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What the standard day temp and pressure
- 15C or 59F
- 29.92Hg 14.69psi 1013.2millibars
What is the effect on pressure and temp as altitude increases?
pressure and temp both decrease
What are the basic parts of a turbine engine?
- air inlet, compressor (cold section)
- combustor, turbines and exhaust (hot section)
What are 4 types of gas turbine engines?
turbo prop, fan, shaft, jet
In a turbine engine, how are the station numbers usually indicated?
Usually in the direction of airflow
how is thrust measured
In a diverging duct, what happens to velocity, temp and pressure?
What is the effect on velocity, pressure and temp in a converging duct?
What happens to velocity and pressure in a divergent duct at subsonic speeds?
What happens to velocity and pressure in a divergent duct at supersonic speeds?
What happens to velocity and pressure in a convergent duct at subsonic speeds?
What happens to velocity and pressure in a convergent duct at supersonic speeds?
What happens according to Boyle's law if the temp is held constant?
As volume increases-pressure decrease
Charles Law states that if pressure is held constant?
and if volume is help constant ?
as temp increases, volume increases
as temp increases, pressure increases
What are the three primary factors effecting thermal efficiency?
- Turbine inlet temp
- Compressor Ratio
- Efficiencies of the compents
What is the limiting factors in the internal temperature of the turbine engine?
limited by the internal componments of the engine melting. The hotter the temp, the more efficient it is
What are some of the factors that effect thrust of a turbine engine?
- Air Density-temp, altitude, airspeed and humidity
- Engine RPM
- Fan Efficiency
If we lose power with less dense air at crusing altitude, why is it common to fly at high altitudes?
we lose power with the less dense air at altitude, but we gain more power by increasing ram air into the engine
What is a limiting factor of engine RPM?
blade tip shock stall, limited by the speed of sound
How can you define thrust ratio?
thrust produced by the fan/thrust produced by the core
Define bypass ratio
amount of air through the bypass/amount of air through the core
Define fan pressure ratio
air leaving fan/air entering fan
What are three factors that effect the Thermal Efficiency of a gas turbine engine?
- Turbine inlet
- Compressor ratio
- effencies of compressor and turbine components
As temperature of air at the turbine inlet increases, thermal efficiencies of the engine will?
increase, (burns fuel hotter)
What are the 3 bypass ratio classifications?
- 1:1 low
- 2:1-3:1 med
- 4:1 high
What type of ducting is used on a inlet to provide a positive supply of air to the compressor?
What do inlet guide vanes do?
directs air to enter compressor properly, reduces swirling
where is it measured?
- engine pressure ratio
- measures pressure at the front and rear of engine to get power
What type of ducting would a subsonic a/c use to provide positive pressure to the compressor?
What is the idea behind supersonic ducting? What type of duct does it use?
slows air down before it enters the engine by using convergent divergent ducting
What type of application would a bellmouth inlet use?
for slow a/c or stationary testing
What is the theory behind inertia seperators?
sand can't go around corners, uses inertia to remove particles from the air
What does a axial compressor consist of?
1 rotor, 1 stator= 1 stage
What is the first stator on the axial compressor?
inlet guide vane
What is the fuction of the rotor and the stator?
Rotor speeds air up, Stator straightens air out and reduces air velocity to increase pressure
How can a rotor stall?
at slow air speeds
What are some advantages to axial compressors?
- high peak efficiencies from ram air effect
- high pressure is created from mulitple stages
- small frontal area
What is the function of the rotor in a axial compressor?
- Rotates to draw air through the compressor
- adds energy to airflow
What is the function of the stator?
- Change the direction of airflow as it leaves each stage of the compressor
- aligns airflow with the next compressor rotor
- decrease air velocity, increase pressure
What controls the RPM of the compressor on a axial compressor type turbine?`
- controlled by the amount of fuel burned
- Hotter the exhaust temps the faster the turbine spins
What are the two parts to a axial compressor?
rotor and stator
What is another name for an inertial seperator that has a helical shape?
Swirl Vane Seperator
What in the fuck is a vortex dissipator?
Bleed air blows air on runway to remove forign objects
what are the two things that the compressor supplies ?
- bleed air
- air for combustion
What are the two different types of compressors?`
- both can be used on the same engine
What are the 4 components of a centrifugal compressor?
Describe the air flow through the centrifugal compressor?
Impellor speeds air up by throwing it outwards through the divergent duct into the diffuser, diffuser pushes air into mainfold
What are some of the benifits of a centrifugal compressor?
- cheap to produce
- high compression ratio
- efficient at a wide range of rpm
what are some of the drawbacks of the centrifugal compressor?
- large frontal area
- restricted to the number of stages
How does compressor stall happen?
failure of the compressor blades to move the air at the designed flow rate
What are three things that control air speeds in the compressor?
