【作者】 李军向；

【导师】 王继辉； 薛忠民；

【作者基本信息】 武汉理工大学 ， 复合材料学， 2008， 博士

【摘要】 近年来化石能源危机,环境危机使得可再生能源得到空前发展。风能作为环保型,无穷无尽之能源,在20世纪80年代后进入了发展的黄金时期。中国作为能源消费大国,近年来风电得到国家层面上的大力支持从而得到快速发展。但起步较晚使中国风电技术与风电发达国家差距很大,MW级以上风电设备设计技术基本依赖进口,作为风电机组关键部件之一的叶片尤其如此。本文在国家“十一五”科技支撑计划项目(2006BAA01A09)支持下,根据现有进口叶片,着重对大型水平轴风机叶片进行气动性能计算和结构设计进行了研究,取得如下成果:(1)风轮气动性能主要包括功率、轴力、转矩以及其对应的功率系数、轴力系数和转矩系数,本文采用叶素动量理论,结合前人研究成果,建立了较完善的风轮叶片气动性能计算模型,考虑风轮实度(叶片数)、安装角、锥角、倾角以及叶片宽度、厚度,风轮偏航等因素,采用迭代法计算叶素诱导因子,编制matlab计算程序,分析了这些因素对风轮气动性能的影响。并在整个叶片翼展方向,对轴向诱导因子和周向诱导因子以及叶素功率分布进行了详细分析。分析结果表明,风轮实度、安装角对功率影响显著,锥角和倾角将会导致风轮各项气动性能下降。叶片宽度和厚度对风轮气动性能影响不大。(2)完成了一整套利用有限元软件对大型叶片进行校核分析的方法,摸索出了具有复杂气动外形和内部铺层结构的复合材料叶片建模的有效方法。并直接利用软件对叶片各截面、各方向刚度进行近似计算,与理论值吻合良好,表明该方法可行、有效。与理论法相比,该方法简便易行,特别适合非规则截面复合材料构件刚度的计算。对叶片动力行为模态进行了理论上的探讨,推导出了叶片自振频率的估算公式,模态分析表明叶片第一阶模态发生在挥舞方向,第二阶发生在摆振方向,高阶模态逐渐复杂化,呈现出混合振型形式。应变的校核分析表明,叶片主要在叶根和最大弦长处有较大应变值。在稳定性分析中,发现叶尖区域是叶片可能发生失稳的一部分。(3)对叶片设计的关键之一,结构铺层设计进行了研究,建立了大型叶片初步结构设计的理论方法。叶片采用分段原则,以叶片挥舞方向极限弯矩为设计载荷,综合运用前人总结的经验公式,以及经典层合板理论和Euler-Bernoulli梁理论,在外形不变的前提下,对现有750KW叶片在结构铺层上进行重新设计研究。研究表明,理论设计不是最终设计,前面的有限元校核分析,修正将起到十分重要的作用。通过对比分析,本文对750KW叶片的结构铺层设计比较合理,在叶片重量、挥舞方向刚度、叶尖挠度均占优势,仅在稳定性方面不如原有叶片。(4)在主梁上用碳纤维材料替代玻璃纤维作为叶片主要承载构件的增强材料,研究了叶片弯扭耦合设计的可行性。首先对叶片弯扭设计进行了参数化研究,建立控制弯扭耦合的主要参数α,从理论和数值分析两个方面估算α可能的取值范围。进行弯扭耦合设计可以从几个方面进行,比如几何外形上,或者将材料主轴与主受力方向成一角度。本文采用后者,在主梁将碳纤维主轴与主受力方向成0°、10°、15°和20°角。对弯扭耦合设计后的叶片整体性能进行了分析,并与本文新设计的叶片结构进行了对比分析,研究表明,运用弯扭耦合设计理念,叶片结构性能在几乎所有方面都有了提高,这表明弯扭耦合的巨大意义,同时也显示了碳纤维运用到叶片结构设计中的潜力。更多还原

【Abstract】 The renewable energy has greatly developed in recent years due to the crisis of fossil energy and environment. As a type of environment-friendly and inexhaustible energy, wind energy went into its golden time of development in 80s, 20th century. China, as a large consumer of energy, wind power has got quick development in recent years with the state’s support. But the MW-class wind turbine technologies almost are all imported because of the deep gap between China and west countries with advanced wind power technology, especially rotor blade, which is one of the key components of wind turbine. With the support of Beijing FRP company and aid of National "11th five-year" Scientific Support Plan (2006BAA01A09), researches were focused on the aerodynamic performance calculation and structural design of rotor blade on the basis of the existing imported blade. The main achievements are as follow:(1) The aerodynamic performance was defined by power, thrust, torque and their corresponding coefficients. In this paper, by the use of blade element and momentum theory and in combination with the research results finished by our predecessors, a relatively complete calculation model for the aerodynamic performance of rotor blade is built with the consideration of rotor solidity (blade number), pitch angle, zone angle, tilt angle and blade width, thickness, yaw angle etc. Matlab codes adopted the iterative algorithm are generated and the influences of these factors on the aerodynamic performance are analyzed. Also, detailed analyses on the distribution of axial and tangential induction factors and the blade element power along the whole blade are performed. Analyses above show that solidity and pitch angle have a great effect on the aerodynamic performance while blade width and thickness affect little and the existences of zone and tilt angle will lead reduction of aerodynamic performance of rotor blade.(2) An entire set of method of large-scale blade analysis is completed by using finite element software, and also an effective approach of building the FE model of composite blade with complex aerodynamic shape and internal laminate structure is investigated. And then directly use software to calculate the sectional stiffness approximately, the results from which are identical with the theoretical ones. Compared with theoretical method, FE method is easy and convenient, especially applied at rigidity calculation of composite structures with irregular cross section. Theoretical investigation is made on blade dynamic behavior (modal analysis), approximate computation equation of blade natural frequency is derived. Modal analysis shows that the first mode happens in flapwise direction and the second in edgewise direction. High order mode shapes are getting complicated, which are mixed mode. It is clear that bigger strains occur In the region of blade root and station with maximum chord length. In the buckling analysis, it is found that blade tip area is one part that maybe easily be buckled.(3) Study work is carried out on the structure design, which is one of the key design of blade, the preliminary structural design theory is achieved. Based on the section-design principle, structural is redesigned with the same external shape as the existing blade by using classical laminate theory and Euler-Bernoulli beam theory. Structure study shows that theoretical design is not the final design, it is important to combine with FE analysis to check and modify repeatedly, through which final structural schedule will be determined. Through comparison of blade weight, stiffness at flapwise and tip deformation with the existing blade, the approach in this paper is reasonable, except the stability.(4) Feasibility of FRP replaced by GRP in spar cap to introduce bend-twist couple design is investigated. First Parametric study of bend-twist design is implemented and then finds out the main controlling parameterα, and then makes an approximation of value range of this parameter from theoretical and numerical aspects. Bend-twist coupling design can be implemented from several aspects, such as geometrically or by using unbalanced off axis fibers oriented at an angle with respect to the primary loading direction. The latter is preferred in this paper and the oriented angles are 0°, 10°, 15°and 20°.respectively. Analysis and comparison work between the blades with different design approach are done and shows that the performance of blade structure is getting higher designed by bend-twist coupling.更多还原