【作者】 赵华；

【导师】 周鹏展；

【作者基本信息】 长沙理工大学 ， 动力工程及工程热物理， 2015， 硕士

【摘要】 为了保障国家能源安全、保护生态环境、促进社会和经济的可持续发展,近年来我国风电产业迅猛发展。受电网“消纳”能力的限制,目前我国风电应用正在向沿海和中部风资源相对丰富、经济比较发达的地区扩张,但由于沿海和中部地区人口比较稠密,风力机在运行时产生的气动噪声会对风电场附近居民的生活造成影响,风力机叶片气动噪声问题已开始引起研究者的关注。本文运用FLUENT软件,对某2MW机型风力机叶片的空气速度场和压力场进行数值模拟,结合气动声学理论对风力机叶片的气动噪声进行预测,通过单参数影响法,逐一分析了来流速度、风轮转速和桨距角等运行参数对风力机叶片气动噪声的影响。研究结果表明:（1）额定工况下,风力机叶片表面气流速度分布呈现出从叶跟到叶尖逐渐增大的特征,并在叶尖达到速度最大值;风力机叶片表面的压力变化梯度呈现出从叶片前缘向后缘逐渐增加的特征,风力机叶片表面静压和总压变化较剧烈,静压脉动是产生气动噪声的主要因素;随着各个监测点距离风轮旋转平面距离的增加,各个监测点的噪声声压级均随之减小,且沿旋转轴（Y正方向）上的衰减幅度越来越小,甚至趋于平缓,在平行于Y轴方向上靠近叶尖区域的辐射噪声较大,衰减的幅度也很大。（2）风力机叶片表面气流速度、风力机叶片表面压力均随着来流速度、风轮转速的增大而增大,且风轮转速对风力机叶片表面气流速度和表面压力影响较大。动压脉动变化较剧烈的区域,随着风轮转速偏离额定转速的增加,从叶尖部分向叶片弦长最大位置移动;随着来流风速的增加从叶片弦长最大位置向叶尖部分移动;叶片桨距角在0^°10°范围内变化时,风力机叶片表面气流速度、表面压力均随叶片桨距角的增大而增大,但变化幅度较小,说明叶片桨距角对风力机叶片空气流场的影响较小。当叶片桨距角增加到15o时,风力机叶片表面气流速度、风力机风叶片表面压力均略有降低;来流速度、风轮转速和叶片桨距角改变时,各个监测点的噪声声压级变化趋势与额定工况下基本一致,且风轮转速对噪声声压级的影响较大。本文基于以上分析,提出了降低风力机叶片运行时的气动噪声的几种方法:（1）适当降低风力机叶片的转速,可以有效降低风力机叶片表面的气压值,从而降低其气动噪声,尤其是风力机叶片后缘噪声;研究表明,对于所研究的2MW机型,转速从额定转速减小1rpm,气动噪声总声压级可降低12dB。（2）适当降低风力机叶片在额定风速时的叶片桨距角,可以有效降低风力机叶片的气动噪声。本文通过对风力机叶片速度场、压力场的模拟和声场的预测,提出几种降低风力机叶片气动噪声的途径,为降低风力机叶片气动噪声、促进在居民区附近的应用提供了理论参考。</sup>更多还原

【Abstract】 In order to ensure the national energy safety, protect the ecological environment, and promote the sustainable development of the society and economy, the Chinese wind power industry is rapidly developed in recent years. Because of the restriction of grid consumptive capability, the applications of large-scale wind turbine are expanded to the areas that have abundant wind resource and developed economy. For the population is densely in these areas, the aerodynamic noise of the wind turbine would have an effect on the inhabitants near the wind plant. It has drawn the interest of the researchers.In this thesis, the velocity field and the pressure field of a kind of 2 MW wind turbine blade model are numerically simulated with the FLUENT software. Based on the aerodynamic acoustics theory, the aerodynamic noise from the wind turbine blades can be predicted. The single parameter method is used to analyze the effect of the operation parameters on the aerodynamic noise, such as wind flow speed, rotate speed and pitch angle. The results show that:(1) Under the rating conditions, the airflow speed distribution on the wind turbine blade surface shows that the speed is gradually increased from the blade root to the blade tip, and it has reached a maximum speed at the blade tip. The pressure gradient change of the wind turbine blade surface shows that the pressure is gradually increased from the blade leading edge to the blade trailing edge, the static pressure and the total pressure changes dramatically. The static pressure change is the major factor to produce the aerodynamic noise. As the distance is increased from the rotor rotating plane to the individual monitoring-station, the noise sound pressure level of the individual monitoring-station is decreased. The attenuating range along the rotational axis is getting less and less, and even to be flat. In parallel to the Y-axis direction, the radiated noise near the zone of the blade tip is large, and its attenuation range is also large.(2) As the wind speed and rotating speed are increased, the airflow speed and pressure on the wind turbine blade surface are also increased. The rotating speed has a greater effect on the airflow speed and the pressure gradient. As the deviation between the rotor speed and the rated speed has increased, the region that the dynamic pressure changes intensely moves from the blade tip to the maximum blade chord position. When the pitch angle is increased from 0 to 10 degree, the airflow speed and pressure gradient on the wind turbine blade surface has increased, but the change ranges are small. It is indicated that the blade pitch angle has less effect than other parameters. When the blade pitch angle has increased to 15 degree, the airflow speed and pressure gradient on the wind turbine blade surface have changed slightly lower. With the change of wind speed, rotating speed and pitch angle, the change trends of the noise sound pressure from the monitoring station are consistent with the rating conditions. The rotating speed has a great effect on the noise sound pressure level.Based on the above analysis, several methods to reduce the aerodynamic noise from the wind turbine blades are proposed:(1) Reducing the rotating speed of the wind turbine blade appropriately can effectively reduce the pressure value of the wind turbine blade surface. Thereby it can reduce its aerodynamic noise, especially the noise from the wind turbine blade trailing edge. Studies have shown that aerodynamic noise of the studied 2MW model can reduce the overall sound pressure level 1 ~ 2dB, as the rotating speed decreases under the rated speed 1rpm.(2) Reducing the blade pitch angle appropriately at the rated wind speed can effectively reduce the aerodynamic noise from wind turbine blades.Based on the simulation of the velocity and pressure field, and the prediction of the sound field of the wind turbine blades, several methods to reduce the aerodynamic noise from the wind turbine blades are proposed. It can provide theoretical reference to reduce the aerodynamic noise from the wind turbine blades, and promote the large-scale wind turbines applications in residential areas.更多还原