Most modern passenger and military aircraft are powered by
engines, which are also called
jet engines. The first and simplest
of gas turbine is the turbojet.
On this page we show an
animation of the temperature variation through the engine.
has been color-coded as described on another page.
How does a turbojet work?
On this slide we show a computer animation of a turbojet engine.
of the engine are described on
other slides. Here, we are concerned with what happens to the air
that passes through the engine. Large amounts of surrounding air are
continuously brought into the engine
(In England, they call this part the intake, which is probably a more
accurate description, since the compressor pulls air into the
engine.) We have shown here a tube-shaped inlet, like one you would
see on an airliner. But inlets come in many shapes and sizes
depending on the aircraft's mission. At the rear of the inlet, the
air enters the
acts like many rows of
with each row
a small jump in pressure. A
compressor is like an electric fan. We have to supply energy to turn
the compressor. At the exit of the compressor, the air is at a much
higher pressure than free stream. In the
a small amount of fuel is combined with the air and ignited. (In a
typical jet engine, 100 pounds of air/sec is combined with only 2
pounds of fuel/sec. Most of the hot exhaust has come from the
surrounding air.) Leaving the burner, the hot exhaust is passed
The turbine works
like a windmill. Instead of needing energy to turn the blades to make
the air flow, the turbine extracts energy from a flow of gas by
making the blades spin in the flow. In a jet engine we use the energy
extracted by the turbine to turn the compressor by
the compressor and the turbine by the central shaft. The
turbine takes some energy out of the hot exhaust, but there is enough
energy left over to provide thrust to the jet engine by increasing
the velocity through the
the exit velocity is greater than the free stream velocity, thrust is
created as described by the
For a jet engine, the exit mass flow is nearly equal to
the free stream mass flow, since very little fuel is added to the
for a turbojet is
given on a separate slide.
EngineSim - Engine Simulator:
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