jet engines

1. History of Jet Engines2. Introduction3. Parts Of Jet Engine4. How A Jet Engine works5. Types Of Jet Engine 5.1 Ramjet 5.2 Turbojet 5.3 Turbofan 5.4 Turboprop 5.5 Turboshaft

6. Comparison Of Turbojets7. Jet Engine Vs Rockets8. Suggestion For Improvement9. Merits And Demerits10. Future Vision

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.

• 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

FAN COMPRESSOR COMBUSTOR TURBINE MIXER NOZZLE

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.

Air Intake 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.

• Ramjet • Turbojet• Turbofan• Turboprop• Turbo shaft

•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

•The turbojet engine is a reaction engine.

•Substantial increases in thrust can be obtained by employing an afterburner

•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.

•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

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

TURBOJET RAMJETS

NO COMPRESSOR, TURBINE LIGHT IN WEIGHTMACH NO 2 TO 5START ONLY AT MACH 2 AND ABOVE

Has got compressor, turbine Heavy Mach no. < 2 Starts with zero initial

velocity

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

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.

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

Decreased gross lift – off weight> Smaller facilities & easier handling

Leading to higher safetyFlights can be aborted, whiles the vehicle glides back to earthMissions can be more flexibleWider range of emergency landing sites for intact abort