Supercharging
The method of
increasing the inlet air density, called supercharging, is usually employed to
increase the power output of the engine. This is done by supplying air at a
higher pressure that the pressure at which the engine naturally aspirates air
from the atmosphere by using a pressure boosting device called a supercharger. The
power output of an engine depends upon the amount of air inducted per unit
time, the degree of utilization of this air and the thermal efficiency of the
engine. Due to engine running at higher speeds, the time available for the
suction of air into the cylinder is very small and also when the engine is being
operated at very high altitudes, the density of air available is very low,
which in turn reduces the power output of the engine. Therefore, a supercharger
is used to increase the density of the air being supplied to the engine.
What is a Supercharger?
A supercharger is a
compressor which is coupled to the engine output shaft i.e., derives its power
from the engine, and supplies high pressure air to the engine.
Objects of supercharging
The increase in the
amount of air inducted per unit time by supercharging is obtained mainly to
burn a greater amount of fuel in a given engine and thus increase its power
output. The objects of supercharging include one or more of the following:
1.
To increase
the power output for a given weight and bulk of the engine. This is important
for aircraft, marine and automotive engines where weight and space are
important.
2.
To compensate
for the loss of power due to altitude. This mainly relates to aircraft engines which
lose power at an approximate rates of one percent per 100 meters altitude. This
is also relevant for other engines which are used at high altitudes.
3.
To obtain
more power from an existing engine.
