Gas Turbine Handbook : Principles and Practices

38 Gas Turbine Handbook: Principles and Practices
tribution of the fuel gas (or greater atomization of the liquid fuel particles)
and more rapid and uniform burning and heat release (Figure
3-13). But the problems of equally distributing fuel to each fuel nozzle
significantly limit the number of fuel nozzles employed.
The second combustor concept is the annular or single combustor.
The single combustor is a stand-alone combustor, generally outside
the envelope of the compressor and turbine. The annular combustor
is also a single combustor but within the envelope of the compressor
and turbine (Figure 3-14). Two main distinctions exist between these
designs. The single combustor is usually configured with a single fuel
nozzle, while the annular combustor must be configured with multiple
fuel nozzles. Secondly, the annular combustor incorporates an
inner wall or liner and heat shield, which is necessary to protect the
rotor. The heavy industrials use a longer combustion chamber, which
makes it more suitable for burning poor quality fuel. However, the
longer combustor also sacrifices combustor efficiency due to reverse
flow pressure losses, a greater surface area to be cooled, and greater
heat loss through convection and radiation. Typical materials used in
the combustor are listed in Table 3-4.
Figure 3-13. Courtesy of Solar Turbines Incorporated. Comparison
of the low NO x
and standard fuel injectors for the Centaur 50 gas
turbine. SoLoNO x
is Solar’s designation for it’s low NO x
emission
engine configuration.