離心風(fēng)機(jī)英文文獻(xiàn)

1、Centrifugal fanA centrifugal fan (also squirrel-cage fan , as it looks like a hamster wheel) is a mecha ni cal device for moving air or gases. It has a fan wheel composed of a nu mber of fan blades, or ribs, moun ted around a hub. As show n in Figure 1, the hub tur ns on a driveshaft that passes thr

2、ough the fan housing. The gas enters from the side of the fan wheel, turns 90 degrees and accelerates due to cen trifugal force as it flows over the fan blades and exits the fan hous inFigure 1Cen trifugal fans can gen erate pressure rises in the gas stream. Accordi ngly, they are well-suited for in

3、 dustrial processes and air polluti on con trol systems. They are also com mon in cen tral heati ng/cooli ng systems.1. Fan comp onentsThe major comp onents of a typical cen trifugal fan in clude the fan wheel, fan hous ing, drive mecha ni sm, and inlet an d/or outlet dampers.2. Types of drive mecha

4、 ni smsThe fan drive determines the speed of the fan wheel (impeller) and the extent to which this speed can be varied. There are three basic types of fan drivSk 2.1Direct driveThe fan wheel can be linked directly to the shaft of an electric motor. This means that the fan wheel speed is identical to

5、 the motor's rotational speed. With this type of fan drive mecha ni sm, the fan speed cannot be varied uni ess the motor speed is adjustable.Figure 2: Cen trifugal fan with a belt driveBelt driven fans use multiple belts that rotate in a set of sheaves mounted on the motor shaft and the fan whee

6、l shaft.This type of drive mechanism is depicted in figure 2. The belts transmit the mecha ni cal en ergy from the motor to the fan.The fan wheel speed depe nds upon the ratio of the diameter of the motor sheave to the diameter of the fan wheel sheave and can be obtained from this equation：(niotcfrw

7、here:rpmfan:=fan wheel speed, revolutio ns per minuterpm motor :=motor n ameplate speed, revoluti ons per minuteDmotor=diameter of the motor sheaveDfan=diameter of the fan wheel sheaveFan wheel speeds in belt-drive n fans are fixed uni ess the belts slip. Belt slippage can reduce the fan wheel speed

8、 several hun dred revoluti ons per minute (rpm).2.2Variable driveVariable drive fans use hydraulic or magn etic coupli ngs (betwee n the fan wheel shaft and the motor shaft) that allow con trol of the fan wheel speed in depe ndent of the motor speed. The fan speed con trols are ofte n in tegrated in

9、to automated systems to mai ntai n the desired fan wheel speedsAn alter nate method of vary ing the fan speed is by use of an electr onic variable-speed drive which controls the speed of the motor driving the fan. This offers better overall en ergy efficie ncy at reduced speeds tha n mecha ni cal co

10、upli ngs.2.3 Fan dampersFan dampers are used to con trol gas flow into and out of the cen trifugal fan. They may be in stalled on the inlet side or on the outlet side of the fan, or both. Dampers on the outlet side impose a flow resistance that is used to control gas flow. Dampers on the inlet side

11、are desig ned to con trol gas flow and to cha nge how the gas en ters the fan wheel.Inlet dampers reduce fan energy usage due to their ability to affect the airflow pattern into the fan 里3. Backward-curved bladesBackward-curved blades, as in Figure 3(b), use blades that curve aga inst the directi on

12、 of the fan wheel's rotati on. The backward curvature mimics that of an airfoil cross secti on and provides good operati ng efficie ncy with relatively econo mical con struct ion tech niq ues. These types of fan wheels are used in fans desig ned to han dle gas streams with low to moderate partic

13、ulate load in gs. They can be easily fitted with wear protecti on but certa in blade curvatures can be prone to solids build-up.Backward curved fans can have a high range of specific speeds but are most ofte n used for medium specific speed applicati on s- high pressure, medium flow applicati ons.Ba

14、ckward-curved fans are much more en ergy efficie nt tha n radial blade fans and so, for high horsepower applicatio ns may be a suitable alter native to the lower cost radial bladed fan.4. Straight radial bladesRadial fan blades, as in Figure 3(c), exte nd straight out from the hub. A radial blade fa

