湍流度对水平轴风力机尾流及转矩特性的影响

基于一台33 kW的水平轴风力机,利用大涡模拟耦合致动线的方法,模拟均匀来流以及不同湍流度来流条件下的风力机尾流流场,研究湍流度对水平轴风力机尾流及转矩特性的影响.结果表明:湍流来流时风力机尾流与周围流场的能量交换比均匀来流时更强,湍流掺混速度更快,从而使得尾流区速度恢复加快,且湍流度越大,速度恢复越快;相较于均匀来流,湍流来流时风力机尾流速度的最大亏损率减小,但湍流度大小对尾流速度最大亏损率影响较小;尾流半径增长速率在风轮平面至风轮后两倍直径范围内逐渐减小,在两倍直径之后基本不变;湍流会使尾流膨胀程度增强,且湍流度越大,膨胀程度越强;在11 m/s风速条件下,湍流度增大导致风轮转矩时均值减小,波动幅度增大,风轮转矩在高频与低频部分的能量升高,并且低频部分能量升高得更快.

Study on turbulence effects on the wake and torque characteristics of horizontal axis wind turbine

Based on a horizontal axis wind turbine of 33 kW, the wake flow field of thewind turbine under condition of uniform flow or turbulent flow of different intensities is simulated by using the method of large eddy current to simulate coupled actuator line, and the effect of turbulence on the wake and torque characteristics of horizontal axis wind turbine is also investigated. Simulated results indicate that: the energy exchange between the wake and the surrounding flow field of the wind turbine in the turbulent flow is stronger than that in the uniform flow. The turbulent velocity is faster therefore, so that velocity recovery in the wake area becomes faster as a result. The greater the turbulence is, the faster the velocity recovery may be. Compared with the uniform flow, the maximum loss rate of the wake velocity of the wind turbine decreases during turbulent flowing, but the degree of turbulence has less effect on the maximum loss rate of the wake velocity. The expanding rate of wake radius decreases gradually in the range from the plane of the wind turbine to twice the diameter of the wind turbine, and remains basically unchanged after twice the diameter. Turbulence will increase expansion of the wake, and the greater the turbulence is, the stronger the expansion will be. Under the condition of 11 m/s wind speed, the increase of turbulence leads to not only the decrease of mean value of the wind turbine torque, and the increase of fluctuation amplitude, but also the increase of energy consumption of the wind turbine torque in high frequency and low frequency ranges. The increase of energy consumption in the range of low frequency is faster.