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《可再生能源》2016,(6)
文章基于CFD方法对NREL Phase VI风机的气动特性进行了数值模拟。根据NREL定桨变速的实验工况,通过求解三维非定常雷诺平均Navier-Stokes方程(RANS),基于k-ωSST湍流模型分析了不同风速工况下的风机叶片流场特性,得到了气流沿叶片展向的流动分布。通过与NREL NASA-Ames风洞实验数据的对比,在低风速时采用CFD仿真的计算结果与实验结果更为吻合;在失速区域,由于气流分离的影响,CFD仿真的计算结果与实验结果对比差异较明显。CFD仿真大体上能够较好地预测实验风机的性能,分析动态失速现象发生的原因,揭示叶片在三维旋转效应下的非定常气动特性。 相似文献
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Mitigating loads on a wind turbine rotor can reduce the cost of energy. Sweeping blades produces a structural coupling between flapwise bending and torsion, which can be used for load alleviation purposes. A multidisciplinary design optimization (MDO) problem is formulated including the blade sweep as a design variable. A multifidelity approach is used to confront the crucial effects of structural coupling on the estimation of the loads. During the MDO, ultimate and damage equivalent loads are estimated using steady‐state and frequency‐domain–based models, respectively. The final designs are verified against time‐domain full design load basis aeroelastic simulations to ensure that they comply with the constraints. A 10‐MW wind turbine blade is optimized by minimizing a cost function that includes mass and blade root flapwise fatigue loading. The design space is subjected to constraints that represent all the necessary requirements for standard design of wind turbines. Simultaneous aerodynamic and structural optimization is performed with and without sweep as a design variable. When sweep is included in the MDO process, further minimization of the cost function can be obtained. To show this achievement, a set of optimized straight blade designs is compared to a set of optimized swept blade designs. Relative to the respective optimized straight designs, the blade mass of the swept blades is reduced of an extra 2% to 3% and the blade root flapwise fatigue damage equivalent load by a further 8%. 相似文献
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Wind turbine wakes have been recognized as a key issue causing underperformance in existing wind farms. In order to improve the performance and reduce the cost of energy from wind farms, one approach is to develop innovative methods to improve the net capacity factor by reducing wake losses. The output power and characteristics of the wake of a utility‐scale wind turbine under yawed flow is studied to explore the possibility of improving the overall performance of wind farms. Preliminary observations show that the power performance of a turbine does not degrade significantly under yaw conditions up to approximately 10°. Additionally, a yawed wind turbine may be able to deflect its wake in the near‐wake region, changing the wake trajectory downwind, with the progression of the far wake being dependent on several atmospheric factors such as wind streaks. Changes in the blade pitch angle also affect the characteristics of the turbine wake and are also examined in this paper. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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通过分析翼型在固定转捩状态下的风洞实验数据,获得了污染对叶片各区域翼型气动性能的影响规律,即污染使叶尖区(0.6r/R≤1)、叶展中区(0.4r/R≤0.6)和近叶根区(0.2r/R≤0.4)翼型的升力系数减小、阻力系数增加、最大升力系数和最大升阻比减小,同时也导致叶根区(r/R≤0.2)翼型升力系数的复杂变化。污染发生在叶片前缘时对气动性能影响最大。风力机叶片在风场被污染后的实验数据表明,随着尘粒变大、污染面积增大,输出功率下降。另外,通过对叶尖区21%相对厚度翼型的几何参数进行设计,获得了抗污效果更好的新翼型。 相似文献
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The accurate prediction of the aerodynamics and performance of vertical‐axis wind turbines is essential if their design is to be improved but poses a significant challenge to numerical simulation tools. The cyclic motion of the blades induces large variations in the angle of attack of the blades that can manifest as dynamic stall. In addition, predicting the interaction between the blades and the wake developed by the rotor requires a high‐fidelity representation of the vortical structures within the flow field in which the turbine operates. The aerodynamic performance and wake dynamics of a Darrieus‐type vertical‐axis wind turbine consisting of two straight blades is simulated using Brown's Vorticity Transport Model. The predicted variation with azimuth of the normal and tangential force on the turbine blades compares well with experimental measurements. The interaction between the blades and the vortices that are shed and trailed in previous revolutions of the turbine is shown to have a significant effect on the distribution of aerodynamic loading on the blades. Furthermore, it is suggested that the disagreement between experimental and numerical data that has been presented in previous studies arises because the blade–vortex interactions on the rotor were not modelled with sufficient fidelity. