Numerical and Experimental Investigation of Aerodynamic Performance of Vertical-Axis Wind Turbine Models with Various Blade Designs

Due to the importance and advantages of Vertical-axis wind turbines (VAWTs) over traditional horizontal-axis wind turbines (HAWTs), this paper is implemented. Savonius turbines with drag-based rotors are adopted from the two more extensive arrangements of vertical wind turbines because of their advantages. In this paper, six diverse rotor plans with measure up to cleared regions are analyzed with exploratory wind burrow testing and numerical reenactments. These proposed models incorporate a conventional Savonius with two different edges criteria and 90 degree helical bend models with two, three and four sharp edges. The models were designed using SolidWorks software then the physical models were 3D printed for testing. A subsonic open-sort wind burrow was utilized for Revolution per Minute (RPM) and torque estimation over a scope of wind speeds. ANSYS Fluent reenactments were utilized for dissecting streamlined execution by using moving reference outline and sliding lattice display methods. A 3-dimensional and transient strategy was utilized for precisely tackling torque and power coefficients. The five new rotor geometries have important advantages such as making a focal point of weight advance from the hub of revolution and causing more noteworthy torque on the turbine shaft contrasted with the customary Savonius turbine. Our new models with the names of CC model and QM model display cross-areas lessen the aggregate scope of negative torque on the edges by 20 degrees, contrasted with the customary Savonius demonstrate. Helical plans are better spread the connected torque over a total transformation resulting in positive torque over every single operational point. Moreover, helical models with 2 and 3 cutting edges have the best self-starting ability in low wind speeds. Helical VAWT with 3 edges starts revolution of 35 RPM at only 1.4 m/s wind speed under no generator stacking. The most noteworthy power coefficient is accomplished, both tentatively and numerically, by the helical VAWT with 2 sharp edges.

Influence of the Blade Bifurcated Tip on the Correlation between Wind Turbine Wheel Vibration and Aerodynamic Noise

To reduce the vibration and aerodynamic noise of wind turbines,a new design is proposed relying on a blade with a bifurcated apex or tip.The performances of this wind turbine wheel are tested at the entrance of a DC(direct-action)wind tunnel for different blade tip angles and varying centrifugal force and aerodynamic loads.The test results indicate that the bifurcated apex can reduce the vibration acceleration amplitude and the vibration fre-quency of the wind wheel.At the same time,the bifurcated apex can lower the maximum sound pressure level corresponding to the rotating fundamental frequency of the wind wheel.According to all thesefindings,the tip angle of the bifurcated apex is the main factor enhancing the effect of the modification.

Safety evaluation for railway vehicles using an improved indirect measurement method of wheel–rail forces

The wheel-rail force measurement is of great importance to the condition monitoring and safety evaluation of railway vehicles. In this paper, an improved indirect method for wheel-rail force measurement is proposed to evaluate the running safety of railway vehicles. In this method, the equilibrium equations of a suspended wheelset are derived and the wheel-rail forces are then be obtained from measured suspension and inertia forces. This indirect method avoids structural modifications to the wheelset and is applicable to the long-term operation of railway vehicles. As the wheel-rail lateral forces at two sides of the wheelset are difficult to separate, a new derailment criterion by combined use of wheelset derailment coefficient and wheel unloading ratio is proposed. To illustrate its effectiveness, the indirect method is applied to safety evaluation of rail- way vehicles in different scenarios, such as the cross wind safety of a high-speed train and the safety of a metro vehicle with hunting motions. Then, the feasibility of using this method to identify wheel-rail forces for low-floor light rail vehicles with resilient wheels is discussed. The values identified by this method is compared with that by Simpack simulation for the same low-floor vehicle, which shows a good coincidence between them in the time domain of the wheelset lateral force and the wheel-rail vertical force. In addition, use of the method to determine the high-frequency wheel-rail interaction forces reveals that it is possible to identify the high-frequency wheel-rail forces through the accelerations on the axle box.

A Preliminary Feasibility Study on Wind Resource and Assessment of a Novel Low Speed Wind Turbine for Application in Africa

This paper posits that a low-speed wind turbine design is suitable for harnessing wind energy in Africa.Conventional wind turbines consisting of propeller designs are commonly used across the world.A major hurdle to utilizing wind energy in Africa is that conventional commercial wind turbines are designed to operate at wind speeds greater than those prevalent in most of the continent,especially in sub-Sahara Africa(SSA).They are heavy and expensive to purchase,install,and maintain.As a result,only a few countries in Africa have been able to include wind energy in their energy mix.In this paper,the feasibility of a novel low-speed wind turbine based on a Ferris wheel is demonstrated for low wind speed applications in Africa.The performance of Ferris wheel wind turbines(FWT)with 61m(200 ft),73m(240 ft)and 104m(341 ft)diameter rims and an 800kW generator are evaluated for selected African cities.The research also compares the Weibull wind distribution of the African cities of interest.A comparison between the FWT and the conventional commercial wind turbines in terms of efficiency,rated wind speed,cost,performance,and power to weight is included.Results show that the FWT has the potential for economic power generation at rated wind speeds of 6.74m/s,which are lower than the average of 12 m/s for conventional wind turbines and have lower power to weight ratios of 5.2 kW/tonne as compared to 6.0-9.2 kW/tonne for conventional wind turbines.

