JET ENGINES
Contents
1.
2.
3.
4.
5.
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History of Jet Engines
Introduction
Parts Of Jet Engine
How A Jet Engine works
Types Of Jet Engine
5.1 Ramjet
5.2 Turbojet
5.3 Turbofan
5.4 Turboprop
5.5 Turboshaft
5.6 SCRamjet
Continued . . .
6.
7.
8.
9.
10.
11.
12.
13.
14.
Comparison Of Turbojets
Jet Engine Vs Rockets
Difficulties
Suggestion For Improvement
Merits And Demerits
Jet Engine Uses
Conclusion
Future Vision
References
1.History Of Jet Engines

The first jet engine was built by
Egyptian scientists during 100 B.C

These device was know as Aeolipile.

Dr. Hans von Ohain and Sir Frank
Whittle were the main developers.
Aeolipile
2.Introduction
•
Jet engine is nothing but a Gas turbine.
•
It works under the principle of Newton’s third law
•
It states that “For every acting force there is an equal
and opposite force”.
•
Gas turbine operates like toy balloon
3.Parts Of Jet Engine
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FAN
COMPRESSOR
COMBUSTOR
TURBINE
MIXER
NOZZLE
4.How A Jet Engine Works ?

Jet engines move the airplane forward with a great force that
is produced by a tremendous thrust and causes the plane to
fly very fast.
Continued . . .
Air Intake
 Sucked in by the compressor
Compressor
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Series of vanes and stators.
The vanes rotate, while the
stator remains stationary.
Compressor
speed
and
temperature
increases
gradually
Fuel Burner

Fuel is mixed with the air,
and electric sparks light the
air, causing it to combust.
Combustion Chamber
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The air is burnt.
Increase in the temperature
of the air, thus increases the
pressure inside the engine.
Continued . . .
Turbine
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Works like a windmill
The blades gain energy from the
hot gases moving past them.
This movement is used to power
the compressor.
Jet Pipe and Propelling Nozzle
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The hot air rushes out of the
nozzle.
High pressure
Hot air rushes out at very high
speed
5. Types Of Jet Engines
•
•
•
•
•
Ramjet
Turbojet
Turbofan
Turboprop
Turbo shaft
5.1 Ramjet
• It has no moving parts.
• Its compression ratio depends
forward speed.
on
• It has no static thrust
• Guided-missile
systems,
vehicles use this type of jet
Space
5.2 Turbojet
• The turbojet engine is a reaction
engine.
• Substantial increases in thrust can
be obtained by employing an
afterburner
5.3 Turbofan
• The objective of this sort of bypass
system is to increase thrust without
increasing fuel consumption.
• It achieves this by increasing the total
air-mass flow and reducing the velocity
within the same total energy supply.
• 75% of thrust is produced by the fan.
5.4 Turboprop
• A turboprop engine is a jet engine
attached to a propeller.
• Modern turboprop engines are
equipped with propellers that have a
smaller diameter but a larger number
of blades for efficient operation at
much higher flight speeds
5.5 Turboshaft

It does not drive a propeller.

It provides power for a helicopter rotor.

It permits the rotor speed to be kept
constant even when the speed of the
generator is varied
5.6 SCRamjet

SCRamjet (Supersonic Combustion Ramjet)
A variant of Ramjet Air-breathing jet engine
where combustion occurs in supersonic airflow.
6. Comparison With Turbojets
Ramjets
Turbojet
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Has got compressor, turbine
Heavy
Mach no. < 2
Starts with zero initial velocity
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No compressor, turbine
Light in weight
Mach no 2 to 5
Start only at Mach 2 and
above
7. Jet Engines Vs Rockets
Jet Engine
Rockets
Oxygen from atmosphere for
combustion
Carry their own oxygen for
combustion
Work only in atmosphere
Work in vacuum and atmosphere
Liquid fuel
Liquid or solid fuel
High Specific Impulse
Low Specific Impulse
Complex Structure
Simple Structure
High Efficiency
Low Efficiency
9. Difficulties
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Time scale of combustion
Total temperature in combustion chamber
Coupling the air frame to the engine
Scramjet cannot operate below mach 4
9. Suggestion For Improvement

Employ active cooling

Designing better materials and alloys which retain their strength
at high temperatures

Smart structures – Structure and material which change their
shapes and properties in flight.
10. Merits And Demerits
Merits of Jet engine over IC
engine

Mechanical efficiency of jet
engine is high as compared
to IC engine.
Demerits Of Jet Engines Over
IC engine
• Thermal efficiency of Jet engine is low
compared to IC engine
• Difficult to start


Weight and speed of jet
engine per HP developed is
better than IC engine.
Ignition and lubricating
systems are much simpler
in jet engine than IC
engine.
• Turbine blades need a special cooling
system due high temperature
11. Jet Engine Uses

The
industry
they’re
most
prominent in is in the transport
industry, where they are used to
propel aircraft, boats, and in some
one of creations such as a
turbojet powered truck.

The first use of the jet engine was
to power military aircraft.

The Bell P-59A Airacomet was
also developed by the Americans.
They had a massive advantage
over propeller driven planes, in
that they were much faster

The General electric company
used a “turboprop” jet engine to
run an electric generator.

The jet engine is not only used
on aircraft but on boats, where
water jets are used to propel
the boat forward..
12.Conclusion

Normal type of jet engine is used for domestic purpose i.e.
Traveling, carrying goods etc.

Ram type of jet engines is used only in Defence sector. Because it
travels at supersonic speed and generally high level of training is
required.
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Since it travels at such a high speed it cannot be used for traveling.
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That is why turbo-jet engines are very common in use.
13. Future Vision
 Decreased gross lift – off weight
> Smaller facilities & easier handling
 Leading to higher safety
 Flights can be aborted, whiles the vehicle glides back to earth
 Missions can be more flexible
 Wider range of emergency landing sites for intact abort
14. Bibilograph
http://www.freepatentsonline.com Harris, William S.
http://www.freepatentsonline.com Jaeckel, Ernst (DE)
http:// www.google.com
http:// www.boeing.com
http:// www.jet engine.com