widely utilized numerical platforms by control engineers and researchers. This paper describes the development of a modularized blade installation simulation toolbox for the purpose of control design in MATLAB/Simulink. The toolbox can be used to simulate several blade installation configurations, both onshore and offshore. The paper presents the key features and equations of the different modules, exemplified by a single blade installation operation. Code-to-code verification results are presented and discussed with both quasi-steady wind and three-dimensional turbulent wind field.
Effect of crowning of dovetail joints on turbine blade root damping
Key Engineering Materials, 2007
Stresses due to resonant vibrations induce fatigue damage in turbomachinery blades jeopardizing their structural integrity. Damping plays a fundamental role in passive control of resonant stresses. In the present work the effect of 'crowning' of dovetail joints on blade-root friction damping is for the first time investigated. In detail, the damping of a simplified blade is measured under varying centrifugal load for two different joint geometries: a customary dovetail attachment and a 'crowned' one. A theoretical model is developed to quantify the damping generated at the contact surfaces. Experimental results and analytical predictions are compared.
Multi-level structural modeling of an offshore wind turbine
Proceedings of the 2011 …, 2011
Offshore wind turbines are complex structural and mechanical systems located in a highly demanding environment. This paper proposes a multi-level system approach for studying the structural behavior of the support structure of an offshore wind turbine. In accordance with this approach, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessment in various sub-problems, which can be solved by means of sub-models at different levels of detail, both for the structural behavior and for the simulation of loads. Consequently, in a first place, the effects on the structural response induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure are inquired. After that, a mesolevel FEM model of the blade is adopted in order to obtain the detailed load stress on the blade/hub connection.