Structural Design Optimization of a Vertical Axis Wind Turbine for Seismic Qualification and Lightweight

Recently, there is a growing interest in seismic qualification of ridges, buildings and mechanical equipment worldwide due to increase of accidents caused by earthquake. Severe earthquake can bring serious problems in the wind turbines and eventually lead to an interruption to their electric power supply. To overcome and prevent these undesirable problems, structural design optimization of a small vertical axis wind turbine has performed, in this study, for seismic qualification and lightweight by using a Genetic Algorithm (GA) subject to some design constraints such as the maximum stress limit, maximum deformation limit, and seismic acceleration gain limit. Also, the structural design optimizations were conducted for the four different initial design variable sets to confirm robustness of the optimization algorithm used. As a result, all the optimization results for the 4 different initial designs showed good agreement with each other properly. Thus the structural design optimization of a small vertical-axis wind turbine could be successfully accomplished.

局部冲刷下砂土中桩-盘复合基础V-H组合承载特性

海上风电基础除承受复杂组合荷载作用外,也受波流冲刷作用.为探讨局部冲刷对砂土地基中V-H联合加载下单桩-摩擦盘复合基础承载特性的影响,基于自行设计的室内水槽试验装置,完成了一系列冲刷及模型载荷试验,获得了复合基础冲刷前后的荷载-位移曲线,经无量纲化处理与曲线拟合,得到复合基础承载包络线及其简化计算公式.计算结果表明:局部冲刷作用使复合基础的竖向及横向抗力明显降低,削弱程度分别约12.1%和26.9%.进一步分析表明:存在一个最优预加竖向荷载(V),其对复合基础的极限横向承载力起到最显著的增强效果;此外,局部冲刷作用导致V-H联合受荷单桩-摩擦盘复合基础的承载包络线明显向内收缩,所提出的简化计算公式可供工程应用参考.

基于液压夹轮制动的门式起重机抗风防滑装置研究

门式起重机作为货物装卸机械的主要机型之一,其动态抗风防滑性能是安全使用的关键因素。针对当前动态抗风防滑装置的研究现状,通过分析液压夹轮器防滑机理,利用传感器技术、液压系统和夹轮器,研发一种门式起重机动态液压抗风防滑装置,实现在带电、停电状态下全过程实施制动,制动响应用时短,能满足不同型号起重机抗风防滑需求。通过试验检测,验证了方案可行性与稳定性,已授权实用新型专利。该装置具有较大的推广价值,为相关门式起重机抗风防滑装置的开发设计提供了参考。

海上兆瓦级风电机组风轮吊具研究

风轮吊具是风电机组吊装风轮的重要装置,由于风轮吊具连接面受限于轮毂结构,通常风轮吊具连接螺栓安全系数在交变载荷的吊装工况下较难满足设计要求,需优化吊具结构和增大吊具连接螺栓安全系数。以某兆瓦级风电机组风轮吊具为例,通过三维软件对吊具进行参数化建模,利用有限元法对风轮吊具抬吊和对接工况进行数值分析。提出了基于梁体的吊具连接螺栓计算方法,通过研究吊具主板厚度、筋板位置、螺栓规格和螺栓拉伸力参数,计算风轮吊具和螺栓强度,并对吊具结构进行对比优化。结果显示:风轮吊具在对接工况下的吊具等效应力约为抬吊工况的1.2倍,而吊具变形则为抬吊工况的一半。各试验工况,风轮吊具的最大等效应力和最大变形均出现在吊具吊耳孔连接处。各试验条件,吊具连接螺栓等效应力波动较大。经优化,螺栓最大等效应力减少了20%。结果表明:对于相同吊装工况,风轮吊具的等效应力和变形波动较小。仅计算吊具等效应力和变形时,可忽略连接螺栓对吊具等效应力的影响。采用上筋板、增大主板厚度和螺栓规格、适当增大轮毂小端侧螺栓拉伸力的方式能一定程度上降低吊具螺栓等效应力。经现场实际验证,优化结果可行,对后续机组的吊具设计优化提供了借鉴和参考。

