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Transcript of supercharger pdf
VISVESVARAYA TECHNOLOGICAL UNIVERSITY, BELGAUM
A technical seminar report on
supercharger
Submitted in partial fulfillment as per VTU curriculum for VIII
semester
Bachelor of Engineering
In
Mechanical Engineering
Of
Visvesvaraya Technological University, Belgaum
Submitted by
ANSHUMAN PANDA (1DS05ME107)
2009-2010Department of Mechanical Engineering
DAYANANDA SAGAR COLLEGE OF ENGINEERINGBANGALORE-560078
VISVESVARAYA TECHNOLOGICAL UNIVERSITY
1
CERTIFICATE
DAYANANDA SAGAR COLLEGE OF ENGINEERINGDepartment of Mechanical Engineering
Bangalore – 560078
This is to certify that the Technical Seminar report entitled “SUPERCHARGER”
has been presented by Mr.ANSHUMAN PANDA, USN: 1DS05ME107 in partial fulfillment for the award of Bachelor of Engineering in Mechanical Engineering of the Visvesvaraya
Technological University, Belgaum during the year 2009-10. It is certified that all correction/suggestions indicated for internal
assessment have been incorporated in the report deposited in the department library.
Date: Sign of HOD/Coordinator
Internal Examiners: Name & sign. 1.
2.
2
ACKNOWLEDGEMENTS
It is with great satisfaction and euphoria that I am submitting the Technical seminar report on “SUPERCHARGER”. I have completed it as a part of the curriculum of our university.
First of all I thank the almighty for providing me with
the strength and courage to present the seminar.
I avail this opportunity to express my sincere
gratitude towards Dr. K. G. Sudhakar , head of
mechanical engineering department, for permitting me to
conduct the seminar.
I am also indebted to all the teaching and non- teaching staff of the department of mechanical engineering for their cooperation and suggestions, which is the spirit behind this report. Last but not the least, I wish to express my sincere thanks to all my friends for their goodwill and constructive ideas.
ANSHUMAN PANDA
CONTENTS
3
1. Supercharger, the engine booster. ----------------- 5
2. Why superchargers?? -------------------------------- 6
3. How it works??? -------------------------------------- 7
4. Working diagram of a supercharger. --------------- 8
5. Classification of superchargers. -------------------- 9
6. Commonly used superchargers. -------------------- 10
7. Roots supercharger. -------------------------------- 11
8. Twin-Screw Supercharger. -------------------------- 12
9. Centrifugal Supercharger. -------------------------- 13
10. Diagrammatic Illustration. ------------------------- 14
11. Drives used in Superchargers. -------------------- 16
12.Supercharger, An edge over turbocharger. ------ 17
13.Nothing is perfect. ---------------------------------- 18
14.Conclusion. ------------------------------------------ 19
15.References. ------------------------------------------ 20
INTRODUCTION
4
To increase the output efficiency of any engine we have to burn
more fuel and make bigger explosion in every cycle. We have
two options for this.
One way to add power is to build a bigger engine. But bigger
engines, which weigh more and cost more to build and maintain,
are not always better.
Another way to add power is to make a normal-sized engine
more efficient. We can accomplish this by forcing more air into
the combustion chamber. More air means more fuel can be
added, and more fuel means a bigger explosion and greater
horsepower. This can be done with the help of a supercharger.
A supercharger is basically an air compressor used for forced
induction of an internal combustion engine. It does the same
work as that of a compressor, i.e. it compresses the air being
delivered to the combustion chamber of an engine. The greater
mass flow-rate provides more oxygen to support combustion
than would be available in a naturally-aspirated engine, which
allows more fuel to be provided and more work to be done per
cycle, increasing the power output of the engine.
Thus a supercharger is extra equipment provided in an engine so
as to boost the capacity and the torque of an engine.
WHY SUPERCHARGER ??
5
A supercharger is used in an engine for various reasons.
Some of the advantages of superchargers are as follows:
Increases the power of an engine.
A supercharger spinning at 50,000 RPM translates to a boost of
about six to nine pounds per square inch (psi).
Increases the torque produced.
An efficiently working engine with supercharger can achieve the
same speed in one third of the time taken by the same engine
without supercharger.
Necessary in airplanes and jets as they have less oxygen at high
altitudes. So they provide the sufficient amount of air by
compressing it to higher pressure. And ensures complete
combustion.
Higher amount of oxygen in compressed air from supercharger
ensures complete combustion of the fuel.
