To move an
through the air,
is generated by some kind of
Most modern fighter
aircraft employ an afterburner on either a low bypass turbofan
or a turbojet. On this page we will discuss some of the fundamentals
of an afterburning turbojet.
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
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
you'll notice that the nozzle of
the basic turbojet has been extended and there is now a ring of flame
holders, colored yellow, 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
much more fuel.
When the afterburner is
turned off, the engine performs like a basic turbojet.
Afterburners are only used on fighter planes and the supersonic
airliner, Concorde. (The Concorde turns the afterburners off once it
gets into cruise. Otherwise, it would run out of fuel before reaching
Europe.) Afterburners offer a mechanically simple way to augment
thrust and are used on both turbojets and
This page shows the pressure variation through an afterburning turbojet.
has been color-coded as described on another page.
thrust of an afterburning turbojet
is given on a separate slide.
- Beginner's Guide Home Page