长叶片考虑约束预扭的扭转恢复计算

传统的长叶片扭转恢复计算是以自由叶片为模型的，它已不适合目前应用较广的整圈连接叶片结构。建立了适合围带和拉筋整圈连接结构的长叶片考虑约束预扭的扭转恢复计算模型，给出了各种约束条件的求解方法和典型算例。     

基于三维实体模型的自带围带叶片扭转恢复角的计算

采用三维实体模型,对自带围带的汽轮机扭曲长叶片的扭转恢复角进行了计算分析。借助通用有限元软件ALGOR,建立了叶片围带间接触约束的分析模型,以探讨阻尼围带对叶片扭转恢复特性的影响。并对1 029mm叶片进行了分析计算,结果表明:自由叶片的扭转恢复角与转速成平方的关系变化;在不同的初始间隙范围,叶顶的扭转恢复角对间隙δ变化的敏感程度不同,在间隙0.50mm~1.00mm时,较为敏感,在设计时,应避开敏感区间;随着θ的增加,叶顶的扭转恢复角增加,基本呈线性变化关系。本文的研究为整圈连接阻尼叶片的设计及优化提供了指导。     

汽轮发电机组轴系弯扭耦合振动研究

对汽轮发电机组轴系的离散质量模型采用传递矩阵方法和模态综合技术研究了中、低压末级长叶片切向弯曲振动对轴系扭转振动的影响。研究表明,长叶片与轴系之间存在着弯扭耦合振动,叶片的切向弯曲振动对轴系扭振特性有影响。     

汽轮机长叶片扭转恢复特性研究

利用有限元分析软件ALGOR,建立基于三维实体模型的汽轮机长叶片扭转恢复特性计算与分析模型.并以国产1029mm叶片为研究对象,研究自由叶片、自带围带阻尼的叶片的扭转恢复特性.研究与分析表明,自由叶片与自带围带阻尼叶片的扭转恢复特性有较大的区别.自由叶片的扭转恢复特性与转速密切相关;自带围带阻尼叶片的扭转恢复特性不但与转速相关,而且与围带阻尼结构的结构参数有着密切的关系.     

自带围带予扭叶片的叶根截面剪应力计算

选取对截面图形的扭转有较大影响的几何特性参数作为图形逼近的特定参数,建立了用矩形截面杆的扭转逼近平行四边形截面杆的扭转最佳逼近数学模型。给出了自带围带予扭叶片的叶根(或轮缘)截面剪应力计算方法,并编制了相应的计算程序。     

扭叶片顶部带有约束的扭转恢复计算

建立了给定扭叶片顶部附加扭矩约束或顶部扭转恢复角的统一离散模式及线性方程组，对不同的约束给出相应的方法及计算实例。     

长叶片和叶片组稳态应力及扭转恢复角的有限元法

本文采用空间扭曲梁单元,建立了一种用于扭曲长叶片和叶片组稳态应力及扭转恢复角计算的有限元法.并对某851mm长叶片进行了计算.图6参7     

基于ANSYS的10 MW风力机叶片弯扭耦合特性研究

为分析弯扭耦合效应对大型风力机叶片气动性能的影响。文中使用三维有限元软件ANSYS建立了10 MW复合材料风力机叶片模型,通过改变梁帽位置单轴向布的铺层角度在叶片中引入弯扭耦合效应,改变铺层角度和耦合区域,分析叶片在气动载荷作用下的变形情况。结果表明:叶片在弯扭耦合作用下产生弯曲变形的同时会发生扭转变形,沿叶片展向变形量增加;该叶片可达到的最大扭转变形量为6度;弯扭耦合系数随着铺层角度的增大而减小。     

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。     

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%。     

平行冠涡轮叶片的干摩擦减振数值模拟

利用叶冠之间的干摩擦力产生的阻尼,是一种抑制叶片振动、降低叶片动应力的有效手段.本文以某型汽轮机中压第一级动叶片为研究对象,建立了带平行冠叶片的Sgn干摩擦阻尼模型,将叶冠接触面之间的干摩擦力转换为等效刚度和等效阻尼.计算了其在不同预扭量条件下的动应力,分析了不同预扭量的减振效果.计算结果表明:采用0.4mm的预扭量,叶片的动应力数值较无预扭情况下减小约50%,预扭工艺的减振效果明显.进一步增进预扭量,动应力减小的幅度非常有限(＜5%),目前采用的预扭量是较为合理的.     

Classical flutter analysis of composite wind turbine blades including compressibility

For wind turbine blades with the increased slenderness ratio, flutter instability may occur at lower wind and rotational speeds. For long blades, at the flutter condition, relative velocities at blade sections away from the hub center are usually in the subsonic compressible range. In this study, for the first time for composite wind turbine blades, a frequency domain classical flutter analysis methodology has been presented including the compressibility effect only for the outboard blade sections, which are in the compressible flow regime exceeding Mach 0.3. Flutter analyses have been performed for the baseline blade designed for the 5‐MW wind turbine of NREL. Beam‐blade model has been generated by making analogy with the structural model of the prewisted rotating thin‐walled beam (TWB) and variational asymptotic beam section (VABS) method has been utilized for the calculation of the sectional properties of the blade. To investigate the compressibility effect on the flutter characteristics of the blade, frequency and time domain aeroelastic analyses have been conducted by utilizing unsteady aerodynamics via incompressible and compressible indicial functions. This study shows that with use of compressible indicial functions, the effect of compressibility can be taken into account effectively in the frequency domain aeroelastic stability analysis of long blades whose outboard sections are inevitably in the compressible flow regime at the onset of flutter.     

