Four engine mounting pads are on the inlet housing. The front
face of the inner housing includes studs to mount the engine oil tank
cover plate and a speed reduction gearbox. The inner housing, figure
5.6 item 9, contains the output shaft, the compressor rotor forward
bearing support structure, the torquemeter head assembly, and a 3.75
gallon oil tank. The outer housing forms the outer wall for the
annular inlet duct. Four struts make the structural connection
between the two housings. The struts are hollow and have passages
for oil and accessory drive shafts.
The compressor rotor assembly, shown in figure 5.7, consists
of a sevenstage, allsteel axial compressor and an alltitanium
centrifugal compressor. The two compressors form a single rotating
assembly providing an 8 to 1 compression ratio.
All axial compressor blades are stainless steel and mounted on
steel compressor disks by dovetail roots and springloaded locking
pins. Seven twopiece stator assemblies are bolted to a twopiece
cast magnesium compressor housing, which encloses the axial and
centrifugal rotors. The housing is split axially to permit complete
access to the compressor rotor for inspection and blade replacement.
The internal surfaces of these housings are coated with epoxy
phenolic and graphite filler. The external surfaces are treated with
epoxy phenolic gray paint.
On the L111 engine, a variable inlet guide vane assembly is
mounted in the front of the compressor housing. The axial compressor
housing has an airbleed system consisting of a series of holes and
machined passages. The system bleeds air from the sixth stage and
thereby improves compressor performance. This system is controlled
by an interstage airbleed system covered later in the chapter.
The air diffuser, shown in item 1 figure 5.8, is constructed
of stainless steel. The diffuser receives highvelocity air from the
centrifugal impeller. This radial airflow is changed to an axial
flow by longitudinal guide. The divergent shape of the diffuser
decreases velocity and increases air pressure. Air pressure at the
diffuser discharge is at its highest value; air temperature is in the
vicinity of 600 F. Temperature and pressure are directly related to
rotational speed of the compressor. Internally, the diffuser supports