风力发电机外文翻译

上传人:hknru****knru 文档编号:76394656 上传时间:2022-04-18 格式:DOC 页数:21 大小:672KB
返回 下载 相关 举报
风力发电机外文翻译_第1页
第1页 / 共21页
风力发电机外文翻译_第2页
第2页 / 共21页
风力发电机外文翻译_第3页
第3页 / 共21页
点击查看更多>>
资源描述
精选优质文档-倾情为你奉上为电力设计并研制三分之一比例的垂直轴风力发电机摘要:本文通过对风力涡轮机技术测量风速的研究来阐述马来西亚的发电技术。测量超过三分之一比例的原型垂直轴风力发电机的风速,其主要目的是预测全尺寸H型垂直轴风力涡轮机的性能。风力发电机产生的电力受发电机的两个主要部分的影响:风力发电和皮带传动系统。叶片、阻力区系统和皮带传动系统决定转化成电力的风力能,转化成电力的风受叶片、阻力区系统和皮带传送系统的影响。本文主要研究风力和皮带传送系统的影响。塞格林工业大学热工学系实验室为这个三分之一规模的风力发电机组设计了一套叶片和拖动装置。风力发电机组分别进行5.89米/秒、6.08米/秒和7.02米/秒的风速测试。从实验中计算出风力分别为132.19W,145.40W和223.80W。目前的研究正在探索最大风力。关键词: 皮带传送系统; 雷诺数; 风力; 风力发电机组引言:风能是一种动能,与大气运动密切相关。它已被用于航行船、磨粮食、灌溉数百年,风力发电系统将动能转化为更加有用其他形式的能量,自古以来风力发电系统就被应用在灌溉、磨坊中;自20世纪初,它就开始被用来发电,许多国家尤其在农村地区都安装了水抽水风车。风轮机是一台把风的动能转换成旋转机械能的机器,然后被用来工作,在更先进的机型里旋转机械能通过发电机被转换成电能,这是能量最通用的形式(菲茨沃特等,1996)。几千年来,人们利用风车抽水或磨粮食,即使进入二十世纪,身材高大、苗条、多叶片完全由金属制成的风力发电机也已经进入美国家庭和牧场将水抽到房子的管道系统或牲畜的饮水槽,第一次世界大战后,主要的工作是开始发展可以产生电力的风力涡轮机,马塞勒斯雅各布在1927年发明了一种可以为收音机和一些灯提供能量的原型,但仅仅如此。当电力需求增加后,Jacobs的小型的有不足的风力发电机开始不用。第一个大型风力涡轮机由帕尔默考斯莱特普特南在1934年美国建立起构思的,完成于1941年。这台机器非常巨大,该身有36.6码(33.5米)高,它的两个不锈钢叶片直径有58码(53米)。Putnam的风力涡轮机可以产生一千二百五十千瓦电力,足以满足一个小城镇的需要(莫内特等,1994)。然而由于机械故障在1945年就被遗弃了。随着20世纪70年代石油禁运,美国又开始考虑从风力涡轮机生产廉价电力的可行性。1975年,Mod-O原型开始运作,这是一个有两个21码(19米)叶片的100千瓦涡轮。更多的原型机(Mod-OA, Mod-1, Mod-2)每个都比前一次更大更有能量。目前,美国能源部的目标是每台机器超越3200千瓦。风力涡轮机以许多不同的模式存在着,其中最引人注目的是垂直轴达里厄风力发电机,其形状极像打蛋器(菲茨沃特等,1996)。该模型由制造商鼎力支持,是一个拥有约100万千瓦能和三个长度不超过33码(30米)叶片的水平轴涡轮机。三叶片风力涡轮机旋转更加顺畅,比两片叶片更容易平衡。另外,更大的风力发电机产生更多的能量,较小的型号是不太可能发生重大机械故障,从而更经济地维护。风力发电场如雨后春笋般遍布了美国,其中最引人注目的是加利福尼亚州。风力发电场是一个在顺风风力涡轮机生产领域的巨大阵列。风力涡轮机的大量互联是必要的,以便产生足够的电力以满足庞大人口的需求。目前,由几个风能源公司拥有在风力发电场的17000台风力涡轮机每年每小时能产生的电力三十七点零亿千瓦,足以满足50万家庭的能源需求。风力涡轮机由三个基本部分组成:塔,机舱,转子叶片。塔是由一个类似电塔的钢格塔和一个钢管塔里面有梯子可以通到发动机舱两部分组成,构建风力涡轮机的第一步是架设塔。虽然塔的钢件在工厂制造,但是它们通常是在现场组装。在安装之前先把零件用螺栓连在一起,然后塔必须与地面保持水平,起重机将塔吊到他指定的位子上,所有螺栓拧紧并稳定,然后再完整的测试,接下来,安装玻璃钢机舱。其在工厂里的内部工作是把主传动轴,齿轮箱和刀片俯仰和偏航控制装配到底座上(哈蒙斯,2004年),然后机舱闩上围绕设备,在现场,机舱是被吊过来与塔一起闩到位,此外,一个在转子表面的风力涡轮机的空气动力学在空气动力学领域内是非常重要的,转子轴带了一个风向标通过在垂直方向安装一个控制轴去定位叶片来改变风向。采用转子叶片间距调节其轴转身使叶片和转子的气动特性得到控制。风能使旋翼飞机跟随变换的风向而导致旋翼飞机偏航,集线器是转子刚性螺栓连接和转子转速相联系是相对固定的电网频率,未来只能得到更好的风力涡轮机。用于风能的潜力大部分尚未开发,美国每年由风产生的潜在电力总量约为10777亿千瓦时(基思,2005)。这些新的风力发电场示范着风能如何可以帮助满足国家日益增长的既经济实惠又可靠的电力需求。随着政府继续鼓励从而加快了其发展,这种可再生能源的竞争日趋激烈的来源将在2020年提供至少百分之六的国家电力。现在正进行研究,以增加对风力资源的知识。这包括在更多的地方测试其建立风力发电厂的可能性,那里的风强大有力且能被利用. 计划实际上是把机器的寿命从5年提高到20年甚至30年,改善叶片的频率,提供更好的控制,发展传动系统使寿命更长从而允许更好的保护和接地。美国能源部最近建立一个计划去开发最新研究,为了打造出比现在一个理想的风力涡轮机效率百分之59.3还要高的风力发电机(Milligan和Artig,1999) ,也就是说,59.3风的能源百分之可以被捕获。在实际使用中涡轮机效率约百分之三十,美国能源部还签约三家公司进行调查以减少机械故障,该项目始于1992年春,将延伸到本世纪末。风力发电机将在未来几年内会变得越加普遍,在世纪之初我们应该看到被妥善安置且高效耐用以及众多的涡轮机。据风力涡轮机的背景调查,H型垂直轴风力发电机在雪兰莪工业大学的热工实验室被设计出来,他们以具备自主研发的能力。此外,这台机器已经被设计允许各种各样的修改,比如叶片的轮廓,而且还进行了多次的测试。这个设计的第一部分包括了研究,集思广益,工程分析,涡轮机的设计选择和样机试验。使用通过适当的调查结果获得的数据,最终完整的涡轮机就被设计建造出来了。