| The wind tower, which is the main load-bearing structure of wind turbines, mainly issubjected to wind load. However， the value and direction of the wind loadare time-varying, frequent wind load effect makes the tower damage more likely due toinsufficient strength caused by fatigue. Therefore, it has very important significance forresearch of tower fatigue under random wind load.Based on the site condition of Inner Mongolia Wu Chuan wind field, the numericalsimulation of random wind load and the wind-induced vibration analysis of tower underrandom wind load upon the finite element software were conducted. The preciseintegration method and direct method were used for wind load identification oftower simplified model. The influence on the load identification accuracy when the towerresponse is mixed with noise was analyzed. Finally, the fatigue cumulative damage oftower in the design service life was obtained according to linear cumulative damagetheory and the S-N curve of tower, the fatigue life of tower was estimated and the safetyassessment of structure was made.The results show that dynamic displacement amplification coefficient at the top ofwind power tower is1.885, and dynamic stress amplification coefficient at the bottom is1.2, which follow that the amplification effect of dynamic response is remarkable. At thetop of tower, the ratio of displacement peak under transient wind speed and calculateddisplacement by the norms is1.691, thus it can be seen that value based on thespecification is small, so increasing the wind vibration coefficient should beproposed.0.45Hz～0.55Hz frequency segment have great contribution to the dynamicresponse of the tower, the proportion of the frequency in the displacement, velocity andacceleration power spectrum is respectively66.73%,79.24%and77.84%; Low frequencycomponent’s influence on the displacement is large than that on the velocity andacceleration, the high frequency part barely is passed on to the tower. With theincrease of the basic wind speed, displacement and stress have parabolic increase under rated wind speed, while which have linear increase and increase speed decreases after therated wind speed. In the case of no noise, load recognition effect of precise integrationand direct method is better, while precise integration has been unable to meet theprecision requirement even in the low level noise after adding noise. And therecognition error of the two methods increases with the tower height increasing, the sickof the identification results appear firstly in higher position. The node at the bottom of thetower is key point of tower fatigue analysis, in addition, the connection parts between thedoorway and the tower and variable thickness of the tower all should be focused onfatigue analysis; The opening position of the door has more greater influence on thenodes at the gate than the tower nodes in fatigue analyzing. When the door was set in theside departing from perennial dominant wind, the anti-fatigue ability of tower will beimproved.The research results can provide reference for wind power tower in wind vibrationanalysis and fatigue analysis. |
PDF Full Text Request