风电机组机舱近尾流的数值模拟研究

Numerical Investigations of Near Wake Flow on Wind Turbine Nacelle

机舱风速是风电机组重要的监测参数。机舱风速受到风轮的尾流影响,与风轮上游来流风速有一定差别。对机舱风速的修正需要研究风电机组的机舱近尾流。采用计算流体力学(CFD)模拟对某大型风电机组在典型风速下机舱附近的近尾流结构进行了研究。在计算功率与设计功率值吻合较好的基础上,分析了下机舱近尾流分布,及机舱风速仪位置的风速变化。研究发现非定常模拟结果比定常模拟更接近设计结果。采用转子冻结法的定常模拟,叶片位置对机舱风速有很大影响。定常计算低估了机舱壁面附近的风速波动。叶片的周期旋转对时均风速大小有一定影响,但并不显著;对机舱风速的方向影响明显,且总是偏向旋转方向。在机舱上方到翼型段高度之间存在一个风速波动较小的位置,更适宜安装风速仪。

Nacelle wind speed is one of important monitor parameters to wind turbine. The flow around the anemometer on nacelle is influenced by the wind turbine rotor, resulting in some difference from the upstream wind speed. The investigation of nacelle near wake flow is used to calibrate the nacelle wind speed. The paper investigated the near wake flow field around the nacelle of a utility-scale wind turbine by using the computational fluid dynamics(CFD) numerical simulation method. The computed power agrees well with the design value. The wake flow field around the nacelle and wind speed profile at anemometer position are analyzed. The simulation results show that the overall performance of unsteady numerical simulation is closer to the design case than that of the steady numerical simulation. The position of blade cause a great impact on the nacelle wind speed by using frozen rotor steady simulation method. It underestimate the wind speed fluctuate around the nacelle. The periodic rotation of blade may cause substantial influence on the nacelle wind velocity magnitude, but not be very obvious. However, blade rotate around one resolution take great influence on the wind velocity direction, and inclined towards the rotation direction. There is a less fluctuating position from the top of nacelle to the height of airfoil section, where is more suitable to install the anemometer.