风力发电机以轴为标准可以被分为两类,水平轴风力机(HAWT)和垂直轴风力发电机(VAWT)。水平轴风力机在近地面很难被操作,动荡的风流会导致叶片的偏航,则叶片轴承得做得更加的光滑来避免更多层次的风流,水平轴风力机也很难去安装,这需要非常高且昂贵的起重机和熟练的操作技巧,顺风变种会遭遇疲劳,由湍流会引起结构失效,它的高度为低空飞行的飞机造成了安全隐患。除此之外,水平轴风力涡轮机的空气动力学是相当复杂的,在叶片上的气流跟远离涡轮机的气流是不一样的。这种十分自然的从空气中提取能量的方式通过涡轮机使风向改变。另外,在旋转体表面,应用于风力发电机的空气动力学包括了几乎在其他应用领域看不到的效用。学者们提出了许多不同构造类型的垂直轴风力发电机。达里厄的垂直型风力发电机是最常见的,我们广泛使用它来产生电能。然而,达里厄的发电机也像劣质的能源市场一样遭受构造性问题。为了提高风力发电机的效用,本文致力于设计并建立三分之一比例的H型垂直轴风力发电机,能够根据风的流动而自我启动。垂直轴风力发电机的高效性能将改变人们对风能被利用的标准的思考,而且能激励未来垂直轴风力发电机的设计和研究。提高风力发电机性能的研究包括对拖动装置的研究。风机设计 理论分析 在这个研究里,皮带驱动系统由皮带的传动计算和被考虑在内的V带这几部分组成,因此主要的计算是在这个系统里小型和大型皮带轮包角、皮带的长度、滑轮的速度、张力比和皮带的传动功率。V带结构如图一所示,阐明了V带的主要部分,例如:大轮的直径用3表示,小轮的直径用2表示,大轮的包角用3表示,小轮的包角用2表示。C表示着大轮和小轮两圆心间的距离。大皮带轮包角大型滑轮包角的定义是(约瑟夫等,2004年) (1)将大轮直径D3 =30.4810-2m,小轮直径D2 =5.08 10 -2m和圆心距C=0.3048m这些数据带入到公式(1)中,可以获得大轮的包角3 = 229.25。小皮带轮包角小型滑轮包角的定义是(约瑟夫等,2004年) (2)在公式(2)中利用上述相同的数据可以得到小轮的包角2 = 130.75。中心半径长中心半径长度的定义是(约瑟夫等,2004年) (3)将大轮直径D3 =30.4810-2m,小轮直径D2 =5.08 10 -2m和圆心距C=0.3048m这些数据带入到公式(3)中,可获得半径长度L =1.221 m。拉紧侧张力和松弛侧张力的比率拉紧侧张力和松弛侧张力的比率的定义是(约瑟夫等,2004年) (4)皮带的摩擦系数为0.25,3是前面提到的小轮包角的弧度(4 rad),T1是张力T2是松弛力,将上述提到的数据代入到公式(3)中,可以得到拉紧侧张力和松弛侧张力的比率T1/T2 = 1.545拉紧侧皮带张力拉紧侧皮带张力的定义是(佐尔格,1996年)T1 = Wg (5) 通过选择涡轮机上部分的总重量W=17kg和采用重力加速度g=9.81 m/s2,然后代入公式(5),可以获得拉紧侧皮带张力T1 = 166.77 N 松弛侧张力使用公式4中T1的数值,可以获得松弛边的张力T2 = 107.94 N。滑轮速度滑轮的速度的定义是(约瑟夫等,2004年) (6)皮带传送的能量皮带传送的能量的定义是(约瑟夫等,2004年)PB = (T1 T2 )V (7) 将拉紧侧张力T1=166.77N、松弛侧张力T2=107.94N和滑轮速度V=2.84m/s带入到公式7中,可以获得皮带传送的能量PB = 167.08 W。原型设计1/3比例的垂直轴风力发电机的组件是在雪兰莪工业大学的结构实验室,通过CATIA软件设计出来的。将这些组件组装在一起能预示实际比例的垂直轴风力发电机的实际效用。风力发电机由三个连接发动机转子的锥形叶片组成,并且在开放性的大厅做过测试。两端的尖顶处为风力发电机叶片的机翼,随着它在气流中的运作而产生可控制的空气动力,如图2所示。接下来会描述另一个已经被设计出来建造风力发电机的重要组件。基面和基表 这个基础材料选择为钢是因为它的高度是6096mm,它的重量为15kg,这个基础本身不支持风力发电机产生的瞬间扭矩,所以设定了基地扩展和连接支架,为了连接4个钢支架,以38.10 mm 76.2 mm的钢铁做成的底托盘为基础钢件,该38.10 mm 38.10 mm结构的钢板提供快速装配和拆卸涡轮机基础结构的能力。底部托架需要四个简单的焊缝,为了达到快速装配,平头螺栓需要焊接在这个位置,用四张1219.20 mm2438.40 mm 19.05 mm大小的钢板来建造一个碱基延伸,为砝码提供大托盘。中心钢板和另外两片在同一边,还有在上面的两片与底部的两片相垂直。这样就建造了一个2438.40 mm 2438.40 mm规模的基表,如图三所示。轴和轴承轴用钢为材料,设计成城邦柄的形状,重14千克,直径为30 mm,长2133.6 mm。它的表面光滑,当与轴承接触的时候,轴旋转的十分平滑。最大限度的减少所需的启动扭矩对风力涡轮机自我启动是十分关键的,因而,也对该项目的成功与否十分重要。设计用于风力涡轮机的轴是不能打捞的。轴承价格昂贵,为特定的项目设定的双轮轴承已经投入使用,主要轴集中在一起。这种组合能使摩擦最小化,轴承寿命最长化,并提供安全的操作环境。每个轴承的直径是88 mm,重300 克。支撑臂和阻力装置钢铁用于三个支撑摇臂去维持携带最小惯性扭距和离心力的轻量级组装,连接臂是叶片和中心轴的介质,拖动设备用轻质塑料(铸塑)制成用来安装在主轴上。拖动装置的长度约为762毫米,宽度182.88毫米。风力发电机叶片设计顶部和底部的每一个叶片都有1066.8 mm 139.7 mm 50.8 mm深矩形截面用来更容易地连接径向臂和被动变桨系统。在这项研究中角尖被设定为叶片的形状,因为叶片有抵抗风流量和在风流量中产生的快速旋转的性能。风力发电机最后的组装定于雪兰莪工业大学的热工实验室里展现在图4中。在装配工程中共有18个零件和15个螺栓组装在一起。在垂直轴风力发电机全部组装期间,轴连接到中心部位和发电机。实验方法雪兰莪工业大学的风力发电机原型被安装在雪兰莪工业大学的热工实验室里,也进行了许多初步的实验,而且都操作成功。在开始操作之前,蓄电池和交流发电机端部都进行严格地检查,它们都连接着灯和开关,这样风力发电机能够旋转。由于风力发电机叶片旋转产生的电压,所连接的电灯就开启了。(图5)产生的电压读数和各自的涡轮旋转都被记录下来了。周边的压力和温度分别用压力机和温度计测量,为了在雪兰莪工业大学的环境实验室里总结出对空气密度的评价。我们也测量了风速产生的能量,记录在标本测量部分。