离心风机的外文翻译

1、.Centrifugal fanA centrifugalfan (alsosquirrel-cagefan,as itlooks likea hamsterwheel) is a mechanical device formoving airor gases. Ithas a fan wheelcomposedof a number of fan blades,or ribs,mounted around a hub. As shownin Figure 1, the hub turns on a driveshaft that passes through the fanhousing.

2、The gas enters from the side of the fan wheel, turns 90 degreesand accelerates due tocentrifugal force asit flows overthe fan bladesand exits the fan housing.Centrifugal fans can generatepressurerises in the gas stream.Accordingly,theyarewell-suitedforindustrialprocessesand airpollutioncontrolsystem

3、s.Theyarealsocommon incentralheating/cooling systems.1. Fan componentsThe major components of a typical centrifugal fan include the fanwheel, fan housing, drive mechanism, and inlet and/or outlet dampers.2. Types of drive mechanismsThe fan drive determines the speed of the fan wheel (impeller) andth

4、e extentto which thisspeed can be varied.There are threebasic typesof fan drivers.2.1 Direct driveThefan wheel can be linkeddirectlyto the shaftof an electricmotor.This meansthatthe fan wheel speed is identicalto the motor s rotationalspeed. With this type of fan drive mechanism, the fan speed canno

5、t bevaried unless the motor speed is adjustable.2.2.1 Belt drive;.Belt drive fans use multiple belts that rotate in a set of sheaves mounted on the motor shaft and the fan wheel shaft.This type of drive mechanism is depicted in figure 2. The belts transmit the mechanical energy from the motor to the

6、 fan.The fan wheel speed depends upon the diameter of the motor sheave to the diameter of the fan wheel sheave and can be obtained from this equation:Where:= fan wheel speed, revolutions per minute= motor nameplate speed, revolutions per minute= diameter of the motor sheave= diameter of the fan whee

7、l sheaveFan wheel speeds in belt-drivenfans are fixedunless the beltsslip.Beltslippagecan reduce the fan wheel speed severalhundred revolutionsper minute (rpm).2.2 Variable driveVariabledrivefans use hydraulicor magnetic couplings(between thefan wheel shaft and the motor shaft) that allow control of

8、 the fan wheel speed independent of the motor speed. The fan speed controls are often integrated into automated systems to maintain the desired fan speed.An alternate method of varying fan speed is by use of an electronic variable-speed drive which controls the speed of the motor driving thefan. Thi

9、s offers better overall energy efficiency at reduced speeds than mechanical couplings.2.3 Fan dampers;.Fan dampers are used to control gas flow into and out of the centrifugal fan. They may be installed on the inlet side or on the outletside of the fan,or both.Dampers on the outlet side impose a flo

10、wresistance that is used to control gas flow. Dampers on the inlet sideare designed to controlgas flowand to change how the gas entersthe fanwheel.Inletdampers reduce fan energy usage due to theirabilityto affectthe airflow pattern into the fan.3. Backward-curved bladesBackward-curved blades, as in

11、figure 3(b), use blades that curveagainstthe directionof the fan wheel s rotation.The backward curvaturemimics that of an airfoil cross section and provides good operatingefficiency with relatively economical construction techniques. Thesetypes of fan wheels are used in fans designed to handle gas s

12、treams withhow to moderate particulateloadings.They can be easilyfittedwith wearprotectionbut certainblade curvaturescan be prone to solidsbuild-up.Backward curved fans can have a high range of specificspeeds but aremost often used for medium specific speed applicationhigh pressure,medium flow appli

13、cations.Backward-curved fans are much more energy efficiency than radialblade fans and so, for high horsepower applications may be a suitablealternative to the lower cost radial bladed fan.4. Straight radial bladesRadial fan blades, as in figure 3(c), extend straight out from thehub. A radial blade

14、fan wheel is often on particular-laden gas streamsbecause it is the least sensitive to solids build-up on the blades, butit is often characterized by greater noise output.High speeds, lowvolumes, and high pressure are commonwith radial fans, and are often used in vacuum cleaners, pneumatic conveying

15、 systems, and similar processes.5. Centrifugal fan ratingsRatings found in centrifugal fan performance tables and curves arebased on standard air SCFM.Fan manufacturers define standard air as clean, dry air with a density of 0.075 pounds mass per cubic foot (1.2kg/m3),with the barometric pressure at

16、 sea level of 29.92 inches of mercury;.(101.325kPa) and a temperature of 70F. Selecting a centrifugal fan tooperateat conditionsotherthan standard airrequiresadjustmenttobothstatic pressure and brake horsepower. The volume of air will not beaffectedina given system because a fan willmove thesame amo

