【作者】 王强；

【导师】 徐建中； 徐宇；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2014， 博士

【摘要】 风力机工作在大气地表边界层环境中,流场环境常常具有三维、非定常等特性,这给水平轴风力机的三维流场研究及相应的气动性能分析带来很大的困难。除此之外,风力机作为目前地球上尺寸最大的旋转式叶轮机械(102m量级),它的气动性能与叶片表面边界层及脱落的尾涡结构(10-3m量级)密不可分。从宏观大尺度到微观小尺度,跨越多个尺度的流场结构给风力机的三维流场研究及三维气动分析提出了新的挑战。现有的风力机气动计算模型按照复杂程度及计算精度的不同主要可以分为BEM模型、涡方法模型及CFD模型。不同的计算模型具有不同的计算特点和数值特征,因而具有不同的适用范围。为了提高气动模型的三维计算能力,本文针对现有的BEM模型、涡方法模型及CFD模型,主要开展了以下几方面的工作：第一,在BEM模型方面：以三维失速延迟修正模型为研究核心,对Corten提出的无粘失速模型进行了系统地分析。得到了该模型的解析解,并基于该解析解建立了风力机三维无粘失速延迟修正模型(ISDM)。与传统的失速延迟分析不同,ISDM模型以流动分离区内展向流动导致的叶片吸力面的负压增加量为核心分析目标,通过简化Navier-Stokes方程,并引入Kirchhoff-Helmholz尾缘分离预估模型,实现在离心力及科氏力影响下的叶片三维失速延迟效应的评估。通过与NREL Phase VI风力机及MEXICO风力机的三维全尺寸风洞实验数据的对比,验证了ISDM模型的准确性。第二,在涡方法模型方面：对具有不同涡量表征形式及复杂程度的升力线模型和三维面元模型进行了研究。对于升力线模型,粘性涡核模型及涡核有效半径模型的引入,有效地解决了升力线模型的数值奇性问题并且提高了三维非定常自由尾涡的计算精度。其次,基于该模型,对后掠叶片的气动性能及尾涡特征进行了计算和分析：在三维面元模型方面,以直接耦合模式将三维面元模型与二维边界层计算模型相结合,构建了粘性无粘耦合模型。该模型提高了附着流工况下计算的准确性,但对于大攻角流动分离工况的计算难以收敛。总体上,涡模型依靠三维尾涡的诱导作用,在很大程度上提高了流场的三维计算能力。第三,在CFD模型方面：以致动模型为研究目标,在现有的致动盘模型(ADM)、致动线模型(ALM)及致动面模型(ASM)基础上,提出将粘性无粘耦合算法与致动模型相结合,建立了三维改进致动面模型(IASM)。IASM模型利用粘性无粘耦合模型的边界元特性,最大程度上完善了现有致动模型中叶片三维几何外形与流场之间的作用机制。通过对比二维、三维流场工况下IASM模型和致动线模型(ALM)的计算结果,验证了IASM模型能够提高致动模型对于近尾流区域计算的准确性。IASM模型为大尺寸、复杂几何外形风力机的三维流场计算及气动性能分析奠定了基础。第四,在实验方面：以中科院工程热物理所0.5m×0.5m小型闭口回流式风洞为平台,设计了后掠翼段实验研究方案,围绕展向三维流动影响下的翼型气动性能的变化开展了实验研究。为了提高实验数据的可靠性,采用了大攻角流动分离条件下的数据修正模型。后掠翼段实验结果表明：升力系数在小攻角线性段与有限直翼段的实验结果十分接近,但在失速阶段,后掠翼段升力系数的实验结果出现大尺度的波动现象,且升力系数的平均值显著地高于相应的直翼段数据。利用后掠翼段实验数据评估ISDM模型,结果显示：ISDM模型可以较准确地预估附着流及初始尾缘分离工况下的升力系数,但对于阻力系数的预估ISDM模型仍存在误差。更多还原

