叶尖预弯加长对风电机组气动特性的影响研究

Investigation on Influence of Blade Tip Pre-bend and Lengthening on Aerodynamic Characteristics of Wind Turbine

叶片加长是有效提升风电机组出力的手段。在叶尖进行加长时需要考虑叶片的预弯。为分析加长段预弯设计对大型风电机组气动特性的影响,以DTU 10MW风电机组为模型,采用CFD数值模拟方法,研究直叶尖加长和预弯叶尖加长两种叶片加长方式对风电机组气动性能的影响,分析叶片延长段不同展向截面的气动力和周围流场的流动特性。研究结果表明,当叶片型线投影长度相等时,两种加长叶片推力增幅基本一致,预弯加长叶片功率增量约为直加长叶片的60%;预弯角使得截面翼型吸力面弦长前半段负压减小,导致翼型上下表面压差减小。叶尖三维流动增大了叶片和周围流体的摩擦损耗,预弯设计进一步增加了叶片附近流向和径向速度的扰动,使得叶尖三维效应作用范围更广,风能吸收效率降低。研究成果可为大型风电机组叶片加长改造提供参考。

Blade lengthening is an effective method to increase the output of wind turbine.When lengthening the blade tip,it is necessary to consider the blade pre-bend.To analyse the influence of lengthening section pre-bend design on the aerodynamic characteristics of large wind turbine,DTU10MW wind turbine was used as model,and CFD numerical simulation method was used to investigate the effects of straight blade tip lengthening and pre-bend blade tip lengthening on the aerodynamic characteristics of wind turbine.The aerodynamic force and flow characteristics of the surrounding flow field at different spanwise sections of the blade lengthening section were analysed.The investigation results indicate that when the projected length of the blade profile is equal,the thrust increase of the two types of lengthening blades is basically same,and the power increase of the pre-bend lengthening blade is about 60%of the straight lengthening blade;The pre-bend angle reduces the negative pressure in the first half of the chord length of the cross-section airfoil suction surface,resulting in a decrease in the pressure difference between the upper and lower airfoil surfaces.The three-dimensional flow at the blade tip increases the friction loss between the blade and surrounding fluid,and prebend design further increases the disturbance of the flow direction and radial direction velocity near the blade,resulting in a wider range of three-dimensional effects at the blade tip and decrease in wind energy absorption efficiency.The investigation can provide reference for blade lengthening reconstruction of large wind turbine.