King Air C90GTi, Pilot Training Manual

Page: 151 / 557

ENGINE AIRFLOW
Inlet air enters the engine through an annu-
l a r p l e n u m c h a m b e r, f o r m e d by t h e c o m -
pressor inlet case, where it is directed forward
to the compressor (Figures 7-7, and 7-8). The
compressor consists of three axial stages
combined with a single centrifugal stage.
A row of stator vanes, located between each
stage of compression, diffuses the air, raises
its static pressure, and directs it to the next
stage of compression. The compressed air
passes through diffuser tubes, which tur n
the air through 90° in direction and convert
velocity to static pressure. The diffused air
then passes through straightening vanes to
t h e a n n u l u s s u r r o u n d i n g t h e c o m b u s t i o n
chamber liner.
The combustion chamber liner has var ying
size perforations which allow entr y of com-
pressor deliver y air. Approximately 25% of
the air mixes with fuel to suppor t combus-
tion. The remaining 75% centers the flame
in the combustion chamber and provides in-
ter nal cooling for the engine. As it enters
the combustion area and mixes with fuel,
the flow of air changes direction 180°. The
fuel/air mixture is ignited, and the resultant
expanding gases are directed to the turbines.
The location of the liner eliminates the need
for a long shaft between the compressor and
the compressor turbine, thus reducing the
overall length and weight of the engine.
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
7-6
FOR TRAINING PURPOSES ONLY
7
POWERPLANT
Figure 7-7. Engine Gas Flow