【Abstract】 The wind turbine works in the atmosphere boundary layer. There the flow field is usually three-dimensional (3D) and unsteady, which makes it very difficult to analyze the3D flow field and the corresponding aerodynamic performance of the Horizontal Axis Wind Turbine (HAWT). Besides, as the largest rotating turbomachinery on the earth, the aerodynamic performance of HAWT (102m magnitude) has very close relationship with the boudary layer on the wind turbine blade and the structure of the shedding vortexes, whose magnitude is only about10"3m. From the macro large scale to the micro small scale, the multiple scale structures of the3D flow field present new challenges to the3D flow field study and the3D aerodynamic research of the HAWT. According to the computational complexity and the accuracy differencies, the existing aerodynamic computational models of HAWT can be mainly divided into three parts. They are the Blade Element and Momontum (BEM) model, Vortex Method Model and the Computational Fluid Dynamics (CFD) model. Because these models have their own independent characters and the computational features for the3D flow field analysis, they have different scopes of application.In this paper, in order to improve the3D computational ability of the current BEM Model, Vortex Method Model and the CFD Model, the following works are carried out:Firstly, for the BEM model part, the3D stall delay modification model is mainly studied. The analytical solution of the Inviscid Stall Delay Model, which is proposed by Cotern, is derived. Based on the solution, the3D Inviscid Stall Delay Modification (ISDM) Model is created. In this model, we treat the stall delay effects differently by the delay of the separation point on the airfoil, and aim to capture the further negative pressure reduction in the separation area. By simplifying the Navier-Stokes equations and introducing the Kirchhoff-Helmholz trailing edge separation prediction model, the3D stall delay effect can be evaluated under the influence of the Centrifugal and Coriolis forces. At last, the ISDM model is validated by the full scale3D wind tunnel experimental results of the NREL Phase VI and MEXICO wind turbines, which verified the accuracy of the ISDM model.Secondly, for the Vortex Method Model part, the Lifting-Line Model and the3D Panel-Method Model, which have different forms of the vorticity representation and the computational complexity, are detailed studied. In the Lifting-Line Model, by introducing the Viscous Vortex Core model and the vortex effective radius concept, the numerical singularity can be effectively resolved and at the same time the accuracy of the3D unsteady free wake model can be improved. Based on the Lifting-Line Model, the aerodynamic performance and the wake characters of the backward-swept wind turbine blade are anaylized. In the Panel-Method Model, the2D boundary layer computational model is involved and based on the Direct Coupling Strategy a simple Viscous and Inviscid Interaction (VII) model is created. Compared with the results of the Panel Method Model, the VII model improves the accuracy of the computation under the attached flow condition. However when the Angle of Attack (AOA) becomes large enough and the flow separates from the surface, the VII model is difficult to get a convergence solution. Overall, because of the3D induced velocity of the3D wake vortex, the Vortex Model greatly improves the computational ability of the3D flow field.Thirdly, for the CFD model part, the study mainly focuses on the Actuator Model. Based the existing Actuator Disc Model (ADM), Actuator Line Model (ALM) and Actuator Surface Model (ASM), a new model named Improved Actuator Surface Model (IASM) is proposed, which is a kind of combination of the Actuator Model and the VII model. By making full use of the Boundary Element features of the VTI model, the IASM improves the interaction mechanism between the3D geometry of the wind turbine blade and the3D flow field to the maximum extent. By comparing the computatinoal results of the IASM and ALM, it is validated that the IASM can increase the accuracy of the flow field results in the near-wake region. The IASM provides an efficient way for the3D flow field computation and the aerodynamic analysis of the large scale wind turbine especially with complex geometry.Fourthly, for the experiment part, based on the0.5m X0.5m closed wind tunnul of the Institute of Engineering Thermophysics (LET), Chinese Academy of Sciences, a special swept airfoil section experiment is designed, which is aim to study the airfoil aerodynamic performance infuenced by the spanwise flow. In order to improve the reliability of the experimental data, a specialized data correction model proposed by Kang, which contains the blockage effect caused by the flow separation, is utilized in this dissertation. The swept airfoil experiment shows that the lift coefficient of the swept airfoil section is close to the results of the finite straight airfoil at small AOA condition, but at the stall stage, the lift coefficient of the swept airfoil section presents big-scale fluctuations and the average value of the lift coefficient is significantly higher than that of the straight airfoil section. Finally, based on the experimental results, the ISDM is detailed evaluaed. The results shows that the ISDM can accurately estimate the lift coefficient undert the attached flow and primary trailing edge separation conditions, but there are still errors exist in the drag coefficient estimated by ISDM.更多还原