缩模风洞实验法预测风力机气动性能的相似原理研究

The method with scaled model wind tunnel test for predicting wind turbine aerodynamic performance is proposed in the project, because the precision of predicting wind turbine aerodynamic performance with the existing methods including BEM, CFD and wind farm test can't meet the design requirements. Wind turbine tested in wind tunnel must be its scaled model because its size is limited by wind tunnel size. The problems that the testing Reynolds number of scaled model in wind tunnel can't reach the same of its prototype, and the roughness on its blade surface is difficult to meet the geometric similarity with its prototype are occurred. The aerodynamic performance similarity of wind turbines therefore becomes the primary problem of aerodynamic performance prediction. A study of similarity principle about aerodynamic performances of scaled wind turbines for accurately predicting wind turbine aerodynamic performance through wind tunnel test is carried out in the project. The project adopts a successive approximation method considering the similarity criteria, and combines the wind tunnel test and numerical simulation to compare and analyze the flow characteristics of scaled wind turbines, including the inflow of stream tube, the flow around blade, the upstream and downstream flow of rotor, the blade tip vortex, blade span-wise flow and so on, in order to investigate the flow information resulting in the difference of aerodynamic performance. In addition, the project investigates the design method about the roughness insensitivity blade according to the design demands of the high-performance blade in order to neglect considering relative surface roughness criterion in the course of aerodynamic performance prediction. The goals are to reveal the similarity principle of aerodynamic performances of scaled wind turbines, and to obtain the similarity law of their aerodynamic performances, and to establish a basis for the befitting similarity theory of wind turbine aerodynamic performance.The achievements are significant for the accurate prediction of wind turbine aerodynamic performance, the improvement of design technique, and the development of offshore wind energy utilization and some related subjects.

缩模风洞实验法预测风力机气动性能是在现有BEM、CFD、风场实验法不能满足预测精度要求的前提下提出的。风力机的风洞实验受风洞尺度的限制必须大比例缩小，造成缩模实验雷诺数难以达到风力机的实际量值、叶片表面粗糙度也不能保证几何相似，使得缩比风力机气动相似性问题成为了气动性能预测的首要问题。本项目主要研究缩比风力机气动相似原理，采用分步逼近相似的研究路线，结合风洞实验和数值模拟，详细比较和分析缩比风力机的流动特性，包括流管入流、叶片绕流、转子上下游流动、叶尖涡和叶展流动等，探索引起气动性能差异的流场变化规律；同时探索符合风力机高性能叶片设计要求的粗糙不敏感叶片的设计方法以解决叶片表面粗糙度不相似问题；最终揭示缩比风力机气动相似原理，获取气动相似规律，为建立适合风力机的气动相似理论奠定基础。本项目的研究成果对风力机气动性能的准确预测、设计技术水平的提高以及海上风能利用与相关学科的发展具有重要意义。

依据相似理论和风力机实际状况，提出了设计粗糙不敏感叶片和探索引起叶片三维流动的叶尖涡、展向流动等随因素雷诺数变化对气动性能的影响和雷诺数效应是解决风力机气动相似问题的关键。.从风场叶片实际污染状况出发，以21%相对厚度翼型为例，采用XFOIL分析得到了污染位置和雷诺数对抗污特性影响规律，所获得的抗污高性能新翼型，将为污染环境中风能利用的提高提供帮助。针对南方风场未考虑防除冰措施的风电机组，在保证安全运行前提下，采取交替控制停机和开机的措施，达到了清除叶片表面覆冰污染的良好效果，提高了发电效率。.S809翼型低雷诺数气动特性的风洞实验获得了自由和固定转捩条件下不同雷诺数的压差升阻力和表面压力分布特性，填补了该翼型低雷诺数气动特性数据的空白。以其中某实验数据为基础，分别采用XFOIL、NUMECA和FLUENT不同湍流模型进行计算比较，结果显示采用FLUENT转捩SST模型的计算值误差最小，适为翼型低雷诺数气动特性CFD计算方法。通过测量光滑与粗糙S809翼段翼尖部位尾流横截面的速度场和翼型表面压力分布获得翼尖涡涡量、涡心位置及翼型压差升阻力系数，分析获得了该翼型翼尖涡涡量和涡心位置随雷诺数和攻角变化趋势以及翼尖涡对压差升阻力系数影响规律，为叶尖涡研究奠定了基础。.比较CFD计算结果获知不同软件、网格质量、湍流模型的差异较大。通过分析NREL风力机及其缩比模型CFD计算的流场信息，揭示了引起气动特性差异的主要原因。计算多种叶尖小翼型式的1.0 m模型，发现小翼安装在压力面的几种型式效果不佳，仅折向吸力面型式对叶片功率有明显增加；该模型风洞实验结果表明：叶尖小翼和扰流环在部分实验参数区域起到了一定作用，同时获得了在该区域相同尖速比和不同雷诺数下，叶尖涡和展向流动因素引起气动性能差异的定量关系；1.0m与1.5m模型实验结果也说明相同雷诺数和尖速比下功率系数存在差异；且CFD计算与实验结果不一致，其准确性有待研究提高。.另外，还开展了风洞实验装置的设计制造、测量方法以及叶片流动控制等相关研究。