共查询到19条相似文献，搜索用时 17 毫秒
1.
The effects of twist and section shape modifications in the inboard region on the aerodynamic characteristics of the NREL 5 MW rotor have been examined using a Reynolds‐averaged Navier–Stokes method OVERFLOW2. The baseline rotor blade was modified by increasing the trailing‐edge thickness over the inboard region by modifying the sections’ thickness distribution aft of the maximum thickness location. Results when compared with the baseline rotor show that a modest increase of trailing‐edge thickness to 10–20%c increased power capture by 1%. Further increases in trailing‐edge thickness decrease in effectiveness to the point of reducing power capture when thicknesses reach 40%c. Increasing trailing‐edge thicknesses also leads to an increase in thrust, but this load is concentrated in the inboard region, resulting in a small increase in root bending moments. The blunt trailing‐edge concept greatly reduces the spanwise extent of inboard flow separation evident in the baseline NREL 5 MW rotor. The low‐pressure region aft of the trailing edge, created by the geometry, acts to reduce the spanwise spreading of the inboard separation. Rotors with modified twist distributions over the inboard 35%R of span are also compared. Inboard twist angles are varied from + 6° to ? 6° from the baseline twist schedule. Increasing inboard blade twist reduces overall rotor power capture but reduces thrust at a faster rate. Power capture remains constant with decreasing inboard geometry twist, whereas thrust increases approximately linearly by 0.75% for a decrease in thrust of 6°. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The effects of modifying the inboard portion of the experimental NREL Phase VI rotor using a thickened, blunt trailing‐edge (or flatback) version of the S809 design airfoil are studied using a compressible, three‐dimensional, Reynolds‐averaged Navier–Stokes method. A motivation for using such a thicker airfoil design coupled with a blunt trailing edge is to alleviate structural constraints while reducing blade weight and maintaining the power performance of the rotor. The numerical results for the baseline Phase VI rotor are benchmarked against wind tunnel measurements obtained at freestream velocities of 5, 7 and 10ms?1. The calculated results for the modified rotor are compared against those of the baseline rotor. The results of this study demonstrate that a thick, blunt trailing‐edge blade profile is viable as a bridge to connect structural requirements with aerodynamic performance in designing future wind turbine rotors. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Wind turbine rotor blades are sophisticated, multipart, lightweight structures whose aeroelasticity‐driven geometrical complexity and high strength‐to‐mass utilization lend themselves to the application of glass‐fibre or carbon‐fibre composite materials. Most manufacturing techniques involve separate production of the multi‐material subcomponents of which a blade is comprised and which are commonly joined through adhesives. Adhesive joints are known to represent a weak link in the structural integrity of blades, where particularly, the trailing‐edge joint is notorious for its susceptibility to damage. Empiricism tells that adhesive joints in blades often do not fulfil their expected lifetime, leading to considerable expenses because of repair or blade replacement. Owing to the complicated structural behaviour—in conjunction with the complex loading situation—literature about the root causes for adhesive joint failure in blades is scarce. This paper presents a comprehensive numerical investigation of energy release rates at the tip of a transversely oriented crack in the trailing edge of a 34m long blade for a 1.5MW wind turbine. First, results of a non‐linear finite element analysis of a 3D blade model, compared with experimental data of a blade test conducted at Danmarks Tekniske Universitet (DTU) Wind Energy (Department of Wind Energy, Technical University of Denmark), showed to be in good agreement. Subsequently, the effects of geometrical non‐linear cross‐section deformation and trailing‐edge wave formation on the energy release rates were investigated based on realistic aeroelastic load simulations. The paper concludes with a discussion about critical loading directions that trigger two different non‐linear deformation mechanisms and their potential impact on adhesive trailing‐edge joint failure. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
Anargyros A. Karakalas Dimitris I. Manolas Theodoros T. Machairas Vasilis A. Riziotis Dimitris A. Saravanos 《风能》2019,22(5):620-637
Upscaling of wind turbine blades calls for implementation of innovative active load control concepts that will facilitate the flawless operation of the machine and reduce the fatigue and ultimate loads that hinder its service life. Based on aeroelastic simulations that prove the enhanced capabilities of combined individual pitch and individual flap control at global wind turbine scale level, a shape adaptive concept that encompasses an articulated mechanism consisting of two subparts is presented. Shape memory alloy (SMA) actuators are investigated and assessed as means to control the shape adaptive mechanism at airfoil section level in order to alleviate the developed structural loads. The concept is embedded in the trailing edge region of the blade of a 10‐MW horizontal axis wind turbine and acts as a flap mechanism. Numerical simulations are performed considering various wind velocities and morphing target shapes and trajectories for both normal and extreme turbulence conditions. The results prove the potential of the concept, since the SMA controlled actuators can accurately follow the target trajectories. Power requirements are estimated at 0.22% of the AEP of the machine, while fatigue and ultimate load reduction of the flap‐wise bending moment at the blade root is 27.6% and 7.4%, respectively. 相似文献
5.