塔影效应下风轮仰角对风力机气动特性的影响

考虑风力机塔影效应的影响,针对风轮仰角导致风力机气动特性更为复杂的问题,文章对不同仰角水平轴风力机流场进行了数值模拟,分析了风力机叶片截面压力分布、涡量以及塔筒表面压力随相位角的变化规律,探究了风轮仰角对风力机输出功率的影响。结果表明:增大风轮仰角会降低叶片表面压力,减小叶尖部分压差,使得叶片表面高涡量区域减小;添加风轮仰角会使叶片对塔筒影响减小,塔筒表面高涡量区域随着风轮仰角的增大逐渐减小,降低塔筒表面压力波动。当叶片经过塔筒时,塔影效应对风力机影响较大,风力机输出功率降低;当叶片竖直向上时,风力机输出功率达到最大。为风力机添加仰角后,随着风轮仰角的增大,风力机的输出功率与输出功率波动均呈现先增大后减小的趋势;风力机输出功率在风轮仰角为3°时最大,输出功率波动在风轮仰角为6°时最小。

基于贝叶斯推理的风电机组风轮偏航协同智能控制方法

风向的变化对风电机组的偏航控制是一个挑战。对于风向的频繁变化,如果风电机组的反应速度过慢,无法及时调整偏航角度,将会影响发电效率。为了准确控制风电机组风轮偏航问题,文章提出了一种基于贝叶斯推理的风电机组风轮偏航协同智能控制方法。在考虑风速随机性的情况下,分析风向信号,获取风向样本数据。引入贝叶斯分类器,结合风向正态分析模型,计算服从上一批样本分布的风向样本后验概率,将其作为警戒值调节基准,建立基于贝叶斯推理的网络警戒值调节机制,通过爬山算法调节警戒值,完成风电机组风轮偏航协同智能控制。实验结果表明,所提方法对风电机组风轮偏航展开协同智能控制后,机舱位置出现偏航的次数为0,且偏航控制时间短,表明该方法可以完成风电机组风轮偏航协同智能控制。

风载作用下高速列车曲线通过性能研究

在风载和曲线欠超高叠加的不利工况下,高速列车的运行安全性表现出复杂的变化规律,因此需要针对风载作用下高速列车的曲线通过安全性进行深入研究。采用空气动力学和车辆动力学相结合的分析方法,考虑车速和风速变化、实际轮轨匹配及线路激励情况,建立瞬态风载模型、横风作用下高速列车空气动力学模型及车辆动力学模型;对高速列车在不同车速和风速作用下的气动载荷变化规律进行分析,并对其以不同速度通过不同欠超高曲线线路时的脱轨系数、轮重减载率和轮轴横向力等车辆关键动力学参数的变化规律进行分析,研究风载和曲线欠超高对高速列车脱轨和倾覆的影响。结果表明:风速变化引起的侧向力系数变化幅度大于车速;在风载和曲线欠超高叠加的不利工况下,除轮重减载率安全裕量明显降低外,轮轴横向力的安全裕量也降低,且车辆关键悬挂部件工作状态恶化,其中二系横向止档的位移迅速增大且工作状态接近压并,左右两侧空气弹簧压力差也迅速增大,车辆动力学性能的安全裕量明显下降。

Effect of additional cylinders on power-extraction performance of a Savonius vertical-axis wind turbine

To improve the power-extraction performance of the Savonius vertical-axis wind turbine(S-VAWT),additional cylinders,which are used to control the fluid flow around the wind turbine blade,were introduced into the blade design.In contrast to the traditional numerical method,a mathematical model in the form of a dynamical system was used in this study.A numerical calculation program that could effectively solve the equations of wind-induced rotation of S-VAWT was developed,and combined with the Taguchi experimental method to investigate the influence of additional cylinders on the power-extraction characteristics of the S-VAWT.The results showed that the additional cylinders have a significant impact on the power-extraction performance of the S-VAWT.At 4-m/s wind speed,the average power coefficient of the S-VAWT with additional cylinders is 15%higher than that of the conventional S-VAWT.After construction of the wind turbine prototype and power-extraction tests,the results showed that compared with a conventional S-VAWT,the output power was 29%higher for the S-VAWT with additional cylinders under the same particular conditions.

