| Offshore wind power has developed rapidly in recent year, the southeast coastal areas in China is in the subtropical monsoon climate, although the areas has abundant wind resource, the extreme wind condition in typhoon weather has brought great challenges for the design of wind turbine blade. Firstly, the coupling of wind and wave at sea has brought a lot of difficulties for the prediction of wind turbine blade limit load. Secondly, the extreme wind speed and high turbulence has taken the higher qualification of wind turbine structure. Thirdly, since the typhoon weather causes the serious damage of wind turbine blade, we desperately need to develop a high strength low load blade. Therefore, this article will focus on three parts, including the prediction of offshore wind turbine blade load, the exploration of the influence caused by extreme wind on the blade strength, and the development of low load high strength large thickness blunt trailing edge blade.Firstly, in order to study the fast and accurate extreme load predication method on offshore wind turbine, the article combined the genetic algorithm with FAST software, and transformed the calculation of extreme load in coupling wind and wave condition to solving the ultimate value. Also the article compared the calculation result with the forecast result by using IEC standard. It is concluded that the method saves the calculation time and improve the calculation accuracy, and has a certain reference value for offshore wind turbine extreme load prediction. And it is concluded that the load of floating wind turbine blade is not only related to wind but also affected by the parameters of waves. When the wind speed is high, significant wave height is highest under this wind, the wave peak period is near the pitch natural frequency of wind turbine, and the angle between the wind and wave direction is negative value, it is easiest to appear the extreme flap bending moment in blade root. By changing the algorithm parameters of constraint conditions, it can make the algorithm applicable to various wind field and sea area, and has a better applicability than IEC61400-3, which provides a effective extreme load prediction method for Chinese special wind environment.Secondly, in order to study the increase of the extreme load effects on blade structure and target to strength blade, the article generate three kinds of blade extreme load envelope based on three different wind condition, and the structure characteristics of100Kw wind turbine blade under different extreme load envelopes are compared. Also the blade under the Chinese wind resource condition is checked. It is concluded that on the extreme load distribution, the blade axial thrust, flapwise bending moment and leadwise bending moment are the main factors which influence the blade strength. Whether wind turbulence or speed is increased, the blade load will increase. And the amplitude of load increase decrease from blade root to tip. And the blade extreme safety factor decreases with the speed and turbulence increase, but the wind speed has more obvious influence than turbulence. The area and material on blade easy to broken are not affected by wind speed or turbulence intensity, and only are influenced by blade itself. The wind speed and turbulence intensity in Chinese southeast coastal areas is higher than IEC standard, which make the blade in axial thrust, flatwise bending moment, leadwise bending moment increase, also the safety factor in the middle part of blade has decreased obviously.Thirdly, in order to explore the effective way of designing the blade with low load and high strength, the article design100kW and6MW wind turbine thick blunt trailing edge blade (TBTEB) in different way, and compared the load and structure characteristics with the original blade. It is concluded that the method of design new blade by using thick blunt trailing edge airfoil CAS450to replace the cylinder is simple and can improve the strength on root, protect the tower and cabin. But this method will increase blade weight, reduce the aeroelastic stability and the strength on blade middle part. So this method is applicable for the condition of wind environment is stable and the length of blade is short. Another method of design new blade by adopting thick airfoil to extent in tip direction, and using CAS airfoil to replace the original airfoil completely can make the blade weight decrease, guarantee the aeroelastic stability, reduce the load and protect the cabin and tower. So the method is applicable to design long blade. But the root structure of new blade needs to strengthen by layer improvement.Finally, in order to explore the topology structure design of TBTEB, the article aimed at the6MW CAS TBTEB and DOWEC blade to layer design by main-assistant cap structure and SPAR structure, and study the applicability to different layers for TBTEB. Then four different layer styles for SPAR structure is designed, and the sensitivity of the main layer parameter-the cap thickness and width for the blade structure is studied, and the most important factor which influent the blade strength is explored. The result shows adopting the SPAR topology structure can obtain more profits in flapwise stiffness, also this structure can improve the aeroelastic stability of TBTEB. The thickness of cap is more sensitive than the width on improving flapwise stiffness, so increasing the thickness of cap is more effective than width to the TBTEB. And the result has certain reference value for the layer optimization of the TBTEB. |
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