This document discusses different types of air breathing jet engines. It describes the basic principles of how they work by using Newton's third law of motion. The key types discussed are turbojets, which work well at high speeds but have limits for other vehicles, and scramjets, which are designed to combust fuel in supersonic airflow. Both types work by compressing incoming air, mixing it with fuel, combusting the mixture, and accelerating it through a nozzle for thrust. However, scramjets do not decelerate the airflow to subsonic speeds like turbojets. The document outlines the components, operation, advantages, and applications of these different jet propulsion systems.

1. JET PROPULSION
Principle – Working – Applications

2. Air Breathing Engines
 The combustion takes place through atmospheric air.
 Some of the Air Breathing Engines are
- Ramjet Engine
- Pulsejet Engine
- Turbojet Engine
- Scramjet Engine
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3. Principle
 Newton’s Third Law : For every action, there’s an equal and opposite reaction
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4. Section of Air Breathing Engines
Cold Section
 Air Intake
 Compressor
 Diffuser
 Shaft
 Bypass Ducts
Hot Section
 Combustion Chamber
 Turbine
 Afterburner
 Exhaust Nozzle
 Supersonic Nozzle
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5. Air Breathing Engine Types
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6. What’s a Turbojet ?
 An air breathing jet engine with gas
turbine and propelling nozzle.
 Works at high speeds
 Limits the usefulness in vehicles
other than aircrafts
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7. History
 In 1921, Frenchman Maxime
Guillaume patented the concept of
using gas turbine to power.
 Hans von Ohain patented a similar
engine in 1935.
 In 1939, Heinkel He 178 became
the first airplane with turbojet
engine.
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8. Breakdown of a Turbojet
 The major working components of a turbojet are
 Diffuser
 Rotary Compressor
 Combustor
 Turbine
 Exhaust Nozzle
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9. Working
 The compressed air from the
compressor is heated.
 The fuel in the combustion chamber
mixes with incoming air.
 Allowed to expand through the
turbine.
 The air-fuel mixture is propelled
through the nozzle where it is
accelerated to high speed to provide
thrust.
 Turbine runs the compressor.
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10. Merits and Demerits
+
 It runs smoothly because of
continuous thrust .
 Low grade fuels such as kerosene,
paraffin can be used.
 High efficiency at greater speeds
-
 Turboprops replace Turbojets for
low speeds.
 Noisier
 High Range-Specific fuel
consumption.
 Sudden decrease of speed is
difficult.
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11. Applications
 Common in Medium Range Cruise Missiles.
 Modified version is Turboshaft.
 Used in Helicopters and Hovercrafts.
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12. What’s a Scramjet?
 A Supersonic combusting ramjet
engine.
 Combustion takes place in a
supersonic airflow.
 Scramjet engines operate on the
same principles as ramjets, but do
not decelerate the flow to subsonic
velocities.
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13. History
 During WW II, German scientists
spent their time on creating high-
speed rockets.
 After the war, US and UK took them
to create their own jets.
 In 2000 DARPA successfully
launched the scramjets at Mach 10.
 In 2010, Australian and US
scientists achieved a speed of 5000
km per hour.
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14. Breakdown of a Scramjet
 The major working components are
 Converging Inlet
 Combustor
 Diverging Nozzle
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15. Working
 Converging inlet compresses the
incoming air.
 Combustor burns fuel with
atmospheric Oxygen.
 The heated air produces thrust.
 Requires high kinetic energy for
compression.
 Hence the vehicle should have a
Turbojet or Railgun.
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16. Why is it different?
 Does not use any rotating components like Fans, Propellers or Turbines.
 Speed itself compresses the air.
 Airflow in scramjet is supersonic along all the components
 Efficient at high speeds.
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17. Merits and Demerits
+
 No rotating components
 Easy Manufacturing
 Less weight
 Can go up to Mach 10
-
 High Cost
 Good Insulation needed
 Special Cooling needed
 Doesn’t operate at atmospheric
pressure
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18. Applications
 Dramatically reduces time – 90 mins to orbit earth
 Proposed for tethering with International Space Station
 Can place the satellites in their respective orbits
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19. THANK YOU
Venkatesan Krishnamurthy