(8) Axial. The axial compressor performs the compression process in a
straight line parallel to the axis of the engine. The axial compressor is
composed of rotating members called rotors and stationary members called
stators. A row of rotors and stators is called a stage. The axial compressor
is composed of a series of stages (Figure 120). During operation, the air is
arrested in the first stage of compression and is turned by a set of stator
vanes, picked up by a set of rotor blades, and passed through each successive
stage to complete the compression process. The rotors increase velocity while
the stators decrease the velocity. The successive increases and decreases in
velocity practically cancel each other, with a result that the velocity, as the
air leaves the compressor, is usually slightly greater than the velocity of the
air at the entrance to the compressor. As the pressure is built up by
successive sets of rotors and stators, less and less volume is required. Thus,
the volume within the compressor is decreased gradually. At the exit of the
compressor, a diffuser section within the engine adds the final touch to the
compression process by decreasing again the velocity and increasing the static
pressure just before the air enters the engine burner section.
Figure 120. Axial Compressor.
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