The centrifugal supercharger (fig. 1-33, view A) has
an impeller equipped with curved vanes. As the impeller
is driven by the engine, it draws air into its center and
throws it off at its rim. The air then is pushed along the
inside of the circular housing. The diameter of the
housing gradually increases to the outlet where the air
is pushed out to the engine intake system.
The Roots supercharger (fig. 1-33, view B) is a
positive displacement type of supercharger that consists
of two rotors inside a housing. As the rotors are driven
by the engine, air is trapped between them and the
housing. The air is then carried to the outlet where it is
discharged. Because of the extremely narrow clearance
between the rotors and the housing, this supercharger is
very sensitive to dirt.
The vane supercharger (fig. 1-33, view C) is a
positive displacement supercharger that has a rotor that
revolves in a body, the bore of which is eccentric to the
rotor. Two sliding vanes are placed 180 degrees apart in
slots in the rotor and are pressed against the body bore
by springs in the slots. When the shaft is rotated, the
vanes pick up air at the inlet port and carry it around the
body to the outlet side where the air is discharged to the
intake system of the engine.
Clean air is essential to the performance and life of
an engine. The air cleaner must remove fine materials,
such as sand, dust, or lint, from the air before it enters
the intake system. The air cleaner normally has a
reservoir large enough to hold material taken out of the
air; therefore, operation over a reasonable time is
possible before cleaning and servicing are necessary.
NOTE: A buildup of dust and dirt in the air cleaner
passages will eventually choke off the air supply,
causing poor combustion.
Multiple air cleaners are sometimes used in
locations where engines are operated under extremely
dusty air conditions or when two small air cleaners must
be used in place of a single large cleaner.
The most common type of air cleaners are the
following: pre-cleaners, dry air cleaners, dry element air
cleaners, and oil bath air cleaners.
Pre-cleaners are devices that remove large particles
of dirt or other foreign matter from the air before it enters
the main air cleaner. This relieves most of the load on
the air cleaner. Pre-cleaners are normally installed at the
end of an air cleaner inlet pipe that extends upward into
the air (fig. 1-34). This locates them in an area relatively
free of dust.
NOTE: Cleaning out the collector bowl of the
pre-cleaner is part of operators maintenance and should
be performed during both prestart and post-operation
Dry Air Cleaners
Dry air cleaners (fig. 1-35) are attached directly to
the intake system and are used on engines in which the
Figure 1-34 .Pre-cleaner.
Figure 1-35.Dry air cleaner.