垂直轴潮流能水轮机研究与利用现状

随着化石能源不断枯竭和环保要求的不断提高,世界各国对潮流能的开发利用愈加重视,垂直轴水轮机是潮流发电装置主要结构形式之一,本中介绍了垂直轴水轮机国内外利用现状和研究方法的进展情况,并指出垂直轴水轮机开发利用所需要解决和突破的技术难点和问题,为垂直轴水轮机开发利用指明了研究重点。     

固定偏角垂直轴潮流能水轮机叶片安装位置试验研究

叶片安装位置是影响固定偏角垂直轴潮流能水轮机水动力性能的关键参数之一,为了研究其对水轮机性能影响的基本规律,建立了垂直轴水轮机水槽模型试验系统,设计了垂直轴水轮机性能和载荷测试方法。通过试验结果的分析,得到了叶片安装位置对水轮机能量利用率、推力系数、侧向力系数和合力系数的影响规律,为水轮机设计提供了试验依据。     

不同交错排布对潮流能垂直轴水轮机性能的影响

为了优化潮流能垂直轴水轮机排布方案,采用计算流体动力学(CFD)方法得到双水轮机在不同轴间距H、不同相对位置角(RPA)β及前后排水轮机不同尖速比λ下平均功率系数CP变化规律,分析流场的速度和涡量云图,解释变化机理.同时,对比单、双水轮机尾流速度分布情况,探究双水轮机尾流特性.结果表明:后排水轮机处于前排水轮机尾流区内...     

基于正反装叶片的垂直轴潮流水轮机水动力性能分析

为了解不对称翼型叶片的正反安装对垂直轴潮流水轮机水动力性能的影响,运用CFD软件技术,建立了不对称叶片正反安装的潮流水轮机模型,分析了不对称叶片在正反两种安装方式下,叶片压力面和吸力面压力系数随叶片相位角不同而发生的变化,同时利用效率公式计算得到了效率。结果表明,叶片的正反安装对水轮机的水动力性能影响较大,当叶片正装即不对称翼型叶片凸向朝外时,垂直轴潮流水轮机效率优于叶片反装时,叶片在相位角为0°~120°区间转动时,转轮扭矩先增大后减小,在60°、180°、300°时得到最大扭矩。     

潮流能水轮机复合材料叶片结构力学性能分析及选型

叶片是潮流能水轮发电机的主要承载构件,直接影响着整机的性能和寿命。文章针对100 k W水平轴潮流能水轮发电机复合材料叶片,结合叶片受力特点,提出了腹板式和箱梁式两种全复合材料叶片结构,并应用有限元软件ANSYS建立了含有复合材料铺层信息的三维模型,分析了叶片的强度、叶尖挠度及材料失效性。通过对两种叶片结构对比分析表明,箱型梁式叶片的结构形式更为合理,叶片自重可减少21%。文章的研究成果可为今后同类叶片的设计提供参考。     

海水中固体颗粒对潮流能水轮机的冲蚀性能影响

潮流能水轮发电机是潮流能电站的核心技术装备之一,海水中固体颗粒的冲蚀损伤对水轮机叶片造成的伤害将直接影响机组的发电效率和运行的稳定性。利用计算机仿真技术,对潮流能水轮机叶片进行数值模拟,分析叶片的冲蚀速率和颗粒相的体积分数,判断叶片受损严重部位,对冲蚀性能进行评价。研究结果表明,该潮流能水轮机叶片的迎流面叶尖外边缘位置受损最严重。随着流速的增大,造成的冲蚀损伤几乎成倍数式增加;颗粒浓度造成的冲蚀损伤大小与速度呈正相关。研究结果对水轮机叶片结构的冲蚀性能评价具有指导意义,也可为结构设计的抗冲蚀性能优化提供参考。     