最佳阵风转速控制参数的现场试验方法

本研究是通过现场试验方法得到的最佳转速控制参数使风电机组在风况不定,风速不稳的阵风条件下达到稳定运行,并兼顾风轮储能、输出稳定以及减少机组及部件的疲劳损坏等多个目标的实现。本文将就机组的阵风控制及控制转速参数寻优的现场试验方法进行阐述。

基于MATLAB与Pro/E的风力机风轮设计及造型

针对风力机风轮设计复杂、造型困难的问题,根据Wilson法的设计流程,采用MATLAB开发了小型风力机叶片气动外形设计的通用程序,自动输出叶片截面空间坐标,解决了MATLAB与Pro/E之间的数据传输问题,程序得到的设计结果直接导入Pro/E,实现了风轮的三维造型。该方法同时完成了风轮的程序化设计和参数化造型,提高了风轮设计与造型的效率和精度。

风力机风轮低频振动特性的实验模态研究

利用国际上先进的PULSE16.1结构振动分析系统,对4个风力机风轮进行模态测试,发现风轮在挂机状态下,低频时存在轴向窜动效应和圆盘效应两种普遍存在的振动方式。振动发生时叶根处分别伴随着往复式和回转式剪切应力,影响到风力机的安全稳定运行和寿命。同时,利用挂机实验对比证明了通常采取的风轮通过夹具安装后在平面上进行模态实验的方法,对风轮振动特性的完整和准确获得均存在一定的影响。初探性分析,轴向窜动效应的产生因主要与塔架的弹性有关;圆盘效应的产生因主要与风轮的安装方式有关。相关研究成果有可能为很多风力机叶片在远短于设计寿命期频繁发生疲劳损伤事故的分析提供新的思路和理论支撑。

基于CFD的旋转风轮气动性能分析

采用Fluent 6.3软件,并结合SSTk-ω模型对1.2 MW风力发电机旋转风轮流场进行了数值模拟,对设计转速为18.44 r/min工况下三叶片风轮与相同叶片单叶片、双叶片以及四叶片风轮流场的输出功率与湍动能进行了比较,并分析了风轮旋转对叶片间流动的影响.结果表明:旋转上游叶片在转动过程中会发生附着涡的脱落,导致旋转下游叶片周围流场的环境发生变化,对叶片转矩及输出功率造成较大影响.在翼型优化中,考虑叶片间作用可以提高风力发电机的效率.

车轮旋转条件下前轮导流板气动减阻机理研究

为优化上海通用某款车型的气动特性,降低风阻系数,利用风洞试验和流场数值模拟研究了不同高度的前轮导流板的减阻效果。数值模拟实现了车轮转动和地面移动,其结果与风洞试验值基本一致,各导流板方案减阻效果明显。根据数值模拟获得的流场分布信息,分析了前轮导流板的减阻机理及其对整车流场特性影响,为导流板减阻设计提供了参考。

小型垂直轴风力发电机风轮效率的试验研究

以提高效率为目的,对影响垂直轴风力发电机风轮效率的叶片曲率、数量及安装角进行了理论分析与试验研究,试验结果证明了理论分析的合理性。给出了采用弧形叶片、30°安装角及叶片数量为12时风轮效率较高的明确结论,为今后的深入研究打下了良好的基础。

风力机风轮振动频率及应力特性试验研究

利用Pulse16.1结构振动分析系统,针对直径为1.4 m的小型水平轴风力机风轮进行静态固有振动频率和动态振动频率测试.研究发现:气动载荷对风轮二阶以下振动动频影响相对较小,且对一、二阶反对称振动动频的影响略大于对称振动动频;离心力对风轮二阶以下振动动频影响较显著,且对一、二阶对称振动动频的影响大于对反对称振动动频.此外,圆盘效应所引起的振动应力高于二阶以下其他振动应力,轴向窜动效应引起的振动应力介于一、二阶振动应力之间,这一结论与风轮静频测试中所获应力结果有很大的差异性,从而也考证了通过风轮静态测试间接分析其动态振动应力的方法并不适用.相关研究成果可为风力机在远短于设计寿命期内频繁发生疲劳损伤或断裂提供新的分析思路,同时为小型风力机风轮结构动力学性能的合理设计提供一定的理论支撑.

风力机风轮结构阻尼比改进方法研究

针对某风力机风轮结构,提出了翼型加厚、新型双夹板式叶片连接、叶片沿翼展方向开槽和加肋3种结构改进方法,利用B&K公司最新研究的PULSE16.1结构振动分析系统对原翼型风轮和3种结构改进的风轮进行模态测试,获得了风轮结构改进对其阻尼比的影响特性。研究发现,3种结构改进方法均可有效改变风轮阻尼比随振动阶数升高跌宕起伏变化的规律,其中尤其以翼型加厚造成的影响最为显著;翼型加厚对通常关注的1,2阶振动的阻尼比影响相对显著,双夹板式叶片连接方式、叶片沿翼展方向的开槽和加肋两种改进方法则对1,2阶振动的阻尼比影响相对较小,且较均匀。相关研究成果对风轮阻尼比的设计和优化具有较重要的实用价值。