Complete combustion reduces pollution to some extent.
PRINCIPLE OF WORKING
6
“More fuel + More air = Bigger explosion = Greater horsepower”.
Every supercharger works on the same above mentioned
tagline.
It is quite evident that to get more output from any engine
we need to burn more fuel. More fuel will result in a bigger
explosion in every cycle, which will then push the piston with
more thrust, and consequently this thrust will be transmitted
to the wheels with the help of crank and shaft. Wheels will
rotate faster and with more power and that is how it works.
But, to burn more fuel in an engine, we need more air in it
(The chemically correct mixture – (14: 1:: air : fuel) – is
essential for an engine to operate perfectly). Thus a
supercharger compresses the air being delivered to the
engine so as to supply more air in the same, limited volume
of the cylinder. This ensures complete combustion of the fuel
and no unburnt fuel comes out of the exhaust. Thus the
supercharger increases the power output of any engine.
7
DIAGRAM OF A WORKING ENGINE EQUIPPED WITH A SUPERCHARGER
A TYPICAL SUPERCHARGER
8
CLASSIFICATION OF SUPERCHARGERS
Based on method of compression, Superchargers can be classified as:-
1. Positive-displacement type, which deliver a nearly-fixed
volume of air per revolution at all speeds and a fairly constant
level of boost regardless of engine speed.
2. Dynamic compressors rely on accelerating the air to high
speed and then exchanging that velocity for pressure by
diffusing or slowing it down & deliver increasing boost with
increasing engine speed.
A supercharger comes in two different variations:
Positive displacement and dynamic compressors.
A positive displacement supercharger pushes air into the
engine at a constant speed, while a dynamic supercharger uses
velocity to manipulate the pressure in the air.
In either case, oxygen is compressed as it is delivered to the
engine, allowing more power to be gained from every explosion
in the combustion chambers.
9
COMMONLY USED SUPERCHARGERS
Nowadays, there are several types of superchargers used in the
engines.
Following are some of the most commonly used superchargers
in the market.
o Roots Superchargers
o Twin-Screw Superchargers
o Centrifugal Superchargers
History of Superchargers
The Roots supercharger is the oldest design of
supercharger used in any type of engine.
Philander and Francis Roots, in 1860, introduced the
concept of such type of equipment. Though they patented
the design as a machine that would help ventilate mine
shafts, later this turned out to be a miraculous invention
for automotive engineers.
In 1900, Gottleib Daimler for the first time included a
Roots supercharger in a car engine which improved the
output of the engine. This was the first step towards its
development.
ROOTS SUPERCHARGER
10
Constructional features: It consists of two meshing lobes that are
fitted on two parallel shafts. Those lobes resembles to a lobe gear
that are in continuous mesh. Both the lobes mesh in such a manner
that the air pockets between these lobes and the side walls goes on
decreasing as air moves from the fill side to the discharge side.
Thus the passing air gets squeezed.
Working of Roots Supercharger: As the meshing lobes spin, air
trapped in the pockets between the lobes is carried between the fill
side and the discharge side & large quantities of air move into the
intake manifold and "stack up" to create positive pressure. This
pressurized air is received at the discharge side.
Roots superchargers are usually large and sit on top of the
engine.
Roots superchargers are the least efficient supercharger for
two reasons:-
1. They add more weight to the vehicle.
2. They provide air in discrete bursts instead of
Providing in a smooth and continuous manner.
TWIN-SCREW SUPERCHARGERS
11
Constructional features: Twin-Screw Superchargers consist of
two meshing lobes that resemble a set of worm gear. The two gears
meshes in such a way that the air pockets between them goes on
decreasing as air moves ahead.
Working of Twin Screw Superchargers: A twin-screw
supercharger operates by pulling air through a pair of meshing
lobes that resemble a set of worm gears.
The rotors have a conical taper, which means the air pockets
decrease in size as air moves from the fill side to the discharge side.
Thus a twin-screw supercharger compresses the air inside the rotor
housing.
As the air pockets shrink, the air is squeezed into a smaller space.
Thus twin-screw superchargers are more efficient compared
to roots supercharger.
They cost more because the screw-type rotors require more
precision in the manufacturing process.
They also make a lot of noise.
The compressed air exiting the discharge outlet creates a
whine or whistle that must be checked with noise suppression
techniques.
