Aerodynamic Performance Of 5 MW Wind Turbine And Fluid-solid Interaction Analysis Of Blades

High-power wind turbines have been regarded as one of the main ways to reduce R&D costs and improve competitiveness in the industry.The enlargement of the wind turbines increases the length and flexibility of the blade,which increases the possibility of coupled deformation of the blade,resulting in unsteady load fluctuations of the blade,affecting the aerodynamic performance of the blade,destroying the structural stability of the blade and affecting the safe operation of wind turbines.In order to study the influence of the coupling deformation of blades on the wind turbines aerodynamics and structure,this paper takes NREL 5MW wind turbine as the object and uses numerical simulation method to conduct aerodynam ic and fluid-solid interaction analysis of wind turbine models under different working conditions.The main work and conclusions are as follows:(1)Three-dimensional modeling and meshing of wind turbines are carried out.Power verification is carried out under four conditions: 8 m/s,11.4 m/s,15 m/s and 20 m/s.Aerodynamic load distribution and surface flow of blades are analyzed when wind speed is 11.4 m/s.The results show that the aerodynamic loads mainly distribute at 75% R of the blade span direction,and the pressure difference between the upper and lower surfaces of the tip part is the largest,which is beneficial to the blade work.The separation flow of the blade root part also shows that the three-dimensional numerical simulation is necessary to study the aerodynamic performance of the wind turbine.(2)The influence of the tower on the wake of the wind turbine was studied by the large eddy simulation(LES)method.The results show that the obstruction of the rotor causes the wake to diffuse to a certain extent in the flow direction,the symmetry of the wake is destroyed caused by tower.The mutual interference between the wake generated by the tower and the tip vortex of the wind turbine destroys the wake boundary of the wind turbine,which increases the turbulence in the wake.(3)The aerodynamic loads and structural characteristics of blade under 8 m/s 11.4 m/s and 20 m/s conditions were compared and analyzed by unidirectional and bidirectional fluid-solid interaction methods.The results show that the aerodynamic torsion angle increases the local aerodynamic load of the blade tip.However,the bending deformation of the blade causes the reduction of the sweeping area of the wind rotor.As a result,the aerodynamic load obtained by two-way fluid-solid interaction method is smaller than one-way fluid-solid interaction;The tip displacement,aerodynamic torsion angle and blade deformation are the largest when the wind speed is 11.4m/s;When the wind speed is 8 m/s and 11.4 m/s,the equivalent stress and strain values in the middle region of the blade are the maximum;The equivalent stress and strain values of the blade root are the largest when the wind speed is 20 m/s.(4)Two-way fluid-solid interaction analysis of wind turbine blades under extreme wind gusts was carried out.The results show that the flow separation under the two conditions first appears at the root of the blade,and gradually expands to the middle of the blade,and the blade stall occu rs when flow separation occurs in most areas of the blade;The increase of blade aerodynamic load is caused by the increase of wind speed and the deformation of blade,when the wind speed decreases,the fluctuation of blade deformation needs more time to restore stability.The aerodynamic attack angle generated by the coupling deformation makes the stall of the blade advance and deepen,which aggravates the effect of gust on the blade.The equivalent stress and strain of the blade fluctuate with the change of the wind speed.one-way and two-way fluid-solid interaction methods are adopted to study the blades of NREL 5MW wind turbine in this paper,and the blade coupling deformation,aerodynamic torsion angle and equivalent stress strain are obtained under different wind speeds and extreme wind gust conditions,which provides a basis for wind turbine blade design and safe operation.