主要的测试都是在塞格林工业大学的热工学系实验室一个开放的大厅进行的,那里的风速为4到 6 m/s,有时阵风会使风速达到7 m/s。 这测试中,风力涡轮机根据设计进行运作,然后打开叶片,风被推动,最终它验证了叶片关闭时产生的足够的升力。似乎涡轮机在不产生升力的地区慢速太多。所以叶片保持开放是为了能够旋转。其次,开放的叶片能检测在阻力位置中可获得的最大转速。在这个位置上,我们观察到很多的能使涡轮机旋转的迎风面。样本计算绝对压力p = 1.01105N/m2 ,温度T = 38.5oC=311.5K。利用理想气体方程式的空气密度的状态是 1.13 kg/m 3,其定义是(伯廷,2002) (8) 其中,压强p是1.01 10 5 N/m2 ,温度T 是311.5 K,空气气体常数R是 287.05 Nm/kg K。空气粘度用萨瑟兰的方程式计算(伯廷,2002),其方程式如下,是动力粘度。 (9) T为311.5 K时,方程式9算出为1.9010-5kg/m s。基于弦长的雷诺数的定义是(安德森,1996) (10) 在方程式10中,用空气密度等于1.13 kg/m3 ,自由流速度= 5.89 m/s,动力粘度=1.9010-5kg/ms,弦长c = 0.1397 m,得出雷诺数Re = 0.4 105。 对余下的速度,其相对应的雷诺数呈现在表1中,长方形叶片的单表面面积的定义如下(贝尔坦,2002):表 1自由流速度和雷诺数序列号 自由流速度y(m/s) 雷诺数1 5.89 0.49 1052 6.08 0.51 1053 7.02 0.58 105S = bc (11) 对于风力发电机总的表面积ST = 1.145 m2 且定义为(贝尔坦,2002):ST = (S1)T + (S2)T (12) 在这里叶片的总表面积为(S1)T = 0.4482 m2 ,总的阻力面面积为(S2)T = 0.6968m2风力涡轮机的功率定义为(法官和云,2004) (13) 在这里空气密度 = 1.130kg/m3,总的表面积ST =1.145m 2 ,风速 = 5.89m/s,把这些值代入方程式13,我们可以得到: 对余下的速度与其相对应的的风能呈现在表2中结果与讨论试验用3个不同的速度5.89 m/s, 6.08m/s and 7.02 m/s在雪兰莪工业大学公开实施,以测量出来的的速度为基础,前面一个环节已经计算出了为原型提供的风能,如表2所示,对于表1中的雷诺数计算值已在上一节得到介绍。在已经实施的测试中,对于测量出的速度变量,风力和雷诺数之间的关系的进一步了解会在下表中呈现。表 2.速度和相对应风能 序列号. 速度 (m/s) 风能 (W) 1 5.89 132.19 2 6.08 145.40 3 7.02 223.80 雷诺数雷诺数的数值越高,表明风力涡轮机能产生更多的力量,这是因为风速值的增加。风速值是在风速为7.02 m/s的测试中测量并记录下来的。翼型几何为三刃垂直轴风力发电机选择适当翼型在设计讨论中是十分重要的。我们必须考虑不同的形状会带来不同的优缺点。然后,由于翼型和刀片而影响风流的喜好是不明显得,在刀片循环中产生的阻力也是可以忽略的。此外,这个模型中设计和使用的刀片不同于国家航空咨询委员会的0012或者0015,它们主要应用于低雷诺数区。但是现在这项方案中选择的型号,当轴在风流中旋转时,仍然具有持久耐用性和高效能性。拖动设备几何当前项目中使用的拖动设备能为叶片提供外部支持,通过收集最大的风流量,初始化叶片和轴的旋转。拖动设备对于小风流也十分敏锐,即使在设定的地点风速十分小叶能让叶片和轴旋转起来。在对于这个模型进行测试期间,风被外部的阻力堵塞或者围绕到其他地方。把净扭距因式分解,然后驱动外部阻力围绕着轴,诱导涡轮旋转,从而产生出离心力。旋转速度会慢慢增大直到一个涡轮机的移动速度足以被上升力驱动的临界点。开式和闭式的阻力机制设计出离心力在这个临界速度克服惯性力和直接力的能力。特别是,这设备在低速尖率比也能有一个非常强大的扭矩特性,意味着它能自动启动。然而困难的是调试的扭矩测量和控制系统目前为止已经推迟了一定的采集测试数据。涡轮机的可行性比较从目前1 / 3规模的风力发电站计算出来的风能看,根据使用类型和估计费用对现有的发电机进行全面的比较,如表3所示。卧龙岗大学的项目已经生产出了使用传动系统可获得最大风能700W,格里菲斯大学已经使用类似的系统生产出了550W电力(库伯&肯尼迪,2003;克瑞克,2003)。在当前项目中被测试的原型用皮带和滑轮系统产生了167W电力。根据对风速的评估,当风速增大时,当前的模型能超越现有的设备。当前的模型能在风速增长到20 m/s时发出567.33W电力,在增长到25 m/s时发出709.17W电力。所有的比较的表面,在价格和产生的能力方面考虑,当前使用皮带和滑轮系统的模型比其它使用传动系统的产品更具有可行性。总结此次实验的总结如下:(1) 当风力最大增加到12 m/s时,模型产生的风力最大能达到1000W。(2) 调查研究表明当20 m/s时产生567.33W电力,在增加到25 m/s时发出709W电力。术语Symbol Meaning Unit p Absolute pressure (N/m)T Temperature (K) R Gas constant (Nm/kg K) Air density (kg/m) Air viscosity (kg m/s) Free stream velocity (m/s) c Chord length (m) Re Reynolds number (Dimensionless) B Blade height (m) S1 Blade frontal surface area (m) S2 Drag device frontal area (m) ST Total frontal area (m) Pwind Wind power (W) 鸣谢 作者对雪兰莪工业大学提供的资金支持,工程学院提供全部的工程设备表示衷心的感谢。参考文献:Anderson, J.D.Jr. (1999) Aircraft Performance and Design. McGraw Hill Companies Inc., U.S.A. Bench, S.E., Cloud, P.K. (2004) The Measure, Predict and Calculate the Power response of an Operating Wind Turbine. 