CENTRIFUGAL SUPERCHARGERS
12
Constructional features: Centrifugal superchargers consist of an
impeller with several blades that rotate at a very high speed at
around 50000 rpm. This impeller throws the air outside due to
centrifugal force. It also consists of a diffuser which exchanges the
speed for high pressure.
Working of Centrifugal Supercharger: As the air is drawn in the
hub of the impeller, centrifugal force causes it to radiate outward.
The air leaves the impeller at high speed, but low pressure.
A diffuser converts the high-speed, low-pressure air to low-speed,
high-pressure air.
Thus pressurized air is achieved.
Impeller speeds can reach ‘50,000 to 60,000 RPM’.
Centrifugal superchargers are the most efficient and the most
common induction systems.
They are small, lightweight and attachable to the front of the
engine.
Thus the centrifugal superchargers are the best among the
above list.
DIAGRAMATIC ILLUSTRATION
13
ROOT SUPERCHARGER WORKING OF A TWIN-SCREW SUPERCHARGER
TWIN-SCREW SUPERCHARGER
14
CENTRIFUGAL SUPERCHARGER
WORKING OF A CENTRIFUGAL SUPERCHARGER
15
DRIVES USED IN SUPERCHARGERS
Drives are basically the equipments that are used to transfer power
from one shaft to another shaft. In a supercharger, drives are used
to transfer part of engine power to the supercharger
There are several types of drives used to empower a supercharger.
These drives are used according to there requirements.
Some of them are as under:
Mechanical:-
Belt (V belt, toothed belt & Flat belt).
Gear drive.
Chain drive.
Exhaust gas turbines:-
Axial turbine.
Radial turbine.
Other:-
Electric motor.
SUPERCHARGERAN
16
EDGE OVER TURBOCHARGER
Superchargers do not suffer lag: - Superchargers have no lag
time because they are driven directly by the crankshaft, whereas
Turbochargers suffers lag because it takes a few moments before
the exhaust gases reach a velocity that is sufficient to drive the
impeller/turbine.
Since the superchargers are directly empowered from the engine,
so as the engine starts, the superchargers can be activated. But in
the case of turbochargers they take some time for the accumulation
of exhaust gases.
Modification of the exhaust system: - Installing a turbocharger
requires extensive modification of the exhaust system, but
superchargers can be bolted to the top or side of the engine, that
makes them cheaper to install and easier to service and maintain.
So this becomes a problem in the case of turbochargers. It becomes
a tough task to modify the exhaust system as well as it adds an
extra cost in the vehicle.
Shutdown procedure: - No special shutdown procedure is
required with superchargers as they are not lubricated by engine
oil. They can be shut down normally. Whereas turbochargers must
idle for about 30 seconds or so prior to shutdown so the lubricating
oil has a chance to cool down.
Thus it creates a problem during shutdown procedure as
turbochargers can’t be shutdown normally.
NOTHING IS PERFECT
17
It derives power from the engine itself: Crankshaft drives superchargers so they steal some of the engine's horsepower. A supercharger can consume as much as 20 percent of an engine's total power output. So it can be considered as a loss of engine power.(But because a supercharger can generate as much as 46 percent additional horsepower, I think the trade-off is worth it). Whereas this is not the case in turbochargers, it empowers itself from the exhaust gas of the engine, which is mainly a waste of the engine.
An added strain on the engine: Supercharging puts an
added strain on the engine, which needs to be strong to handle
the extra boost and bigger explosions. Engine and the other
connected mechanisms have to be made robust enough to bear
the extra pressure. So this makes the design engineer task
tougher.
An extra expense: Heavy-duty components, design complexity
& maintenance add an extra burden on the expenses. And these
expenses have to be made for better performance without any
compromise.
Though this seems too much, but when compared to its output,
this seems a good deal.
CONCLUSION
18
Despite their disadvantages, superchargers are still the
most cost-effective way to increase horsepower.
Superchargers can result in power increase of 50 to 100
percent, making them great for racing, towing heavy
loads or just adding excitement to the typical driving
experience.
It is a must use component in an airplanes.
As superchargers ensure complete combustion, it greatly
reduces the pollution problem.
With the use of high octane premium-grade gas, I think it
is a miracle invention for speed junkies.
REFERENCES
19
http://auto.howstuffworks.com/supercharger5.htm
http://www.howstuffworks.com/search.php?
terms=supercharger
http://www.superchargerpros.com/
http://en.wikipedia.org/wiki/Supercharger
http://en.wikipedia.org/wiki/Supercharger#History
http://www.magnusonproducts.com/
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