海流能柔性叶片水轮机获能区的分析与研究

以柔性叶片水轮机获能区的研究为重点,分析柔性叶片水轮机的受力特性,提出正负获能区的概念,明确获能区的分布情况,在此基础上提出一种通过减小负获能区的不利影响来提高柔性叶片水轮机整体获能能力的方法,并利用数值模拟和水槽模型实验进行分析和验证。最后根据柔性叶片水轮机获能区的特点,针对不同的环境条件提出相关工程应用方案。     

柔性叶片水轮机力学性能测算方法研究

针对一种新型潮流能发电获能装置--柔性叶片水轮机,采用风浪流水槽模型试验和Fluent数值模拟两种方法测算水力学性能参数,分析了两者测算结果的差异,并通过数值模拟法测算了柔性叶片水轮机力学特性,方法简便,对柔性叶片水轮机的开发利用具有指导意义.     

柔性叶片弦向变形对潮流能水轮机轴向载荷影响的研究

采用自适应翼型尾缘的建模方法,通过快速成型技术制作柔性叶片模型,在理论分析与数值模拟的基础上探究柔性叶片的变形规律,在水槽实验中以水轮机转子所受轴向载荷为主要研究目标,分析在低流速下叶片变形对其轴向载荷的影响。通过仿真与实验对比分析可得,柔性叶片弦向变形量随流速增加而增大,与刚性叶片对比,柔性叶片水轮机所受的轴向载荷较小,同时验证以Fluent为基础的双向流固耦合仿真方法对研究大变形柔性叶片的可行性。     

多工况条件下变叶片数潮流能水轮机能量及流动特性研究

文章建立了潮流能水轮机水动力性能数值计算模型,通过实验验证了利用该模型预测水轮机尾流的准确性,并利用该模型研究了潮流能水轮机在不同叶片数和不同叶尖速比条件下的能量和流动特性。研究结果表明:该数值计算模型在预测尾流速度亏损和湍流强度方面具有较好的精度,尤其在远尾流区,数值计算结果与实验结果保持一致;当叶尖速比(TSR)为4.5左右时,3叶片和4叶片的潮流能水轮机具有相对较高的获能系数,此结果对于水平轴潮流能水轮机的设计具有一定的指导意义。     

一种新型潮汐能水轮机的性能分析

文章基于CFD和模型实验的方法为国内某工程开发了一种转轮直径为0.8 m的新型超低水头潮汐能水轮机。利用数值模拟的方法对海工及机组模型进行1∶1的建模,并根据当地潮差数据确定计算工况点。对比分析了水轮机的内特性和5种不同叶片安放角下水轮机的出力和效率,确定了不同潮差对应的机组进出口水头。在此基础上,利用数值模拟确定的机组进出、口水头进行转轮直径为0.4 m的模型实验,对比分析了5种叶片安放角下模型的出力和效率,并对叶片安放角为28°的模型实验数据和数值模拟数据进行了对比,发现两者的数据比较接近,由此验证了数值模拟的可靠性。     

潮流能水轮机叶片在多安装角下的水动力研究

为精确控制潮流能水轮机的输出功率与载荷,得到叶片安装角控制规律,基于动量叶素理论、粘性CFD数值模拟以及模型试验的方法,对1 k W水轮机模型在不同安装角度下的水动力性能进行研究,计算水平轴潮流能水轮机叶片在不同安装角下的水动力性能与载荷。数值模拟与理论计算的结果表明:叶片安装角度的改变对水轮机的输出功率与载荷均有较明显影响,并呈现一定规律;通过模型实验验证了数值模拟方法的可靠性。     