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。     

Discharge path observation and the statistical characteristics of discharge paths for long–air gap discharge for in‐operation wind turbines

When a wind turbine is in normal operation, the blades are rotating, and this blade rotation may affect the process of lightning striking the wind turbine. To investigate this problem, long‐gap discharge tests are performed in this study. Moreover, a multiple physical parameter synchronous observation platform is designed for a scaled wind turbine. Long‐gap discharge tests of a static and rotary‐scaled wind turbine with blade tip‐electrode gap distances of 1 to 8 m are conducted, and the discharge paths under different gaps and wind turbine operating conditions are obtained. The characteristic parameters—arc shape upon discharge, lengths of the downward and upward leaders, blade angle at the moment of discharge, and angle of upward leader initiation—are statistically analyzed. The analysis of the aforementioned data indicates that rotation has opposite effects on the discharge characteristic parameters under short and long gap distances. According to the analysis, blade rotation reduces the space charge density of the corona discharge near the tip, which leads to an increase in the field strength near the blade tip and a decrease in the field strength away from the blade tip. Short and long gaps have different degrees of influence on discharge, which changes the difficulty of upward leader initiation at the blade tip and consequently alters the entire discharge process. The obtained results can provide a reference for the lightning protection of wind turbines.     

Tower shadow induced blade loads for an extreme‐scale downwind turbine

The downwind rotor configuration provides a structural advantage compared with an upwind design. However, tower shadow has long been a concern for downwind systems. The tower shadow negatively affects the blade by introducing a load impulse during the wake passage. An aerodynamic fairing could shroud the tower reducing the wake. However, there is no clear consensus on the importance of a tower shadow for utility‐scale wind turbines. Simulations were conducted in FAST to determine the general parameters that influence the importance of the tower shadow effect for the differently sized wind turbines. The lock number of the blade was a significant driving quantity. Lower lock numbers (typical of small‐scale wind turbines) lead to greater relative fatigue damage from tower shadow effects. It was determined that a fairing is very helpful for small‐scale wind turbines operating in a low‐turbulence environment (such as a subscale wind tunnel test). However, the tower shadow increased the damage equivalent loading on an extreme scale blade by less than 5% in a turbulent environment. These results indicate that the cost of a tower fairing is likely unnecessary for utility‐scale wind turbines in operation.     

带粒透平中叶片冲蚀的数值计算及振频变化预估

基于欧拉－拉格朗日解基本思想,在模拟计算了双级跨音速燃气透平三元粘性湍流场基础上,采用颗粒随机轨道模型和PSIC法求解了低颗粒浓度气固双向耦合后两种不同密度的分布直径颗粒的运动轨迹,并据此计算了叶片的冲蚀率,其分布规律与实物叶片的冲蚀情况比较接近。然后利用所建立的叶片冲蚀率与叶片振频的相互关系,预估了叶片振频因冲蚀而随时间发生的变化,为探索叶片冲蚀对振频的影响作了有益的尝试。     

Numerical Analysis of the Aeroelastic Behaviour for the Last Turbine Stage in 3D Transonic Flow

An understanding of the physics of the mutual interaction between gas flow and oscillating blades, and the development of predictive capabilities is essential for improving overall efficiency, durability and reliability. In this study presented the algorithm proposed involving the coupled solution of 3D unsteady flow through a turbine stage and dynamic problem for rotor blades motion by action of aerodynamic forces without separating outer and inner flow fluctuations. There has been performed the calculations for the last stage of the steam turbine under design and off-design regimes. It has investigated the mutual influence of both outer flow non-uniformity and blades oscillations. It has shown that amplitude-frequency spectrum of blade oscillations contains the high frequency harmonics, corresponding to rotor moving one stator blade pitch, and low frequency harmonics caused by blade oscillations and flow non-uniformity downstream from the blade row.     

基于Monte Carlo方法的叶片顶部间隙不确定性分析

以燃气轮机压气机叶片Rotor 37的叶片为研究对象,分析了叶片顶部间隙的不确定性对叶片性能的影响。基于Monte Carlo方法中伪随机数的产生方法、正态分布变量产生方法以及均匀抽样方法,采用C++语言完成了Monte Carlo方法的编程并进行验证。采用该程序抽取了满足正态分布的顶部间隙样本,利用商用CFD(计算流体力学)软件NUMECA计算分析顶部间隙的不确定性对叶片绝热效率的影响。结果表明:在该样本条件下,计算得出的叶片绝热效率基本满足正态分布且叶片绝热效率随着前缘间隙的增大而降低。     

600MW等级二缸空冷汽轮机长叶片开发

介绍了基于STC长叶片设计平台完成的600MW等级二排汽空冷汽轮机长叶片的设计开发,主要从气动和强度振动两方面阐述了末级叶片的设计要点和工作特性。结果表明,该末级叶片具有良好的振动特性和变工况特性,并对新的长叶片的设计开发有一定的指导意义。