Most modern passenger and military aircraft are powered by
gas turbine engines, which are also called
jet engines. Jet engines come in a variety
of shapes and sizes but all jet engines have certain parts
Jet engines are complicated pieces of machinery with many moving
parts. To help understand how the machines work, engineers often draw
simplified diagrams, called schematics, of the engine. The
schematic is often a flat, two-dimensional drawing of the engine
representing the important components. It is not meant to be a
"picture" of the engine, but only to indicate the important parts of
the engine. On this slide we show a three-dimensional computer model
of an afterburning turbojet at the top and
the corresponding schematic drawing at the bottom. Various parts on
the computer model are labeled and the corresponding parts on the
schematic are indicated. When we discuss the fundamentals of
and turboprop operation, we will use
similar schematic drawings.
As a further shorthand for propulsion engineers, locations
on the engine schematic are assigned station numbers.
stream conditions are labeled 0 and the entrance to the
inlet is station 1. The exit of the inlet,
which is the beginning of the compressor,
is labeled station 2.
The compressor exit and burner
entrance is station 3 while the burner exit
entrance is station 4. The exit of the turbine is station 5 and
the flow conditions upstream of the afterburner occur at station 6.
Station 7 is at the entrance to the nozzle
and station 8 is at the nozzle throat. Some nozzles have an
additional section downstream of the throat which would be station
Why do engineers assign numbers to the stations?
First, it simplifies the language used when describing the operation
of a gas turbine engine. With this
numbering convention, engineers can refer to the "turbine inlet
temperature" as simply "T4", or the "compressor exit pressure" as
"P3". It makes technical reports, documents, and conversations much
more concise and easy to understand.
Second, in a gas turbine engine the stations correspond to the beginning
and the end of thermodynamic processes in the engine. The
describes the thermodynamics of a gas turbine engine and
when describing the processes on a
p-V or T-s diagram,
we denote the end of a process by using the station number.
For example, the end of the
isentropic compression performed
by the compressor is designated with a 3 on a T-s diagram.
You can see the location of the engine stations for various engines
by using the
interactive Java applet.
If you choose "Graphs" for the output display, the station numbers will
appear on the engine drawing and on the corresponding T-s or p-V diagram.
Parts of a Jet Engine:
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