Research On Structure Design Of Wind Turbines With Combined Blades

Wind turbine blades are the core component of converting wind energy into mechanical energy, its design theory and manufacturing technique is the key to the wind turbines. With the increasing capacity of Wind turbines, blades are getting longer and longer, increasing the difficulty of manufacture and long-distance transportation and cost, restricted the large-scale development of wind turbines. Therefore, adopt combined blade, manufacture in sections, segmented transport, site assembly, can well solve the problem of manufacturing and transport. Funded by the national science and technology support project "5.0MW doubly-fed variable speed constant frequency offshore wind turbine design, integration and demonstration"(2009BAA22B02),around the aerodynamic design and structure design method, theory and the key technology research of large combined blade,mainly for the following works:(1) Research on the basic theory and method of blade aerodynamic design. Established the mathematical model of blade based on the theory of momentum blade element. Optimized5MW wind turbine blade using the improved adaptive genetic algorithm calculated the chord length and torsional Angle of blade each section analysis of the aerodynamic performance of blades. The results show that it can get ideal pneumatic parameters using adaptive genetic algorithm.(2) In the whole life cycle, blade suffered variety of force coupling effect, including aerodynamic force, gravity, inertia force and additional force of operational control. Paper presented the wind turbulence model in the case of extreme wind speed based on analyzing the characteristic of wind,calculate various extreme operating conditions of blade used GH Bladed software, presented the selecting principle of limit load, determine the limit load of5MW blade.(3) Main beam are the the main load-bearing components of the blade, are the key and difficult points of blade structure design. Research on the traditional main beam structure types of blade, adopted the structure of main beam with single beam cap and double web. Established a mathematical model with the design objective of weight and bending strength according to mechanics of materials,optimization use the multi-objective genetic algorithm (GA), and validated he rationality and feasibility of the method by an example.(4) According to the composite laminated plate theory and beam theory, the strength and stiffness as constraints, large blade structure overlay design theory is studied. In order to improve the blade stiffness and reduce weight, in the blade skin, spar cap and web, carbon fiber/glass fiber reinforced plastic hybrid overlay are used, and the finite element method is applied to check the strength of the various parts. The results show that the carbon fiber/glass fiber reinforced plastic hybrid overlay can significantly improve the strength of the blade, and this method has obvious application value in engineering. Blade vibration characteristics and stability analysis is studied.(5) According to blade load distribution characteristics and structural features, the combined of blades staging location were determined. In accordance with the principles removable and easy to install, the structure size of the modular blade spar cap, webs, skin and other connector parts were designed. Based on the theory of mechanics of materials, diameter of bolt and overlay program in the connecting parts were determined. Overlay thickness and structure of conector were analysed with finite element theory to check parts strength. The results showed that design strength of demand is satisfied, overlay design method is feasible.(6) Through a combination of modular blade and one-piece blade, the distribution of composite multiple bolted and the stress variation, strain, displacement, vibration characteristics, stability of blade spar caps, webs, skin and other key parts were summed up. A detailed analysis of the limit load in the connector section and structural changing effection on the overall performance of the blade were studied.