1 st Ed., London, Jepson Pub, 366 p. Bertin, J. J. (2002) Aerodynamics for the Engineer. New Jersey, Prentice Hall, Inc., U.S.A. Cooper, P., Kennedy, O. (2003) Development and Analysis of a Novel Vertical Axis Wind Turbine. Bachelor. Thesis, University of Wollongong, NSW 2522, AustraliaFitzwater, L.M., Cornell, C.A., Veers, P.S. (1996) Using Environmental Contours to Predict Extreme Events on Wind Turbines. Wind Energy Symp., AIAA/ASME, 9, 244258. Hammons, T.J. (2004) Technology and Status of Developments in Harnessing the Worlds Untapped Wind-Power Resources. Electricity Power Components and Systems. No.12, p. 32. Joseph, E.S, Charles, R.M, Richard, G.B. (2004) Mechanical Engineering Design. 7 th Ed., United State of America. p. 1030. Keith, David W. (2005) The Influence of Large-Scale Wind Power on Global Climate. Proc. National Academy of Sciences, Washington D.C, Vol. 101, pp. 1256.Kirke, B.K. (2003) Evaluation of self-starting vertical axis wind turbines for stand alone applications. PhD Thesis, Griffith University, Australia. Milligan, M.R. & Artig, R. (1999) Choosing Wind Power Plant Locations and Sizes Based on Electric Reliability Measures Using Multiple-Year Wind Speed Measurements. National Renewable Energy Laboratory, 8, 52p. Monett, G., Poloni, C. & Diviacco, B. (1994) Optimization of wind turbine positioning in wind farms by means of large development. J. of Wind Engng and Ind. Aerod 23(4), 10516 Sorge, F. (1996) A qualitative-quantitative approach to v-belt mechanics.ASME,J.of Mechanical Design 118(8)DESIGN AND DEVELOPMENT OF A 1/3 SCALE VERTICALAXIS WIND TURBINE FOR ELECTRICAL POWERGAbstract: This research describes the electrical power generation in Malaysia by the measurement of wind velocity acting on the wind turbine technology. The primary purpose of the measurement over the 1/3 scaled prototype vertical axis wind turbine for the wind velocity is to predict the performance of full scaled H-type vertical axis wind turbine. The electrical power produced by the wind turbine is influenced by its two major part, wind power and belt power transmission system. The blade and the drag area system are used to determine the powers of the wind that can be converted into electric power as well as the belt power transmission system. In this study both wind power and belt power transmission system has been considered. A set of blade and drag devices have been designed for the 1/3 scaled wind turbine at the Thermal Laboratory of Faculty of Engineering, Universiti Industri Selangor (UNISEL). Test has been carried out on the wind turbine with the different wind velocities of 5.89 m/s, 6.08 m/s and 7.02 m/s. From the experiment, the wind power has been calculated