基于Fluent的叶片展长对卧式水轮机水动力性能影响的数值研究

提出了一种能够利用波浪能发电的装置,其吸收海水能量的主要构件是卧式水轮机.为了研究卧式水轮机的水动力学性能,采用有限体积法,并利用非定常SST k-ω湍流模型和滑移网格技术,对其进行了三维数值模拟与实验研究,分析了在六种不同叶片展长下叶轮的水动力学特性.通过将数值计算结果和实验结果进行比较,验证了SST k-ω湍流模型和滑移网格技术的可行性.结果发现:叶片展长递增对水轮机叶片的合力系数几乎没有影响,但是对轮机转矩系数和叶轮能量利用率影响很大;在低尖速比时,叶片展长对水轮效率影响不大,当尖速比大于2.5时,叶片展长对水轮效率的影响明显加大;叶片展长越长,叶片切向力越大,水轮机对水能的吸收能力越强.     

叶片参数对潮流能自由变偏角水轮机性能影响规律研究

采用基于粘性CFD理论的多体耦合方法对不同叶片参数下潮流能垂直轴自由变偏角水轮机的运动和动力特性进行数值模拟研究。研究表明:叶片偏角变化规律是决定该水轮机性能的重要因素,主要由水动力和惯性力所产生的俯仰力矩决定。通过分析叶片质量以及叶片自转轴与叶片质心距离对叶片摆动过程中俯仰力矩的影响规律,给出叶片参数对水轮机运动和动力特性的控制规律。     

一种新型垂直轴潮流能水轮机性能的初步研究

针对普通潮流能垂直轴3叶片水轮机难以自行启动的缺点,文章提出了一种新型6叶片水轮机。通过数值模拟和模型试验两种方法,分别研究了新型6叶片水轮机与普通3叶片水轮机的自启动性能和能量捕获性能,并将两者进行了比较分析。研究结果表明,新型6叶片水轮机的总体性能优于普通3叶片水轮机,是一种很有发展潜力的结构形式。     

水平轴潮流能水轮机性能的数值模拟与实验

为预测所设计水轮机的水动力学性能,分别采用滑移网格与多参考系的旋转模型在ANSYS workbenchFluent中对设计的潮流能水轮机进行数值模拟,得到不同桨距角、不同尖速比下水轮机的轴向力系数、扭矩系数、功率系数。利用3D打印技术制作水轮机模型,并在实验水槽中进行模型实验。实验表明,所设计的水轮机具有较好的水动力学性能,实验值与2种旋转模型数值模拟对比表明,利用滑移网格旋转模型比利用多参考系旋转模型进行数值模拟得到的结果更加精确,计算时间相应有所增加。另外,利用滑移网格的方法得到不同尖速比下水轮机转子叶片的正负压力分布规律,可为水轮机工况分析与水轮机叶片加工制造提供指导。     

风力机旋转叶片的多体动力学数值分析

在现代柔性多体系统动力学理论的框架上，研究了风力机叶片的空间旋转运动与其弹性变形问的耦合关系；对旋转叶片进行有限元离散，采用凯恩（Kane）方法，建立了一般形式的大型风力机叶片柔性多体动力学方程；结合大型叶片几何构形特点，导出了旋转叶片的空间梁单元动力矩阵的显式形式；以1．5MW风力机叶片为例，计算了该叶片的固有频率并与常规有限元数值分析结果进行了比较，体现了旋转叶片的动力刚化效应，更准确地反映了叶片的动力学特性。     

具有温度场的冷却叶片振动特性计算方法研究

根据稳态热传导的相关理论,建立了透平冷却叶片温度场和热应力场的四面体三维有限元分析模型和方法,并在此基础上建立了透平冷却叶片振动特性三维有限元分析方法,开发了相关计算软件。对某航空发动机透平高压第1级冷却叶片在不同工作条件下的振动特性进行了计算分析,同时研究了热应力、温度场、转速等对叶片振动特性的影响,表明本文中所建立模型和方法是科学、合理和精确的,为开展透平冷却叶片的设计和振动安全性评价奠定了基础。     

Time‐accurate blade surface static pressure behaviour on a rotating H‐Darrieus wind turbine

