四维时空不均匀尾流影响下风力机功率及气动载荷分析

Analysis of wind turbine power and aerodynamic loads influenced by four-dimensional spatiotemporal non-uniform wake

  • 摘要: 处于尾流区与处于自由流场的风力机气动特性差异明显。为了量化风力机气动特性受尾流影响规律,提出了一种基于三维时变尾流模型(3DJGF-T)耦合改进的叶素动量理论(BEM)的风力机气动特性计算方法。首先,分别以正弦风、自由风作为上游机组输入风况,使用3DJGF-T尾流模型计算,得到尾流场内风况的时空变化特征,并进行外场实验验证;其次,以上述尾流场内随空间位置点和时间的不均匀分布的流场为边界条件,研究处于不同尾流下游纵向位置(x=5D、6D、7D、8D)及水平位置处(全尾流、1/2尾流、3/4尾流、全偏尾流)的风轮和单叶片功率、转矩、轴向力的时空变化规律。对比分析结果显示:下游纵向位置变化会同时改变尾流的时间与空间特性,对载荷及功率产生更加复杂的波动影响,纵向距离每增加1D,风轮功率增大约10%;相比之下,风力机水平位置的变化仅影响尾流的空间特性,风轮功率损失随着靠近尾流中心而逐渐增大,相较于全偏尾流,1/2尾流、3/4尾流和全尾流的功率平均值相对损失分别为23.7%、44.3%、61.2%;当来流为自由风时,其风速变化比正弦风更快、随机性更强,导致风力机机组承受的载荷功率波动更大。

     

    Abstract: The aerodynamic characteristics of wind turbines operating in the wake region exhibit significant differences compared to those in free-flow conditions. In order to quantify the influence of wake on the aerodynamic characteristics of wind turbines, this paper proposes a method for calculating the aerodynamic characteristics of wind turbines based on a three-dimensional time-varying wake model (3DJGF-T) with a coupling-improved blade element momentum (BEM) model. Firstly, using sinusoidal and free-stream wind conditions as upstream turbine inputs, the 3DJGF-T wake model is employed to obtain the spatiotemporal characteristics of the wind field within the wake, and the external field experiments are conducted for validation. Secondly, utilizing the unevenly distributed flow field within the wake as the boundary condition in terms of spatial location points and time, the spatiotemporal variations of wind turbine rotor and single-blade power, torque, and axial force are investigated at different downstream longitudinal positions (x=5D, 6D, 7D, 8D) and horizontal positions (fully wake, 1/2 wake, 3/4 wake, and full-half wake) with the comparative analyses are performed. Results indicate that changes in the downstream longitudinal position will simultaneously alter the temporal and spatial characteristics of the wake, resulting in more complex fluctuations in load and power. With every increase of 1D in longitudinal distance, the rotor power increases by approximately 10%. In contrast, variations in the horizontal position of the wind turbine only affect the spatial characteristics of the wake, with rotor power losses gradually increasesing as the turbine approaches the center of the wake. Compared to the full-half wake, the relative average power losses of 1/2 wake, 3/4 wake, and full wake are 23.7%, 44.3%, and 61.2%, respectively. When the inflow is free wind, it exhibits faster variations in wind speed and stronger randomness compared to sinusoidal wind, causing greater fluctuations in the load power of the wind turbine.The findings of this study provide important reference value for wake regulation and micro-siting in wind farms.

     

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