水平轴风力机尾迹流场掺混流动的实验研究

摘要

为研究风力机尾迹的流动状态以及掺混规律,在水平轴风力机模型不同尖速比、不同风速的条件下,利用高频PIV系统对风力机下游远至4.5倍风轮直径范围内的尾流数据进行采集.首先对轴向平均速度云图和曲线图进行分析,发现尾迹流场与外部主流区的掺混现象;对比尖速比为4和6,相对半径为0.1R处的平均轴向速度曲线图,发现随着尖速比的增加,尾迹区域的轴向速度恢复的更快,掺混现象更加严重.然后观察径向平均速度云图,发现风轮后方的流体在径向方向的运动规律是外部主流区的流体通过叶尖涡诱导效应区的输运和卷吸作用下持续进入尾迹区域,并与之掺混.最后通过对比不同相对半径处的径向曲线图,得到尾迹流场的状态:先节流降压膨胀,然后压力恢复尾迹收缩;随着外部高压流体的的持续流入,尾迹再次膨胀,直至恢复到来流状态.%The wake data within the range from downstream of wind turbine to 4.5 times of the wind wheel were collected by utilizing the TR-PIV under different wind velocities and tip speed ratio to research the flow regime and the rule of blending on the wake of the wind turbine. Firstly, the phenomenon of blending between the wake field and external mainstream was discovered based on the analysis of cloud chart and curve graph of the average axial velocity, and after comparing the curve graph of the average axial velocity with the tip speed ratios of 4 and 6 and relative radius of 0.1R, it was found that the recovery of the axial velocity in the wake region was faster and the blending was more serious with the increase of the tip speed ratio. Next, by observing the cloud chart of average radial velocity, it is found that the motion of the fluid behind the wind wheel in the radial direction is that through the transport and entrainment of the region of inductive effect of the tip vortex, the fluid of external mainstream continuously comes into wake region and blends with wake field. Finally, by comparing the curve graph of average radial velocity at different relative radius, the result shows that the state of the wake field is: the fluid throttles before the recovery of the pressure and the contraction of wake; with the continuously inflow of external high pressure fluid, the wake re-expands until the recovery of incoming flow state.