垂直轴潮流水轮机数值模拟研究

采用单向耦合欧拉-拉格朗日方法对垂直轴潮流水轮机( Vertical Axis Tidal Turbine)水动力性能和尾迹进行数值模拟研究,其中连续相采用雷诺平均Navier-Stocks方程(RANS)结合SST湍流模型求解,分散相颗粒的运动轨迹通过牛顿第二定律确定,叶片的尾迹通过颗粒的轨迹示踪.以文献[10]中在水槽中进行的垂直轴风力机试验为计算模型.将模拟结果与试验结果进行对比,叶片受力和叶片尾迹均与试验结果符合很好;对比前人的结果得到的叶片在不同位置角的瞬时受力规律也更加接近试验测得规律.     

同轴双转子H-Darrieus型潮流能水轮机起动扭矩研究

在各种潮流能水轮机中,垂直轴直叶片的H-Darrieus型水轮机结构简单、易于制造,而且具有适应不同方向来流的突出优点。但它的缺点是在低流速时自起动能力较差。为了克服这个缺点,文章把两个三叶片HDarrieus型水轮机转子同轴安装,且两转子对应叶片之间有一定夹角。利用数值模拟的方法,对这种双转子的H-Darrieus型水轮机的自起动性能进行了研究,表明双转子的安装夹角为60°时,水轮机的自起动性能最好。     

数据驱动的潮流能水轮机叶片翼型性能保真替代计算模型对比研究

在对翼型Bezier-PARSEC参数化软件FanOpt的应用方式改进后建立数据集,以翼型升阻比特性为目标,分别利用支持向量回归（SVR）、决策树、随机森林回归、全连接神经网络、一维卷积神经网络等机器学习模型进行拟合,训练模型比较拟合精度。结果表明,全连接神经网络、一维卷积神经网络作为替代计算模型在测试集上对升阻比的预测准确率可达97.86%,但相比于一维卷积神经网络,全连接神经网络在处理这种结构不复杂的数据集时更有优势。     

垂直轴潮流能水轮机不同翼型叶片空化规律

为研究垂直轴水轮机叶片翼型形状对叶片空化的影响,采用数值模拟方法,对相同条件下相同相对厚度不同相对弯度的翼型,以及相同相对弯度不同相对厚度的翼型做了空化仿真。仿真结果表明,相同相对厚度不同相对弯度的薄、厚两种翼型,随着相对弯度增大,空化现象越易出现。相同相对弯度不同相对厚度的对称、相对弯度不为零的两种翼型,随着相对厚度增大,空化现象越易出现。同时监测了不同情况下翼型的升力系数和阻力系数,考虑到空泡的出现对翼型升力和阻力有所影响,将能量转化参数中的升力系数、阻力系数和升阻比与空化性能结合起来讨论。并将翼型按照相对弯度与相对厚度分组,分别探讨了相对弯度和相对厚度对翼型空化的影响规律,翼形相对厚度相同时,相对弯度越大,或者翼形相对弯度相同,相对厚度越大,则更容易空化。     

Three-dimensional effects and arm effects on modeling a vertical axis tidal current turbine

Three-dimensional effects in studying a vertical axis tidal current turbine are modeled using a newly developed vortex method. The effects on predicting power output and wake trajectory are analyzed in particular. The numerical results suggest that three-dimensional effects are not significant when the height of the turbine is more than seven times the turbine radius. Further discussions are presented focusing on the relationship between the turbine height and the angle of attack and the induced velocity on a blade of the turbine without arms. Besides the three-dimensional effects, arms effects are quantified with an analytical derivation of the polynomial formula of the relationship between arm effects and the tip speed ratio of the turbine. Such a formula provides a correction for existing numerical models to predict the power output of a turbine. Moreover, a series towing tank tests are conducted to study the three-dimensional effects as well as the arm effects. Good agreements are achieved between the results obtained with numerical calculations with the arm effects correction and the towing tank tests. Finally, three-dimensional effects are examined experimentally together with the arm effects by using an end-plate test, which suggests that the combinational effect is rather minimal. For turbine designers at the early design stage, we recommend that a two-dimensional model is acceptable considering the high cost of the three-dimensional model.     

