DOC AIRBUS | AMM A320FBEARING COMPARTMENT COOLING AND SEALING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. The engine main bearings are contained in three bearings compartments:
(1) The front bearing compartment.
(2) The N°4 bearing compartment.
(3) The rear bearing compartment.
Front Bearing Compartment SealingA. Description
The front bearing compartment contains three bearings, No. 1 ball bearing and No. 2 roller bearing for the low spool shaft and No. 3 ball bearing for the high spool shaft.
The wall of the front bearing compartment is made up of the inner wall of intermediate case and the No. 1 bearing support (Ref. 72-32). The compartment is sealed against the high spool shaft and the low spool shaft with two carbon seals, a hydraulic seal and one labyrinth seal.
The carbon seal in front of No. 1 bearing seals the compartment against the low spool shaft. The hydraulic inter-shaft seal is used to seal the compartment against 8th stage compressor bleed air in the annulus between the high and low rotor shaft.
The combination of a labyrinth seal and a carbon seal rear of No. 3 bearing seals the compartment against the high spool shaft.
The front bearing compartment contains three bearings, No. 1 ball bearing and No. 2 roller bearing for the low spool shaft and No. 3 ball bearing for the high spool shaft.
The wall of the front bearing compartment is made up of the inner wall of intermediate case and the No. 1 bearing support (Ref. 72-32). The compartment is sealed against the high spool shaft and the low spool shaft with two carbon seals, a hydraulic seal and one labyrinth seal.
The carbon seal in front of No. 1 bearing seals the compartment against the low spool shaft. The hydraulic inter-shaft seal is used to seal the compartment against 8th stage compressor bleed air in the annulus between the high and low rotor shaft.
The combination of a labyrinth seal and a carbon seal rear of No. 3 bearing seals the compartment against the high spool shaft.
B. Operation
Pressurizing air from low pressure compressor goes to the space in front of No.1 bearing and the carbon seal.
Pressurizing air to the space rear of No. 3 bearing and between the labyrinth seal and the carbon seal is supplied through low compressor air from the 2.5 stage.
Air in the compartment is vented to a de-oiler to keep proper seal differential pressure.
Pressurizing air from low pressure compressor goes to the space in front of No.1 bearing and the carbon seal.
Pressurizing air to the space rear of No. 3 bearing and between the labyrinth seal and the carbon seal is supplied through low compressor air from the 2.5 stage.
Air in the compartment is vented to a de-oiler to keep proper seal differential pressure.
3. No. 4 Bearing Compartment Cooling and Sealing
A. General
The No. 4 bearing compartment is cooled by 12th stage air. An external plumbing carries this air from a single diffuser case port through an air cooled air cooler and back to the diffuser case at three locations.
Internal diffuser case plumbing carries the cooled air to the No. 4 bearing compartment where it is distributed between the compartment walls forming a thermal barrier. The air exhausts through holes into the front and rear annuli formed by the HP rotor shaft and the bearing compartment.
This air in the annuli flows in two directions. Some air flows past the front and rear carbon seals into the bearing compartment. The remainder flows into the diffuser case inner cavity. This system prevents ingestion of hot 12th stage compressor air in the diffuser case inner cavity from entering the bearing compartment should a carbon seal fail.
Before entering the No. 4 bearing compartment the 12th stage air passes through an air cooled air cooler to be cooled.
The No. 4 bearing compartment is cooled by 12th stage air. An external plumbing carries this air from a single diffuser case port through an air cooled air cooler and back to the diffuser case at three locations.
Internal diffuser case plumbing carries the cooled air to the No. 4 bearing compartment where it is distributed between the compartment walls forming a thermal barrier. The air exhausts through holes into the front and rear annuli formed by the HP rotor shaft and the bearing compartment.
This air in the annuli flows in two directions. Some air flows past the front and rear carbon seals into the bearing compartment. The remainder flows into the diffuser case inner cavity. This system prevents ingestion of hot 12th stage compressor air in the diffuser case inner cavity from entering the bearing compartment should a carbon seal fail.
Before entering the No. 4 bearing compartment the 12th stage air passes through an air cooled air cooler to be cooled.
4. Air Cooled Air Cooler
A. Description
The No. 4 bearing compartment air cooler is installed on the turbine casing. The matrix of cooler is made of 283 dimpled hairpin stainless steel tubes, rounded to match the fan air routing radius, vacuum-furnace brazed to a stainless steel tubesheet and contained within a stainless steel casing. Upper and lower casing sideplates are strengthened by five (5) attached baffles, through which the tubes may move freely to agree with thermal expansion.
The exchanger is held by its coolant air duct flanges.
The No. 4 bearing compartment air cooler is installed on the turbine casing. The matrix of cooler is made of 283 dimpled hairpin stainless steel tubes, rounded to match the fan air routing radius, vacuum-furnace brazed to a stainless steel tubesheet and contained within a stainless steel casing. Upper and lower casing sideplates are strengthened by five (5) attached baffles, through which the tubes may move freely to agree with thermal expansion.
The exchanger is held by its coolant air duct flanges.
B. Operation
Fan air goes into the No. 4 bearing compartment air cooler and makes a single pass over the tubes. Bleed air from 12th stage compressor goes through tubes which are assembled in a two-pass cross-contra flow configuration, then goes into No. 4 bearing compartment cooling air jacket.
Fan air goes into the No. 4 bearing compartment air cooler and makes a single pass over the tubes. Bleed air from 12th stage compressor goes through tubes which are assembled in a two-pass cross-contra flow configuration, then goes into No. 4 bearing compartment cooling air jacket.