A Study of Wind Generator Set Blades Dynamic Analysis

2012 ◽  
Vol 522 ◽  
pp. 413-416
Author(s):  
Jian Jie Zhang ◽  
Wen Lei Sun

This paper on wind generator set blades had a simple introduction, and the modal analysis was used on the blades dynamic analysis, the conclusion that blades the different stage in the direction of the force and deformation was drawn, it can be concluded: the first three-order natural frequency at, the blades are expressed as a pure bending vibration. It can be seen from the blade vibration figure: a frequency of blades waving in the direction of the first natural frequency, first natural frequency of the second-order frequency blades shimmy direction, three frequencies for the blades waving direction of the second-order natural frequency, torsional frequency of fourth order for the direction of the shimmy, five order of frequency of blades placed waving direction of the three natural frequencies. According to the theory of vibration, the vibration in the process of energy is concentrated in bands 1 and 2, so the first stage waving vibration (bending vibration) is the main vibration of the wind generator set blades; 4 and 5 vibration modes performance for bending dominated accompanied shimmy and torsional vibration. Visible, the shimmy vibration and torsional vibration in high-end part is still not the main vibration.It provides the theoretical basis so as to improve the quality of the design of wind turbine blades. Blade is one of the wind generator set key components, many aerodynamic problems are faced, the aerodynamic efficiency of the blades is to be considered an important factor in the blade design, and their job security is more important factor. The wind turbine power source is the natural randomness of strong wind, the blades often run in the stall condition, the system has a strong stochastic dynamic process, the transmission of abnormal is irregular power input, the main structural components to withstand higher than normal rotation mechanical fatigue loading several times, forming a unique wind turbine dynamics. Wind generator set blades as a flexible structure, the load acting on has a cross and random variability, which is an inevitable occurrence of vibration, the vibration characteristics of their study is very necessary. Blades the structure and strength of the wind generator set reliability plays an important role. With the emergence of high-power wind generators, finite element numerical analysis of the theories and methods have been applied to the structural design of wind generator set. Modern wind generator set blades shape and internal structure complex calculations,it is necessary to study the exact dynamics model and the analysis of blades structure [. The institutional dynamics is to constitute the institutional elements of the inertia and institutions in the rigid parts caused by the vibration of a subject. The kinetic analysis features include: regular modal complex eigenvalue analysis, frequency and transient response analysis, (noise) acoustic analysis, random response analysis, the response and the impact of spectrum analysis, power sensitivity analysis. Here only the blade to vibrate and modal to be analysed [.

Author(s):  
Hiroyuki Fujiwara ◽  
Tadashi Tsuji ◽  
Osami Matsushita

In certain rotor systems, bending-torsion coupled resonance occurs when the rotational speed Ω (= 2π Ωrps) is equal to the sum/difference of the bending natural frequency ωb (= 2π fb) and torsional natural frequency ωθ(= 2πfθ). This coupling effect is due to an unbalance in the rotor. In order to clarify this phenomenon, an equation was derived for the motion of the bending-torsion coupled 2 DOF system, and this coupled resonance was verified by numerical simulations. In stability analyses of an undamped model, unstable rotational speed ranges were found to exist at about Ωrps = fb + fθ. The conditions for stability were also derived from an analysis of a damped model. In rotational simulations, bending-torsion coupled resonance vibration was found to occur at Ωrps = fb − fθ and fb + fθ. In addition, confirmation of this resonance phenomenon was shown by an experiment. When the rotor was excited in the horizontal direction at bending natural frequency, large torsional vibration appeared. On the other hand, when the rotor was excited by torsion at torsional natural frequency, large bending vibration appeared. Therefore, bending-torsion coupled resonance was confirmed.


2013 ◽  
Vol 446-447 ◽  
pp. 721-727
Author(s):  
Xi Song ◽  
Yin Guang Wu ◽  
Jie Yu Li ◽  
Rong Zhen Zhao

Based on a kind of 1.5MW large-scale horizontal axis wind turbine tower, the mechanical modeling of a wind turbine tower-foundation is established, the static and dynamic analysis of the model is carried out by ANSYS software. The top displacement of the system is calculated by the static analysis to meet the design requirements in engineering. In dynamic analysis, each pile foundation is equivalent to a group of springs for the simulation of horizontal and vertical rigidity of the pile. The influence of top mass and foundation elasticity on wind turbine tower modes is analyzed, and calculated the natural frequency of the tower within a certain scope of rigidity in different directions about the piles foundation. The results show that the natural frequency of the wind turbine tower is influenced significantly by the mass on the tower top and foundation rigidity. The study provides a theoretical basis for optimal design of the wind turbine.


Author(s):  
Fasuo Yan ◽  
Cheng Peng ◽  
Jun Zhang ◽  
Dagang Wang

Offshore turbines are gaining attention as means to capture the immense and relatively calm wind resources available over deep waters. A coupled dynamic analysis is required to evaluate the interactions between the wind turbine, floating hull and its mooring system. In this study, a coupled hydro-aero dynamic response analysis of a floating wind turbine system (NREL offshore-5MW baseline wind turbine) is carried out. A numerical code, known as COUPLE, has been extended to collaborate with FAST for the simulation of the dynamic interaction. Two methods were used in the analysis; one is coupled method and the other is limited coupled method. In the coupled method, the two codes are linked at each time step to solve the whole floating system. The limited coupled method assumes wind load is from a turbine installed on top of a fixed base, namely it doesn’t consider real-time configuration of floating carrier at each time step. Coupled technique is also mentioned to integrate the hydro-aero dynamic analysis in this paper. Six-degrees of freedom motion and mooring tensions are presented and compared. The numerical results derived in this study may provide crucial information for the design of a floating wind turbine in the future.


