is only satisfactory for compressors where rotor
The disc-type rotor consists of separately
and centrifugal stresses are relatively 10 w.
machined discs and spacers flanged to fit one
The drum and disc-type rotor assemblies are
against the other in sequence. The entire assembly
shown in figures 1-21 and 1-22. Many engine
is held together by through-bolts, tie-bolts, or
designs now use combination disc and drum
bolted individually to one another. Blades may
compressor rotor assemblies due to their split-
be attached to the disc rim by the dovetail or bulb
spool design concept. The F404-GE-400 and the
design locking feature. Similar provisions to those
TF34-GE-400 are examples of the combination
on the drum-type assembly are made for bearing
compressor rotor assembly.
supports and splined drive shafts.
The coverage of axial-flow compressors up to
Another method of rotor construction is to
this point has dealt solely with the conventional
machine the discs individually, and shrink fit the
single-rotor type. Actually, there are two
discs over a steel drive shaft (heating the disc and
configurations of the axial compressor now in use.
freezing the shaft to assemble the rotor).
The single rotor and the dual rotor, sometimes
However, this type of compressor construction
referred to as solid spool (fig. 1-23) and split spool
(fig. 1-24).
One version of the solid-spool compressor uses
variable inlet guide vanes. This is the arrangement
found on the J79-GE-10 engine. The engine has
a 17-stage compressor. The angles of the inlet
guide vanes and the first six stages of the stator
vanes are variable. During operation, air enters
the front of the engine. Air is directed into the
compressor at the proper angle by the variable
inlet guide and variable stator vanes. The air
is compressed and forced into the combustion
section. A fuel nozzle extending into each
combustion liner atomizes the fuel for combus-
tion. These variables are controlled in direct
relation with the amount of power the engine
requires to produce the pilot's power lever
position.
One version of the split-spool compressor is
in Pratt and Whitney's J52 engine. It uses two
Figure 1-21 .-Drum-type compressor rotor.
Figure 1-23.-Solid-spool compressor--single rotor turbine.
Figure 1-24.-Split-spool compressor--dual rotor turbine.
Figure 1-22.-Disc-type compressor rotor.
1-17
