周期性喘振风力机的相平均动力学
Phase-Averaged Dynamics of a Periodically Surging Wind Turbine
摘要：
在流向方向上平移的风力机的不稳定发电与漂浮的海上风力机、风筝安装的空中风力机和其他非传统风能系统有关。为了通过实验研究这个问题，在加州理工学院自主系统与技术中心（CAST）的风扇阵列风洞中，获得了在周期性喘振运动中致动的水平轴风力机的扭矩、转子速度和功率的测量值。实验是在基于直径的雷诺数为$Re_D=6.1\times10^5$和叶尖速度比在5.2和8.8之间进行的。正弦和梯形波的最大浪涌速度高达23%的自由来流速度波形进行了测试。推导了一个线性常微分方程（时间上的一阶）形式的模型，以捕获喘振涡轮机的时间分辨动态。它的系数是利用固定涡轮机的扭矩测量值获得的，不需要非定常校准。它的预测与实测的振幅和相位响应数据相比毫不逊色。此外，在高叶尖速比和喘振速度下，在实验中观察到周期平均功率比稳定参考情况增加高达6.4%，这可能是由于非定常或非线性空气动力学效应。相反，在低叶尖速比时，平均功率随喘振速度增加而减小，这可能是涡轮叶片失速开始的结果。这些结果为周期性喘振风力机非定常发电的优化和控制策略的发展提供了信息，并激发了对风能系统非定常空气动力学的进一步研究。
英文摘要：
The unsteady power generation of a wind turbine translating in the streamwise direction is relevant to floating offshore wind turbines, kite-mounted airborne wind turbines, and other non-traditional wind-energy systems. To study this problem experimentally, measurements of torque, rotor speed, and power were acquired for a horizontal-axis wind turbine actuated in periodic surge motions in a fan-array wind tunnel at the Caltech Center for Autonomous Systems and Technologies (CAST). Experiments were conducted at a diameter-based Reynolds number of $Re_D=6.1\times10^5$ and at tip-speed ratios between 5.2 and 8.8. Sinusoidal and trapezoidal surge-velocity waveforms with maximum surge velocities up to 23% of the free-stream velocity were tested. A model in the form of a linear ordinary differential equation (first-order in time) was derived to capture the time-resolved dynamics of the surging turbine. Its coefficients were obtained using torque measurements from a stationary turbine, without the need for unsteady calibrations. Its predictions compared favorably with the measured amplitude- and phase-response data. Furthermore, increases in the period-averaged power of up to 6.4% above the steady reference case were observed in the experiments at high tip-speed ratios and surge velocities, potentially due to unsteady or nonlinear aerodynamic effects. Conversely, decreases in mean power with increased surge velocity at low tip-speed ratios were likely a result of the onset of stall on the turbine blades. These results inform the development of strategies to optimize and control the unsteady power generation of periodically surging wind turbines, and motivate further investigations into the unsteady aerodynamics of wind-energy systems.
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