Turbojet Engine
What is a turbojet engine?
Most modern passenger and military aircraft are powered by gas turbine engines, which are also called jet engines. The first and simplest type of gas turbine is the turbojet, now largely superceded by the more fuel efficient turbofan engine.
Turbojets are the oldest kind of jet engine but as knowledge has grown, turbofans at the top end, and turboprops at the lower end have largely replaced this basic engine type in modern aircraft..
The design was arrived at the same time by two different engineers, Sir Frank Whittle in Britain and Hans von Ohain in Germany.
In order for fighter planes to fly faster than sound (supersonic), they have to overcome a sharp rise in drag near the speed of sound.
A simple way to get the necessary thrust is to add an afterburner to a core turbojet. In a basic turbojet some of the energy of the exhaust from the burner is used to turn the turbine.
The afterburner is used to put back some energy by injecting fuel directly into the hot exhaust. In the diagram above, you'll notice that the nozzle of the basic turbojet has been extended and there is now a ring of flame holders, colored orange, in the nozzle.
When the afterburner is turned on, additional fuel is injected through the hoops and into the hot exhaust stream of the turbojet. The fuel burns and produces additional thrust, but it doesn't burn as efficiently as it does in the combustion section of the turbojet. You get more thrust, but you burn much more fuel. When the afterburner is turned off, the engine performs like a basic turbojet.
Afterburners are only used on supersonic aircraft like fighter planes and used to ber used on the Concorde supersonic airliner.
Once it had reached sufficient height and speed, the Concorde pilots then turned the afterburners off. Otherwise, the aircraft would run out of fuel before crossing the Atlantic.
No commercial aircraft today use a true Turbojet afterburning engine.
