What is an afterburning turbojet engine?
When people use the term jet engine, they are usually thinking of what is really an Afterburning Turbojet.
An afterburning turbojet is a jet engine that has the ability to burn excess gasses (from the equivalent of an exhaust) to achieve incredibly high speeds.
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 straightforward turbojet engine.
The afterburner is used to put back some of the engines energy by injecting fuel directly into the hot exhaust.
When the afterburner is turned on, additional fuel is injected 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 was previously used on Concorde.
(The Concorde used to turn the afterburners off once it got into cruise mode. Otherwise, it would run out of fuel before crossing the Atlantic.)
To our knowledge, there are no passenger jets in use today that use afterburner turbojets. Almost all use Turbofans or Turboprops instead.