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P. K. Chaviaropoulos 《风能》1999,2(2):99-112
The scope of this article is to investigate the aeroelastic stability of wind turbine blade sections subjected to combined flap/lead–lag motion. The work is motivated by recent concern about destructive ‘edgewise' vibrations of modern, half‐megawatt‐scale, blades. The aeroelastic governing equations derive from the combination of a spring–mass–damper equivalent of the structure and a ‘non‐stationary' aerodynamic model. The aerodynamic model used in the present context is the differential dynamic stall model developed at ONERA. The resulting equations of motion are linearized and their stability characteristics are investigated in terms of the system entries, expressed through suitable, non‐dimensional, structural and aerodynamic parameters. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Direct numerical simulations were carried out for an S822 wind turbine blade section at a chord Reynolds number of Re = 100, 000 and an angle of attack of α = 5°. Results for a stationary non‐rotating blade section compare favorably with wind tunnel data by the University of Illinois at Urbana‐Champaign and XFoil predictions. By adding volume forcing terms to the right‐hand side of the Navier–Stokes equations, the Coriolis and centrifugal accelerations resulting from blade rotation are modeled in the blade section simulations. Blade rotation is shown to delay separation especially near the hub, resulting in a lift increase of up to 100% and a drag reduction. The simulations provide insight into a physical mechanism that offers an explanation for the lift increase observed for rotating blade sections when compared with stationary blade sections, which is commonly referred to as rotational augmentation. Rotation is shown to lead to a radial velocity component toward the blade tip in areas where the velocity is substantially different from its free‐stream value, such as near the stagnation point and especially in the separated flow region, and to the appearance of stationary and traveling crossflow vortices. A linear stability theory analysis that compares favorably with the simulation data provides proof that the primary instabilities are of a mixed type, including both a two‐dimensional mode (Tollmien–Schlichting and Kelvin–Helmholtz type) and a stationary and unsteady crossflow mode. The crossflow instabilities accelerate transition, leading to separation delay, lift increase and drag reduction. This effect is very pronounced at 20% blade radius and still present at 80% radius. Because periodicity conditions were applied in the spanwise direction, the present results provide an explanation for rotational augmentation that is not based on the transfer of fluid from the inboard region toward the blade tip (‘centrifugal pumping’). For the low Reynolds number conditions considered here, crossflow instabilities, which destabilize the flow leading to earlier transition and a separation delay, may contribute to rotational augmentation. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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This paper presents a novel framework for the structural design and analysis of wind turbine blades and establishes its accuracy. The framework is based on a beam model composed of two parts—a 2D finite element‐based cross‐section analysis tool and a 3D beam finite element model. The cross‐section analysis tool is able to capture the effects stemming from material anisotropy and inhomogeneity for sections of arbitrary geometry. The proposed framework is very efficient and therefore ideally suited for integration within wind turbine aeroelastic design and analysis tools. A number of benchmark examples are presented comparing the results from the proposed beam model to 3D shell and solid finite element models. The examples considered include a square prismatic beam, an entire wind turbine rotor blade and a detailed wind turbine blade cross section. Phenomena at both the blade length scale—deformation and eigenfrequencies—and cross section scale—3D material strain and stress fields—are analyzed. Furthermore, the effect of the different assumptions regarding the boundary conditions is discussed in detail. The benchmark examples show excellent agreement suggesting that the proposed framework is a highly efficient alternative to 3D finite element models for structural analysis of wind turbine blades. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigated by using of wind turbine blade design software, PROPID. Firstly, a wind turbine blade of 2MW class was designed with DU-serics airfoils in the inner part and with aNACA series airfoil as a main airfoil in the outer part. Lift distribution was set to have near L/D maximum at each span station. Then, lift and drag curves were modified to observe effect of L/D variation. Drag and lift change with constant L/D on blade power coefficient was also studied for sensitivity investigation. Each case was optimized with Newtonian iteration incorporated in PROPID. High design lift coefficient results in less chord length and twist angle to maintain same aerodynamic load level. And, power coefficient wasn't improved much with high L/D. During the process, optimal inputs such as lift distribution, design lift and induction factors were suggested. As results, it was found that L/D maximization was important to obtain high efficiency. For the L/D maximization, lift maximization was important to minimize structural weight, but decreasing drag didn't affect the blade shape. 相似文献
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Asger Bech Abrahamsen Justine Beauson Kristine Wilhelm Lund Erik Skov Madsen David Philipp Rudolph Jonas Pagh Jensen 《风能》2024,27(2):165-178
A model of the evolution of the onshore wind turbine blade mass installed in Denmark is proposed described by a Weibull distribution, and the age of the blades is estimated from decommissioning data to = 29 years when half of the blade mass of an installation year has been decommissioned. This is considerably longer than the 20 year design lifetime of onshore turbines, which is often assumed to be an estimate of the End-of-Life of turbine blades. Thus, blade waste predictions using the simple assumption may predict that installed blade masses are entering recycling processes about 9 years sooner that what is observed in Denmark. The blade mass for decommissioning in Denmark is estimated to peak at 2000 and 5000 ton/year in 2028 and 2045 using the Weibull model. 相似文献
