Accessories of A Gas Turbine Engine

 

Gas Turbine Engines

BEARING, SEALS, & APU

 

Bearings 

Function: 

Acts as the critical support to the rotor shaft which makes up the main engine power

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Number of bearings is determined by the rotorlength shaft.and the weight of the 

Eample: a nine!stage nine !stage aial compressor re"uires re"uir es more bearings than a two stage centrifugal compressor.

 

Bearings used 

#n a Gas Turbine Engine$ BALL and ROLLER Bearings are used to support the engine%s main rotor shaft.

 

Bearings used 

Both are assemblies pro&ide support and hold lubricating oils. These two are preferable because they: 

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o'er little rotational resistance. enable precision alignment of rotating elements. tolerate high momentary o&erloads.

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are easily replaced. are relati&ely inepensi&e. are simple to cool$ lubricate$ and maintain. accommodate both radial and aial loads. are relati&ely resistant to ele&ated temperatures. temperat ures.

 

Ball Bearing

(oller Bearing

 

)il *ampened Bearing 

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A special type of bearing used in turbine engines. )il is routed into a ca&ity formed by the bearing housing and race. )nce pressuri+ed pressuri+ ed by the lubrication system$ oil ,lm is produced that e'ecti&ely dampens &ibration and compesates misalignment.

 

*isad&antages 

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(oller and ball bearings are &ulnerable to damage by foreign elements and could fail without warning.  Therefore$  Therefo re$ proper proper lubrication and sealing is essential.

 

-eals 

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-eals are used in bearings to pre&ent foreign matter from damaging the bearings.  The following seals are are used: 

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abyrinth seals /elical -eals 0arbon -eals

 

abyrinth -eal 

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*i'erent from other seals in that the seal does not touch nor rub to outer surface to create a seal. #nstead$ it uses rotating ,ns that come &ery close$ but do not touch a ,able abatable race. 1ith this type of seal$ air pressure on one side of the seal leaks past each ,n$ decreasing the air pressure at each ,n. By the time the air reaches the opposite side of the seal$ its pressure is near +ero. Therefore$ the positi&e pressure pre&ents oil from leaking past the seal.

 

abyrinth -eal

 

abyrinth -eal

 

abyrinth -eal

 

/elical and 0arbon -eals 

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/elical -eals are similar to labyrinth seals ecept ecept the helical seals depend d epend on re&erse threading threading to stop oil oi l leakage 0arbon -eals are -eals are completely di'erent in that they are spring! di'erent loaded to hold the carbon ring against the rotating shaft$ much like carbon brushes in an electric motor.

 

/elical -eal

 

Auiliary 2ower 3nits 4A235 

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Are turbine power plants dri&ing an electric electri c generator generator..  They are are used to help meet the demands and re"uir re"uirements ements for ground power when aircraf aircraftt engines are not running. As any turbine engines$ bleed air loads generally places the greatest demand on an A23.

 

Auiliary 2ower 3nits 4A235 

#n addition$ A23%s compressor supplies bleed air to a load compressor for heating$ cooling$ anti!ice$ and engine starting.

 

/ow does it work6 

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An A23 is typically started using its own electric starter motor and aircraft battery bat tery power power.. 1ith fuel supplied from an aircraft%s fuel tank an A23 can start$ pro&ide electric power$ heat or cool the cabin$ and start the main engines without aid from an outside source.

 

/ow does it work6 

An A23 runs at its rated speed$ regardless regar dless of the electric and pneumatic loads imposed. To do this$ howe&er$ an A23%s fuel control unit must automatically automa tically ad7ust the th e fuel 8ow. 8ow.

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Eample: #f A23 bleed air is used to start one of the 

aircraft%s engine$ it would automatically meters enough etra fuel to satisfy the load increase$ keeping the A23 on!speed.

 

/ow does it work6 

An A23 is protect p rotected ed by load control the modulates the 2neumatic oad oad to maintain safe load temperatur temperature e in case of operation near its maimum ehaust gas temperature.

 

0ool *own 2eriod 

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 To keep  To keep from damaging damaging an A23$ speci,ed speci,ed A23 cool!down period is needed before shutting it down.  This cool!down period re"uires re"uires the bleed bleed &al&e closed$ and ehaust gas temperature 4EGT5 temperature  4EGT5 stabili+ed. Typical duration is 9 minutes. minutes.  This cool down period minimi+es minimi+es the possibility of Thermal -hock when a hea&y loaded$ /ot A23 is abruptly -hut down.