Time‐accurate blade pressure distributions on a rotating H‐Darrieus wind turbine at representative tip speed ratios during start‐up are presented here, which allow blade dynamic stall and laminar separation bubbles to be observed clearly and which provide a rare experimental demonstration of the flow curvature effect inherent in H‐Darrieus turbine operation. The convection of a dynamic stall vortex along the blade surface at high reduced frequency has also been clearly identified. This study provides new information of the complex aerodynamics of the vertical axis wind turbines (VAWTs) and provides unique experimental data to validate the transient blade static surface pressure distribution predicted by CFD models. To the best of the authors' knowledge, this is the first time that the instantaneous pressure variation around the blade has been measured and recorded directly for an H‐Darrieus wind turbine.     

模态应变能理论及其在风力机叶片损伤识别中的应用

文章给出了风力机叶片的动力特性计算模型、结构体模态应变能的概念及其计算模型,定义了结构体损伤状态下的模态应变能变化率概念并给出其计算模型。在此基础上,以15 kW风力机叶片为研究对象,在ANSYS中建立有限元分析模型,计算该叶片在不同损伤位置与不同损伤程度下的频率以及模态应变能变化率,并以模态应变能变化率作为表征结构损伤的标识量,对含损伤的风力机叶片结构进行损伤辨识仿真。通过神经网络建立起损伤标识量和损伤状态之间的映射模型,为实现叶片损伤的诊断提供理论依据。     

考虑叶片旋转及土-结构相互作用对风电结构动力特性影响的研究

风力发电建设场地土特性及叶片转速变化会引起风力发电机动力特性及响应发生变化。基于西北地区某风电场的2 MW三桨叶水平轴风力发电机,利用ANSYS软件建立风力发电机整机模型,考虑叶片旋转及土-结构相互作用对风力发电机动力特性的影响,研究风力发电机在不同叶片转速、不同场地条件及两者共同作用下的动力特性变化规律,并利用坎贝尔图分析上述工况下风力发电机的共振特性。结果表明:叶片转速增加使风力发电机的自振频率逐渐增大,塔筒与叶片的耦合变形使频率增长加快;考虑土-结构相互作用时,风力发电机频率降低,且场地土越软风力发电机频率越小;当两种工况共同作用时,叶片旋转只对一阶频率产生影响,对高阶频率影响甚微,且风力发电机频率降低;考虑叶片旋转时风力发电机在1P转频内不产生共振点,在3P转频内一阶频率的共振点为14 r/min。此外在不同场地土下风力发电机均会产生共振点,其中Ⅲ类土的共振频率最远离额定转频。因此在风电场的场地选择、结构设计及日常运行时应注意其动力特性变化,使其频率远离共振区域,为风力发电机安全运行提供保障。     

A method for defining wind turbine setback standards

Setback distances established by regulatory authorities to minimize the probability of blade fragment impact with roads, structures and infrastructure can often have a significant impact on wind farm development. However, these minimum distance requirements typically rely on arbitrary rules of thumb and are not based on a physical or probabilistic analysis of blade throw. The work reported here uses a probabilistic approach to evaluate the effectiveness of current standards and to propose a new technique for determining setback distances. This is accomplished through the use of a dynamic model of wind turbine blade failure coupled with Monte Carlo simulation techniques applied to three different wind turbines. It is first shown that common setback standards based on turbine height and blade radius provide inconsistent and inadequate protection against blade throw. Then, using a simplified dynamic analysis of a thrown blade fragment, it is shown that the release velocity of the blade fragment is the critical factor in determining the maximum distance fragments are likely to travel. The importance of release velocity is further verified through simulation results. Finally, a new method for developing setback standards is proposed based on an acceptable level of risk. Given specific wind turbine operational parameters and a set of failure probabilities, the new method leverages realistic blade throw modeling to produce setback standards with a valid physical foundation. Copyright © 2011 John Wiley & Sons, Ltd.     