2013 ◽  
Vol 341-342 ◽  
pp. 383-386
Author(s):  
Zhong Guo Bian ◽  
Shu Qin Liu ◽  
Guo Zhi Han

According to the characteristics of the vertical axis wind turbine, research about the mechanical analysis and inherent frequency in design of the small vertical axis wind generator pole is complete, and simulation on the influence of the structure forms and pole wall thickness on natural frequency has been done. The results can help solve the problem such as resonance between the wind turbine pole and the rotating turbine.


Author(s):  
Fateh Ferroudji

AbstractThe study deals with the numerical analysis aspects that are necessary for identifying of modal parameters of the tower structure as the most important part of the horizontal axis wind turbine, which are basic for the dynamic response analysis. In the present study, the modal behavior of an actual 55-m-high steel tower of 850 KW wind turbine (GAMESA G52/850 model) is investigated by using three-dimensional (3D) Finite Element (FE) method. The model was used to identify natural frequencies, their corresponding mode shapes and mass participation ratios, and the suggestions to avoid resonance for tower structure under the action wind. The results indicate that there is a very good agreement with the fundamental vibration theory of Euler-Bernoulli beam with lamped masse in bending vibration modes. When the rotor of the wind turbine runs at the speed of less than or equal to 25.9 rpm it will not have resonant problems (stiff–stiff tower design). Furthermore, in case the rotor runs at the speed of between 25.9 and 30.8 rpm, the adequate controller is necessary in order to avoid the corresponding resonant susceptible area of the tower structure (soft–stiff tower design).


Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3051
Author(s):  
Yue Zhao ◽  
Jijian Lian ◽  
Chong Lian ◽  
Xiaofeng Dong ◽  
Haijun Wang ◽  
...  

Stochastic dynamic analysis of an offshore wind turbine (OWT) structure plays an important role in the structural safety evaluation and reliability assessment of the structure. In this paper, the OWT structure is simplified as a linear single-degree-of-freedom (SDOF) system and the corresponding joint probability density function (PDF) of the dynamic response is calculated by the implementation of the path integration (PI) method. Filtered Gaussian white noise, which is obtained from the utilization of a second-order filter, is considered as horizontal wind excitation and used to excite the SDOF system. Thus, the SDOF model and the second-order linear filter model constitute a four-dimensional dynamic system. Further, a detailed three-dimensional finite element model is applied to obtain the natural frequency of the OWT and the efficient PI method, which is modified based on the fast Fourier transform (FFT) convolution method, is also utilized to reduce the execution time to obtain the PDF of the response. Two important parameters of wind conditions, i.e., horizontal mean wind speed and turbulence standard deviation, are investigated to highlight the influences on the PDF of the dynamic response and the reliability of the OWT.


Author(s):  
Takeshi Kudo ◽  
Koki Shiohata ◽  
Osami Matsushita ◽  
Hiroyuki Fujiwara ◽  
Akira Okabe ◽  
...  

An experimental investigation was conducted to confirm the bending-torsion coupled vibration of a rotor system with a bladed disk. For a rotor with relatively long blades such as in the latest low-pressure steam turbines, coupled vibration with shaft torsional vibration represents the bladed disk natural frequency of a nodal diameter (k) of zero (umbrella mode). Today this well-known behavior is reflected in the design of steam turbine rotor systems to prevent the blade vibration resonance due to torque excitation caused by the electric power grid, a standard for which is proposed by ISO 22266-1. The bending-torsion coupled resonance of rotor systems occurs, however, under specific conditions due to rotor unbalance. When the rotor’s rotational speed (Ω) is equal to the sum/difference of the bending natural frequency (ωb) and torsional natural frequency (ωθ), namely, Ω = ωθ ± ωb, there is coupled resonance, which was experimentally observed with a rotor with a relatively simplified shape. In this study, the test apparatus for a flexible rotor system equipped with a shrouded bladed disk driven by an electric motor was constructed to confirm the vibration characteristics, by envisioning the bending-torsion coupled resonance as applied to actual rotor systems of turbo machinery. A radial active magnetic bearing (AMB) was employed to support the rotor by controlling bearing stiffness and damping, and applying lateral directional excitation of forward and backward whirl to the rotor. A servomotor was also equipped at the end of the rotor system to excite the torsional vibration. The resonance of a bladed disk with nodal diameter (k) of zero, which was coupled with the rotor’s torsional vibration, was observed under the above condition (Ω = ωθ − ωb) through AMB excitation of the rotor’s bending natural frequency. Conversely, the torsional excitation caused by the servomotor was confirmed as causing the coupled resonance of rotor bending vibration.


2011 ◽  
Vol 291-294 ◽  
pp. 2529-2536
Author(s):  
Jia Jun Si ◽  
Kuan Jun Zhu ◽  
Bin Liu ◽  
Yao Ding

The dynamic analysis has been adopted for the calculation of the low-order natural frequency and harmonic response data of the steel tower of vertical axis wind turbine, as well as the dynamic relation between the wind turbine and the tower. When the wheel rotates at 160rpm, the harmonic load has a very serious destructive damage to the tower. In order to avoid the system failure caused by the system resonance in the engineering design, some optimizations have been taken on satisfying the security and reliability of the tower. This study provides the scientific basis for the dynamic design and the optimization. The conclusion shows that the most effective method of raising the natural frequency is to reduce the weight of the structure when the material and the structural style are determined. As a result, the difference between harmonic response and resonance frequency of the structure rises to 21.3% from 0.3% after reducing the weight of the tower by 21.3%.


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