15、n wheel is ofte n used on particulate-lade n gas streams because it is the least sensitive to solids build-up on the blades, but it is often characterized by greater noise output. High speeds, low volumes, and high pressures are com mon with radial fans, and are ofte n used in vacuum clea ners, pn e

16、umatic material con vey ing systems, and similar processes.(a/ Fcrviard Curved(Jb) BzK-kwardl Curve«l屯R 尺耳日Figure 35. Cen trifugal fan rati ngsRati ngs found in cen trifugal fan performa nee tables and curves are based on sta ndard air SCFM. Fan manu facturers defi ne sta ndard air as clea n, d

17、ry air with a den sity of 0.075 pounds mass per cubic foot (1.2kg/n)3with the barometric pressure at sea level of 29.92 inches of mercury (101.325kPa) and a temperature of 70 (21 °). Selecti ng a cen trifugal fan to operate at con diti ons other tha n sta ndard air requires adjustment to both s

18、tatic pressure and brake horsepower. The volume of air will not be affected in a given system because a fan will move the same amount of air regardless of the air den sity.If a cen trifugal fan is to operate at a non-sta ndard den sity, the n correct ions must be made to static pressure and brake ho

19、rsepower. At higher tha n sta ndard elevati on (sea level) and higher tha n sta ndard temperature, air den sity is lower tha n sta ndard density. Centrifugal fans that are specified for continuous operation at higher temperatures n eed to be selected tak ing into acco unt air den sity correct ions.

20、Agai n, a cen trifugal fan is a con sta nt volume device that will move the same amount of air at two differe nt temperatures.If, for example, a centrifugal fan moves 1,000 ft2min (28 mmin) at 70 F ° (21 C) it will also move 1,000 ft3/min (28 mmin) at 200 F (93 C°. Centrifugal fan air volu

21、me delivered by the centrifugal fan is not affected by density. However, since the 200 F°(93 C°air weighs much less than the 70 F (21 C)°r, the centrifugal fan will create less static pressure and will require less brake horsepower. Selecting a centrifugal fan to operate at conditions

22、 other than standard air requires adjustment to both static pressure and power. When a centrifugal fan is specified for a given CFM and static pressure at conditions other than standard, an air density correction factor must be applied to select the proper size fan to meet the new con diti on. Since

23、 20F (93 C) air weighs only 80% of 70 F (21 C)air, the centrifugal fan will create less pressure. To get the actual pressure required at 20F (93 C), the designer would have to multiply the pressure at sta ndard con diti ons by an air den sity correct ion factor of 1.25 (i.e., 1.0 / 0.8) to get the s

24、ystem to operate correctly. To get the actual power at 200 F°(93 C), the designer would have to divide the power at standard conditions by the air den sity correct ion factor.離心風(fēng)機(jī)是一種機(jī)械裝置移動(dòng)空離心風(fēng)機(jī)（也鼠籠式風(fēng)扇，因?yàn)樗雌饋?lái)像倉(cāng)鼠輪）氣或氣體。它有一個(gè)風(fēng)扇輪組成若干風(fēng)扇葉片，或肋骨，裝在一個(gè)樞紐。如圖1所示，該中心將在驅(qū)動(dòng)軸，穿越風(fēng)扇住房。氣體進(jìn)入從側(cè)面的風(fēng)扇方向盤(pán)，把90度，并加快由于離心力因?yàn)?/p>

25、它流動(dòng)的風(fēng)扇葉片和出口風(fēng)扇住房。1 離心式風(fēng)機(jī)可產(chǎn)生壓力上升氣流。因此，他們非常適合工業(yè)加工和空氣污染 控制系統(tǒng)。他們還共同在中央供暖/冷卻系統(tǒng)。圖11.風(fēng)機(jī)組件主要組成部分典型的離心式風(fēng)機(jī)包括風(fēng)扇輪， 風(fēng)扇住房，驅(qū)動(dòng)機(jī)制，進(jìn)口和/或出口閘。2類(lèi)型的驅(qū)動(dòng)機(jī)制風(fēng)扇驅(qū)動(dòng)器決定的速度，風(fēng)扇輪（葉輪）以及在何種程度上這樣的速度可以多 種多樣。有三種基本類(lèi)型的風(fēng)機(jī)驅(qū)動(dòng)器。1 2.1直接驅(qū)動(dòng)風(fēng)扇輪可以直接聯(lián)系的骨干一個(gè)電動(dòng)馬達(dá)。 這意味著，風(fēng)扇輪速是相同的電 機(jī)轉(zhuǎn)速。這種類(lèi)型的風(fēng)機(jī)驅(qū)動(dòng)機(jī)制，風(fēng)扇轉(zhuǎn)速不能更改，除非是可調(diào)的電機(jī)轉(zhuǎn)速。 帶傳動(dòng)rpm圖2 :離心風(fēng)機(jī)用皮帶驅(qū)動(dòng)風(fēng)扇driveBelt使用多重皮帶旋

