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Axial Flow Ventilation Fans

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					A variable pitch blade in axial fan blower is used where precise control of static
pressure within supply ducts is required. The fan wheel will spin at a constant RPM .
The blades follow the control pitch hub. As the hub moves toward the rotor the blades
increase their angle of attack and an increase in flow results.
  Axial flow ventilators have blades that force air to move along the shaft about which
the blades rotate. Axial fans blow air across the axis of the fan, linearly, hence their
name. This type of fan is used in a wide variety of applications, ranging from small
cooling fans for electronics to the giant fans used in wind tunnels.
  Some examples of axial fans are:
  Table fan - Basic elements of a typical table fan include the fan blade, base, armature
and lead wires, motor, blade guard, motor housing, oscillator gearbox, and oscillator
shaft. The oscillator is a mechanism that motions the fan from side to side. The axle
comes out on both ends of the motor, one end of the axle is attached to the blade and
the other is attached to the oscillator gearbox. The motor case joins to the gearbox to
contain the rotor and stator. The oscillator shaft combines to the weighted base and
the gearbox. A motor housing covers the oscillator mechanism. The blade guard joins
to the motor case for safety.
  Electro-mechanical fans - among collectors, are rated according to their condition,
size, age, and number of blades. Four-blade designs are the most common. Five-blade
or six-blade designs are rare. The materials from which the components are made,
such as brass, are important factors in fan desirability. Ceiling fan with light. Ceiling
fan - A fan suspended from the ceiling of a room is a ceiling fan.
  In automobiles, a mechanical fan provides engine cooling and prevents the engine
from overheating by blowing or sucking air through a coolant-filled radiator. It can be
driven with a belt and pulley off the engine's crankshaft or an electric fan switched
on/off by a thermostatic switch.
  In centrifugal fan, as opposed to axial flow fan, the air is moving perpendicularly to
the fan shaft. 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.
  A mixed flow fan - is an air moving device in between axial flow fan and centrifugal
fan. Mixed Flow fans are an excellent choice for return air, supply, or general
ventilation applications where low sound is critical. As compared to similarly sized
tubular centrifugals and vane axials, a mixed flow fan will be 5-20 dB quieter! In
addition, the mixed flow wheel is extremely efficient and will cut down on operating
expenses.
  For          additional           information           please          refer          to
http://www.canadianblower.com/fans/index.html.
 Oleg Cthecetl Industrial Process Ventilation    Engineer   Canada   Blower
http://www.canadianblower.com/index.html
http://www.canadianblower.com/news/index.html

				
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posted:2/18/2011
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