基于遗传算法的定速定桨距HATT叶片优化设计

叶片外形是定桨距水平轴洋流机能量利用率的主要影响因素。为优化其叶片外形,基于叶素动量理论计算叶片功率特性,同时考虑叶片抗汽蚀水平,通过Bezier曲线表示叶片各径向位置截面的弦长和扭角,以低流速下利用率最高为设计目标,通过遗传算法进行优化,并与Wilson设计方法比较,结果表明:优化设计叶片在叶根部分扭角更小,整体弦长平均减小了27%;低流速区域的能量利用率平均提高6.8%,全工况最大能量利用率提高3.36%,达到了优化设计目的。     

水平轴风力机叶片优化设计方法

为避免风力机叶片设计陷入局部最优解,通过Bezier参数化曲线定义叶片弦长及扭角分布规律,采用遗传算法优化曲线控制点位置,以年发电量最大为优化目标,全局寻优叶片外形参数,并与Wilson设计叶片比较。分别计算两种设计叶片在额定风况及变风况下的气动性能,结果表明:通过遗传算法设计的叶片弦长、扭角更小;额定风况下,遗传算法设计叶片推力系数更小,最大功率系数更大;变风况下,两种设计叶片输出功率相差不大,但Wilson设计叶片的叶根弯矩和风轮推力更大,整个工作风速区平均为4.7%和7.3%。     

水平轴风力机叶片扭角和弦长的理想分布

为得到风力机功率、转矩和推力等性能随尖速比和翼型升阻比变化的极限公式,需求解叶片的理想扭角和弦长沿翼展变化的解析表达式,同时这项研究也可为叶片外形设计提供理论参考。为此首先从效率最大化的原则出发,用极值的微分算法证明最佳攻角就是使翼型升阻比最大的攻角;其次利用最佳攻角和入流角公式推导出叶片理想扭角沿展向的解析表达式;然后根据动量-叶素理论,推导出叶片理想弦长沿展向的解析表达式。研究表明:叶片理想扭角是设计尖速比、最佳攻角和风轮半径的函数,叶片理想弦长是设计尖速比、风轮半径以及对应最佳攻角的升力和阻力系数的函数。这两个表达式均可表示为显函数的形式。     

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。     

小型风力提水机的低实度风轮设计及其数值模拟

针对传统风力提水机实度大、风能利用率低的缺点,采用NACA4412航空翼型及叶素动量理论对小型风力提水机叶片的气动外形进行设计,采用6叶片风轮形式,引入修正因子,并根据工程实际优化了叶片的弦长及安装角,并采用CFD方法对风轮进行数值模拟。结果表明,设计的风力提水机在2.8 m/s的微风下可起动,在额定工况下风能利用系数达0.43,叶片具有很好的三维流动特性,风能利用系数高,降低了传统风力提水机风轮的实度,扩大了风能的利用范围。研究结果对风力提水机的改进设计有指导意义。     

船舶燃气轮机进气系统惯性级滤清器叶片优化设计

惯性级滤清器性能是影响船舶燃气轮机进气系统出口流场品质的重要因素,也在一定程度上决定了船舶的动力水平。本文采用气-液两相流数值模拟方法,以低总压损失和高过滤效率为共同目标,结合试验设计方法,分别构建了总压损失、过滤效率与叶片几何参数间的响应面方程,并采用多目标遗传优化算法对惯性级滤清器叶片参数进行优化设计。结果表明：优化后的惯性级滤清器在所研究速度条件下均以更小的总压损失实现了更高的过滤效率。2 m/s的速度方案下,优化后的总压损失减少了16.98%,过滤效率提升37.61%;7 m/s的速度方案下,优化后的总压损失减少16.7%,而过滤效率提升20.83% ;流速高时应选用叶片间距更小、坡度更低、叶片越长的滤清器;而低流速应该改用间距更大、长度更短、坡度更高的惯性级滤清器叶片。优化后的滤清器叶片结构既减小了叶片背风区的分离,使总压损失减小,也增加了液体颗粒与叶片的接触而提升了过滤效率,从而提高了滤清器的整体性能。     

基于元胞遗传算法的风力机叶片优化设计

采用经过叶尖损失、轮毂损失及失速状态下动量理论修正的片条理论为基础,在满足设计功率的前提下,以最大升阻比系数为优化目标,以叶片的形状参数弦长、扭角为优化设计变量,通过元胞自动机遗传算法对风力机叶片进行优化。最后应用该优化模型对某2 MW变桨距风力机叶片进行优化设计,并对优化结果进行比较分析,验证了该算法的有效性,为风力机叶片的后续研究奠定了基础。     

