investigation of a prototype industrial gas turbine combustor using ...

2. Gas Turbine Combustor
Figure 2.4: Schematic illustration of a general combustor.
zone, and no cooling air or dilution air is supplied to the combustion.
Prior to the primary combustion zone, this burner consists of three concentric
sections (Figure 2.5). The first section is the RPL (Rich-Pilot-
Lean). It is a central body pre-combustor and can be operated from fuel
lean to fuel rich conditions. The choice of lean or rich conditions for the
RPL can be optimized to satisfy combustion stability concerns [21] and
to minimize NO X emissions [22]. The purpose of the RPL is to supply
heat and radicals to the other burner sections. The second burner section,
the pilot, serves as an intermediate link between the RPL and the
Main section, in which the fuel flow can be adjusted to ensure combustion
stability. The third section, the Main, is where most fuel and air is
supplied (79 %). All three combustors have their own swirler. After the
burner configuration, there is a throat followed by the Quarl (Figure 2.5).
The Quarl is a diffuser that has several positive effects. Most easily understood
is the expansion effect that lowers the velocity that lowers the
total pressure drop through the burner [14]. Another reason, specifically
for swirl stabilized burners, is that the Quarl causes the recirculated mass
flow to be higher than for burners with a straight nozzle (sudden expansion)
for the same swirl number (Figure 2.6) [17,23]. In this thesis, the
burner section up to and including the Quarl section was supplied by
SIT. The downstream section, the liner, was designed to achieve high
combustor efficiency.
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