The basic idea of the turbojet engine is simple.
Air taken in from an opening in the front of the engine is compressed
to 3 to 12 times its original pressure in compressor. Fuel is added to
the air and burned in a combustion chamber to raise the temperature of
the fluid mixture to about 1,100°F to 1,300° F. The resulting hot air
is passed through a turbine, which drives the compressor. If the
turbine and compressor are efficient, the pressure at the turbine
discharge will be nearly twice the atmospheric pressure, and this
excess pressure is sent to the nozzle to produce a high-velocity stream
of gas which produces a thrust. Substantial increases in thrust can be
obtained by employing an afterburner. It is a second combustion chamber
positioned after the turbine and before the nozzle. The afterburner
increases the temperature of the gas ahead of the nozzle. The result of
this increase in temperature is an increase of about 40 percent in
thrust at takeoff and a much larger percentage at high speeds once the
plane is in the air.
The turbojet engine is a reaction engine. In a reaction engine,
expanding gases push hard against the front of the engine. The turbojet
sucks in air and compresses or squeezes it. The gases flow through the
turbine and make it spin. These gases bounce back and shoot our of the
rear of the exhaust, pushing the plane forward.