Centrifugal supercharger (fig. 5-39). The
centrifugal supercharger has an impeller
equipped with curved vanes. As the engine
drives the impeller, 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.
Rotor (Rootes) supercharger (fig. 5-40). The
Rootes supercharger is of the positive
displacement type and consists of two rotors
inside a housing.
As the engine drives the
rotors, air is trapped between them and the
housing. Air is then carried to the outlet where it
is discharged. The rotors and the housing in this
type of supercharger must maintain tight
clearances and therefore are sensitive to dirt.
Vane-type supercharger (fig. 5-41). The vane-
type supercharger has an integral steel rotor and
shaft, one end supported in the pump flange and
the other end in the cover, and revolves in the
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 rotates, the vanes pick up a charge of air at
the inlet port, and it is carried around the body to
the outlet where the air is discharged. Pressure
is produced by the wedging action of the air, as it
is forced toward the outlet port by the vane.
Figure 5-39.Centrifugal supercharger.
The term supercharger generally refers to a blower
driven by a belt, chain, or gears. Superchargers are used
on large diesel and racing engines.
Figure 5-40.Rootes supercharger.