Analysis And Design Of The Third Web Layout On The Of Large Wind Turbine Blades

With the rapid development of the wind energy industry all over the world,the unit capacity of wind turbines has continued to increase greatly.The size and weight of blades have also increased significantly,which has made stricter demand of the safety and reliability of blade structures.Among a large number of practical wind turbines,there always exists different degrees of damage states of the blades,such as leading edge erosion,skin folding,back panel convex,trailing edge cracking and so on.The trailing edge is one of the most critical regions where blades are sensitive to be damaged.Blades tend to come about local nonlinear buckling in trailing edge under long-term fatigue loading and extreme limit loading,resulting in trailing edge adhesive debonding and back panel delamination.As a consequence,several super large-scale wind turbine blades adopt a triple-web layout scheme which is based on the traditional double-web layout scheme installing an extra shear web between the maximum chord length and the middle of the blades.By this method,it can enhance the stability of trailing edge,decreasing the dangers of the damage of composite materials and failure of cohesive bonding.Whereas this scheme has some certain potential risks such as aero-elastic instability as well.In order to comprehensively evaluate the influence of the third web on the blade structural performance,an in-depth study about the inner mechanism of the third web is needed.Moreover,it is necessary to explore the disciplines of its several characteristic variables for the extreme limit loads of the blade structures.Additionally,prompting the efficiency and flexibility of the structural design of the triple-web wind turbine blades is needed.Based on finite element analysis theory,a study related to the triple web scheme for large-scale wind turbine blades was carried out under the local-global pyramid test framework of wind turbine blades.Firstly,a blade segment sub-component model was constructed,which was originated from the geometry and layups of a classic cross-section of a large-scale wind turbine blade,besides reasonable boundary conditions and loading method were set.Under the full cycle bending directions,the traditional double-web and the triple-web blade segments were respectively measured to obtain the buckling resistance.After that,an automated modeling platform aiming to the configuration scheme of the cross-section of triple-web blades was established for the sake of achieving the effective mass dispose of wind turbine subcomponents.Then multiple geometrical and layups characteristic parameters about the third web were selected to complete the stimulation analysis.Finally,a mixed beam-shell structure model of a full-scale blade was built by combining the advantages of traditional beam model and shell model,by employing a cross-section structural properties computational tool.Relevant results illustrated that the third web mainly plays a role in the side of the minimum edgewise direction,which restrains the extension of the buckling wave of the span-wise and chord-wise directions apparently,significantly improving the stability of the trailing edge and the integrity of the whole segment.Throughout the load-displacement curve,surface distribution of stress strain,composite materials failure modes,buckling wave transformation etc.,the interior mechanism of the third web during the response process was comprehensively analyzed and the influence of the third web on wind turbine blade was discovered.What's more,compared results demonstrated that the distance between the third web and trailing edge and inclination angle have relatively greater impact on its buckling resistance,while the total thickness of the third web and the relative thickness of the core material have limited space for the improvement of buckling.Comprehensive verifications and comparisons among these three models in various aspects,such as deformation displacement,stress strain,and calculation time,illustrating that this mixed model has relatively high accuracy.In the meantime,it has rapid solution speed,which is more advantageous especially in the nonlinear calculation.According to these corresponding conclusions from this thesis,it can provide a targeted design methods for the triple-web configuration of future super large wind turbine blades,ensuring that the structural performance is effectively improved while reducing its adverse effects as possible.Moreover,The mixed beam-shell model can greatly prompt the efficiency of blade design,which has broad engineering prospects.Besides,it can be used to be a high-efficient and flexible optimization platform for the structural layout design of triple-web wind turbine blades.