安装于跨海桥梁下部结构的竖轴潮流能水轮机水动力性能研究

文章采用物理模型实验和基于Fluent的二维数值模拟方法研究了竖轴水轮机安装在典型桥梁下部结构(单圆桩、圆端形墩台、四圆桩)且相对尺寸发生变化时,水轮机水动力性能的变化情况.研究结果表明:与桥梁下部结构组合后,竖轴水轮机的能量输出显著提升,单圆桩提升幅度最大,圆端形墩台次之,四圆桩最小;单圆桩和圆端形墩台相对水轮机尺寸...     

Fluid dynamic performance of a vertical axis turbine for tidal currents

This paper is concerned with the study of a novel design of turbine for tidal currents or fast-flowing streams, called the ‘Hunter Turbine’. The turbine consists of several flapping blades that are hinged on a revolving drum. Flow visualization experiments on a small model were conducted to provide some basic rules from which the movement of every flapping blade at every drum position could be determined. Two-dimensional quasi-steady CFD was then used to obtain detailed information about the flow field, including pressure and velocity contours, and the pressure distribution on the surface of the blades. It was found that the Hunter Turbine gives very satisfactory performance over a restricted range of flow coefficient. Under these conditions, the kinetic energy of the incident flow can be effectively transferred into the movement of the rotor, so that the average power coefficient (based on the projected area with an open blade) reaches a value of 0.19. Using the CFD results, a polynomial function is fitted to the dependence of an effective force coefficient for all blades on the rotational angle and the flow coefficient. The net forces acting on the surfaces of the blades can thus be interpolated between the calculated data points.     

水平轴潮流能水轮机尾流特性研究

文章以水平轴潮流能水轮机为研究对象,采用CFD方法对水轮机的尾流特性进行分析。通过网格无关性验证与已发表文献的比对,验证了CFD方法的精度。通过不同叶尖速比下的水轮机性能曲线,进一步分析了水轮机的尾流场速度分布特征。通过分析尾流场中轴向、径向和切向速度的分布特点,研究了水平轴潮流能水轮机尾流的微观结构特征及其演化规律。研究结果表明:尾流横向影响范围在以中心轴线为中心的1D范围内;在近尾流处,尾流速度具有周期性,轴向速度随着尾流下移而逐渐减小;在尾流旋转过程中,径向速度向外扩散并逐渐衰减,切向速度分量沿轴向逐渐衰减。     

导流涵道对垂直轴水轮机性能影响的研究

垂直轴水轮机作为重要的潮流能捕获装置,相比于水平轴水轮机,它具有结构简单、适应任意水流等优点,但获能效率较低。为了增大垂直轴水轮机的获能效率,文章提出了一种导流涵道装置。采用CFD方法研究了其增速性能,并探究了水轮机在导流涵道下的输出扭矩特性,最后讨论了水轮机与导流涵道之间的间距对获能效率和转矩的影响。研究表明:导流涵道在一定程度上增大了来流的速度,涵道中心处速度可增大至原来的2倍。在导流涵道作用下,水轮机转矩脉动系数减小了0.474。水轮机与导流涵道的间距对效率与转矩产生了显著的影响,当间距为0.175倍水轮机直径时,其能源利用率达到最大,同时转矩系数在0.1倍直径时降至最小。     

Hydrokinetic energy harvesting by an innovative vertical axis current turbine

This study proposes an innovative turbine that consists of a vertical flat plate, which is allowed to rotate freely about a vertical axis of symmetry and exploits the autorotation phenomenon to harvest the energy from the current. This system is called here Vertical Axis Autorotation Current Turbine (VAACT). The VAACT utilizes the extra mass moment of inertia to improve the rotational quality which is state of the art in this turbine. This paper covers the principle behind the VAACT and outlines procedures and results for experiments proving the basic feasibility. Also, the operation of the turbine will be discussed by experimental results of the torque coefficient, performance and kinematic parameters. Tests were conducted in LOC (Laboratory of Wave and Current) at COPPE/Federal University of Rio de Janeiro (COPPE/UFRJ).Utilizing the extra mass moment of inertia on the VAACT causes to extract the energy as an efficient turbine in very low head current. The maximum VAACT efficiency has been obtained experimentally in optimum non-dimensional moment of inertia in range of 0.5 and 0.6.     

