Influences Of Inflows On Aero-acoustic Noise Of Horizontal-axis Wind Turbine

The large-scale utilization of wind power has effectively alleviated power shortage and environmental pollution,but the operation of wind turbines will bring noise and cause harm to human health.Therefore,the noise of wind turbines has become one of the main obstacles to the development of wind power.In this paper,a1.5MW three-blade horizontal axis wind turbine is taken as the research object,use the CFD numerical calculation method based on the combination of IDDES turbulence model and FW-H acoustic model to study the influences of inflows on the aerodynamic noise of large horizontal axis wind turbines under facing the wind.The research content and research results are as fo llows:Under the uniform inflow,the changes of the pressure field,velocity field and vortex field of the wind turbine under different wind velocity,different blade tip speed ratios and different turbulence intensities are explored respectively,based on flow field analysis,further explore the noise influence on the wind turbine blade and its surroundings,the strong vortex area(the tip of the blade near the wak e,the center of the hub,and the center near the wake)and the wake area.The results show that under different wind velocity(6m/s?8m/s?10m/s,turbulence intensity is 5%),the decay rate of the noise on the upper and lower surface of the blade is much greater than that of the leading edge and trailing edge of the blade,but the noise decay rate slows down as the wind velocity increases.As the wind velocity increases from 6m/s to 10m/s,the noise at the monitoring points of the hub center,the blade tip near the wake,the center near the wake,and the wake increase respectively by 7.9dB,3.1dB,2.4dB,and 3.7dB,but the growth rate of the strong vortex area decreases.The SPL(sound pressure level)on each section of the wake is axis-symmetric at a phase angle of 90~o,and the SPL at 90~o is 4.1dB greater than that of 0~o and 180~o.At different tip speed ratios(?=5?6?7,wind velocity is 10.4m/s,turbulence intensity is 5%),the decay rate of the noise on the upper and lower surfaces of the blade is much greater than the leading and trailing edges of the blade,and the noise radiation distance is farther than the upper and lower surfaces of the blade.When?is 5 and 7,the noise radiation near the trailing edge of the blade tip is strengthened,and the SPL increases by 4.5dB;but the noise radiation with?=6 is less affected,and its SPL has only increased by 0.5dB.As the tip speed ratio increases,the noise decay rate in the wake region slows down,and its SPL decreases by 6.3dB in the downstream extension.Under different turbulence intensity(I=14%?16%?18%?20%?25%,wind velocity is10.4m/s),when the turbulence intensity increased from 14%to 18%,the noise at t he monitoring points of the hub center,blade tip near wake,center n ear wake,and wake increased respectively by 8.8dB,3.3dB,6.3dB,7.1dB,but increased At the highest turbulence intensity(20%and 25%),it respectively decreased by 8.2dB,2.8dB,5.6dB,and 4.4dB.At high turbulence intensity,the slower the noise decay rate of the wake,the longer the noise radiation distance and the longer the noise propagation.Under the shear inflow,the flow field characteristics of each part under differen t shear indexes are studied.Based on the flow field analysis,the influence on the noise of each area of the wind turbine is discussed.The results show that the SPL of the blade and its surroundings increased by 1.2dB at low shear index(0.1,0.15 and 0.2),but increased by 5.8dB at high shear index(0.25 and 0.3).Under the high shear index,the noise decay rate of the blade and its surroundings is slower than that under the low shear index.At the center of the hub,the SPL at the high shear index is increased by10.3dB compared to the low shear index,but the noise decay rate is slower,and the longer the noise radiation distance.At the center near the wake,the noise decay rate is higher at a higher shear index and faster at a lower shear index.At the wake,the noise decay rate at high shear index is slow,and its radiated noise travels further downstream.At high shear index,the sound source level in the near field increases slightly,but the small difference in SPL in the near field is enhanced in the far field SPL.Based on the analysis of wind turbine flow field,this paper explores the chan ges of aerodynamic noise of large horizontal axis wind turbines under inflows,which has certain reference significance for optimizing the aerodynamic design of wind turbines,and also provides a certain reference for limiting wind turbine noise.