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

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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.

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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

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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

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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 ??

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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

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“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.

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DIAGRAM OF A WORKING ENGINE EQUIPPED WITH A SUPERCHARGER

A TYPICAL SUPERCHARGER

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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.

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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

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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

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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

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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

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ROOT SUPERCHARGER WORKING OF A TWIN-SCREW SUPERCHARGER

TWIN-SCREW SUPERCHARGER

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CENTRIFUGAL SUPERCHARGER

WORKING OF A CENTRIFUGAL SUPERCHARGER

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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

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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

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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

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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

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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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