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 TM 9-8000
Figure 10-6. Air Inlet Section
and passed through each successive stage to complete
speed and flows through a set of diffuser vanes which
compression. The rotors increase velocity while the
decelerates the flow of air, converting high-velocity air to
stators decrease the velocity. The successive increases
high-pressure energy. The diffuser vanes also serve to
and decreases in velocity practically cancel each other,
straighten airflow. A typical centrifugal compressor is
with a result that the velocity, as the air leaves the
shown in figure 10-8. Centrifugal compressors achieve
compressor, is usually slightly greater than the velocity of
efficiency ratings of 78 to 84 percent and compression
the air at the entrance to the compressor. As the
ratios of approximately 5:1.
pressure is built up by successive sets of rotors and
stators, less and less volume is required. Thus, the
10-10.
Combustion Chamber.
The combustion
volume within the compressor is decreased gradually. At
chamber (fig. 10-9) is designed to burn a mixture of fuel
the exit of the compressor, a diffuser section within the
and air, and to deliver the resulting gases to the turbine
engine adds the final touch to the compression process
at a temperature that will not exceed the allowable limits
by decreasing again the velocity and increasing the static
at the turbine inlet. The chamber, within a very limited
pressure just before the air enters the engine burner
space, must add sufficient heat energy to the gases
section.
passing through the engine. This accelerates their mass
enough to produce the desired power for the turbine
b.
Centrifugal Compressors.
This type of
section. Combustion chambers are built in a number of
compressor consists of two main parts: an impeller and a
different designs. The construction is such that less than
diffuser. Centrifugal compressors operate by taking in
one-third of the total volume of air entering the chamber
air near the hub of the impeller and accelerating it
is permitted to mix with the fuel. The remaining air is
outward by centrifugal action. The impeller vanes guide
used downstream to cool the combustor surfaces, and to
the air toward the outer circumference of the
mix with and cool the burned gases before they enter the
compressor, building up the velocity by means of the
turbines.
high rotational speed of the impeller. Air leaves the
TA233508
impeller at high
10-7
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