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2011-12-04 11:00:21
Turbine Theory

Turbine Theory
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  1. What the standard day temp and pressure
    • 15C or 59F
    • 29.92Hg 14.69psi 1013.2millibars
  2. What is the effect on pressure and temp as altitude increases?
    pressure and temp both decrease
  3. What are the basic parts of a turbine engine?
    • air inlet, compressor (cold section)
    • combustor, turbines and exhaust (hot section)
  4. What are 4 types of gas turbine engines?
    turbo prop, fan, shaft, jet
  5. In a turbine engine, how are the station numbers usually indicated?
    Usually in the direction of airflow
  6. how is thrust measured
    in pounds
  7. In a diverging duct, what happens to velocity, temp and pressure?
    • velocity-decreases
    • temp-increases
    • pressure-increases
  8. What is the effect on velocity, pressure and temp in a converging duct?
    • vel-increases
    • temp-decreases
    • pressure-decreases
  9. What happens to velocity and pressure in a divergent duct at subsonic speeds?
    • vel-decreases
    • pressure-increases
  10. What happens to velocity and pressure in a divergent duct at supersonic speeds?
    • vel-increases
    • pressure-decreases
  11. What happens to velocity and pressure in a convergent duct at subsonic speeds?
    • vel-increases
    • pressure-decreases
  12. What happens to velocity and pressure in a convergent duct at supersonic speeds?
    • vel-decreases
    • pressure-increases
  13. What happens according to Boyle's law if the temp is held constant?
    As volume increases-pressure decrease
  14. 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
  15. What are the three primary factors effecting thermal efficiency?
    • Turbine inlet temp
    • Compressor Ratio
    • Efficiencies of the compents
  16. 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
  17. What are some of the factors that effect thrust of a turbine engine?
    • Air Density-temp, altitude, airspeed and humidity
    • Engine RPM
    • Fan Efficiency
  18. 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
  19. What is a limiting factor of engine RPM?
    blade tip shock stall, limited by the speed of sound
  20. How can you define thrust ratio?
    thrust produced by the fan/thrust produced by the core
  21. Define bypass ratio
    amount of air through the bypass/amount of air through the core
  22. Define fan pressure ratio
    air leaving fan/air entering fan
  23. What are three factors that effect the Thermal Efficiency of a gas turbine engine?
    • Turbine inlet
    • Compressor ratio
    • effencies of compressor and turbine components
  24. As temperature of air at the turbine inlet increases, thermal efficiencies of the engine will?
    increase, (burns fuel hotter)
  25. What are the 3 bypass ratio classifications?
    • 1:1 low
    • 2:1-3:1 med
    • 4:1 high
  26. What type of ducting is used on a inlet to provide a positive supply of air to the compressor?
    Divergent Ducting
  27. What do inlet guide vanes do?
    directs air to enter compressor properly, reduces swirling
  28. Define EPR?
    where is it measured?
    • engine pressure ratio
    • measures pressure at the front and rear of engine to get power
  29. What type of ducting would a subsonic a/c use to provide positive pressure to the compressor?
  30. 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
  31. What type of application would a bellmouth inlet use?
    for slow a/c or stationary testing
  32. What is the theory behind inertia seperators?
    sand can't go around corners, uses inertia to remove particles from the air
  33. What does a axial compressor consist of?
    1 rotor, 1 stator= 1 stage
  34. What is the first stator on the axial compressor?
    inlet guide vane
  35. 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
  36. How can a rotor stall?
    at slow air speeds
  37. What are some advantages to axial compressors?
    • high peak efficiencies from ram air effect
    • high pressure is created from mulitple stages
    • small frontal area
  38. What is the function of the rotor in a axial compressor?
    • Rotates to draw air through the compressor
    • adds energy to airflow
  39. 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
  40. 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
  41. What are the two parts to a axial compressor?
    rotor and stator
  42. What is another name for an inertial seperator that has a helical shape?
    Swirl Vane Seperator
  43. What in the fuck is a vortex dissipator?
    Bleed air blows air on runway to remove forign objects
  44. what are the two things that the compressor supplies ?
    • bleed air
    • air for combustion
  45. What are the two different types of compressors?`
    • Centrifugal
    • Axial
    • both can be used on the same engine
  46. What are the 4 components of a centrifugal compressor?
    • impeller
    • diffuser
    • compressor
    • mainfold
  47. 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
  48. What are some of the benifits of a centrifugal compressor?
    • cheap to produce
    • high compression ratio
    • efficient at a wide range of rpm
  49. what are some of the drawbacks of the centrifugal compressor?