26、轉(zhuǎn)的一套滑輪 安裝在電機(jī)軸和風(fēng)扇輪軸。這種類(lèi)型的驅(qū)動(dòng)機(jī)制是描繪在圖2。皮帶傳遞機(jī)械 能的電機(jī)風(fēng)扇。風(fēng)扇輪速取決于比例的直徑電機(jī)帶輪的直徑風(fēng)扇輪輪和可從該方程：1 其中：ooo圖2rpmfa n =范輪速，每分鐘的革命rpmmotor =電機(jī)銘牌速度，每分鐘的革命Dmotor =直徑電機(jī)輪Dfan =直徑風(fēng)扇輪輪范車(chē)輪速度皮帶驅(qū)動(dòng)風(fēng)扇是固定的，除非帶滑。帶滑移可以降低風(fēng)扇輪速幾百革命每分鐘（每分鐘轉(zhuǎn)速）2.2.變頻驅(qū)動(dòng)器范減震器是用來(lái)控制氣體流量流入和流出的離心式風(fēng)機(jī)。他們可能會(huì)被安裝輪。范進(jìn)閘減少能源使用量，由于他們有能力影響氣流的模式風(fēng)扇。1 3.向后彎曲葉片這些類(lèi)型的風(fēng)機(jī)輪轂中使用的風(fēng)扇設(shè)

27、計(jì)來(lái)處理天然氣流與低到中等顆粒負(fù)荷。他們可以很容易地安裝的抗磨損保護(hù)，但某些刀片曲率可以容易固體建設(shè)。向后彎曲的球迷可以有很高的一系列具體的速度，但往往是用于具體的高速應(yīng)用中-高壓力，介質(zhì)流應(yīng)用。向后彎曲的球迷更能源效率比徑向葉片風(fēng)扇，因此，對(duì)于大功率的應(yīng)用可能是一個(gè)合適的替代成本更低徑向葉片風(fēng)扇可變液壓驅(qū)動(dòng)風(fēng)扇使用或磁性聯(lián)軸器（范之間輪軸與電機(jī)軸），使控制風(fēng)扇輪速獨(dú)立的電機(jī)轉(zhuǎn)速。該風(fēng)扇轉(zhuǎn)速控制常常被納入自動(dòng)化系統(tǒng)， 以保持理想風(fēng)扇輪速。1 替代的方法不同的風(fēng)扇速度是使用電子變速驅(qū)動(dòng)器的速度控制的電機(jī)驅(qū)動(dòng)風(fēng)扇。這提供了更好的整體能源使用效率，同時(shí)降低速度比機(jī)械聯(lián)軸器2.3范減震器在入口旁或出口一側(cè)的風(fēng)扇，或兩者兼而有之。阻尼器的出口方面實(shí)行流動(dòng)阻力,用于控制氣流。阻尼器的進(jìn)氣口一側(cè)的目的是控制氣體流量和改變氣體進(jìn)入風(fēng)機(jī)后向彎曲的刀片，在圖3（ b），使用該曲線對(duì)葉片的方向風(fēng)扇輪的自轉(zhuǎn)。落后的曲率模仿的翼型截面，并提供良好的運(yùn)營(yíng)效率相對(duì)經(jīng)濟(jì)的施工技術(shù)。4.徑向直葉片徑向風(fēng)扇葉片，如在圖3 ( c )項(xiàng)，擴(kuò)大直接從樞紐。徑向葉片風(fēng)扇車(chē)輪 上經(jīng)常使用的顆粒拉丹天然氣流，因?yàn)樗亲蠲舾械墓腆w建立的葉片，但它的特 點(diǎn)往往是更大的噪聲輸出。高速，