Gas Turbine Handbook : Principles and Practices

64 Gas Turbine Handbook: Principles and Practices
Figure 4-12. Comparing characteristic curves of axial and centrifugal
compressors.
reached. Also, the centrifugal compressor is stable over a greater flow
range than the axial compressor, and compressor efficiency changes
are smaller at off design points.
For the same compressor radius and rotational speed the pressure
rise per stage is less in an axial compressor than in a centrifugal
compressor. But, when operating within their normal design range,
the efficiency of an axial compressor is greater than a centrifugal
compressor.
BURNER SECTION
The burner section is made up of the diffuser duct, the combustor,
fuel nozzle and the transition duct.
The velocity of the air leaving the compressor is decreased before
it enters the combustor in order to reduce the burner pressure
loss and the air velocity in the burner. According to Bernoulli’s Law
a decrease in velocity, and its resultant increase in static pressure, is
achieved in the diffuser. [ Bernoulli’s Law states that at any point in a
passageway through which a gas (or liquid) is flowing, the sum of the
pressure energy, potential energy, and kinetic energy is a constant.]