Mechanical Analysis On Support Structure Of New Type Vertical-axis Tidal Current Turbine

Tidal current energy is a clean and renewable energy which has attracted more and more attention because of the broad development prospect. The support structure of the tidal current turbine is the basis of tidal power whose safety and stability in the complex ocean environment is the premise to ensure the smooth progress of the tidal power generation and a new focus in this research field. Therefore, mechanical, modal and transient dynamic analysis on the support structure of tidal current turbine is very important to tidal power project.This paper bases on the National Marine renewable energy special fund "Research and experiment of a new type vertical-axis tidal current turbine" and researches the support structure. The paper mainly emphases on the following contents:Firstly, hydrogeological conditions and environmental loads are analysed. Then the constraint of structural basis and wave and current factors are confirmed. Wave and current loads in the static analysis are calculated using the Morison equation and wave time course load is calculated in transient dynamic analysis using the fifth order Stokes waves theory.Secondly, based on the general Finite Element Method software, ANSYS, the finite element model of the support structure is presented. Then, the structure is calculated using linear static analysis in three different working conditions. The results show that the structure can satisfy the intensity requirement and the maximum stress point appears at the intersection of bars, constraint or the point of DOF coupling of different parts of the structure. The stress and displacement of the structure are maximum in working condition three which is more dangerous.Thirdly, the structure is calculated using geometric nonlinear static analysis in working condition three which is more dangerous. The results show that the stress and displacement distribution of the structure is consistent with the result of linear static analysis and the maximum stress and displacement are slightly larger than that got from linear static analysis.Fourthly, the structure is calculated using modal analysis and the first ten natural frequencies and vibration modes are distilled. The results show’that the vibration frequency of the turbine when it attains the rated power is smaller than the minimum natural frequency of the structure. Therefore, resonance will not occur.Fifthly, the structure is calculated using transient dynamic analysis. The results show that the vibration of the structure under the exciting force is stable after a certain period of time and the maximum stress and displacement are slightly larger than that got from linear static analysis in the same working condition.