Jeroen Smit Lars O. Bernhammer Sachin T. Navalkar Leonardo Bergami Mac Gaunaa 《风能》2016,19(4):607-624
An extension of the spectrum of applicability of rotors with active aerodynamic devices is presented in this paper. Besides the classical purpose of load alleviation, a secondary objective is established: optimization of power capture. As a first step, wind speed regions that contribute little to fatigue damage have been identified. In these regions, the turbine energy output can be increased by deflecting the trailing edge (TE) flap in order to track the maximum power coefficient as a function of local, instantaneous speed ratios. For this purpose, the TE flap configuration for maximum power generation has been using blade element momentum theory. As a first step, the operation in non‐uniform wind field conditions was analysed. Firstly, the deterministic fluctuation in local tip speed ratio due to wind shear was evaluated. The second effect is associated with time delays in adapting the rotor speed to inflow fluctuations caused by atmospheric turbulence. The increase in power generation obtained by accounting for wind shear has been demonstrated with an increase in energy production of 1%. Finally, a control logic based on inflow wind speeds has been devised, and the potential of enhanced power generation has been shown by time‐domain simulations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
结合层流翼型与钝尾缘的特性,通过Hicks-Henne型函数对翼型参数化修型,基于多岛遗传算法及Xfoil气动分析,针对大型水平轴风力机翼型进行多目标函数、多设计工况、多约束条件下的优化设计,得到适用于大型风力机的高性能翼型族（USST翼型族）。其升阻比在大多数攻角下均高于同厚度的FFA、DU系列等现有风力机翼型族,且在同样的升力系数下具有更大的升阻比。最后为考核优化设计得到的翼型族,采用数值模拟方法对优化结果进行验证,证明设计得到的新型风力机翼型族具有优越的气动性能。 相似文献
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Active load reduction strategies such as individual pitch control (IPC) and trailing edge flap (TEF) actuation present ways of reducing the fatigue loads on the blades of wind turbines. This may enable development of lighter blades, improving the performance, cost effectiveness and viability of future multi‐megawatt turbine designs. Previous investigations into the use of IPC and TEFs have been limited to turbines with ratings up to 5 MW and typically investigate the use of these load reduction strategies on a single turbine only. This paper extends the design, implementation and analysis of individual pitch and TEFs to a range of classically scaled turbines between 5 and 20 MW. In order to avoid designing controllers which favour a particular scale, identical scale‐invariant system identification and controller design processes are applied to each of the turbines studied. Gain‐scheduled optimal output feedback controllers are designed using identified models to target blade root load fluctuations at the first and second multiples of the rotational frequency using IPC and TEFs respectively. The use of IPC and TEFs is shown in simulations to provide significant reductions in fatigue loads at the blade root. Fatigue loads on non‐rotating components such as the yaw bearing and tower root (yaw moment) are also reduced with the use of TEFs. Individual pitch performance is seen to be slightly lower on larger turbines, potentially due to a combination of reduced actuator bandwidth and movement of the rotational frequency of larger turbines into a more energetic part of the turbulent spectrum. However, TEF performance is consistent irrespective of scale. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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开发中高温储热材料及其制备方法是储热技术发展的关键之一.本文结合中高温储热材料的分类、特点、应用及存在的问题对中高温储热材料的研究进展进行了综述,主要包括显热储热材料、热化学储热材料以及潜热储热材料.探讨了复合结构储热材料及其制备工艺,进一步介绍了其最新研究进展,并对中高温储热材料的下一步研究进行了展望,提出开发高性能纳微复合结构储热材料是未来研究的重点. 相似文献
10.
