风电叶片气动噪声研究

发布时间：2018-06-17 21:35

本文选题：风力机噪声 + 半经验公式　；参考：《中国科学院研究生院(工程热物理研究所)》2014年博士论文

【摘要】：随着风电行业的快速发展,风电机组的单机容量越来越大,叶片长度也越来越长,辐射噪声水平也随之快速增加。已有研究和分析表明,现代大型风电机组的主要辐射噪声来源于叶片的气动噪声,并且气动噪声水平近似和叶尖速度的5次幂成正比关系。风电叶片长度的增加使得叶片柔性增大,产生气动弹性问题,从而诱发额外的辐射噪声。为了满足环境噪声标准的要求,风力机的设计转速需要控制在一定范围内,致使在额定风速下,风能利用系数远离设计最优值,如果能降低叶片的气动噪声使得风力机的限制转速提高,额定风速相应降低,风能就可以得到更充分的利用,同时提高转速还可以降低作用在轴上的扭矩,减少机组的主轴、齿轮箱、发电机等部件的载荷,增强结构安全可靠性。另外,在叶片设计过程中,通过低噪声叶片设计提高风力机的限制转速,从而将最优风能利用系数对应的尖速比进一步提高,可以降低叶片的实度,减少叶片的重量并降低成本。作者利用BPM翼型自身噪声半经验公式和Amiet来流湍流半经验公式预测研究了某2.5MW风力机(GW109/2500)的辐射噪声,噪声预测结果和现场实验结果吻合较好。来流风速对辐射噪声的影响研究结果表明,风力机辐射噪声主要受转速影响,来流风速变化对噪声的影响较小,同理来流风剪切对辐射噪声的影响也较小。另外,研究表明,叶片辐射噪声最大的位置位于叶片展向的80-95%,对于地面某一观察点而言,叶片处于某—特定位置的时刻辐射噪声最大,这些结论都和现场实验测量结果—致。作者对中国科学院工程热物理研究所研发设计的大厚度、钝尾缘翼型的辐射噪声进行了研究,发现来流风速较小时,翼型分离失速噪声占主导,而当来流风速较大时,钝尾缘脱落涡噪声超过分离失速噪声成为主要声源。另外,为了深入分析研究由于叶片的非定常运动引发的气动噪声问题,作者建立了运动翼型的噪声预测模型,并进行了数值验证。推导了二维FW-H方程的频域运动单极子声源公式用于运动翼型的辐射噪声计算,结果表明,由于翼型的非定常运动引起的单极子声源强度大于由于翼型表面非定常载荷引起的偶极子声源强度。随后对运动翼型的非定常流场和声场进行了研究。对于定常入流速度下的浮沉和俯仰运动的翼型,随着翼型运动频率的增大,升阻力系数幅值增大,远场辐射噪声也随之增强。对于湍流来流情况,当翼型浮沉频率较小时,湍流来流使得升阻力系数较定常来流时增大；当翼型浮沉频率增大到0.5Hz时,湍流来流并没有使升阻力系数增大,而是和定常来流结果很相近,作者认为这可能是由于尾涡结构发生改变,导致涡结构对流场的影响超过湍流来流的作用。对于湍流来流下的俯仰运动翼型,可以得到类似结论。
[Abstract]:With the rapid development of wind power industry, the single unit capacity of wind turbine becomes larger and larger, the length of blade becomes longer and longer, and the level of radiation noise increases rapidly. It has been studied and analyzed that the main radiated noise of modern large-scale wind turbine is from the aerodynamic noise of blade, and the level of aerodynamic noise is proportional to the fifth power of blade tip velocity. With the increase of blade length, the blade flexibility increases, resulting in Aeroelastic problem, which induces additional radiation noise. In order to meet the requirements of environmental noise standards, the design speed of wind turbine needs to be controlled within a certain range, so that under rated wind speed, the wind energy utilization coefficient is far from the optimum design value. If the limited speed of the wind turbine can be increased by reducing the aerodynamic noise of the blade, and the rated wind speed is reduced accordingly, the wind energy can be utilized more fully, and at the same time, the torque acting on the shaft and the main shaft of the unit can be reduced by increasing the speed. Gear box, generator and other parts of the load, enhance structural safety and reliability. In addition, in the process of blade design, the limited speed of wind turbine can be increased through the design of low noise blade, so that the tip speed ratio corresponding to the optimal wind energy utilization coefficient can be further increased, and the real degree of blade can be reduced. Reduce blade weight and cost. By using the semi-empirical formula of self-noise of Amiet airfoil and the semi-empirical formula of Amiet turbulent flow, the authors have studied the radiated noise of a 2.5MW wind turbine GW 109 / 2500). The results of noise prediction are in good agreement with the field experiment results. The results show that the radiation noise of wind turbine is mainly affected by the rotational speed, the change of the incoming wind speed has little effect on the noise, and the influence of the shear of the incoming wind on the radiation noise is also small. In addition, it is shown that the position of the maximum radiation noise of the blade lies in the 80-95b of the blade span. For a certain observation point on the ground, the time when the blade is at a certain position is the most radiated noise. These conclusions are all due to the results of the field experiments. The authors have studied the large thickness and the radiation noise of the blunt tail flange airfoil developed and designed by the Institute of Engineering Thermal Physics of the Chinese Academy of Sciences. It is found that the airfoil separation stall noise is dominant when the incoming wind speed is small, but when the incoming flow velocity is large, the airfoil separation stall noise is dominant. The obtuse edge shedding vortex noise is more than the separated stall noise as the main sound source. In addition, in order to analyze the aerodynamic noise caused by the unsteady motion of the blade in depth, the noise prediction model of the moving airfoil is established and verified numerically. In this paper, the frequency domain monopole sound source formula of two dimensional FW-H equation is derived to calculate the radiated noise of moving airfoil. The results show that, The intensity of monopole source caused by unsteady motion of airfoil is larger than that of dipole source caused by unsteady load on airfoil surface. Then the unsteady flow field and sound field of the moving airfoil are studied. For the airfoil with steady inflow velocity, the amplitude of the lift resistance coefficient increases with the increase of the motion frequency of the airfoil, and the far field radiation noise is also enhanced with the increase of the motion frequency of the airfoil. In the case of turbulent flow, when the floatation frequency of airfoil is small, the coefficient of lift resistance increases when the frequency of airfoil is small, and when the frequency of floating and sinking of airfoil increases to 0.5 Hz, the coefficient of rising resistance is not increased when the frequency of airfoil is increased to 0.5 Hz. The results are very close to those of the steady flow. The authors think that this may be due to the change of the wake vortex structure, which results in the effect of the vortex structure on the flow field exceeding the effect of the turbulent flow. A similar conclusion can be obtained for the pitching airfoil under turbulent flow.
【学位授予单位】：中国科学院研究生院(工程热物理研究所)
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM315

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