1. JET ENGINES

2. Contents 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

3. Continued . . .
6. Comparison Of Turbojets 7. Jet Engine Vs Rockets 8. Difficulties 9. Suggestion For Improvement 10. Merits And Demerits 11. Jet Engine Uses 12. Conclusion 13. Future Vision 14. References

4. 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.

5. Aeolipile

6. 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

7. 3.Parts Of Jet Engine
FAN
COMPRESSOR
COMBUSTOR
TURBINE
MIXER
NOZZLE

8. 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.

9. Continued . . . Fuel Burner Air Intake Compressor Combustion Chamber
Sucked in by the compressor
Compressor
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
The air is burnt.
Increase in the temperature of the air, thus increases the pressure inside the engine.

10. Continued . . . Turbine Jet Pipe and Propelling Nozzle
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
The hot air rushes out of the nozzle.
High pressure
Hot air rushes out at very high speed

11. 5. Types Of Jet Engines
Ramjet
Turbojet
Turbofan
Turboprop
Turbo shaft

12. 5.1 Ramjet It has no moving parts.
Its compression ratio depends on forward speed.
It has no static thrust
Guided-missile systems, Space vehicles use this type of jet

13. 5.2 Turbojet The turbojet engine is a reaction engine.
Substantial increases in thrust can be obtained by employing an afterburner

14. 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.

15. 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

16. 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

17. 5.6 SCRamjet SCRamjet (Supersonic Combustion Ramjet)
A variant of Ramjet Air-breathing jet engine
where combustion occurs in supersonic airflow.

18. 6. Comparison With Turbojets
Ramjets
No compressor, turbine
Light in weight
Mach no 2 to 5
Start only at Mach 2 and above
Has got compressor, turbine
Heavy
Mach no. < 2
Starts with zero initial velocity

19. 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

20. 9. Difficulties Time scale of combustion
Total temperature in combustion chamber
Coupling the air frame to the engine
Scramjet cannot operate below mach 4

21. 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.

22. 10. Merits And Demerits Merits of Jet engine over IC engine
Demerits Of Jet Engines Over IC engine
Merits of Jet engine over IC engine
Mechanical efficiency of jet engine is high as compared to IC engine.
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.
Thermal efficiency of Jet engine is low compared to IC engine
Difficult to start
Turbine blades need a special cooling system due high temperature

23. 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..

24. 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.
Since it travels at such a high speed it cannot be used for traveling.
That is why turbo-jet engines are very common in use.

25. 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

26. 14. Bibilograph
Harris, William S. Jaeckel, Ernst (DE) engine.com