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作者签名: 日 期:
6
摘 要
风力机叶片工作在复杂的三维旋转流场中,为进一步弄清风力机流场特性,本文通过采用数值模拟的方法,对风力机流场进行了深入的分析,并对叶尖涡进行了控制研究。
本文是基于二维翼型压力分布来展开研究的,首先讨论了二维翼型压力分布受攻角和雷诺数(入流速度)影响的变化趋势,结果表明:压力分布随攻角的变化十分敏感,主要体现在前缘处压力峰及吸力峰的变化,且在流动分离之前后缘基本不受影响;而入流速度的变化则会影响压力分布整体的形态,包括后缘处。因此,在其他条件等同的情况下,通过压力分布可以判断入流攻角的大小。
风力机风轮上下游流速同一径向处沿周向均呈现周期性变化,且受到风力机叶片参数及叶片尾流的相互影响,风力机叶片气动性能也会受入流情况而相应改变。为掌握叶片各区域的气动性能,本文通过比较计算提出一种判定叶片气动性能的新方法,该方法表明:叶片中部大部分区域压力分布与二维情况吻合较好,根部尤其是尖部 %叶片长度的压力分布受到叶尖涡的破坏。
最后本文通过安装叶尖小翼来控制叶尖涡的影响,改善了叶片压力分布,使尖部压力分布更接近二维分布情况,提高了气动性能和叶片效率,削弱了叶尖涡在下游的发展,为风场下游风力机提供了较高品质的气流。
关键词:风力机,数值模拟,压力分布,叶尖小翼,叶尖涡
Abstract
In order to study the characteristic plicated three-dimensional and rotating flow field of wind turbine, in this paper, the flow field is deeply analyzed via numerical simulation. And further more, the winglet is applied to control the tip vortex properly.
This paper is based on the pressure distribution of the two-dimensional airfoil which is affected by the angle of attack and Reynolds Number(inflowing velocity). The results show that the pressure distribution is sensitive with the angle of attack, especially on the leading edge before flow separation. While the pressure distribution changes entirely parison with the inflowing velocity changing, of course including the trailing edge. Thus, the angle of attack can be confirmed by the pressure distribution under the same flowing condition.
The upstream and downstream velocities vary periodically along circumferential direction and are affected by the parameters and wake flow of the blades. A new approach is introduced to judge the aerodynamic performance. It shows that the pressure distribution of central section of the blades coincides well with that of two-dimensional airfoils. While the pressure of the root especially the blade tip, which