大型下风向柔性叶片参数化建模及两目标优化设计

为了应对超大型风力机的发展对叶片带来的挑战，利用叶片多目标设计方法重点研究大型下风向柔性叶片气动与结构参数的优化设计。构建叶片弦长、扭角和挥舞刚度参数模型，以下风向布局的NREL 5 MW风力机叶片为优化对象，基于快速非支配排序遗传算法开展单机年发电量最大和叶根挥舞弯矩最小的两目标下风向叶片优化设计，得到符合预期的Pareto最优解集。取解集中3套具有代表性的最优解进行分析，由于下风向离心力矩可抵消一部分挥舞弯矩，所以叶根挥舞弯矩均有大幅降低，其中A叶片以牺牲0.963%年发电量的代价，使其叶根挥舞弯矩和叶片挥舞刚度分别减小7.951%和27.071%，可实现大型下风向柔性风轮的轻量化优化设计。以选取的3套叶片为基础，分析弦长、扭角、挥舞刚度对优化目标的影响机制，发现叶片挥舞刚度参数对两优化目标的影响最大。     

轴流压气机叶片优化设计

开发了基于梯度法的数值优化程序,并与三维粘性流场求解程序相结合对跨音压气机动叶片进行了以绝热效率最大为目标的三维气动优化设计。先对其进行了沿弦长方向掠设计,绝热效率可提高约0．65％。再对所得掠叶片进行叶型中弧线优化设计得到最终叶片,与初始叶片相比绝热效率提高达1．05％。优化结果表明,动叶片的单纯掠型叶片改进气动性能有限,而弦向掠与中弧线的联合优化设计可以显著改善叶片排内流动状况,并具有良好的变工况性能。     

计及几何和工程约束的风电叶片气动与结构特性分析

为分析气动外形参数小幅度变化对风电叶片气动与结构特性的影响，以某5 MW海上风电叶片为研究对象，构建叶片CFD（计算流体力学）气动模型与复合材料有限元结构模型，考虑某个翼型参数改变引起其所在叶素段曲面形状变化的几何约束，在满足展向光顺性工程约束的前提下，计算不同位置叶素段翼型弦长与扭角的试验水平改变量，设计气动外形参数交互作用下的正交试验方案，采用极差分析和方差分析方法，选取来流风速分别为8.0、11.4、14.0 m/s的3种工况，分析气动外形参数对风电叶片气动扭矩和叶尖挠度的影响。结果表明，气动外形参数3%的试验水平改变量，能影响约6.7%的气动性能改变和约15.0%的结构性能改变；不同位置段气动外形参数主效应不同；不同位置段参数间的交互作用对叶片气动扭矩和叶尖挠度有着不同程度的影响。     

Shape design and numerical analysis on a 1 MW tidal current turbine for the south-western coast of Korea

The study concentrates on the shape design and numerical analysis of a 1 MW horizontal axis tidal current turbine (HATCT), which can be applied near the southwest regions of Korea. On the basis of actual tidal current conditions of south-western region of Korea, configuration design of 1 MW class turbine rotor blade is carried out by blade element momentum theory (BEMT). The hydrodynamic performance including the lift and drag forces, is conducted with the variation of the angle of attack using an open source code of X-Foil. The optimized blade geometry is used for Computational Fluid Dynamics (CFD) analysis with hexahedral numerical grids. This study focuses on developing a new hydrofoil and designing a blade with relatively shorter chord length in contrast to a typical TCT blade. Therefore, after a thorough study of two common hydrofoils, (S814 and DU-91-W2-250, which show good performance for rough conditions), a new hydrofoil, MNU26, is developed. The new hydrofoil has a 26% thickness that can be applied throughout the blade length, giving good structural strength. Power coefficient, pressure and velocity distributions are investigated according to Tip Speed Ratio by CFD analysis. As cavitation analysis is also an important part of the study, it is investigated for all the three hydrofoils. Due to the shorter chord length of the new turbine blade in contrast to a typical TCT blade design, a Fluid Structure Interaction (FSI) analysis is also done. Concrete conclusions have been made after comparing the three hydrofoils, considering their performance, efficiency, occurrence of cavitation and structural feasibility.     

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.     

用于发电系统的局部进气跨声速涡轮气动设计和优化

为了解决高速机载涡轮发电系统效率较低的问题,通过一维计算和三维数值模拟相结合的方法,对以拉法尔喷管作为静叶、三维叶片作为动叶的局部进气跨声速涡轮级进行了研究。在对原型涡轮级流场分析后,通过ISIGHT优化软件集成NX,NUMECA和ANSYS等模块,采用多岛遗传算法,以喷管扩张角、扩张部分长度、周向排布角度以及动叶叶片进口几何角、出口几何角和轴向弦长作为优化变量对涡轮级进行了优化设计。最终得到给定设计工况下的最优几何参数。优化结果表明：优化得到的涡轮级功率达到了74 530 W,效率达到了79.60%,较原型提升了5.1%。     

Numerical optimization of axial turbine with self‐pitch‐controlled blades used for wave energy conversion

Wells turbines are among the most practical wave energy converters despite their low aerodynamic efficiency and power produced. It is proposed to improve the performance of Wells turbines by optimizing the blade pitch angle. Optimization is implemented using a fully automated optimization algorithm. Two different airfoil geometries are numerically investigated: the standard NACA 0021 and an airfoil with an optimized profile. Numerical results show that each airfoil has its own optimum blade pitch angle. The present computational fluid dynamics optimization results show that the optimum blade pitch angle for NACA 0021 is +0.3° while that of the airfoil with an optimized profile equals +0.6°.The performance of the investigated airfoils is substantially improved by setting the blades at the optimum blade pitch angle. Both the turbine efficiency and tangential force coefficient are improved, especially at low flow rate and during turbine startup. Up to 4.3% average increase in turbine efficiency is achieved by optimizing the blade pitch angle. A slight improvement of the tangential force coefficient and decrease of the axial force coefficient are also obtained. A tangible increase of the stall‐free operating range is also achieved by optimizing the blade pitch angle. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimization of cycloidal water turbine and the performance improvement by individual blade control

