Centrifugal blowers are capable of developing air pressures up to
2,100 mm H2O. Obviously the higher the pressure or the blower
capacity, the more expensive the blower. Choosing the most ade
quate blower is important as for the rating the motor needs to satisfy
the required features (capacity and pressure). The capacity is more
influent than the pressure.
Above the pressure limiting value mentioned above piston compres
sors or rotary pumps are necessary.
A centrifugal blower creates some draft (negative pressure) where
the blades converge towards the rotating and support shaft. The air
velocity is slower at the shaft and higher at the impeller or rotor
edges where blades diverge. The dynamic pressure (function of
speed) is maximum where the air leaves the blade edges and is con
verted into static pressure in the scroll of the blower.
The blades of the combustion air blower must be kept clean: fouling
accumulating on the surface of the blades increases the friction of
air and consequently decreases the capacity of the blowers. The phe
nomenon may also be controlled by means of checks of the electrical
load of the engines. In industrial applications and some particular cir
cumstances, we recommend that some proper filtering systems be
adopted on the air inlets of the blowers.
In some cases, in order to obtain higher air pressures, blowers in
series are used. In this application, the air inlet of the downstream
blower is connected to the pressing mouth of the upstream blower, so
as to obtain a system where the supplied pressure is equal to the
sum of the pressures generated by the single blowers.
Description provided by deepti airsystem & fabricators private limited.
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