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As an essential ingredient in the blade element momentum theory, the tip loss effect of rotors plays an important role in the prediction of wind turbine performance. Various tip loss corrections based on the Prandtl tip loss function are analysed in the article. Comparisons with measurements and theoretical analyses show that existing tip loss correction models are inconsistent and fail to predict correctly the physical behaviour in the proximity of the tip. A new tip loss correction model is proposed that remedies the inconsistency. Comparisons between numerical and experimental data show that the new model results in much better predictions of the loading in the tip region. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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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. 相似文献
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As wind turbines continue to grow in size, it becomes increasingly important to ensure that they are as structurally efficient as possible to ensure that wind energy can be a cost‐effective source of power generation. A way to achieve this is through weight reductions in the blades of the wind turbine. In this study, topology optimization is used to find alternative structural configurations for a 45 m blade from a 3 MW wind turbine. The result of the topology optimization is a layout that varies along the blade length, transitioning from a structure with trailing edge reinforcement to one with offset spar caps. Sizing optimization was then performed on a section with the trailing edge reinforcement and was shown to offer potential weight savings of 13.8% when compared with a more conventional design. These findings indicate that the conventional structural layout of a wind turbine blade is sub‐optimal under the static load conditions that were applied, suggesting an opportunity to reduce blade weight and cost. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The concept of a smart wind turbine system 总被引:1,自引:0,他引:1
A smart wind turbine concept with variable length blades and an innovative hybrid mechanical-electrical power conversion system was analyzed. The variable length blade concept uses the idea of extending the turbine blades when wind speeds fall below rated level, hence increasing the swept area, and thus maintaining a relatively high power output. It is shown for a typical site, that the annual energy output of such a wind turbine that could double its blade length, could be twice that of a corresponding turbine with fixed length blades. From a cost analysis, it is shown that the concept would be feasible if the cost of the rotor could be kept less than 4.3 times the cost of a standard rotor with fixed length blades. Given the variable length blade turbine system exhibits a more-or-less linear maximum power curve, as opposed to a non-linear curve for the standard turbine, an innovative hybrid mechanical-electrical power conversion system was proposed and tested proving the feasibility of the concept. 相似文献
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Fatigue testing of a 48.3 m wind turbine blade needs to utilize the blade's oscillation range of 8.4 m along the flapwise direction for one million cycles. Control of such a remarkable oscillation range makes flapwise fatigue testing difficult and requires a large supply of energy. This study minimized the actuating force required for flapwise fatigue testing using an on‐board‐type resonance exciter with constant amplitude. Constraints related to the exciter's stroke and capacity and the maximum error between target loads and test loads were also considered. Based on a new algorithm suggested in this study, first, we found test setup candidates minimizing the maximum error under a given testing frequency and then found more candidates having slightly larger maximum errors as the exciter's location moved toward the blade's tip. Next, using damping ratio equations for the test blade, a required actuating force of the exciter at each test setup candidate was calculated. Considering the exciter's capacity, we found an optimum test setup that requires a minimum actuating force in the vicinity of the minimum of the maximum error between target loads and test loads. To conclude, the approach suggested in this study was able to conclusively achieve the required fatigue testing of the test blade, avoiding the adverse increase of fatigue testing time possible to happen due to a required actuating force larger than the exciter's capacity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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During the last decade, the development of tidal current industries has experienced a rapid growth. Many devices are being prototyped. For various purposes, investors, industries, government and academics are looking to identify the best device in terms of of cost of energy and performance. However, it is difficult to compare the cost of energy of new devices directly because of uncertainties in the operational and capital costs. It may however be possible to compare the power output of different devices by standardizing the definition of power coefficients. In this paper, we derive a formula to quantify the power coefficient of different devices. Specifically, this formula covers ducted devices, and it suggests that the duct shape should be considered. We also propose a procedure to quantify the efficiency of a tidal current turbine farm by using the power output of the farm where no hydrodynamic interaction exists between turbines, which normalizes a given farm's power output. We also show that the maximum efficiency of a farm can be obtained when the hydrodynamic interaction exists. 相似文献
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Most blades available for commercial-grade wind turbines incorporate a straight, span-wise profile and airfoil-shaped cross-sections. These blades are found to be very efficient at low and medium wind speeds compared with the potential energy that can be extracted. This paper explores the possibility of increasing the efficiency of the blades by modifying the blade design to incorporate a swept edge. The design intends to maintain efficiency at low to medium wind speeds by selecting the appropriate orientation and size of the airfoil cross-sections based on an oncoming wind speed and given constant rotation rate. The torque generated from a blade with straight-edge geometry is compared with that generated from a blade with a swept edge as predicted by CFD simulations. To validate the simulations, the experimental curve of the NTK500/41 turbine using LM19.1 blades is reproduced using the same computational conditions. In addition, structural deformations, stress distributions and structural vibration modes are compared between these two different turbine blade surfaces. 相似文献
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大型水平轴式风电叶片的结构设计 总被引:1,自引:0,他引:1
风电叶片是风力发电设备的关键部件之一,其制造成本占总成本的20%~30%.叶片结构是叶片捕获风能的保证,并直接影响风力发电设备的运行寿命.因此,叶片结构设计的好坏在很大程度上决定了风力发电设备的可靠性和利用风能的成本.文章从材料、结构形式、铺层设计、结构分析等4个方面详细地阐述了风电叶片结构的设计技术. 相似文献
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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。 相似文献