Jet Propulsion Systems in Aircraft : Jet Propulsion Systems in Aircraft By:
Roll No 137
Mech “C” Contents : Contents History of Jet Engines
Parts Of Jet Engine
How A Jet Engine works
Types Of Jet Engine
5.5 Turboshaft Continued . . . : Continued . . . 6. Comparison Of Turbojets
7. Jet Engine Vs Rockets
9. Suggestion For Improvement
10. Merits And Demerits
11. Jet Engine Uses
13. Future Vision
14. References 1.History Of Jet Engines : 1.History Of Jet Engines The first jet engine was built by Egyptian scientists during 100 B.C.
The device was known as Aeolipile and used steam power directed through two nozzles to cause a sphere to spin rapidly on its axis
It was not used for supplying mechanical power and was simply considered a curiosity
Dr. Hans von Ohain and Sir Frank Whittle were the pioneers behind today’s jet engines. 2.Introduction : 2.Introduction The term jet engine loosely refers to an Internal Combustion Air Breathing Jet Engine (a duct engine). These typically consist of an engine with a rotary (rotating) air compressor powered by a turbine ("Brayton cycle"), with the leftover power providing thrust via a propelling nozzle.
Jet engine is nothing but a Gas turbine.
It works under the principle of Newton’s third law which states that “For every acting force there is an equal and opposite force”. 3.Parts Of Jet Engine : 3.Parts Of Jet Engine FAN
NOZZLE 4.How A Jet Engine Works ? : 4.How A Jet Engine Works ? Jet engines propels an aircraft forward with a great force which is produced by a tremendous thrust from them, hence allowing the plane to fly. Continued . . . : Continued . . . Air Intake
sucked in by the 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 mixture causing it to combust.
The air is burnt along with fuel.
Hence increasing the temperature and pressure of the air inside the engine. Continued . . . : Continued . . . Turbine
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.
Hot air rushes out at very high speed 5. Types Of Jet Engines : 5. Types Of Jet Engines Ramjet
Turbo shaft 5.1 Ramjet : 5.1 Ramjet It has no moving parts.
Its compression ratio depends on forward speed.
They consist of three sections; an inlet to compressed oncoming air, a combustor to inject and combust fuel, and a nozzle
Require a relatively high speed to efficiently compress the oncoming air.
They are most efficient at supersonic speeds, It has no static thrust
guided-missile systems, Space vehicles use this type of jet 5.2 Turbojet : 5.2 Turbojet The turbojet engine is a reaction engine.
A turbojet engine works by compressing air with an inlet and a compressor, mixing fuel with the compressed air, burning the mixture in the combustor, and then passing the hot, high pressure air through a turbine and a nozzle
Substantial increases in thrust can be obtained by employing an afterburner
Used in fighter planes, and were used in the Concorde. Recent Turbojet Engine : Recent Turbojet Engine The Rolls-Royce/Snecma Olympus 593 was a reheated (afterburning) turbojet which powered the supersonic airliner Concorde.
Length: 4039 mm (159 in)
Diameter: 1212 mm (47.75 in)
Dry weight: 3175 kg (7,000 lb) Micro-turbojets for Weapons : Micro-turbojets for Weapons 5.3 Turbofan : 5.3 Turbofan A turbofan engine is a gas turbine engine that is very similar to a turbojet. Turbofans differ from turbojets as they have an additional component, a fan
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. 5.4 Turboprop : 5.4 Turboprop A turboprop engine is a jet engine attached to a propeller.
Majority of their thrust is from the propeller, though hot-jet exhaust is an important design point, and maximum thrust is obtained by matching thrust contributions of the propeller to the hot jet.
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 : 5.5 Turboshaft Turboshaft engines are very similar to turboprops, differing in that nearly all energy in the exhaust is extracted to spin the rotating shaft.
They therefore generate little to no jet thrust.
It does not drive a propeller and provides power for a helicopter rotor.
It permits the rotor speed to be kept constant even when the speed of the generator is varied . 6. Comparison With Turbojets : 6. Comparison With Turbojets Turbojet Ramjets
No compressor, turbine
Light in weight
Mach no 2 to 5
Start only at Mach 2 and above Has got compressor, turbine
Mach no. < 2
Starts with zero initial velocity 7. Jet Engines Vs Rockets : 7. Jet Engines Vs Rockets 8. Difficulties : 8. Difficulties 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 : 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.
Design engines which switch from scramjets to ramjets. 10. Merits And Demerits : 10. Merits And Demerits 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 higher 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 Demerits Of Jet Engines Over IC engine 11. Jet Engine Uses : 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 AirComet 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.
These engines are also used to propel Naval ships due to their high power to weight ratio and ability to take up sudden loads. 12. Conclusion : 12. Conclusion Normal type of jet engine is used for domestic purpose i.e. Traveling, carrying goods etc.
Ram and scram type of jet engines used in only in Defence sector. Because it travels at supersonic speed and generally high level of training is required.
Since it travels at such a speed it is can not used for traveling.
So that common type of jet engines are very common in use. 13. Future Vision : 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. Bibliography : 14. Bibliography http://science.howstuffworks.com/transport/flight/modern/turbine.htm
http:// www.jet engine.com Thank You : Thank You Slide 28: Back