Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
16 Cards in this Set
- Front
- Back
|
Centrifugal flow compressor |
Diffuser red velocity & inc press of air after flowing through compressor (which accelerates air outwards)
Characterisitcs: - low compression ratio - durable - less moving parts - large frontal area (more drag) - fast acceleration over wide range of RPM |
|
|
Axial flow compressor |
Inlet guide vanes - dec velocity & inc press prior to compression i) Variable - control angle at which air enters compressor - match angle w/ compressor RPM & help prevent compressor stalls ii) stator - stationary at optimal angle
Stators convert velocity of air to pressure while rotors accelerate air. - done in stepwise fashion
Characteristics - high compression ratio - small frontal area - more efficient - slow acceleration over wide range of RPM - more challenging design *all turbines are axial flow |
|
|
Preventing compressor stalls |
1) compressor bleed valve 2) variable inlet guide vane 3) fuel metering Symptoms - loud explosive bangs - lower toque or N1 readings - higher EGT or ITT readings - engine surging |
|
|
Bypass ratio |
Turbojet - all air passes through combustion chamber Turbofan - some air bypasses compressor, burner, and turbine sections High bypass - fan air accounts for majority of thrust (~ 70%) - mixed with exhaust stream Bypass ratio - ratio of air drawn through turbofan that bypasses engine core to rate passing though engine core - 5:1 |
|
|
EPR |
-measure of amount of energy imparted to airstream by jet engine - ratio of turbine discharge total to total pressure at compressor inlet - correction factor may be needed on non-standard temp days |
|
|
Compressor bleed valve |
2 purposes: a) offload compressor during startup b) offload compressor during large throttle changes
- prevent compressor stall/surge - open: a) under control of FCU OR b) in event of pressure build up |
|
|
Reverse thrust |
*by moving pwr lever into selected range, redirect flow of thrust forward - cold thrust = bypass air - hot thrust = jet thrust air
Target type: - more efficient - hot & cold thrust 1) clamshell 2) bucket doors
Cascade type: - less efficient - only cold thrust - use blocker doors to seal off fan exit as a sleeve moves to expose the cascade |
|
|
Prop beta range |
- zero thrust range - *Power levers control both: - blade angle (prop RPM) and fuel flow |
|
|
Low pitch stop |
- prevents props entering beta or reverse in flight - mechanical linkage senses blade angle - linkage causes valve to close to stop flow of oil going to prop dome - once oil blocked off, low pitch stop created |
|
|
Compressor stalls |
Compressor will stall if encounter air at AoA > critical angle - air enters inlet at too steep angle = turbulence in inlet = air stikes blades at high AoA - dirt on compressor blades = separation of airflow - wear/damage changes shape of compressor blades - icing on 1st stage of compressor - failure of surge-bleed valve to open on schedule
= disruption of airflow through entire engine - thrust inc/dec out of control (surge) - often w/ series of bangs |
|
|
Combustion chamber |
- double walled - about 30% of incoming air goes to combustion - air/fuel ratio 15:1 Excess fuel or shortage of air = engine runs hot |
|
|
Starts |
Hot start - fuel intoduced with too low compressor RPM - most commonly low starter battery - slow engine acceleration causes high temp w/out rearward press flow Hung start - *not reaching fast enough RPM to maintain IDLE - in mid N range - often due bleed air valve stuck close - LP compressor stalls - FCU keeps supplying fuel - overtemp |
|
|
Quickest way to get rid of smoke |
Raise cabin altitude |
|
|
Turbocharger |
Pressurizes intake air vs Supercharger compresses fuel air mix after leaves carb
Turbocharged when wastegate closed |
|
|
EEC / ECU |
Regulate engine fuel flow to maintain specific pwr settings as flight and environmental conditions change |
|
|
Flex temperature |
Assumed temp used in calculating reduced thrust settings for take off |
