基于流固耦合偏航状态下风力机气动噪声研究

Aerodynamic noise of wind turbine blades becomes one of the most important factor restricted its promotion in recent years. The wind turbine works always in a yawing state for the variable wind direction in nature, and it is the main reason of the aerodynamic performance of wind turbine decreased and the wind turbine suffered fatigue damage easily. Meanwhile, this problem caused the asymmetry around the blade aerodynamic field of and turbulent flow and vortex enhanced. However, the influence and regulation mechanism of the aerodynamic noise of wind turbine in yawing state are still interpreted completely and described in principles and most of the aerodynamic and strength properties are isolated and without consider the interactions between the blade aerodynamic pressure and the blade deformation. The aerodynamic asymmetry around the blade, the turbulence and vortex with the yaw factors in yawing state were studied in this project via the high-frequency PIV monitor flow field. Moreover, the variety performance of wind turbine aerodynamic noise with flow field were also analyzed through the analysis system monitor of vibration and noise of the collection with the 60 channels. Based on the above work,the aerodynamic properties of the blade considered the effect of aerodynamic pressure and deformation were obtained according to the repeated numerical iteration of the blade deformation and flow by the interpolation method of the fluid solid coupling surface. The associated mechanism of the yaw factors associated with the aerodynamic noise in two-way fluid-structure coupling were discussed.

风电叶片的气动噪声问题已成为其推广的重要制约因素之一。自然界中风向的多变，使风力机处在偏航状态下工作，是造成风力机气动性能下降、风力机发生疲劳损伤的主要诱因，还引起叶片周围气动场的不对称性及湍流和涡旋的增强。但是，至今偏航对风力机气动噪声的影响规律和调控机理仍未得到完整的解释和原理性描述，且大多分别针对气动和强度性能单独进行，没有考虑叶片气动压力和叶片变形的相互作用。本项目拟通过高频PIV监测流场变化，获得偏航状态下叶片周围气动场的不对称性、湍流和涡旋随偏航因素的变化特性。同时，通过60通道的振动噪声采集分析系统监测风力机气动噪声随流场变化的表现。在上述两项工作的基础上，通过在流固耦合面插值的方法，考虑叶片变形和流动区域的反复迭代并数值求解，得到稳定的考虑气动压力和变形效应的叶片气动性能，寻找偏航因素变化与气动噪声间的关联性和关联机理。

气动噪声问题已成为风力机推广的重要制约因素之一。自然界中风向多变，使风力机处在偏航状态下工作，是造成风力机气动性能下降、发生疲劳损伤的主要诱因，还引起叶片周围气动场的不对称性及湍流和涡旋的增强。风力机叶片受到自然风的作用会导致叶片变形，而叶片变形又会影响风力机周围的流场，进而影响气动噪声。.本项目利用高频PIV监测不同材质叶片风力机绕流及尾迹流场变化，获得偏航状态下叶片周围气动场的不对称性、湍流和涡旋随偏航因素的变化特性；采用双向流固耦合方法模拟风力机流场及声场，得到考虑变形效应的叶片气动性能及气动噪声；利用声阵列研究偏航状态下不同工况声源特征和传播路径，寻找偏航对风力机气动噪声影响；利用自回归滑动平均方法研究风力机在极端工况下的动力响应特性；验证耦合风电场参数化模型的天气预报模式对大规模风电场风资源特性评估的准确性。.结果表明：叶尖涡沿径向位置开始出现明显的差异，出现一上一下的“交互跳跃”现象，中心涡是以旋转方向相反的正负涡成对出现，呈现一排；沿叶片展向轴向平均速度和平均动能逐渐增大，轴向脉动速度呈先减小后增大的趋势，在相对半径0.85R处降到最低；未耦合方法低估了吸力面压强的变化，流固耦合发现风力机输出功率随偏航角增大的下降程度增大，且更接近实验值，找到耦合前后声压级随轴向距离变化规律，最大声压级出现在叶片中部；偏航导致风力机尾迹中心产生一定程度的偏斜，尾迹形状卷曲不对称，尾迹缩短；随着偏航角的增大，尾迹偏转角增大，风轮上、下侧尾迹偏转差别增大，声压级呈上升趋势；旋转噪声源位置不随工况及偏航角度的改变而变化，噪声源最大位置在靠近叶尖0.78R处；风力机在极端的工况下主要振型为扭转，尾流效应的强度和范围不仅与风资源特性有关，还与风电场的规模及地形特征密切相关。.本项目发展了风力机近场气动特性研究的实验和数值模拟方法，建立了风力机偏航流动和气动噪声的数值模拟计算平台，实验对比显示该平台拥有较高的精度，为今后风力机流动和噪声的研究提供了一种新方法。