15.4 COMPRESSORS

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CENTRIFUGAL TYPE

SINGLE STAGE COMPRESSOR

TWO STAGE COMPRESSOR SINGLE STAGE DOUBLE ENTRY

CENTRIFUGAL ASSY

CENTRIFUGAL FEATURES

• ADVANTAGE– Cheap and simple– Not prone to FOD and icing– Stable, no stall and surge– Large rise in air pressure over distance

• DISADVANTAGE– Limited compression ration 4:1– Large frontal area– Capacity is limit by impaler tip speed– Easyly loss pressure due to severe change airflow direction

AXIAL TYPESINGLE SPOOL TWIN SPOOL

TRIPLE SPOOL

OPERATING PRINCIPLE• Continuous compression

through each stage .• Stage is defined as rotor and

stator• Its form divergence duct

(continouse pressure rise) in each stage

CASCADE EFFECT

• Ability of the air to travel from low pressure area to the high prassure area

AXIAL ASSY

AXIAL FEATURES

• ADVANTAGE– High compression ratio– Low fuel consumption– Small frontal area and high volume of air– Suit to high thrust

• DISADVANTAGE– Complicated and expensive – Poor acceleration– Very severe to FOD– Prone to stall and surge

COMPONENT• Rotor Blade :

– Airfoil section and twist to provide correct angle of attack (maintain uniform airflow)

– Stager angle ( angle of incident of blade)• Stator Vanes :

– Airfoil section and secure with casing– Providing divergen blade spacing to effect sec stage compression– Control direction airflow

• Fan type– To produce thrust for turbofan engine and to pass air that not required for

combustion– Engine more quiter and durable using fan– High aspect ratio : thin and long blade (have clapper support)– Low aspect ratio : wide chord and smaller blade

ROTOR BLADE

Blade design

Blade Attachment

STATOR VEIN

Variable stator

Fixed stator

FAN

• FAN BALANCING– Balance to prevent vibration and stress due to

high rotational speed– Two type of balance: • Single Plane or Static balance• Two plane or dynamic balance

MIX COMPRESSOR

STALL AND SURGE• Stall :

– Angle of attack of blade become to high or low due to airflow entry condition.– Indicate by increase in EGT, vibration and coughing noise– Transition stall If slight vibration and poor acceleration occur shortly – Hung stall cause all stage compressor stall and airflow will become reverse

flow (surge)

• Surge :– Complete breakdown of airflow (all compressor stage stall)– Due FOD, distored airfoil, bleed valve mailfunction cause the rear compressor

stage chock or exessive pressure ratio– Indicate by abnormal engine noise, high EGT, vibration, flame emiting in

exhaust – In extream condition, engine completely destroy

AIRFLOW VARIATION

AIRFLOW CONTROL

• Anti-surge device – To prevent or reduce risk stall/surge and maintain

smooth airflow.– By controlling the movement of airflow or

dumping the unstable airflow from compressor.– Type :• Variable intake guide vanes• Variable stator vanes• Compressor bleed valve

ANTI-SURGE

Variable Inlet guide vanes control

Variable stator and actuator mechanism

Bleed Valves

COMPRESSOR RATIO

• Calculated by dividing total pressure after last stage of compresssion by total inlet pressure.

• Varies with RPM, intake temperature and blade damage

• Overall pressure ratio for axial compressor is 30:1