| High-rise thin-shell tube structure is adoptted on modern large-scale wind turbine tower(hereinafter referred to as tower); the height is nearly100m, the bottom diameter beyond5m and the wall thickness less than1/100compared diameter, which belongs to typicalslender shell structure. For constraints boundary conditions, tower is fixed at the bottom,the top is free and bear loads form gravity and aerodynamic of nacelle and rotor, which isprone to cause vibration and instability. With increase of power capacity of wind turbine,the mass and geometric dimension of wind turbine are increasing, the height of tower isalso increasing, therefore, the gravity loads and aerodynamic loads on the tower are morevariable. In recent years, the accident of tower falling down as instability and bucklinghappened sometimes during operation. Therefore, the structural dynamic response andstability on tower are essential to wind turbine’s reliability and security.A2.5MW wind turbine tower is adopted as subject in this study. Theoretical analysisand numerical simulation method are used to study tower structure dynamic, fatigue andbuckling stability. Considering the wind is main source load during the operation of windturbine, aerodynamic load generated by wind is the direct cause of tower dynamicresponse, fatigue and buckling stability. First, the wind conditions and wind speeddistribution are analyzed in theoretical method refer to IEC standard, and wind speedprobability distribution and wind turbulence distribution are simulated in specializedwind turbine software-GH Bladed. Second, the loads of wind turbine components areanalyzed theoretically. According to German Lloyd (GL2010) and Bladed manualprinciple, the running loads under operating conditions (such as start, normal powergeneration, emergency brake, stopping, etc.) are simulated in GH Bladed，and theaerodynamic loads are transfer equivalently to the top of tower through coordinatetransformation matrix. Finally, tower dynamic response, fatigue and buckling stability areanalyzed in theory and simulated in ANSYS software. In the course of this study, someconclusions are summarized as follows:(1) In structural dynamic response of wind turbine tower, lower modal dominateresponse and contribution of higher modal is very tiny. Moreover, since the role ofstructural damping, high-level part of response decays quickly which is negligible.(2) Total gravity of nacelle and rotor on the top of tower has great impact on thefrequency of bending vibration, and the vibration frequency of tower is significantlyreduced with increase of gravity. (3) Tower accompanied by transient dynamic response during wind turbine operating;dynamic load on tower from wind and operating conditions produce large transient stressand deformation, and its instantaneous value is much larger than response superpositionvalue which cause instantaneous impact damage on tower.(4) In cut-out speed and rated wind speed, the tower damage array mainly happens inlow stress area which is not enough to cause the failure of tower; in limit wind speed, thedamage of tower happens in high-stress district which is damage to tower.(5) Axial compression load and lateral load of tower play a major role in towerbuckling. Tower tube is defect-sensitive structure, and opening at the bottom of towerhave significant impact on tower buckling. In the same load case, arc-shaped opening hasbetter buckling performance than rectangular opening.The frame along door edge ishelpful to improve tower buckling strength.In this paper, the loads of wind turbine are analyzed in theory, and running loads aregot by simulation in Bladed. The dynamic response of tower in typical operatingcondition shows that stress and strain meet the material mechanical scope; tower bucklinganalysis shows that tower buckling strength meets safety requirement; the fatigueanalysis in different wind speed conditions show that tower fatigue life satisfyrequirement of design life. |
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