Research On Load Characteristic Analysis And Optimal Design Of Offshore Wind Turbine Nacelle Cover

The nacelle cover is a large-scale shell component that protects offshore wind turbines.It has been eroded by offshore wind,rain and snow for a long time,and the weather environment is harsh.It requires high structural strength and rigidity.In this regard,this article takes a large-megawatt offshore wind turbine nacelle cover as the research object,comprehensively uses CFD and finite element analysis methods to carry out aerodynamic drag reduction optimization and structural lightweight design research on the large-megawatt offshore wind turbine nacelle cover,and achieves satisfactory performance the required lightweight structure design scheme.The research results of the thesis provide a solution for the lightweight design of the nacelle cover of a large offshore wind turbine,which has high engineering application value.The main research contents and results of the thesis are as follows:(1)Analysis of load characteristics of nacelle cover.The calculation uses the MRF model to simulate the rotation of the impeller,and the shared surface is used to transfer data between the rotating domain and the outer basin.The data shows that the rotation of the wind wheel causes the airflow near the nacelle cover to spiral backward and remotely around the surface of the nacelle cover.The wind speed and wind pressure at the location show obvious periodic changes.Calculation data under extreme wind conditions show that the incoming flow forms a high-pressure area in the center area of the windward surface,and airflow separation occurs at the edge area of the windward surface,and the air pressure is lower on the side and back of the nacelle cover.(2)The shape of the nacelle cover is optimized for drag reduction.Severe airflow separation at the edge of the windward surface will cause greater wind resistance.Therefore,combined with the structural characteristics of the nacelle cover,a variety of cross-sectional schemes are designed and CFD calculations are used.The results show that by changing the curvature of the windward surface,the angle between the windward surface and the side the wind resistance can be effectively reduced.Compared with the original plan,the wind resistance of the side and the back of the optimized plan is reduced by 14.97% and 29.15%,respectively.(3)Optimize the layout of stiffeners.The shape optimization method is used to explore and study the layout of the stiffeners of the nacelle cover.The strategy based on the proxy model combined with the search algorithm is adopted to effectively solve the problem of the distribution of the flexibility weight ratio of each working condition,and the shape optimization calculation the result provides ideas for the layout of the ribs and speeds up the design speed of the ribs of the shell structure.(4)Optimization of the composite layer structure.Taking into account the complexity of the nacelle cover structure,the design first ignores the shell boundary constraints,performs a unified optimization of the partitions according to the structural force characteristics,and finally determines the optimization process of the specific laying plan for a single shell.When optimizing the zoning ply parameters,the discrete ply parameters are used as design variables,and the numerical analysis and multidisciplinary optimization methods are combined.At the same time,the method of optimizing the design of different types of paving parameters such as the paving angle and number of composite materials,the process is simple.After optimization,the quality of the nacelle cover was reduced from 7.02 tons to 5.2 tons,a decrease of 25.93%,and the performance met the design requirements,indicating that the adopted method can systematically solve the optimization design problem of the large-scale composite shell structure composed of multiple parts.