低风速风机非光滑叶片减阻特性研究

Drag reduction characteristics of non-smooth blade of low wind speed fan

针对复杂地形低风速条件下,风力发电机叶片所受阻力增大导致气动性能降低等问题,以2.5 MW低风速风机叶片为研究对象,结合凸包非光滑表面减阻理论,对非光滑叶片减阻特性进行了研究。首先,定义了变异凸包的结构参数,确定了凸包模型的尺寸阈值,设计了4因素4水平的正交试验,得到了16组不同形状的变异凸包单元;其次,基于低风速工况分析,将变异凸包非光滑表面结构布置于叶片尾翼,利用Fluent软件对不同低风速工况下变异凸包非光滑叶片的减阻性能进行了数值仿真分析,对不同凸包结构参数对非光滑叶片减阻特性的影响进行了研究;最后,对变异凸包非光滑表面减阻的效果与作用机理进行了研究。研究结果表明:低风速条件下非光滑叶片最大减阻率为5.89%,影响叶片减阻性能的凸包主次参数为底面半径R、高度H、排列间隔D、顶点偏移距离L;变异凸包非光滑表面通过拟序结构改变了壁面剪切应力分布,有序的速度与压力梯度变化促进了边界层流体的流动,提升了低风速条件下叶片的减阻性能。

Aiming at the problem of aerodynamic performance reduction caused by increased drag on wind turbine blade under complex terrain and low wind speed conditions,taking 2.5 MW low wind turbine blade as the research object,combined with the non-smooth surface drag reduction theory of convex hull,the drag reduction characteristics of non-smooth blade were studied.Firstly,the structural parameters of variable convex hull were defined,and the size threshold of convex hull model was determined,sixteen groups of variable convex hull elements with different shapes were obtained by orthogonal experiments with four factors and four levels.Secondly,based on the analysis of low wind speed conditions,the variable convex hull non-smooth surface structure was arranged on the blade tail fin.Fluent software was used to carry out numerical simulation analysis on the drag reduction performance of the variable convex hull non-smooth blade under different low wind speed conditions,and the influence of different convex hull structural parameters on the drag reduction performance of the non-smooth blade was studied.Finally,the effect and mechanism of drag reduction on non-smooth surface of variable convex hull were studied.The results show that the maximum drag reduction rate of non-smooth blades is 5.89%under low wind speed.The primary and secondary parameters of convex hull affecting the drag reduction performance of blades are as follows:base radius R,height H,spacing D,vertex offset distance L;The non-smooth surface of the variable convex hull changes the shear stress distribution on the wall through the quasi-ordered structure.The ordered velocity and pressure gradient changes promote the flow of boundary layer fluid,and improve the drag reduction performance of the blade at low wind speed.