2. The Process of Increasing the inlet air
or charge density in order to increase the
poweroutput of the engine is called
supercharging.
The device used for increasing the
pressure of air above atmospheric
pressure is called supercharger.
3. The include charge by the supercharge during
suction helps in better mixing of fuel and air
during its compression stroke due to the turbulent
effect created by the supercharger and the increased
temperature helps in vaporization offuel.
The increase in temperature of charge, however,
reduces the charge density and it is detrimental in
case of S.I. engine since it develops the tendency to
detonation
4. Fig. shown the difference between the theoretical
(p – v ) diagrams of an naturally aspirated (un
supercharged) engines the difference between the two
are:
a) Increased pressure over the naturally
aspirated engine cycle.
b) Pumping loop of supercharged engine is
positive, therefore, the work output equivalent
to this area is be added instead of being
subtracted.
5.
6. To increase the power output of the engine by
increasing the density of charge at intake.
To reduce the weight to power ratio. It is very useful in
case of aircraft, racing cars and marine applications.
To overcome the loss of power at high altitude either in
case of static engines or in case of aircraft applications.
The loss of power of an engine is estimated to be 1% per
100 metre of altitude.
To reduce the bulk of the engine where weight and space
are important considerations like in case if locomotives
and marine engines.
9. Centrifugal supercharger :-
A centrifugal supercharger is similar to a
turbocharger but is mechanically driven by
the engine instead of being powered by the
hot exhaust gases.
Roots-type supercharger :-
The roots-type supercharger is called a
positive displacement design because all
of the air that enters is forced through the
unit.
Aroots-type supercharger uses two lobes to
force the air around the outside of the
housing into the intake manifold.
11. Vane – type
S upercharg er :-
It consists of spring loaded
vanes mounted
eccentrically inside the
casting.
Thevanes are usually made
of non – metallic fibers or
carbon. The action of vane
type blower is similar to root
blowers.
12. Advan tag es :-
1. Power required is less for given pressure ratio.
2. Can handle small to large volumes ofair.
3. Initial cost and maintenance cost is low.
4. Weight / of air handle is low.
Disadvantagme
3
s :-
1. Space requirement is high.
2. Increased temperature of fuel/air mixture
increases risk of detonation.
13. 1. Gear Driven S upercharg er :-
The arrangement of compressor (supercharger)
driven by engine shaft through gearing to
increase the speed of the compressor.
In this method, the powerrequired to drive the
compressor is supplied from the engine output.
Therefore, net poweroutput of the supercharged
engine is equal to the difference of poweroutput
of engine and powerrequired to drive the
compressor.
14.
15. 2. Turbocharg er :-
In this arrangement the exhaust energy if
engine is utilized to run a gas turbine. The
output of the gas turbine is used to drive the
compressor directly coupled to it.
Therefore, the gas turbine and compressor
used are independent of the engine and the
total engine output is enhanced.
16.
17. 3. Coupled Eng ine, Compressor and
Turbine Supercharger :-
In this method, the turbine is coupled to
engine through step up gearing which drives
the compressor mounted on the same shaft.
The advantage of this system is that if the
turbine output is not sufficient to run the
compressor particularly at part load running
of the engine, the extra powerrequired to run
the compressor is taken from the engine.
18.
19. 4 . Gear Driven S upercharg er and Free
Turbine :-
In this method, the compressor is driven through
step up gearing by the engine and the engine
exhaust gases drive the powerturbine separately.
Such plants are also called as free piston engine.
The thermal efficiency of the plant depends on the
boost pressure ratio.
Due to this its thermal efficiency is reduced at part
loads. Also, at low loads the engine exhaust has tobe
blown off to surroundings since the powerturbine
cannot run belowcertain compressor pressures.