Diego Cárdenas Alejandro A. Escárpita Hugo Elizalde Juan José Aguirre Horacio Ahuett Piergiovanni Marzocca Oliver Probst 《风能》2012,15(2):203-223
This paper presents a numerical validation of a thin‐walled beam (TWB) finite element (FE) model of a realistic wind turbine rotor blade. Based on the theory originally developed by Librescu et al. and later extended to suit FE modelling by Phuong, Lee and others, this computationally efficient yet accurate numerical model is capable of capturing most of the features found in large blades including thin‐walled hollow cross section with variable thickness along the section's contour, inner reinforcements, arbitrary material layup and non‐linear anisotropic fibre‐reinforced composites; the present application is, for the time being, restricted to linearity. This one‐dimensional (1D) FE model allows retaining information of different regions of the blade's shell and therefore approximates the behaviour of more complex three‐dimensional (3D) shell or solid FE models more accurately than typical 1D FE beam models. A 9.2 m rotor blade, previously reported in specialized literature, was chosen as a case study to validate the static and dynamic behaviour predicted by a TWB model against an industry‐standard 3D shell model built in a commercial software tool. Given the geometric and material complexities involved, an excellent agreement was found for static deformation curves, as well as a good prediction of the lowest frequency modes in terms of resonance frequencies, mode shapes and frequency response functions; the highest (sixth) frequency mode shows only a fair agreement as expected for an FE model. It is concluded that despite its simplicity, a TWB FE model is sufficiently accurate to serve as a design tool for the recursive analyses required during design and optimization stages of wind turbines using only readily available computational tools. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
11.
随着能源和环境问题的日益突出以及电子电动设备的迅猛发展,传统锂离子电池已经越来越难以满足人们对于高能量密度电池的需求.锂硫电池因其能量密度高,成本低以及无污染等优点,被认为是极有潜力的下一代高能量密度储能体系.然而由于锂硫电池中正极材料电子,离子电导率低,充放电过程中电极体积变化大,聚硫化物等中间产物的溶解和伴随的\"穿梭效应\"以及锂负极的使用所带来的锂枝晶等一系列问题,导致锂硫电池的循环寿命差,阻碍其产业化的应用发展.锂硫电池体系中碳质材料的引入可以提高材料导电性,缓冲体积变化,抑制聚硫化物穿梭,是提高其电化学性能的有效手段.本文综述了近年来最新的锂硫电池中碳质材料的应用研究进展,包括硫/碳复合物,柔性自支撑电池和碳质锂硫电池负极,分析了其对锂硫电池性能提升的作用机理,并展望了锂硫电池将来可能的发展方向. 相似文献
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双极板作为液流电池的关键材料之一,起到连接电池内部不同单电池的正极和负极,导通电池内电路,阻隔双极板两侧电解液相互渗透的重要作用.根据双极板材料的不同,可以分为金属板,石墨板与复合材料板.复合材料板克服了金属板,石墨板的缺点,耐腐蚀性强,机械强度好,能够满足液流电池的需要.碳纤维具有良好的导电性,力学性能和化学稳定性,通过加入碳纤维来改善双极板的性能,成为了研究人员常用的方法.本文综述了近年来国内外主要的碳纤维增强型复合材料双极板的研究成果,对不同的方法进行了比较,并指出了碳纤维增强型复合材料双极板的发展趋势. 相似文献
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Le Thi Nhu Trang 《热应力杂志》2018,41(4):418-438
Buckling, postbuckling, and nonlinear responses of composite cylindrical panels reinforced by single-walled carbon nanotubes (CNTs), supported by an elastic foundation, exposed to elevated temperature and axially compressed by uniform load are investigated in this article. Distribution of CNTs is uniform or graded in the thickness direction and the effective properties of CNT-reinforced composite are assumed to be temperature dependent, and are estimated by extended rule of mixture through a micromechanical model. Governing equations are established based on thin shell theory taking von Kármán–Donnell nonlinearity, initial geometrical imperfection, Pasternak-type elastic foundation and tangential elastic constraints of boundary edges into consideration. Approximate solutions of deflection and stress functions are assumed to satisfy simply supported boundary conditions, and Galerkin method is applied to derive explicit expressions of load–deflection relation from which critical buckling loads can be obtained. Unlike works in the literature, the present study accounts for elasticity of tangential restraint of two unloaded straight edges in model of cylindrical panel. The study also gives conditions for which bifurcation type buckling response can occur and novel findings in numerical examples. 相似文献
14.
Fuchuang Huang Qinghai Zhao James Yang Hongxin Zhang Fangchao Xu 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(14):1675-1680
This paper is to investigate the mesophase sphere soft carbon material with micro-nano composite structure and its application in the energy-storage Li-ion battery and electrochemical performance of the battery through experimental tests. The results show that the ball diameter is below 10 μm. For button half-cell, the first coulombic efficiency at 0.1C rate is about 87.1%, the ratio that charging capacity of 2C divided by the charging capacity of 1C is 84.8%, and the charging capacity retention rate after 50 cycles at 0.5C rate is 99.9%. For a full battery of 50 Ah, the discharge capacity can still maintain at 80% or more at the 2C or 3C discharging rate, its discharge rate can still reach more than 80% at a temperature of ?20℃, and the capacity retention is 97.7% after 500 cycles. 相似文献
15.
