水平轴风力机尾迹流场PIV实验研究

在水平轴风力机模型不同尖速比条件下,利用PIV粒子图像测速技术对风轮尾迹流场进行了测量。采用锁相平均测量技术,获得了风轮尾迹流场的瞬时速度场、时均速度场、涡量场等有关定量信息,为准确计算风力机的流场、载荷和气动特性等提供了依据。实验结果表明:风轮叶片尾缘后侧的尾迹中存在轴向速度亏损区。尾迹在叶片尾缘生成后,随即发生膨胀。直到风轮下游2倍弦长以后,尾迹低速区逐渐衰减,轴向速度不断增加,尾迹区同时发生收缩现象。风轮尾迹涡从叶片尾缘脱落后,在向下游发展传播过程中,尾迹涡的涡心所形成的运动轨迹是与风轮叶片旋转方向相反的螺旋线,涡量数值随着螺旋线向风轮下游的延伸而减小。由于风力机叶片数少,相邻叶片之间的尾迹基本上不存在互相干扰的现象。

PIV EXPERIMENTAL STUDY ON THE WAKE FLOW OF HORIZONTAL-AXIS WIND TURBINE MODEL

The near-wake velocity field of a model horizontal-axis wind turbine (HAWT) model was measured with a particle image velocimetry (PIV) using a phase-locked averaging technique over a range of tip speed ratios. The data of the instantaneous velocity field, the time-averaged velocity field and vortex field of the wake were obtained. These data can be used to identify and better understand the physical attributes of the complex flow field and to aid the accurate prediction of the performance of HAWT. The distribution of the axial velocity behind the HAWT rotor reveals the expansion and decay of the wake. Two chord lengths downstream of the rotor, the axial velocity defect decreases with developing of the wake, suggesting slightly contracting of the wake there. The results show that the track of the wake centre forms a helical curve whose rotation direction is opposite to that of the rotor during the downstream development of the wake. The magnitude of vorticity decreases with downstream developing of the wake vortex. Because there are few blades in HAWT, the wake system of contiguous blades do not disturb each other.