Research On Strain Detection Method Of Wind Turbine Blade Based On Fiber Bragg Grating

Wind power generation plays a key role in solving global climate and energy problems.It is of great significance to ensure the safe and stable operation of wind turbines.Blade is one of the key components of large wind turbine.Its health state is related to the safety,stability and efficient operation of the whole system,and affect the efficiency of power generation.Therefore,it is necessary to conduct in-depth research on wind turbine blade health monitoring technology.The strain signal on the blade surface can reflect the health state of the blade comprehensively and is convenient to collect,so it is an ideal carrier signal of state information.Based on the fiber grating sensing technology,this study researches on the strain detection method of wind turbine blades,aiming at making breakthroughs and innovations in related basic science research,and solving the urgent needs of strain detection of wind turbine blade components,which can ensure the efficient work of the wind turbine,reduce operation and maintenance cost and increase the utilization rate of wind energy to improve the climate and energy status.The thesis mainly focuses on the following aspects:1.The classical aerodynamics theory of wind turbine blades is studied and studied,and the coupling effect theory between blades and air flow field is comprehensively considered.Then the loads of wind turbine blades(including gravity load,centrifugal force load and starting load)are analyzed theoretically.Based on the boundary conditions and the idea of finite element analysis,the stress and strain calculation theory of wind turbine blade was studied in detail.It provides a theoretical basis for the subsequent numerical simulation analysis and experimental design.2.The establishment of three-dimensional digital model of wind turbine blades is established,and multi-objective numerical simulation is carried out according to different working conditions.The load distribution law,deformation variation trend and strain distribution law of single blade and impeller were obtained,and the sensitive position and direction of blade surface were found.Finally,through modal analysis,the first five natural frequencies and vibration shapes of the blade are obtained,which provides sufficient preparation for the following research work.3.Starting from the application of fiber Bragg grating(FBG)detection technology in blade strain detection,the principle of FBG strain detection was firstly studied.Secondly,the hardware and software of the detection system are researched and developed.Including the sensor of various parameters,the number of layout,paste position and installation angle and other aspects of the design.After comparing the characteristics of various demodulation methods and multiplexing technologies of FBG,the most suitable type is selected and the architecture of FBG detection system is designed.It also includes the software development of signal acquisition and recording program and data processing and analysis program.This provides technical support and theoretical guidance for the subsequent experimental exploration.4.According to the detection method of FBG designed above,the platform of the detection system of blade surface strain FBG is built.The feasibility and effectiveness of the proposed method were verified by testing the blade strain under two different conditions of linear distributed load and impact load.Aiming at the problem of blade surface impact detection,a new method of wind turbine surface impact location was proposed,which transformed the complex physical problem into a simple mathematical parameterized problem.In the data processing work,the variational mode decomposition(VMD)algorithm was innovatively introduced into the wind turbine blade surface strain detection,combined with the Teager energy operator to enhance the instantaneous energy characteristics of the signal and improve the time resolution.The experimental results show that the relative error of more than 97% is less than 0.03,and the detection effect achieves a high accuracy,which provides a new idea for the accurate positioning of wind turbine blade surface impact.