INTRODUCTION
1. In the gas turbine engine, compression of the air before expansion
through the turbine is effected by one of two basic types of compressor,
one giving centrifugal flow and the other axial flow. Both types are
driven by the engine turbine and are usually coupled direct to the
turbine shaft.
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| Fig. 3-1 A typical centrifugal flow compressor. |
2. The centrifugal flow compressor (fig. 3-1) is a single or two stage
unit employing an impeller to accelerate the air and a diffuser to
produce the required pressure rise. The axial flow compressor (fig. 3-7
and fig. 3-8) is a multi-stage unit employing alternate .rows of
rotating (rotor) blades and stationary (stator) vanes, to accelerate and
diffuse the air until the required pressure rise is obtained. In some
cases, particularly on small engines, an axial compressor is used to
boost the inlet pressure to the centrifugal.
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Fig. 3-2 Specific fuel consumption and
pressure ratio. |
3. With regard to the
advantages and disadvantages of the two types, the centrifugal
compressor is usually more robust than the axial compressor and is also
easier to develop and manufacture. The axial compressor however consumes
far more air than a centrifugal
