Study On Influence Factors On Blade Root CokNection Strength Of Large-scale Wind Turbines Under Hoisting Conditions

With the rapid development of wind power technology,long blade wind turbines have become the development trend of onshore and offshore wind turbines,and the safety and economy of blade hoisting are increasingly demanded.The slice hoisting scheme is more economical than the traditional two-blade and three-blade hoisting method,but it has less domestic application.In this paper,the blade hoisting of a large wind turbine is taken as the research object.The basic theory of blade root connection calculation and the influencing factors of blade root connection strength under the condition of blade hoisting are studied.The safety check analysis and optimization of key components are carried out,which provides a solution for blade hoisting of large wind turbine and has high engineering application value and theoretical significance.The main contents of this paper include:(1)Basic theory of blade root connection calculation under blade hoisting condition.The external load analysis theory of blade root connection under hoisting conditions-blade element momentum theory,VDI2230 high strength bolt connection theory and bearing contact theory are studied,which provide theoretical basis for subsequent simulation and model verification.(2)Analysis and Modeling Technology of Hub-Variable Propeller Bearing-Blade Root Connection Structure under Lifting Conditions.According to the load characteristics of blade hoisting operation and the mechanical characteristics of screw pairs when bolts are connected,the finite element analysis technique is applied to simulate the bolt connection of bearing with blade and hub by using beam equivalent method.By comparing and analyzing various modeling methods of four-point support variable-pitch bearing,the hub-variable-pitch bearing-blade root connection structure analysis technique under hoisting operation with consideration of calculation efficiency is discussed.(3)The bolt cokNection strength of key components in hoisting condition is analyzed.Under the initial hoisting condition,the cokNection strength is analyzed,and the bolt stress distribution map,bearing bolt hole wind distribution map,blade root bolt clearance map and hub stress distribution map are obtained.The model is validated by comparison with the engineering calculation of bolts and bearings,and the correctness of the model is studied,which lays a foundation for subsequent analysis and optimization.(4)The effect of bolt preload on the strength of blade root connection was studied.The strength of blade root connection under different pre-tightening forces was studied,and the range of pre-tightening forces satisfying the conditions of blade lifting and hooking was obtained.(5)The influence of hub process hole distribution on joint strength was studied.The influence of the distribution of process holes in different hub on the strength of blade root connection was analyzed,and the relationship between the distribution of process holes in different hub and installation time was also analyzed.Finally,on the premise of satisfying the safety conditions of lifting hook,the distribution of technological holes in hub was optimized,and the bolt distribution satisfying the conditions of lifting hook was determined.