How do Gas turbines/Jet propulsion engines work ?

Rotary/gnome engines were used to power aircrafts during WW-I & radial engines during WW-II. Then came the era of jet engines which completely revolutionized the aviation technology ! Jet engines were very much efficient & powerful than those used during World wars ! The power jet engines deliver is so high that an airplane weighing hundreds of tons lifts off the ground with such ease. How are they capable of producing so much of power/thrust ?
So lets not waste our time & have a look on how do jet engines work ?

Jet Engines :-

A jet engine can also be called as a reaction engine because the reaction produced by the engine propels the aircraft or vehicle. Jet engines are internal combustion engines discharging hot exhaust gases at high velocity that generate thrust. Unlike the internal combustion engines in automobiles & trucks which convert the up & down movement of the piston to rotary movement of crankshaft, jet engines simply produces power by sucking air at the front side & discharging it at the back side.

Parts in Jet Engines :-

Parts of a jet engine

Parts of a jet engine. source:-

Compressor :-
The compressor is the first component of the engine. It has many blades & is attached to the main shaft. The compressor sucks & squeezes the air as it moves further which results in very high pressure of air.

Combustor :-
In this part, the compressed air is mixed with the fuel & ignited. The heat can reach upto 2700 C.

The exhaust gases are made pass through turbine, causing the turbine blades to rotate. They are fixed on same shaft on which the compressor is attached. But why do we need it ? We’ll come to it soon.

Nozzle :-
The nozzle is the exhaust duct of the engine. This is the part of the engine which produces thrust & propels the aircraft. The converging design of the nozzle helps to accelerate the gases to a very high velocity.

Working of Jet engine :-

Animation of working of a jet engines

An animation of working of a jet engine. You can see that the speed of gases is more while leaving the engine than the air while entering. source:-

  1. The compressor sucks the air & compresses it. This highly compressed air is then forced into combustion chamber.
  2. Multiple nozzles inject fuel into the air & igniter(similar to spark plug) causes air to catch fire. The fuel burns with oxygen present in compressed air producing hot expanding gases.
  3. These gases are passed through the turbines which causes the blades to rotate. This turning of turbine also rotates the shaft to which it is fixed. The same shaft in turn rotates the compressor. Which means instead of just letting out those hot gases, they are indirectly used to suck fresh air at the same time. This is the reason we need turbine after the combustion chamber section.
  4. After coming out of the turbine, then the gases are allowed to exit the engine through a converging shaped nozzle.
  5. The force of the exhaust gases pushing backwards(action) produces equal & opposite forward force(reaction)(Newton’s third law of motion). We call this forward force as thrust which powers the aircraft or vehicle forward.

Types of Jet Engines :-

  1. Turbojet engine
  2. Turbofan engine
  3. Turbo-prop engine
  4. Turboshaft engine
  5. Ramjet
  6. Scramjet

Know in depth – Types of jet engines

Interesting facts :-

  • In 1903, the Wright Brothers flew, The Flyer, with a 12 horse power gas powered engine.
  • It was Frank Whittle, a British pilot, who designed and patented the first turbo jet engine in 1930. The Whittle engine first flew successfully in May, 1941.
  • Jet engines not only power aircraft but also cruise missiles & Unmanned Aerial Vehicles(UAV or we also call them drones).
  • A car named SSC Thrust, currently holding the land speed record, is powered by a jet engine.

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