实度对低风速风电机组风轮气动性能影响研究

为提高低风速地区的风能利用率,研究风轮实度对低风速风电机组气动性能的影响。考虑影响风轮实度因素（叶片数量、弦长及安装角）,设计2组不同弦长叶片与可调安装角轮毂。安装角改变时不仅会引起实度变化,还会使叶尖速比发生改变。通过车载试验验证安装角不同时对风轮气动性能的影响主要与叶尖速比相关。根据不同风轮表面压力分布数值模拟结果得出：相同风速下,弦长由叶根到叶尖逐渐增大的叶片更易启动。相同条件下,试验机组输出功率与数值模拟机组输出功率最大相差5.37%,说明数值模拟结果可信。随着风轮实度的增加,风速5 m/s时,其风能利用系数呈增大趋势,风速8 m/s时,其风能利用系数呈减小趋势,两趋势相交时实度为25.38%,得出该实度下风轮气动性能较优,即可得到适合低风速地区的风轮实度。     

定常吸气对垂直轴风力机性能影响研究

定常吸气装置可有效提高垂直轴风力机气动性能,改善风轮流场结构及翼型动态失速特性。基于CFD方法对垂直轴风力机进行数值模拟,研究不同叶尖速比（TSR）下定常吸气对风力机气动及流场特性的影响,对比分析原始风力机及定常吸气作用下的风能利用率、整机转矩系数及涡量分布。结果表明：不同尖速比下定常吸气均可显著提高风力机气动性能,减小风轮载荷波动,降低最佳叶尖速比,提高风力机运行稳定性;叶尖速比为2.51时,风能利用系数增加34.69%;定常吸气削弱了风轮叶片间尾涡脱落的影响,抑制叶片前缘涡的形成,减缓了叶片的动态失速现象,对风轮流场有良好的改善效果。     

TMT40.3大型风力机叶片气动性能分析

基于BLADED软件平台,对TMT40.3大型风力机叶片的气动性能进行了分析.分析结果表明:TMT40.3大型风力机叶片应用在GL3A风场时的额定功率能达到1 650 kW,所承受的疲劳强度和极限载荷均能满足该款风力机叶片的设计要求,在叶尖速比为7.8～11.4的风能利用系数均在0.46以上,最高可达0.486,具有较好的气动性能和较宽的风速适应范围.     

变速变桨距风力发电机气动特性研究

基于动量叶素理论,考虑了叶尖损失、风轮锥角以及修正的轴向和切向诱导因子等因素的影响,推导出速度诱导因子的迭代计算公式。考虑了影响风力发电机气动性能的各种因素,较为准确地建立了风轮计算模型。结合实例计算分析了速度诱导因子及叶片受力沿叶片展向的分布规律,分析了桨距角、转速和叶尖速比等参数对风力机气动特性的影响,得到风力发电机的气动特性曲线。在此基础上,分析了提高风力机风能利用率和减小载荷波动的方法,为风力发电机的动态设计及运行特性分析奠定了基础。     

叶片数及弦长对升力型垂直轴风力机的影响

文章基于非对称翼型NACA4415,以功率系数为依据,以CFD仿真为手段,研究了在不同尖速比下叶片数与叶片弦长对升力型垂直轴风力机气动性能的影响,以及不同尖速比和叶轮实度不同时,垂直轴风力机功率系数的变化。研究结果显示,该类升力型垂直轴风力机叶轮实度取0.25~0.45,尖速比λ取2.5~3.4时,具有较高的功率系数。流场分析表明,当叶片弦长与叶片数的变化对流场的扰动能力小于垂直轴风力机从流场中获取风能的能力时,叶片弦长与叶片数的变化会增加垂直轴风力机的功率系数;反之,垂直轴风力机的功率系数降低。该研究为此类20 k W垂直轴风力机的设计与选型提供依据。     

风力机叶片高升力系数法的气动设计研究

在动量-叶素理论和Betz理论的基础上,结合PROPID软件进行功率为1.5 MW水平轴风力机叶片的气动设计研究。叶片气动设计采用高升力系数法,叶片剖面采用NPU-WA系列高升力、高升阻比风力机专用翼型,在叶片性能预测中采用叶尖损失、轮毂损失和Viterna失速模型。设计结果表明采用先进风力机翼型并运用高升力系数法设计的大功率风力机叶片的弦长较小,叶片面积较小,有利于减轻叶片的重量,同时降低制造成本。     