Numerical analysis of the characteristics of vertical axis tidal current turbines

Tidal current is considered to be one of the promising alternative green energy resources. Tidal current turbines are devices used for harnessing tidal current energy. The development of a standard for tidal current turbine design is a very important step in the commercialization of tidal current energy as the tidal current industry is growing rapidly, but no standard for tidal current turbines has been developed yet. In this paper, we present our recent efforts in the numerical simulation of the characteristics (e.g., power output, torque fluctuation, induced velocity, and acoustic emission) of tidal current turbines related to the development of the standard. The relationship between the characteristics and the parameters of an example turbine are extensively discussed and quantified. The findings of this paper are expected to be helpful in developing the standards for tidal current turbines in the near future.     

Experimental study on kinetic energy conversion of horizontal axis tidal stream turbine

The present study aims to understand the energy conversion mechanism of a 100 kW horizontal axis tidal stream turbine by analyzing thrust, torque, and wake flow measurements. The scale ratio of the turbine model was 1/20 and model tests for power and wake measurements were conducted in a towing tank facility. Wake fields were measured by a towed underwater stereoscopic particle image velocimetry (SPIV) system. The chord-length based Reynolds number at 40% of the radius of the turbine ranged from 53,000 to 63,000 in the test conditions. The turbine model showed the highest power coefficient at a tip speed ratio (TSR) of 3.5, and the magnitude of power coefficient was 0.278. Three TSR conditions were selected for SPIV measurement after power measurement tests, representing heavy loading, highest efficiency, and light loading, respectively. In the wake field measurement results, conversion of kinetic energy of the turbine wake was investigated, decomposing it into effectively extracted work, loss due to the drag on the turbine system, kinetic energy of the time-mean axial flow, local flow structures, turbulence, and secondary flow loss. In high TSR conditions with a small angle of attack onto the turbine blade, the secondary flow loss was minimized.     

Wind tunnel and numerical study of a small vertical axis wind turbine

This paper presents a combined experimental and computational study into the aerodynamics and performance of a small scale vertical axis wind turbine (VAWT). Wind tunnel tests were carried out to ascertain overall performance of the turbine and two- and three-dimensional unsteady computational fluid dynamics (CFD) models were generated to help understand the aerodynamics of this performance.Wind tunnel performance results are presented for cases of different wind velocity, tip-speed ratio and solidity as well as rotor blade surface finish. It is shown experimentally that the surface roughness on the turbine rotor blades has a significant effect on performance. Below a critical wind speed (Reynolds number of 30,000) the performance of the turbine is degraded by a smooth rotor surface finish but above it, the turbine performance is enhanced by a smooth surface finish. Both two bladed and three bladed rotors were tested and a significant increase in performance coefficient is observed for the higher solidity rotors (three bladed rotors) over most of the operating range. Dynamic stalling behaviour and the resulting large and rapid changes in force coefficients and the rotor torque are shown to be the likely cause of changes to rotor pitch angle that occurred during early testing. This small change in pitch angle caused significant decreases in performance.The performance coefficient predicted by the two dimensional computational model is significantly higher than that of the experimental and the three-dimensional CFD model. The predictions show that the presence of the over tip vortices in the 3D simulations is responsible for producing the large difference in efficiency compared to the 2D predictions. The dynamic behaviour of the over tip vortex as a rotor blade rotates through each revolution is also explored in the paper.