17、unt ofairregardless of the air density.If a centrifugal fan is to operate at a non-standard density, thencorrections must be made to static pressure and brake horsepower. Athigherthanstandardelevation(seaveal)and higherthanstandardtemperature,air densityislowerthan standarddensity.Centrifugalfanstha

18、t are specified for continuous operation at higher temperatures needto be selected taking into account air density corrections. Again, acentrifugalfan is a constant volume devicethatwillmove thesameamountof air at tow different temperatures.If, for example, a centrifugal fan moves 1,000ft3/min (28 m

19、3/min)at70F itwill also move 1,000ft3/min(28m3/min)at200F. Centrifugalfanairvolume deliveredby the centrifugalfan is not affectedby density.However, since the 200f air weights much less than the 70f air, thecentrifugal fan will create less static pressure and will require lessbrake horsepower. Selec

20、ting a centrifugal fan to operate at conditionsother than standard air requires adjustment to both static pressure andpower. When a centrifugal fan is specified for a given CFM and staticpressure at conditions other than standard, an air density correctionfactor must be applied to select the proper

21、size fan to meet the newcondition.Since 200fair weighs only 80%of70fair,thecentrifugalfanwill create less pressure.To get theactual pressure required at 200f ,the designer would have to multiply the pressure at standard conditionsby an air density correction factor of 1.25 (i.e.,1.0/0.8) to get thes

22、ystem to operate correctly.To get theactualpower at200f,the designerwould have to divide thepower at standardconditions by theair densitycorrection factor.离心风机离心风机（也称鼠笼式风扇， 因为它看起来像仓鼠笼） 是一种机械装置移动空气或气体。它有一个风扇轮组成若干风扇叶片，或肋骨，装在一个枢纽。如图1 所示，该中心将在驱动轴，穿越风扇住房。气体进入从侧面的风扇方向盘，把90 度，并加快由于离心力因为它流动的风扇叶片和出口风扇住房。离心式风

23、机可产生压力上升气流。 因此，他们非常适合工业加工和空气污染控制系统。他们还共同在中央供暖 /冷却系统。;.1. 风机组件主要组成部分典型的离心式风机包括风扇轮、 风扇住房、驱动机制、 进口和出口闸。2. 驱动机制的类型风扇驱动器决定的速度、 风扇（叶轮）以及在何种程度上这样的速度可以多种多样。有三总基本类型的风机驱动器。2.1 直接驱动风扇轮可以直接连接一个电动机。 这意味着，风扇与电动机转速相同。 这种类型的风机驱动机制，除非电机转速可调否则风扇的转速不能更改。2.1.1 带传动应用带传动的风机使用多重皮带连接电机轴和风扇轴。这种类型的驱动机制如图2 所示。皮带将机械能由电动机传递给风机。

24、风机的转速取决于电动机的转速以及电动机输出轴及风扇轴上皮带轮直径的比值，可根据下面的方程求得：除非皮带打滑， 一般情况下风扇的转速是固定的。 当皮带打滑打滑时会使风机的转速每分钟降低几百转。;.2.2 无级变速器可变的驱动风机采用液压或磁力联轴器（风机的叶轮轴和电机轴之间） ，使风轮转速独立的电机速度控制。 风扇转速控制通常集成到自动系统来维持期望的风扇速度。不同的风扇速度的另一种方法是采用电子调速控制驱动风扇电机的速度。这提供了更好的整体能源效率降低的速度比的机械接头。2.3 风扇阻尼器风阻尼器是用来控制气体流入和流出的离心风机。 他们可以安装在进气侧或在风扇出口侧，或两者。在出口侧阻尼器施加阻力，用于控制气体流量。在进气侧的阻尼器设计控制气体流量和改变气体进入风轮。进口阻尼器减少风扇的能耗由于其影响气流进入风机能力。3。后弯叶片后弯叶片，如图 3（ b），用刀片曲线对风轮的旋转方向。这些类型的风轮中使用的风扇设计处理气体流， 如何适度的微粒负荷。 他们可以很容易的安装和磨损保护，但某些叶片的曲率可以容易固体积聚。向后弯曲的球迷可以有特定的速度高的范围， 但最经常使用的应用程序中的特定的速度压力高，流量的应用中。向后弯曲风扇比径向叶片风扇和这么多更多的能源效率， 高功率的应用可能是成本较低的径向叶片的风扇一个合适的替代品。4。径向直叶片径向风扇叶片，