This paper investigates an advanced vertical axis turbine to enhance power generation from water energy. The turbine, known as a cycloidal water turbine, is a straight-bladed type adopting a cycloidal blade system that actively controls the rotor blades for improved turbine efficiency, according to the operating conditions. These characteristics enable the turbine to self-start and produce high electric power at a low flow speed, or under complex flow conditions. A parametric study has been carried out by CFD analysis, with various characteristics including different number of blades, chord length variations, variety of tip speed ratios, various hydrofoil shapes, and changing pitch and phase angles. Optimal parameters have been determined, and the performance of the turbine has achieved approximately 70% better performance than that of a fixed pitch turbine. An experimental study has also been carried out which shows that the results correlate quite well with the theoretical predictions although the power output was reduced due to the drag forces of the mechanical devices. Another numerical optimization was carried out to improve the rotor performance by adopting an individual blade control method. Controllable pitch angles were employed to maximize the rotor performance at various operating conditions. The optimized result obtained using genetic algorithm and parallel computing, shows an improvement in performance of around 25% compared with the cycloidal motion.     

Multi-objective numerical optimization of the front blade pitch angle distribution in a counter-rotating type horizontal-axis tidal turbine

In order to exploit renewable energies from tidal stream, tandem propellers of a unique counter-rotating type horizontal-axis tidal turbine was firstly designed based on the blade element momentum (BEM) theory. And then a multi-objective numerical optimization method coupled the response surface method (RSM) with the genetic algorithm (GA) was employed to obtain desirable blade profiles. The front blade pitch angle distribution was taken as optimization variable in this paper, as it plays an important role in affecting the inlet conditions of the rear blade. The numerical results show that both optimization objectives of power coefficient and thrust coefficient can be significantly improved. It was verified that the performance of the power unit with the optimized blades increases obviously by optimizing the pitch angle.     

风力机叶片制造误差对功率和推力影响的量化研究

为量化叶片制造误差对风力机功率和推力的影响,以NREL Phase VI S809风力机叶轮为研究对象,基于区间分析法和修正叶素动量理论,建立风力机不确定气动响应模型,量化弦长扭角制造误差对功率和推力影响的相对波动幅度,采用极差分析法进行敏感性分析,获得不确定影响敏感位置。结果表明,叶片扭角误差对性能影响更为显著;当弦长误差和扭角误差为±0.02c和±0.6°时,功率和推力最大相对波动达到3.26%和8.09%;弦长误差影响敏感位置为叶根,而扭角误差敏感位置为叶尖,可在此部位施加质量参数要求以控制性能偏差。     

Optimum aerodynamic design for wind turbine blade with a Rankine vortex wake

This paper presents a model to optimize the distribution of chord and twist angle of horizontal axis wind turbine blades, taking into account the influence of the wake, by using a Rankine vortex. This model is applied to both large and small wind turbines, aiming to improve the aerodynamics of the wind rotor, and particularly useful for the case of wind turbines operating at low tip-speed ratios. The proposed optimization is based on maximizing the power coefficient, coupled with the general relationship between the axial induction factor in the rotor plane and in the wake. The results show an increase in the chord and a slightly decrease in the twist angle distributions as compared to other classical optimization methods, resulting in an improved aerodynamic shape of the blade. An evaluation of the efficiency of wind rotors designed with the proposed model is developed and compared other optimization models in the literature, showing an improvement in the power coefficient of the wind turbine.     

基于滑移网格的垂直轴潮流水轮机的三维数值模拟

为了探究翼型对垂直轴水轮机水力效率的影响,基于叶素理论分析建立了垂直轴潮流水轮机在水槽中的物理模型,采用滑移网格技术在Fluent软件中对模型的流场进行了三维数值模拟。在保持转速一定、更改来流速度即改变叶尖速比的条件下,分析了两种不同NACA翼型直叶片的潮流水轮机内部流场以及水力性能。结果表明,翼型以及叶片安装角对垂直轴潮流水轮机的利用效率影响很大,其流动特性与来流速度、叶片布置形式有重要联系,为新型潮流水轮机的设计和翼型的选择应用提供了依据。     

变桨距风力机叶片的气动优化设计

首先利用Wilson方法进行叶片的外形初步设计,然后以设计攻角作为变量,以额定风速下功率系数最大为优化目标,建立了1 MW变桨距风力机叶片气动外形优化模型,采用遗传算法进行了优化再设计。通过对3叶片1 MW风力机进行的气动性能评价结果表明,优化后的风力机具有更好的气动性能,说明采用该优化方法进行变桨距风力机设计具有明显的优越性。