| Wind energy is one of the clean energy sources of renewable energy.As an important equipment for utilizing wind energy,large-scale horizontal-axis wind turbines have always been a hot research topic.In recent years,with the promotion of distributed wind power,the installed location of wind turbines is getting closer and closer to the range of human activities,and the noise problem is also increasing.Past studies have shown that the noise generated by wind turbines can affect people’s physical and mental health.The aerodynamic noise from the blades is the main source of wind turbine noise.Therefore,this paper has carried out the research on the aerodynamic noise of wind turbine special airfoils and wind turbine blades,and carried out the optimization design of noise reduction blades.First of all,in this paper,the special airfoil NH02＿40 for wind turbines is used as the research object,and the CFD/FW-H method is used to study the influence of incoming flow parameters on the airfoil aerodynamic noise,and reveal the relationship between airfoil wake vortex shedding and airfoil aerodynamic noise emission.The results show:(1)Within the range of 0° to 15° angle of attack,the airfoil has the lowest aerodynamic noise at 3° angle of attack.Except for 3° angle of attack,other attack angles show that the larger the angle of attack,the higher the noise emission level.it is found that there is a positive correlation between the aerodynamic noise emission level of the airfoil and the strength of the shedding vortex behind the trailing edge of the airfoil.The higher the intensity of the shedding vortex behind the trailing edge of the airfoil,the higher the noise radiation level;The aerodynamic noise of the airfoil has a small loss in the upstream and downstream directions of the chord line,showing the propagation characteristics of a dipole sound source;as the monitoring distance increases,the aerodynamic noise decreases significantly.(2)Under the condition of small angle of attack,the frequency of the aerodynamic noise peak at different wind speeds is relatively close.When the angle of attack is larger,the lower the wind speed,the lower the frequency of the noise peak;At the same angle of attack and different wind speeds,the airfoil also shows a positive correlation between the aerodynamic noise radiation level and the strength of the vortex shedding behind the trailing edge of the airfoil;the airfoil aerodynamic noise sound pressure level at the two wind speeds both presents a dipole sound source;As the angle of attack increases,this dipole characteristic becomes less obvious.(3)Numerical simulation results show that the change of turbulence has little effect on the aerodynamic noise of the airfoil,which may be related to the faster attenuation of turbulence in the calculation domain.At most angles of attack,when the turbulence degree increases,the low-frequency noise of the airfoil slightly increases;The change of turbulence has almost no effect on the airfoil aerodynamic noise propagation characteristics,and the airfoil aerodynamic noise still presents the propagation characteristics of a dipole sound source.At most angles of attack,when the degree of turbulence increases,the low-frequency noise of the airfoil rises slightly;Under different turbulence intensities,the airfoil aerodynamic noise emission still exhibits the propagation characteristics of a dipole sound source.Secondly,this paper takes a 3MW wind turbine as the research object,couples the wind turbine blade element momentum theory and the airfoil aerodynamic noise BPM theory,develops integrated prediction code for wind turbine aerodynamic performance and blade aerodynamic noise,and studies the aerodynamics of the wind turbine blades under different incoming flow conditions and different operating parameters.Noise characteristics,comparing the effects of different sound sources on the aerodynamic noise of wind turbine blades.The results show:(1)The value prediction by BPM model and the experiment value agree well,that is,BPM theory can be used to predict the aerodynamic noise of wind turbines.(2)The wind speed increases,the blade turbulent inflow noise changes little,but the bluntness trailing edge noise of the blade self-noise is reduced.The separation-stall flow noise and the turbulent boundary layer trailing edge noise rise more obviously,and the wind speed increases from 8m/s to 16 m /s,the total sound pressure level of the blade has increased by 6.93 d B;The change of the incoming wind shear index has little effect on the aerodynamic noise of the wind turbine blades.The wind shear index increases from 0 to 0.4,and the total blade sound pressure level does not exceed 0.15 d B;The change of the incoming flow turbulence has a more obvious impact on the blade aerodynamic noise.The turbulence degree increases from 5% to 25%,and the blade turbulent inflow noise continues to rise,but the rising amplitude gradually slows down,and the total sound pressure level rises by6.86 d B.(3)the speed of the rotor speed increases,and the turbulent flow noise of the blade has increased to a certain extent.The bluntness trailing edge noise of the blade self-noise has the most obvious rise,separation-stall flow noise and the turbulent boundary layer trailing edge noise rises slowly.The rotor speed increases from 10.8rpm to 14.8rpm,and the total blade sound pressure level increases by 4.67 d B;the pitch angle increases,and the blade turbulent flow noise basically does not change,the separation-stall flow noise and turbulent boundary layer trailing edge noise of The blade self-noise.The noise at the trailing edge of the boundary layer decreased significantly,the pitch angle was increased from-2° to 2°,and the total sound pressure level of the blade dropped by 3.57 d B.Finally,using the improved NSGA-Ⅱ algorithm,based on the wind turbine BEM theory and the airfoil aerodynamic noise BPM model,the shape parameters of the blade are used as the optimized variables,and the wind turbine has the largest annual power generation and the smallest blade aerodynamic noise sound pressure level as Optimize the target,optimize the shape of the blades of a 3MW wind turbine.The results show that:(1)There is a mutual restriction between the two optimization goals of the maximum annual power generation of the wind turbine and the minimum aerodynamic noise sound pressure level.When the annual power generation of the wind turbine increases,the aerodynamic noise of the blades also increases.(2)Through this optimization design,a new blade with a 2.84 d B(4.08%)reduction in aerodynamic noise is obtained without a decrease in annual power generation and a new blade that meet the requirement of no increase in aerodynamic noise and an increase in annual power generation of 534.51MWh(4.87%). |
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