as 132.19 W, 145.40 W and 223.80W.The maximum wind power is considered in the present study.Keywords: Belt power transmission system; Reynolds number; wind power; wind turbine INTRODUCTION Wind energy is the kinetic energy associated with the movement of atmospheric air. It has been used for hundreds of years for sailing, grinding grain, and for irrigation. Wind energy systems convert this kinetic energy to more useful forms of power. Wind energy systems for irrigation and milling have been in use since ancient times and since the beginning of the 20th century, it is being used to generate electric power. Windmills for water pumping have been installed in many countries particularly in the rural areas.Wind turbine is a machine that converts the winds kinetic energy into rotary mechanical energy, which is then used to do work. In more advanced models, the rotational energy is converted into electricity, the most versatile form of energy, by using a generator (Fitzwater et al., 1996). For thousands of years people have used windmills to pump water or grind grain. Even into the twentieth century tall, slender, multi-vaned wind turbines made entirely of metal were used in American homes and ranches to pump water into the houses plumbing system or into the cattles watering trough. After World War I, work was begun to develop wind turbines that could produce electricity. Marcellus Jacobs invented a prototype in 1927 that could provide power for a radio and a few lamps but little else. When demand for electricity increased later, Jacobss small inadequate wind turbines fell out of use. The first large-scale wind turbine built in the United States was conceived by Palmer Cosslett Putnam in 1934; he completed it in 1941. The machine was huge. The tower was 36.6 yards (33.5 meters) high, and its two stainless steel blades had diameters of 58 yards (53 meters). Putnams wind turbine could produce 1,250 kilowatts of electricity, or enough to meet the needs of a small town (Monett et al., 1994). It was, however, abandoned in 1945 because of mechanical failure. With the 1970s oil embargo, the United States began once more to consider the feasibility of producing cheap electricity from wind turbines. In 1975 the prototype Mod-O was in operation. This was a 100 kilowatt turbine with two 21-yard (19-meter) blades. More prototypes followed (Mod-OA, Mod-1, Mod-2, etc.), each larger and more powerful than the one before.Currently, the United States Department of Energy is aiming to go beyond 3,200 kilowatts per machine. Many different models of wind turbines exist, the most striking being the vertical-axis Darrieus, which is shaped like an egg beater (Fitzwater et al., 1996). The model most supported by