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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The blade element momentum (BEM) method is widely used for calculating the quasi‐steady aerodynamics of horizontal axis wind turbines. Recently, the BEM method has been expanded to include corrections for wake expansion and the pressure due to wake rotation (), and more accurate solutions can now be obtained in the blade root and tip sections. It is expected that this will lead to small changes in optimum blade designs. In this work, has been implemented, and the spanwise load distribution has been optimized to find the highest possible power production. For comparison, optimizations have been carried out using BEM as well. Validation of shows good agreement with the flow calculated using an advanced actuator disk method. The maximum power was found at a tip speed ratio of 7 using , and this is lower than the optimum tip speed ratio of 8 found for BEM. The difference is primarily caused by the positive effect of wake rotation, which locally causes the efficiency to exceed the Betz limit. Wake expansion has a negative effect, which is most important at high tip speed ratios. It was further found that by using , it is possible to obtain a 5% reduction in flap bending moment when compared with BEM. In short, allows fast aerodynamic calculations and optimizations with a much higher degree of accuracy than the traditional BEM model. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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基于动网格技术,通过编写UDF代码成功实现了叶片的一阶弯振及一二阶叠加弯振。数值模拟过程中,采用大涡模拟(LES)分析刚性叶片与低阶弯振后风轮近尾迹速度与涡量特征。运用FW-H方程,以风轮表面为声源面,通过选取不同测试线上的监测点分析叶片不同运动状态下辐射声频谱及声压级变化。研究结果表明:施加振动后,在0.71R处出现轴向速度亏损,且在叶尖位置亏损最大;振动风轮整体噪声增大。文章通过研究模拟振动风轮的尾迹流动和噪声分析,为实际运行的风力机产生的气动噪声及声辐射传播特性提供一定参考。 相似文献
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The velocity field in the wake of a two‐bladed wind turbine model (diameter 180 mm) has been studied under different conditions using a two‐component hot wire. All three velocity components were measured both for the turbine rotor normal to the oncoming flow as well as with the turbine inclined to the freestream direction (the yaw angle was varied from 0° to 20°). The measurements showed, as expected, a wake rotation in the opposite direction to that of the turbine. A yawed turbine is found to clearly deflect the wake flow to the side, showing the potential of controlling the wake by yawing the turbine. An unexpected feature of the flow was that spectra from the time signals showed the appearance of a low‐frequency fluctuation both in the wake and in the flow outside the wake. This fluctuation was found both with and without freestream turbulence and also with a yawed turbine. The frequency expressed as a Strouhal number was shown to be independent of the freestream velocity or turbulence level, but the low frequency was only observed when the tip speed ratio (or equivalently the drag coefficient) was high. The shedding frequency changed also with the yaw angle. This is in agreement with the idea that the turbine sheds structures as a bluff body. The phenomenon, noticeable in all the velocity components, was further investigated using two‐point cross‐correlations of the velocity signals. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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This paper presents a model for the evaluation of aerodynamic and inertial contributions to a vertical-axis wind turbine (VAWT) blade deformation. Through the use of a specially designed coupling code, a solid modeling software, capable of generating the desired blade geometry depending on the design geometric parameters, is linked to a finite volume Computational Fluid Dynamic (CFD) code for the calculation of rotor performance and to a Finite Element Method (FEM) code for the structural design analysis of rotor blades. After describing the computational model and the relative validation procedure, a full RANS unsteady calculation is presented for a three-bladed rotor architecture, characterized by a NACA 0012 profile. Flow field characteristics are investigated for a constant unperturbed free-stream wind velocity of 9 m/s, determining the torque coefficient generated from the three blades as a function of rotor azimuthal coordinate. The emphasis is subsequently placed on obtaining an estimate for both pressure/tangential forces and centrifugal ones to blade structural loadings, thus assessing the influence of aerodynamic and inertial contributions to blade stresses and deformations. 相似文献
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利用有限元理论,基于Ansys Workbench工作平台,针对某小型水平轴风力发电机组,计算了不同工况时叶片应变特性的变化。计算结果显示:叶片在气动力作用下最大应变位置位于叶根与叶片径向的0.65 R处、叶片在离心力作用下最大应变位置位于叶根处;在恒定来流风速、低尖速比时,气动力引起的叶片应变大于离心力引起的应变,但随着尖速比的增加,离心力引起的应变值大于气动力作用时的应变值,其原因为离心力正比于尖速比和风速乘积的二次方,而气动载荷仅正比于风速的二次方;气动力与离心力耦合作用时,最大应变位置位于叶根处,离心力与气动力耦合作用时引起的应变不等于离心力与气动力单独作用引起应变之和。研究结果可为风力机叶片机械强度设计提供一定的理论支撑。 相似文献
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涡流发生器是风电机组中控制流动分离的一种有效方式。以目标风场的具体空气密度、风况等作为主要输入,对拟加装的涡流发生器的形状和安装位置进行模拟仿真,获得理论最优解,仿真计算发电量可提升1%。涡流发生器在风电场进行现场安装试验,对运行整1年的运行数据进行分析,分别对加装涡流发生器的机组和相邻对照组从实际发电量、实际功率曲线估算应发电量等方面评估发电量增益情况。结果表明:在年平均风速为5.06 m/s时,通过加装涡流发生器,发电量提升约为1%,与前期仿真计算值相符合;此外,由于湍流、偏航误差等的存在,加装涡流发生器后,功率值提升的风速范围较理论值有所拓宽。 相似文献