    • large frontal area
    • restricted to the number of stages
  50. How does compressor stall happen?
    failure of the compressor blades to move the air at the designed flow rate
  51. What are three things that control air speeds in the compressor?
    • var. guide vanes
    • bleed valve
    • modulating ring
  52. 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
  53. In the compressor, what open at low speed to prevent stall?
    bleed valve
  54. What controls the velocity of air through the compressor?
    bleed valve
  55. What do the modulating ring do?
    used to reduce airflow by advancing, keeps air moving efficiently
  56. What will happen if the engine begins to stall?
    the bleed valve will open
  57. (generally) what is P3 air?
    • highest pressure in the engine
    • closes the bleed valve when the engine is at speed
  58. Name the four ways that turbine blades can be attached to the hub of the compressor?
    • Fir tree
    • bulb
    • dovetail
    • Integral Casting
  59. Which blade attachment method uses a pin or a lock tab?
    Intergal Casting
  60. What is the most important consideration is blade tip designs?
    they need to control the wing tip vorticies
  61. What are four blade shape designs
    • Machine tips
    • squeler tips
    • Profile tips
    • End Bend
    • (replaceable materail on the case)
  62. 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
  63. What is N1 in a axial compressor and how is it measured?
    N1=rpm, measured as a %
  64. What is a double spool compressor?
    • 2 seperate shafts, high and low speed
    • supplies a constant volume of air to the combustion chamber
  65. 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
  66. Where is the diffuser scrool usually located?
    between the compressor and combustion chamber
  67. 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)
  68. What are the three different types of combustion sections?
    • Annular
    • can
    • can annular
  69. What is the basic prinicpal of the combustion section?
    • mixes fuel and air for combustion
    • exhaust gases are delivered to the turbine section
  70. What is the most efficient combustion chamber?
  71. Whats the purpose of the flame tube in the combustion chamber?
    used to transfer a spark to different cans
  72. 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
  73. 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
  74. What are the 2 main components of the turbine section?
    • nozzel (like stator in combustion section)
    • wheel (like rotor)
  75. What is the purpose of Shrouds in the turbine section?
    Set tip clearence on the turbine wheel
  76. What part of the engine is subject to the most heat stress of any part of the engine?
    1st stage turbine nozzle
  77. Whats a gill hole?
    • used for cooling
    • slots in nozzle to allow air to flow through and discharge out through trailing edges
  78. what does CT stand for
    compressor turbine
  79. 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
  80. Define creep in the turbine blades?
    Elongation of the blades in the elasticty zone, slowly over time
  81. 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
  82. What do these stand for?
    • Temp
    • Pressure
    • high pressure compressor
  83. What kind of corrosion would be caused by acid raid?
  84. 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
  85. What is Jo-Coating used for?
    corrosion prevention
  86. What is the sheer zone? What is a major byproduct of the sheer zone?
    exhaust sheers with ambient air, creates loud noise
  87. Blocker doors and clam shell doors are 2 examples of what?
    thrust reverser
  88. What are three forms of thrust agmentation?
    • afterburner
    • water injection
    • water methanol injection
  89. what make water meth and water injection an effective form of thrust agumentation?
    increases air density
  90. What are the four parts required to make a turbine assembly?
    • wheel
    • nozzle
    • case
    • shroud
  91. name 3 types of turbine blades?
    • impulse
    • reaction
    • impulse reaction
  92. 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
  93. Why are the return luberication lines always bigger than the incoming lines?
    to account from expansion due to heat
  94. When comparing axial compressor air input velocity to the output velocity at full power we see?
    very little change in velocity
  95. What are some of the components mounted to the AGB?
    • starter
    • fuel controls
    • fuel pump
    • airconditioning compressor
    • oil pumps
    • hydraulic
  96. 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
  97. 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
  98. The cooling process in turbine blades which sends cooler combustion section air through slot gills is called?
    Convection Cooling
  99. Where is the fuel pump mounted on a free turbine?
    N1-turing during start, needs fuel
  100. Where would you find variable inlet guide vanes?
    axial compressor
  101. On a free turbine turbo shaft engine the gas producer section would be described as ?
  102. What would the shape of the nozzle used for the following
    • Reaction-Straight
    • Impulse-Converging