离心风机的外文翻译

1、Centrifugal fanA centrifugal fan (also squirrel-cage fan, as it looks like a hamster wheel) is a mechanical device for moving air or gases. It has a fan wheel composed of a number of fan blades, or ribs, mounted around a hub. As shown in Figure 1, the hub turns on a driveshaft that passes through th

2、e fan housing. The gas enters from the side of the fan wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing.Centrifugal fans can generate pressure rises in the gas stream. Accordingly, they are well-suited for industrial processes

3、 and air pollution control systems. They are also common in central heating/cooling systems.1. Fan components The major components of a typical centrifugal fan include the fan wheel, fan housing, drive mechanism, and inlet and/or outlet dampers.2. Types of drive mechanisms The fan drive determines t

4、he speed of the fan wheel (impeller) and the extent to which this speed can be varied. There are three basic types of fan drivers.2.1 Direct drive The fan wheel can be linked directly to the shaft of an electric motor. This means that the fan wheel speed is identical to the motors rotational speed.

5、With this type of fan drive mechanism, the fan speed cannot be varied unless the motor speed is adjustable.2.2.1 Belt driveBelt 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 b

6、elts transmit the mechanical energy from the motor to the 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 min

7、ute = diameter of the motor sheave= diameter of the fan wheel sheave Fan wheel speeds in belt-driven fans are fixed unless the belts slip. Belt slippage can reduce the fan wheel speed several hundred revolutions per minute (rpm).2.2 Variable driveVariable drive fans use hydraulic or magnetic couplin

8、gs (between the fan wheel shaft and the motor shaft) that allow control of 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 var

9、iable-speed drive which controls the speed of the motor driving the fan. This offers better overall energy efficiency at reduced speeds than mechanical couplings.2.3 Fan dampersFan dampers are used to control gas flow into and out of the centrifugal fan. They may be installed on the inlet side or on

10、 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 are designed to control gas flow and to change how the gas enters the fan wheel.Inlet dampers reduce fan energy usage due to their ability to affect t

11、he airflow pattern into the fan.3. Backward-curved bladesBackward-curved blades, as in figure 3(b), use blades that curve against the direction of the fan wheels rotation. The backward curvature mimics that of an airfoil cross section and provides good operating efficiency with relatively economical

12、 construction techniques. These types of fan wheels are used in fans designed to handle gas streams with how to moderate particulate loadings. They can be easily fitted with wear protection but certain blade curvatures can be prone to solids build-up.Backward curved fans can have a high range of spe

13、cific speeds but are most often used for medium specific speed applicationhigh pressure, medium flow applications.Backward-curved fans are much more energy efficiency than radial blade fans and so, for high horsepower applications may be a suitable alternative to the lower cost radial bladed fan.4.

14、Straight radial blades Radial fan blades, as in figure 3(c), extend straight out from the hub. A radial blade fan wheel is often on particular-laden 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

15、 volumes, and high pressure are common with radial fans, and are often used in vacuum cleaners, pneumatic conveying systems, and similar processes.5. Centrifugal fan ratingsRatings found in centrifugal fan performance tables and curves are based on standard air SCFM. Fan manufacturers define standar

16、d air as clean, dry air with a density of 0.075 pounds mass per cubic foot (1.2kg/m3), with the barometric pressure at sea level of 29.92 inches of mercury (101.325kPa) and a temperature of 70F. Selecting a centrifugal fan to operate at conditions other than standard air requires adjustment to both

17、static 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 density.If a centrifugal fan is to operate at a non-standard density, then corrections must be made to static pressure and brake horsepo

18、wer. At higher than standard elevation (sea veal) and higher than standard temperature, air density is lower than standard density. Centrifugal fans that are specified for continuous operation at higher temperatures need to be selected taking into account air density corrections. Again, a centrifuga

19、l fan is a constant volume device that will move the same amount of air at tow different temperatures.If, for example, a centrifugal fan moves 1,000ft3/min (28 m3/min) at 70F it will also move 1,000ft3/min (28 m3/min) at 200F. Centrifugal fan air volume delivered by the centrifugal fan is not affect

20、ed by density. However, since the 200f air weights much less than the 70f air, the centrifugal fan will create less static pressure and will require less brake horsepower. Selecting a centrifugal fan to operate at conditions other than standard air requires adjustment to both static pressure and pow

21、er. 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 condition. Since 200f air weighs only 80% of 70f air, the centrifugal fan will create less pre

22、ssure. To get the actual pressure required at 200f , the designer would have to multiply the pressure at standard conditions by an air density correction factor of 1.25 (i.e.,1.0/0.8) to get the system to operate correctly. To get the actual power at 200f, the designer would have to divide the power

23、 at standard conditions by the air density correction 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

24、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。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

25、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