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 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
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 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-SURGEVariable Inlet guide vanes control Bleed Valves Variable stator and actuator mechanism
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
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