Combustion
The combustion section (Figure 7-5) is that
portion of the engine in which fuel is added
to the compressed air and ignited.
The section consists of the outer and inner
casing, combustion liner, No. 3 bearing and its
support, and the first-stage turbine nozzle.
The outer combustion casing is bolted to the
mainframe at the front and the turbine casing
at the rear. Two igniter plugs are mounted in
the casing at the one and seven o’clock posi-
tions. Fuel trapped in the combustion section
during engine shutdown drains through a com-
bustion drain at the six o’clock position.
The inner combustion casing is one piece. At the
front, it is bolted to the inner casing of the main-
frame, at the rear, to the No. 3 bearing support.
The combustion liner consists of a cowl section,
a dome section, and an outer and inner shell.
Air enters the combustion dome through swirl
cups to support combustion and provide dome
cooling. Thimble holes direct air into the burn-
ing area, while louvers provide a boundary
layer of cool air along the inner surface of the
liner.
The No. 3 bearing and carbon seal are at the
aft end of the inner combustion casing. The No.
3 bearing support is part of the balance piston
chamber and is used to resist forward thrust
of the engine shaft.
7-6
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
LINER
IGNITER BOSS
SWIRL CUP
HAFT SHIELD
INSULATION BLANKET
FIRST-STAGE TURBINE NOZZLE
INNER CASING
OUTER LABYRINTH SEAL
INNER LABYRINTH SEAL
NO. 3 CARBON SEAL
NO. 3 BEARING
OUTER CASING
COMBUSTOR DRAIN BOSS
Figure 7-5. Combustion Section