commercial manufacturers, however, is a horizontal-axis turbine, with a capacity of around 100 kilowatts and three blades not more than 33 yards (30 meters) in length. Wind turbines with three blades spin more smoothly and are easier to balance than those with two blades. Also,while larger wind turbines produce more energy, the smaller models are less likely to undergo major mechanical failure, and thus are more economical to maintain. Wind farms have sprung up all over the United States, most notably in California. Wind farms are huge arrays of wind turbines set in areas of favorable wind production. A great number of interconnected wind turbines are necessary in order to produce enough electricity to meet the needs of a sizable population. Currently, 17,000 wind turbines on wind farms owned by several wind energy companies produce 3.7 billion kilowatt-hours of electricity annually, enough to meet the energy needs of 500,000 homes. A wind turbine consists of three basic parts: the tower, the nacelle, and the rotor blades. The tower is either a steel lattice tower similar to electrical towers or a steel tubular tower with an inside ladder to the nacelle. The first step in constructing a wind turbine is erecting the tower. Although the towers steel parts are manufactured off site in a factory, they are usually assembled on site. The parts are bolted together before erection, and the tower is kept horizontal until placement. A crane lifts the tower into position, all bolts are tightened, and stability is tested upon completion. Next, the fiberglass nacelle is installed. Its inner workings main drive shaft, gearbox, and blade pitch and yaw controls are assembled mounted onto a base frame at a factory (Hammons, 2004). The nacelle is then bolted around the equipment. At the site, the nacelle is lifted onto the completed tower and bolted into place. In addition, the aerodynamics of a wind turbine at the rotor surface is very much important in aerodynamic fields. The rotor axis is brought to a vertical orientation with a wind vane mounted on a control shaft to orientate the blades with changing wind direction. Using pitch regulation the rotor blades turn around their axis so that the aerodynamic characteristics of the blade and rotor are controlled. The rotor is yaw out of the wind which turns the rotor plane to follow the changing wind direction. The hub is connected to the rotor with rigid bolt connection and the rotational speed of the rotor is fixed relative to the frequency of the grid. The future can only get better for wind turbines. The potential for wind energy is largely untapped. The total amount of electricity that could potentially be generated from wind in the United States has been