| Wind energy is the third largest source of power in china,and the blades are the key components of the turbine.In order to improve the performance and quality of blades,various composite materials have been widely used in turbine blades.In recent years,with the rapid development of wind power industry,the fracture of turbine blade due to resonance and stress concentration occurs frequently.Therefore,it is important to study the structural characteristics of composite materials turbine blades.The three dimensional orthogonal woven composites and four axial warp knitting composites are all the mainstream material for making the wind turbine blade at present.The two material reinforcements in this paper are glass fiber,and the matrix is the same resin.The blade molding is all vacuum assisted resin transfer molding process,and the weight difference is not more than 4%.So the two kinds of blades have good comparability in structural characteristics.The study of wind turbine blade structure characteristics mainly include the experimental method and the finite element method.In this paper,the PLUSE16.1 system is used to test the static modes of two kinds of blades,and the results are compared with the numerical simulation results.Verify the accuracy of the ACP model and provide a guarantee for the next research.The traditional calculation of the structural characteristics of the wind turbine mostly chooses a single working condition,which ignores the influence of wind speed change.In this paper,gradual wind is used as the wind speed model.The four working states of the fan from start to brake are dispersed into 31 working conditions,and the acceleration caused by the variation of wind speed is added,which is closer to the actual working process of the turbine.In the Campbell diagram drawn for two kinds of material wind wheel,it can be seen that the natural frequency of the fan from starting to the rated condition is a curve of rising.Secondly,the first two order natural frequencies of the three dimensional orthogonal woven composite wind turbine are higher than three times the rotational frequency,and the dynamic design is qualified.However,the first natural frequency of the four axial warp knitted composite wind turbine intersects with the three times rotational frequency at the rated speed 190 rpm,which does not meet the design requirements,and needs redesign.In the working process of the wind turbine,the acceleration of the wheel will weaken the effect of the stress tempering.The effect of the deceleration is the opposite and more significant.Although the effect of acceleration on frequency is very weak in this paper,the effect can not be ignored if the acceleration is larger or in the gust condition.By comparing the structural characteristics of two different material wind turbines,it is found that under the same working conditions,the stress distribution of the two kinds of wind turbines has obvious step change along with the decrease of ply thickness.But the stress distribution of the 3DOWC wind wheel is relatively uniform,and the stress concentration phenomenon is not easy to occur.From start to brake,the total deformation trend of the two kinds of material wind wheel is the same,which is positively related to the change of wind speed and rotational speed.However,due to the smaller deformation value of the 3D orthogonal woven composite material of Z yarn,it is more safe and reliable for large blades and high wind speed.However,due to the effect of Z yarn,the deformation value of the 3D orthogonal woven composite material wind wheel is smaller,which is more reliable for large blades and high wind speed condition. |
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