Figure 2-28.--HP turbine.
Thirty vortex-inducing axial swirl cups in the
dome (one at each fuel nozzle tip) provide flame
Figure 2-27.--LM2500 GTE combustor.
stabilization and mixing of the fuel and air. The
interior surface of the dome is protected from the
the compressor stator by the frame's forward
high temperature of combustion by a cooling-air
film of the 16th-stage air. Accumulation of
flange, the aft end of the compressor rotor by
carbon on the fuel nozzle tips is minimized by
the No. 4R and 4B bearings, and the forward
end of the HP turbine rotor by the 4R and 4B
venturi-shaped spools attached to the swirler.
The combustor liners are a series of over-
lapping rings joined by resistance-welded and
Combustor Section
brazed joints. They are protected from the high
combustion heat by circumferential film cooling.
The LM2500 GTE combustor (fig. 2-27) is an
annular type and has four major components
Primary combustion and cooling air enters
through closely spaced holes in each ring. These
riveted together-the cowl (diffuser) assembly, the
holes help to center the flame and admit the
dome, the inner liner, and the outer liner.
balance of the combustion air. Dilution holes on
The cowl assembly and the compressor rear
the outer and inner liners provide additional
frame serve as a diffuser and distributor for
mixing to lower the gas temperature at the
the compressor discharge air. They furnish
turbine inlet. Combustor/turbine nozzle air seals
uniform airflow to the combustor throughout a
at the aft end of the liners prevent excessive air
large operating range. This provides uniform
leakage and also provide for thermal growth.
combustion and even-temperature distribution at
About 30 percent of the total airflow is used
the turbine. The combustor is mounted in the
in the combustion process. To understand this,
compressor rear frame on 10 equally spaced
you need to know that the ideal fuel/air ratio for
mounting pins in the forward (low temperature)
combustion is about 15 to 1 (15 parts of air to
section of the cowl assembly. These pins provide
1 part of fuel). The rated airflow of the LM2500
positive axial and radial location and assure
GTE is 123 lb/sec or 442,800 lb/hour. At rated
centering of the cowl assembly in the diffuser
power, the engine burns about 9,000 pounds of
passage. The mounting hardware is enclosed
fuel per hour. At the ideal fuel/air ratio of
within the compressor rear frame struts so it will
15 to 1, only 135,000 pounds of air per hour, is
not affect airflow. Strength and stability of the
required (30.5 percent of 442,800).
cowl ring section are provided with a truss
The remaining 70 percent of the airflow is used
structure. The structure has 40 box sections
for cooling, seal pressurization, and ship's
welded to the cowl walls. The box sections also
service use. This breaks down to 5.5 percent
serve as aerodynamic diffuser elements. The cowl
(maximum) used for ship's service and about 0.5
assembly leading edge fits within and around the
percent for seal pressurization. The rest is used
compressor rear frame struts. This arrangement
for cooling, the majority of which reenters the
provides a short overall combustor system
mass flow cycle.
length.
2-24
