Acoustic Array Measurement Of Sound Pathway Of Near Wake Track Of Yaw Underwind

Wind energy is a kind of pollution-free renewable energy.Using wind power generation technology to solve the energy shortage in production and life is a reliable way.Developing wind power is a trend in the world and it is very important for human production and life.As the single-machine power of wind turbines continues to increase,the noise generated by wind turbines in large-scale wind farms has become more and more prominent,causing certain impacts on the production and living of surrounding humans and animals in the natural world.As people's awareness of environmental protection gradually increases,the research on the aerodynamic noise of wind turbines becomes more and more important.However,there are few relevant studies on the propagation rules of noise paths in the near-wake flow field of the running wind wheel.Based on the open end of the wind tunnel,the main distribution of low-frequency noise sources and the propagation path of the maximum acoustic energy of the horizontal-axis wind turbine under different yaw angles are studied.The characteristics of the sound source of different leaf structures are compared.The trajectory of the propagation path of the maximum acoustic energy of the near wake of the wind turbine and the relationship between the vortex sounds were initially found.In this experiment,when studying the propagation trajectory of the acoustic energy concentration location,11 different measurement sections of the rotation plane adjacent to the rear were arranged at equal intervals L,and the data were collected and analyzed and the acoustic noise of each section was used in the acoustic post-processing software.The source coordinates are averaged and a propagation path map is made.It is found that the concentrated sound energy propagation path of the wind turbine at each rotating fundamental frequency is in the form of a helical curve with gradually decreasing arc to the axial direction outside the tip,and the direction of rotation is opposite to that of the rotation of the wind wheel during the propagation process;It is known that the sound pressure level SPL is gradually decreasing as the distance between the measurement section and the rotating surface increases.In the B1/K2 wind tunnel laboratory,which can provide wind speeds of up to 20m/s,the array noise source location test technology is applied to horizontal axis wind turbines,and the noise data acquisition is performed by optimizing the array measurement position,and acoustic post-processing is combined with acoustics.The calculation area grid of the software is refined to obtain the position information of the sound source and the spectrum of the sound signal.The result of the experiment shows that the sound field data of the rotating wind turbine can be obtained through the acoustic array,which provides a theoretical basis for future research on the aerodynamic noise of the wind turbine.Through analysis of the noise spectrum map and sound source distribution map,it is found that the acoustic energy of the wind turbine noise source is mainly from the low frequency range(200 Hz)at different yaw angles,and the frequency of the maximum acoustic energy of the noise is at the fundamental frequency of the wind turbine blade rotation.The experimental results show that as the wind speed or the tip speed ratio of the wind turbine increases,the sound pressure level SPL and the rotating fundamental frequency of the wind wheel rotation noise gradually increase,while at the same speed,with the increase of the yaw angle,The sound pressure level SPL under the same working conditions also showed an upward trend;when measuring the position of the rotational noise source under the same section,it was found that it did not change with the change of operating conditions and yaw angle,and the noise was measured at the rotating surface of the wind turbine.The location of the source is at 0.78 R near the tip of the blade;when studying the airfoil noise data of the same model with different leaf structure,it was found that only the sound pressure level SPL has decreased under the same working conditions and decreased with the increase of wind speed.The trend has increased,and the location of sound energy has not changed.