全向导叶作用下叶片实度对垂直轴风力机气动特性的影响

为研究全向导叶作用下不同实度对垂直轴风力机气动性能的影响,通过改变叶片数及弦长调整实度并分析其对全向导叶垂直轴风力机气动性能的作用。结果表明：全向导叶使垂直轴风力机周围流体提速效果显著,最大风能利用率和力矩系数较原始垂直轴风力机分别提高41.6%和25%;随实度增大时,全向导叶垂直轴风力机最佳尖速比降低;改变弦长时,风能利用率峰值随弦长增大呈现先增后减的趋势,且在小尖速比工况下,高实度全向导叶垂直轴风力机力矩系数较高,最大可达0.192;改变叶片数时,风能利用率峰值随叶片数增多而降低,且大尖速比下的低实度全向导叶垂直轴风力机力矩系数较大,但不同实度的全向导叶垂直轴风力机最大力矩系数相差较小。     

风力机预弯叶片多目标优化设计

在风力机预弯叶片的设计中,叶片弦长扭角分布、铺层结构与弯曲型线之间存在着复杂的耦合设计关系,具有良好性能的叶片不仅要求年发电量高、重量轻,而且要求对主机产生的载荷小。为了使设计叶片在其生命周期内能经受各种复杂的工况,文章提出在组合危险工况下进行叶片的极限设计载荷计算,基于提出的叶片预弯型线设计方法构建了预弯叶片的气动外形和铺层结构一体化优化设计模型,以叶片的年发电量最大、质量最小和对主机的载荷最小为目标,以叶片的气动外形及叶片铺层结构的关键参数为设计变量,在满足材料强度、叶尖最大变形、振动频率的约束条件下,采用多目标粒子群算法(MOPSO)对现有的某1.5 MW风力机叶片进行优化设计。结果表明,优化设计得到的叶片Pareto最优解集可满足主机不同的匹配需要,对最优解集叶片进行分析,挑选得到了综合性能比原1.5 MW风力机叶片均有较大提高的新叶片。     

某1 MW水平轴风力机叶片气动设计及载荷计算

基于片条理论,考虑了叶尖损失、叶根损失、叶柵影响和重载荷下对片条理论参数修正的情况下,完成了某1 MW水平轴风力机叶片的气动设计,并对其气动性能进行了评估;最后根据IEC规范对叶片在不同风况状态下进行载荷计算,所得结果可为同类风力机气动设计和结构设计提供参考。     

扭曲叶片对小型对转风轮机性能影响的研究

与单叶轮风轮机相比,对转双叶轮风轮机具有更高的风能利用率,文章在直叶片对转风轮机试验研究的基础上,采用数值模拟的方法研究了扭曲叶片对风轮机气动性能的影响规律。计算结果表明,扭曲叶片能在一定程度上提高对转风轮机的性能。当叶轮采用扭曲叶片时,通过模拟扭转角、叶尖速比和来流风速对风轮机输出功率的影响,优化出了进行后续试验研究的前级叶轮设计参数:扭转角θ为15°、叶尖速比λ为0.5。     

Assessment of optimum tip speed ratio in wind turbines using artificial neural networks

Wind turbine blade design depends on several factors, such as turbine profile used, blade number, power factor, and tip speed ratio. The key to designing a wind turbine is to assess the optimal tip speed ratio (TSR). This will directly affect the power generated and, in turn, the effectiveness of the investment made. TSR is suggested to be taken between 7 and 8 and in practice generally taken as 7 for a 3-blade network-connected wind turbine. However, the optimal TSR is dependent upon the profile type used and the blade number and could fall out of the boundaries suggested. Therefore, it has to be assessed accordingly. In this study, the optimal TSR and the power factor of a wind turbine are predicted using artificial neural networks (ANN) based on the parameters involved for NACA 4415 and LS-1 profile types with 3 and 4 blades. The ANN structure built is found to be more successful than the conventional approach in estimating the TSR and power factor.     

Optimized linearization of chord and twist angle profiles for fixed-pitch fixed-speed wind turbine blades

The chord and twist angle radial profiles of a fixed-pitch fixed-speed (FPFS) horizontal-axis wind turbine blade are based on a particular design wind speed and design tip speed ratio. Because the tip speed ratio varies with wind speed, the originally optimized chord and twist angle radial profiles for a preliminary blade design through optimum rotor theory do not necessarily provide the highest annual energy production (AEP) for the wind turbine on a specific site with known wind resources. This paper aims to demonstrate a novel optimal blade design method for an FPFS wind turbine through adopting linear radial profiles of the blade chord and twist angle and optimizing the slope of these two lines. The radial profiles of the blade chord and twist angle are linearized on a heuristic basis with fixed values at the blade tip and floating values at the blade root based on the preliminary blade design, and the best solution is determined using the highest AEP for a particular wind speed Weibull distribution as the optimization criteria with constraints of the top limit power output of the wind turbine. The outcomes demonstrate clearly that the proposed blade design optimization method offers a good opportunity for FPFS wind turbine blade design to achieve a better power performance and low manufacturing cost. This approach can be used for any practice of FPFS wind turbine blade design and refurbishment.     