estimated at 10,777 billion kWh annually (Keith, 2005). These new wind farms demonstrate how wind energy can help to meet the nations growing need for affordable, reliable power. With continued government encouragement to accelerate its development, this increasingly competitive source of renewable energy will provide at least six percent of the nations electricity by 2020. Research is now being done to increase the knowledge of wind resources. This involves the testing of more and more areas for the possibility of placing wind farms where the wind is available and strong. Plans are in effect to increase the life span of the machine from five years to 20 to 30 years, improve the efficiency of the blades, provide better controls, develop drive trains that last longer, and allow for better surge protection and grounding. The United States Department of Energy has recently set up a schedule to implement the latest research in order to build wind turbines with a higher efficiency rating than is now possible (the efficiency of an ideal wind turbine is 59.3 percent (Milligan & Artig, 1999). That is, 59.3 percent of the winds energy can be captured. Turbines in actual use are about 30 percent efficient). The United States Department of Energy has also contracted three corporations to investigate ways to reduce mechanical failure. This project began in the spring of 1992 and will extend to the end of the century. Wind turbines will become more prevalent in upcoming years. The turn of the century should see wind turbines that are properly placed, efficient, durable, and numerous. From the investigation of this wind turbine background, an H-type, vertical axis wind turbine has been designed and built in thermal Laboratory Universiti Industri Selangor that has the capability to self-start. In addition, this turbine has been designed to allow a variety of modifications such as blade profile and pitching to be tested. The first part of the design process, which included research, brainstorming, engineering analysis, turbine design selection, and prototype testing have been incorporated. Using data obtained through proper investigation results, the final full-scale turbine has been designed and built. Wind turbines can be separated into two types based by the axis in which the turbine rotates namely horizontal axis wind turbine (HAWT) and the vertical axis wind turbine (VAWT). HAWT has difficulty oper
展开阅读全文
相关资源
相关搜索

最新文档


当前位置:首页 > 办公文档 > 教学培训


copyright@ 2023-2025  zhuangpeitu.com 装配图网版权所有   联系电话:18123376007

备案号:ICP2024067431-1 川公网安备51140202000466号


本站为文档C2C交易模式,即用户上传的文档直接被用户下载,本站只是中间服务平台,本站所有文档下载所得的收益归上传人(含作者)所有。装配图网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私,请立即通知装配图网,我们立即给予删除!