In designing an engine, the balance between higher power on the
one hand and lower weight and smaller size on the other must be taken into
consideration. One way to make the engine able to meet both requirements is to
equip it with a turbocharger or supercharger. This allows a greater volume
and weight of compressed air to be burnt with a greater amount of fuel, resulting
in a greater power output for an engine of a given size.
WAYS TO INCREASE POWER
In most internal combustion engines, the amount of power that
can be obtained from an engine of given displacement is determined by the
amount of air that is drawn into the combustion chamber in a given period of
time. Due to this fact, there are several different methods that can be used to
increase engine output. Three typical ways are shown below:
INCREASING ENGINE DISPLACEMENT
This is the most obvious way, but because the weight of the engine may also
increase if this is done, there is not much improvement in terms of the
weight-to power ratio.
INCREASING MAXIMUM ENGINE SPEED
Conventional engines are limited to about 6,000 rpm due to the increased
friction loss, noise and vibration, and decreased intake efficiency that occur
at high speeds.
CHARGING CYLINDERS WITH DENSER AIR (USE OF
TURBOCHARGER OR SUPER-CHARGER)
Using this method, the amount of air necessary
forcombustion of the extra fuel can be greatly increased,resulting in increased
FEATURES OF TURBOCHARGER AND SUPERCHARGER
The turbocharger and the supercharger are both a kind of air
pump, which force the intake air into the cylinders to increase its density. The
pressure of the intake air thus supplied to the cylinders by the turbocharger or
the supercharger becomes greater than atmospheric pressure and its
density increases because the cylinders are closed vessels.
These features are summarized in the following table: