Fault Diagnosis And Reliability Analysis Of Wind Turbine Pitch Bolt

As the key equipment to convert wind energy into electrical energy,megawatt wind turbine is a new trend in the future,The development trend of large scale wind turbine sets a higher requirement for the structural strength of the key components.The main components of wind turbine blades,frame,cylinder,spindle,hub,etc.High strength bolt is one of the key components of these key components.The function of high strength bolt is connected,transfer force and torque,positioning and sealing.Therefore,the safety and reliability of high strength bolt will directly affect the stability and safety of the whole machine.As the unit becomes larger and larger,the working environment is getting worse and worse,the important connection system for wind turbine,in particular,the high failure rate of high strength bolts in the screw pitch system is higher,which directly affect the normal operation of the unit and caused huge economic losses.Therefore,it is of great significance to study the fault diagnosis of the high strength bolt fracture of the wind turbine system.In this paper,the problem of high strength bolt failure of large scale wind turbine pitch system is studied from the following aspects.(1)According to the basic principle of aerodynamics,the structure and working principle of the variable pitch system of wind turbine are presented,which are used to analyze the distribution of the root load.Finally,the method for calculating the load of the blade flange bolt is obtained.The results provide a theoretical basis for the study of high strength bolt strength and fault diagnosis methods.(2)In view of the limitations of traditional mechanical fault diagnosis methods----based on linear system,which is not consistent with the nonlinear failure state of the pitch system.The nonlinear research method is less used in the wind power high strength bolt failure.In this paper,a fault diagnosis method based on the theory of nonlinear system is proposed,The nonlinear contact model is built by using the finite element software,Then,The theoretical calculation and simulation results are compared to verify the accuracy of the model.The analysis method provides a theoretical basis for the high strength bolt test.(3)Based on scientific rigor,to find out the real reason for the failure of high strength bolts,We need to analyze the experimental data on the spot.According to the simulation results of the previous chapter,we provide the sensor placement position and theoretical basis for the test.Through the analysis of the measured signal,the reasons for the failure of high strength bolts are obtained.(4)In order to find the root cause,According to the nonlinear contact relationship of the pitch system,based on the nonlinear theory of SchmidtandNeuper,The relationship between the flange bolt connection system is analyzed,The relationship between the working load and the stress of the bolt under the central moment of the blade flange is derived.Through theoretical analysis and simulation results,the rationality and applicability of Schmidtand-Neuper nonlinear theory in bolt fault diagnosis are verified.Finally,Based on the results of finite element analysis and the experimental results,the origin of high strength bolt fracture is obtained.The accuracy and effectiveness of the proposed method are verified by the results.