Study On Aerodynamic Characteristics And Structural Response Of Wind Turbine Blade With Pitch Failure At Cut Out Wind Speed

With the rapid development of wind power generation,wind turbines are moving towards large-scale development,and their installed scale and capacity are constantly increasing.The increase in length and flexibility of large-sized wind turbine blades leads to more complex aerodynamic loads,which poses a challenge to how to ensure the stability of blades and ensure the safe operation of wind turbines.Among many accidents such as blade damage,fracture,or complete machine overturning,a certain proportion of accident damage occurs when the wind turbine reaches the cut-out wind speed due to pitch failure,which makes the blades unable to withstand the load.Based on the above issues,this paper takes the NREL 5 MW wind turbine as the research object and uses numerical simulation methods to study the complex aerodynamic loads and structural dynamic response of blades caused by pitch failure of wind turbines under cut out wind speed.The main job responsibilities are as follows:Firstly,the calculation principles in relevant numerical simulation methods are used to analyze the pitch fault of wind turbines.Computational fluid dynamics(CFD)method is used to discretize the computational domain of the aerodynamic side in fluid analysis and fluid solid coupling through finite volume method;In the numerical simulation of fluid solid coupling,the solid side adopts the finite element analysis method,and the computational domain is discretized using the finite element method.The analysis of data exchange between fluid and solid domains in numerical simulation of fluid solid coupling lays a theoretical foundation for subsequent related research.Secondly,the NREL 5 MW wind turbine was parameterized and three-dimensional modeling was carried out,and the blade composite material was laid,and the finite element model of the wind turbine blade was built according to the actual production process.At the same time,the tensile strength of the main beam structure is tested,and the test results are compared with the numerical simulation results to verify the accuracy of the blade composite material layup,which has practical application value for the study of aerodynamic load and structural response of the blade.Then,numerical simulation analysis was conducted on the blade aerodynamic load during pitch failure and successful pitch change,and the accuracy of numerical calculations based on the SBM model was verified by comparing the simulation results of the SBM model and the FBM model.Analyze the aerodynamic load and flow field characteristics during pitch failure and successful pitch change,and demonstrate the necessity of numerical simulation of blade pitch failure.At the same time,analyze the aerodynamic load and flow field characteristics of blade pitch faults at different azimuth angles,further study the characteristics of blade pitch faults,and provide relevant research and data for subsequent research.Finally,a bidirectional strong fluid solid coupling numerical simulation was used to investigate the aerodynamic characteristics and structural response of wind turbine blades with pitch failure and successful pitch adjustment.The influence of azimuth angle was also explored by studying typical pitch failure blades at azimuth angles.At the same time,the structural characteristics of the blades were analyzed through bidirectional weak fluid solid coupling and compared with the simulation results of bidirectional strong fluid solid coupling.Research has found that compared to aerodynamic analysis alone,the fluctuation range of the flapping direction torque in fluid solid coupling is larger,and the difference between torsional torque and shimming torque is smaller.Buckling instability phenomenon occurs at different azimuth angles,and the 0 ° azimuth angle is the most obvious.In some cases,bidirectional weak fluid solid coupling can obtain blade structural characteristics by saving considerable computational resources,but the impact of inertia effects and geometric nonlinearity on blade structure cannot be considered.