Jet Engines

Definition

Jet engines are a type of reaction engine that propel aircraft by expelling a high-speed jet of hot exhaust gases. They are the primary means of propulsion for modern commercial and military aircraft, providing the thrust necessary for high-speed, high-altitude flight.

5 Must Know Facts For Your Next Test

1. Jet engines work by burning fuel to create a high-pressure, high-velocity stream of exhaust gases that push the aircraft forward.
2. The key components of a jet engine are the air inlet, compressor, combustion chamber, turbine, and exhaust nozzle.
3. Turbofan engines are the most common type of jet engine used in modern commercial aircraft, as they are more fuel-efficient than traditional turbojet engines.
4. Jet engines are capable of producing thrust at high altitudes, where the reduced air density would make propeller-driven engines less effective.
5. The thrust produced by a jet engine is directly proportional to the mass flow rate and the change in velocity of the exhaust gases.

Review Questions

• Explain the basic principle of how a jet engine generates thrust.
  • A jet engine generates thrust by burning fuel in a combustion chamber, which creates a high-pressure, high-velocity stream of exhaust gases. As these exhaust gases are expelled through the engine's nozzle, they exert a force on the engine in the opposite direction, propelling the aircraft forward. This is an application of Newton's third law of motion, where the force exerted by the exhaust gases on the engine is equal and opposite to the force exerted by the engine on the exhaust gases.
• Describe the key components of a turbojet engine and how they work together to produce thrust.
  • The key components of a turbojet engine are the air inlet, compressor, combustion chamber, turbine, and exhaust nozzle. The compressor draws in and compresses the incoming air, which is then mixed with fuel and ignited in the combustion chamber. The hot, high-pressure exhaust gases then pass through the turbine, which drives the compressor. Finally, the exhaust gases are expelled through the nozzle, creating a high-velocity jet that generates the thrust necessary to propel the aircraft forward.
• Analyze the advantages of turbofan engines over traditional turbojet engines in the context of commercial aircraft propulsion.
  • Turbofan engines are more fuel-efficient than turbojet engines, making them the preferred choice for modern commercial aircraft. This is because turbofan engines use a large, slow-moving fan to draw in and accelerate a large volume of air, which is then mixed with the hot exhaust from the core engine. The increased mass flow rate and lower exhaust velocity of turbofan engines result in higher propulsive efficiency and lower fuel consumption, allowing commercial aircraft to fly longer distances with greater payload capacity while consuming less fuel.

Related terms

Turbojet Engine: A type of jet engine that uses a turbine to drive an air compressor, which in turn forces air into the combustion chamber, where fuel is added and ignited.

Turbofan Engine: A type of jet engine that uses a fan to draw in and accelerate a large amount of air, which is then mixed with the hot exhaust from the core engine to produce thrust.

Ramjet: A type of jet engine that uses the vehicle's forward motion to compress the incoming air, without the need for a mechanical compressor.