Wenwen Chen Zhongliang Liu Junxian Hou Yu Zhou Xiaoge Lou Yanxia Li 《International Journal of Hydrogen Energy》2018,43(3):1816-1823
Super-capacitor (SC) activated-carbon (AC) carbon-nanotubes (CNTs) (SC-AC-CNTs) is a kind of AC-based composite material and it combines the advantages of carbon nanotubes and activated carbon, including a series of peculiar properties such as low charge transmission resistance, super large specific area and excellent power characteristic. In this study, SC-AC-CNTs are first used to modify the carbon cloth (CC) anodes of microbial fuel cells (MFCs) and compared with that of SC-AC and CC. The measurements show that the specific surface area is increased from 219.519 m2 g?1 to 283.643 m2 g?1 after modification. The new anode is assembled in a urine-powered MFC (UMFC) to test its effectiveness. It is found that the amount of microorganisms attached on the new anode is much larger than that on the blank anode in UMFC. The maximum power densities of the UMFC assembled with SC-AC-CNTs and SC-AC modified anodes are 899.52 mW m?2 and 555.10 mW m?2, which are 2.9 and 1.8 times of that of the blank UMFC, respectively. The tests also shows that the UMFC with SC-AC-CNTs-modified anode creates a much longer duration of 105 h at high-voltage plateau in a single cycle that is about 2–3 times of the other two groups. These findings demonstrate that these two double layer capacitor materials can effectively boost overall MFC performance. 相似文献
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《International Journal of Hydrogen Energy》2019,44(46):25199-25206
The new functional FeO/C composite carbon materials are successfully fabricated by controlling the adding amounts of Fe3O4 particles in mixtures of coal tar pitch and Fe3O4 particles. The structures of prepared FeO/C composite carbon materials were verified by XRD measurements. The excellent electrochemical performances of FeO/C composite carbon materials were evaluated in detail. For instance, the prepared materials show the high cycling performances at 679 mAh/g after carrying out charge-discharge 100 cycles. Meanwhile, the high rate performances and long cycle life characteristics of FeO/C composite materials were also observed. As a result, it is palpable that the carbon contents and specific area are the vital factors to improve the electrochemical performances of FeO/C composite materials, which effectively provides the reference to design the transition metal oxide/carbon composite materials as Li+ ion storage materials. 相似文献
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This paper presents a detailed analysis of the rotor–tower interaction and the effects of the rotor's tilt angle and yaw misalignment on a large horizontal axis wind turbine. A high‐fidelity aeroelastic model is employed, coupling computational fluid dynamics (CFD) and structural mechanics (CSM). The wind velocity stratification induced by the atmospheric boundary layer (ABL) is modeled. On the CSM side, the complex composite structure of each blade is accurately modeled using shell elements. The rotor–tower interaction is analyzed by comparing results of a rotor‐only simulation and a full‐machine simulation, observing a sudden drop in loads, deformations, and power production of each blade, when passing in front of the tower. Subsequently, a tilt angle is introduced on the rotor, and its effect on blade displacements, loads, and performance is studied, representing a novelty with respect to the available literature. The tilt angle leads to a different contribution of gravity to the blade deformations, sensibly affecting the stresses in the composite material. Lastly, a yaw misalignment is introduced with respect to the incoming wind, and the resulting changes in the blade solicitations are analyzed. In particular, a reduction of the blade axial displacement amplitude during each revolution is observed. 相似文献
19.
Rotating stall around a small-scale horizontal axis wind turbine was experimentally studied to characterize and assess smart rotor control by plasma actuators. Phase-locked Particle Image Velocimetry was used to map the flow over the rotor blade suction surface at numerous radial stations at a range of tip-speed-ratios. Flow separation occurred from the inboard of the blade and spread radially outwards as the tip-speed-ratio reduced. Plasma actuators placed along the span that produced a chord-wise body force had very little effect on the flow separation, even when operated in pulsed forcing mode. In contrast, plasma actuators along the blade chord that produced a body force into the radial directions (plasma vortex generators) successfully mitigated rotating stall. Torque due to aerodynamic drag was reduced by up to 22% at the lowest tip-speed-ratio of 3.7, suppressing stall over the outboard 50% of the blade. This was due to quasi-two-dimensional flow reattachment in the outboard region, and shifting of a fully stalled zone towards the hub in the inboard region because the plasma-induced body force counteracted the Coriolis-induced radial flow. This can significantly increase the turbine power output in unfavourable wind conditions and during start-up. 相似文献