基于升力线理论的大型风力机气弹响应研究

针对风力机不断向大型化发展的趋势,导致结构柔度增加,气弹耦合特性和振动增强,研究了大型风力机高效精确的气弹响应分析方法。为了更准确模拟大型风力机气流沿叶片展向的三维流动现象,采用螺旋尾涡升力线模型代替传统叶素动量理论,建立了叶片气动载荷分析模型,进而结合风力机多体系统动力学模型,构建了机组的气弹耦合动力学方程和数值求解方法。以某10 MW风力机叶片为例,研究了稳态风况下不同风速的叶片气动性能,以及有效攻角、切向力等沿叶展方向的分布特点,并与采用修正叶素动量理论的气弹分析程序（HAWC）对比,结果表明,升力线理论无需引入经验修正模型即能获得叶素动量理论经修正后的分析精度。最后,通过非稳态风况下风力机的气弹响应分析,证明本文方法对大型风力机气弹耦合分析的有效性和准确性。     

Numerical modeling of the hydraulic blade pitch actuator in a spar‐type floating wind turbine considering fault conditions and their effects on global dynamic responses

This paper deals with numerical modeling of the hydraulic blade pitch actuator and its effect on the dynamic responses of a floating spar‐type wind turbine under valve fault conditions. A spar‐type floating wind turbine concept is modeled and simulated using an aero‐hydro‐servo‐elastic simulation tool (Simo‐Riflex [SR]). Because the blade pitch system has the highest failure rate, a numerical model of the hydraulic blade pitch actuator with/without valve faults is developed and linked to SR to study the effects of faults on global responses of the spar‐type floating wind turbine for different faults, fault magnitudes, and environmental conditions. The consequence of valve faults in the pitch actuator is that the blade cannot be pitched to the desired angle, so there may be a delay in the response due to excessive friction and the wrong voltage, or slit lock may cause runaway blade pitch. A short circuit may cause the blade to get stuck at a particular pitch angle. These faults contribute to rotor imbalance, which result in different effects on the turbine structure and the platform motions. The proposed method for combining global and hydraulic actuator models is demonstrated in case studies with stochastic wind and wave conditions and different types of valve faults.     

汽轮机叶片防冲蚀表面处理的冷态筛选试验研究

针对某饱和汽轮机的工作环境,选择了适合于其叶片工况的多种表面抗冲蚀处理方案,同时根据汽轮机叶片的破坏机理,建立了筛选叶片表面处理工艺的冷态冲蚀试验的装置及试验程序,并对选定的表面处理工艺方案进行了筛选试验。通过本试验筛选出几种可供进一步进行汽轮机叶片热态冲蚀试验的较好表面处理方案,为下一进的叶片热态冲蚀试验奠定了基础。     

New vortex‐lift and tangential‐force models for HAWT aerodynamic load prediction

Horizontal axis wind turbines (HAWTs) experience three‐dimensional rotational and unsteady aerodynamic phenomena at the rotor blades sections. These highly unsteady three‐dimensional effects have a dramatic impact on the aerodynamic load distributions on the blades, in particular, when they occur at high angles of attack due to stall delay and dynamic stall. Unfortunately, there is no complete understanding of the flow physics yet at these unsteady 3D flow conditions, and hence, the existing published theoretical models are often incapable of modelling the impact on the turbine response realistically. The purpose of this paper is to provide an insight on the combined influence of the stall delay and dynamic stall on the blade load history of wind turbines in controlled and uncontrolled conditions. New dynamic stall vortex and nonlinear tangential force coefficient modules, which integrally take into account the three dimensional rotational effect, are also proposed in this paper. This module along with the unsteady influence of turbulent wind speed and tower shadow is implemented in a blade element momentum (BEM) model to estimate the aerodynamic loads on a rotating blade more accurately. This work presents an important step to help modelling the combined influence of the stall delay and dynamic stall on the load history of the rotating wind turbine blades which is vital to have lighter turbine blades and improved wind turbine design systems.