大型风力发电机组独立桨叶控制系统

设计出独立桨叶控制系统的机构方案，依据空气动力学分析，提出模糊控制结合以桨叶空间方位角作为主体因素的加权系数的控制策略，建立了系统模型，仿真结果表明，在风速高于额定风速时，作用在桨叶上的负载波动大为减小，输出功率维持在额定功率附近。     

Testing basic performance of a very small wind turbine designed for multi-purposes

A very small wind turbine system for multi-purposes was developed and its performance was reported in this paper. The rotor diameter of the turbine is 500 mm. The tests of the energy output, turbine speed, power coefficient, and torque of turbine were carried out for a wide rage of free stream velocity. The flow around the wind turbine and the influence of the turbulence were investigated with a particle image velocimetry. Experimentally obtained power coefficient was 0.4 in maximum and 0.36 in the rated running condition, respectively. The tip speed ratio corresponding to the optimum driving condition was 2.7. Comparing with the other commercial turbines, the performance was excellent at a slow turbine speed. By the flow visualization and PIV measurement around the wind turbine, the approaching flow velocity and the accelerated flow field passing the blade tip was obtained. It was confirmed that the actual flow passed through the blades was about 20% slower than the ideal flow. Tip vortex shed from the blade tip was also visualized clearly.     

气动力和离心力对风力机叶片应力影响研究

针对自行研制的NACA4415翼型水平轴风力机,通过流固耦合的数值模拟计算方法,考虑气动力和离心力以及两者耦合作用,选取叶片最大弦长、中部弦长、气动中心线展向以及最大应力点位置,分析风力机叶片在不同工况下的应力特性分布规律。结果表明:在气动力作用下,叶片相同弦长位置处迎风面应力小于背风面应力,且随尖速比和入流风速增大而增大,最大应力点位置随着尖速比增大沿翼展向外且靠近叶片前缘方向延伸;在离心力作用下,叶片相同弦长位置处迎风面应力大于背风面应力,且随尖速比增大而增大,而最大应力点均在叶根最大弦长位置(9.93 mm,10.80 mm,-126.33 mm);在耦合作用下,叶片相同弦长位置处迎风面应力大于背风面应力,随尖速比和入流风速增大而增大,且依次大于气动力和离心力产生的应力,而最大应力点均在叶根最大弦长位置。仿真结果对于风力机翼型的选择及优化设计具有重要的理论意义及参考价值。     

吸气控制策略对垂直轴风力机气动性能影响研究

针对垂直轴风力机复杂气动特性,将吸气孔置于风力机翼型上下表面,提出不同吸气控制策略以改善其气动性能。基于CFD方法,研究不同叶尖速比下吸气策略对风力机风能利用率、叶片切向力系数及流场特性的影响,综合考虑能量消耗与风力机输出功率。结果表明：提出的3种控制策略在低叶尖速比下均能大幅提升整机气动效率。效果最佳的迎、背风区交替吸气策略可显著推迟分离点,延缓翼型动态失速发生,并减少分离涡周期性脱落造成的损失。此外,该策略对动态尾迹效应有良好的控制效果,同时降低整机转矩波动幅值,消除中低叶尖速比下风轮负转矩,从而提高获能效率且延长风力机使用寿命。     

垂直轴风力机两种翼型气动性能比较研究

叶片是风力机最重要的组成部分,在不同的风能资源情况下,翼型的选择对垂直轴风力机气动特性有着重要的影响。文章分别以NACA0018翼型(对称翼型)和NACA4418翼型(非对称翼型)建立3叶片H型垂直轴风力机二维仿真模型。应用数值模拟的研究方法,从功率系数、单个叶片切向力系数等方面比较两种风力机模型在不同叶尖速比下的气动特性,并采用风洞实验数据验证了流场计算的准确性。CFD计算结果表明:在低叶尖速比下,NACA4418翼型风力机气动特性优于NACA0018翼型风力机,适用于低风速区域;在高叶尖速比下,NACA0018翼型风力机气动特性较好,适用于高风速地区。而且在高叶尖速比时,NACA0018翼型在上风区时,切向力系数平均值要高于NACA4418翼型,在下风区时,NACA418翼型切向力系数平均值高。该研究可为小型垂直轴风力机翼型的选择提供参考。     

A practical approach for selecting optimum wind rotors

The main objective of this paper is to categorize practical families of horizontal-axis wind turbine rotors, which are optimized to produce the largest possible power output. Refined blade geometry is obtained from the best approximation of the calculated theoretical optimum chord and twist distributions of the rotating blade. The mathematical formulation is based on dimensionless quantities so as to make the aerodynamic analysis valid for any arbitrary turbine models having different rotor sizes and operating at different wind regimes. The selected design parameters include the number of blades, type of airfoil section and the blade root offset from hub center. The effects of wind shear as well as tower shadow are also examined. A computer program has been developed to automate the overall analysis procedures, and several numerical examples are given showing the variation of the power and thrust coefficients with the design tip speed ratio for various rotor configurations.