- var. guide vanes
- bleed valve
- modulating ring
What is the name of the component in the compressor that can be moved to change the angle that the air hits the rotor?
Variable guide vanes
In the compressor, what open at low speed to prevent stall?
What controls the velocity of air through the compressor?
What do the modulating ring do?
used to reduce airflow by advancing, keeps air moving efficiently
What will happen if the engine begins to stall?
the bleed valve will open
(generally) what is P3 air?
- highest pressure in the engine
- closes the bleed valve when the engine is at speed
Name the four ways that turbine blades can be attached to the hub of the compressor?
- Fir tree
- Integral Casting
Which blade attachment method uses a pin or a lock tab?
What is the most important consideration is blade tip designs?
they need to control the wing tip vorticies
What are four blade shape designs
- Machine tips
- squeler tips
- Profile tips
- End Bend
- (replaceable materail on the case)
Why is there shrouds on the outer edge of the stator?
- Stops the air from travelling around the outer edge like a fence
- helps control the airflow
What is N1 in a axial compressor and how is it measured?
N1=rpm, measured as a %
What is a double spool compressor?
- 2 seperate shafts, high and low speed
- supplies a constant volume of air to the combustion chamber
How does N1 and N2 differ from one another in a double spool compressor?
- N1-not governored, speeds up at altitude
- N2-governored by fuel system
Where is the diffuser scrool usually located?
between the compressor and combustion chamber
What is the function of the diffuser scrool?
- reduce the velocity of the airflow (don't blow the flame out)
- increase pressure of the air (P3 highest in engine)
What are the three different types of combustion sections?
What is the basic prinicpal of the combustion section?
- mixes fuel and air for combustion
- exhaust gases are delivered to the turbine section
What is the most efficient combustion chamber?
Whats the purpose of the flame tube in the combustion chamber?
used to transfer a spark to different cans
What type of turbine engine would you most likly find a reverse flow annular combustion chamber?
- turbo props and turbo fans
- shorter and lighter engines
What type of turbin doesn't require a clutch and why?
- Free Turbine-no direct connestion between rotor and engine
- starter spins compressor, air moves to combustion section, rotor doesn't spin right away
What are the 2 main components of the turbine section?
- nozzel (like stator in combustion section)
- wheel (like rotor)
What is the purpose of Shrouds in the turbine section?
Set tip clearence on the turbine wheel
What part of the engine is subject to the most heat stress of any part of the engine?
1st stage turbine nozzle
Whats a gill hole?
- used for cooling
- slots in nozzle to allow air to flow through and discharge out through trailing edges
what does CT stand for
Why is the tip to shroud clearence so critical?
- helps reduce air loss at the blade tip
- too loose, proformance loss
- to tight, it rubs
Define creep in the turbine blades?
Elongation of the blades in the elasticty zone, slowly over time
What are the 3 stages of creep?
- primary-grows rapidly at first
- secondary-grows slowly to life limit
- tertiary-grow rapidly to destruction after life limit
What do these stand for?
- high pressure compressor
What kind of corrosion would be caused by acid raid?
Name the 3 stages of corrosion?
- Initial coating deterioration-rust color, dark grey
- Small scattered blisters-corrosion of base material has started
- Clusters of ruptured blisters-blades need to be replaced
What is Jo-Coating used for?
What is the sheer zone? What is a major byproduct of the sheer zone?
exhaust sheers with ambient air, creates loud noise
Blocker doors and clam shell doors are 2 examples of what?
What are three forms of thrust agmentation?
- water injection
- water methanol injection
what make water meth and water injection an effective form of thrust agumentation?
increases air density
What are the four parts required to make a turbine assembly?
name 3 types of turbine blades?
- impulse reaction
What the fuck is a shrouded turbine wheel?
shaped so the ends of the blades form a shroud that is sealed with a knife edge running surface
Why are the return luberication lines always bigger than the incoming lines?
to account from expansion due to heat
When comparing axial compressor air input velocity to the output velocity at full power we see?
very little change in velocity
What are some of the components mounted to the AGB?
- fuel controls
- fuel pump
- airconditioning compressor
- oil pumps
What is a RGB used for?
- used to reduce the engine RPM on a turbo prop/fan engine
- may contain a governor for the N2 prop
How would you measure the output of a turbo jet/fan?
- EPR-total exhaust pressure/total inlet pressure
- Torque-torque meter, piston and helical gear
The cooling process in turbine blades which sends cooler combustion section air through slot gills is called?
Where is the fuel pump mounted on a free turbine?
N1-turing during start, needs fuel
Where would you find variable inlet guide vanes?
On a free turbine turbo shaft engine the gas producer section would be described as ?
What would the shape of the nozzle used for the following