Module 15 Gas Turbine Engine 100 Important Sentences for Revision

 1. Basic Principles

1. A gas turbine engine operates on the Brayton cycle.
2. The Brayton cycle consists of intake, compression, combustion, expansion, and exhaust.
3. Thrust is produced by accelerating a mass of air rearward.
4. Newton’s third law is the basis of jet propulsion.
5. The faster the exhaust gases, the greater the thrust.
6. The main sections of a gas turbine are intake, compressor, combustion, turbine, and exhaust.
7. Air enters through the intake with minimum pressure loss.
8. The compressor raises the air pressure.
9. The combustion section adds heat to the compressed air.
10. The turbine extracts energy from hot gases to drive the compressor.

2. Engine Components

11. The intake directs air smoothly into the compressor.
12. The compressor may be centrifugal, axial, or mixed-flow.
13. Centrifugal compressors are common in small engines.
14. Axial compressors are used in large engines for higher pressure ratios.
15. The diffuser slows down air to increase static pressure.
16. The combustion chamber burns fuel continuously.
17. The turbine converts heat energy into mechanical work.
18. The exhaust nozzle accelerates gases to produce thrust.
19. Bearings support rotating shafts.
20. Accessory gearboxes drive pumps and generators.

3. Compressor Section

21. Compressors increase air pressure and temperature.
22. Axial compressors consist of rotating and stationary blades.
23. Rotor blades accelerate the air.
24. Stator blades convert velocity into pressure.
25. Multi-stage axial compressors achieve high pressure ratios.
26. Centrifugal compressors use impeller and diffuser action.
27. Compressor efficiency affects overall engine performance.
28. Surge is a total breakdown of airflow through the compressor.
29. Stall occurs when air separates from the blade surface.
30. Variable stator vanes and bleed valves prevent stall and surge.

4. Combustion Section

31. Combustion occurs at nearly constant pressure.
32. The air-fuel ratio must be correct for complete burning.
33. There are three types of combustion chambers: can, annular, and can-annular.
34. Igniters provide spark during engine start.
35. Fuel injectors atomize and mix fuel with air.
36. The liner directs flame and protects casing from heat.
37. Cooling air flows through liner holes to reduce temperature.
38. Combustion efficiency affects thrust and fuel economy.
39. Flameout occurs when the flame is extinguished during operation.
40. Relight systems restart combustion after flameout.

5. Turbine Section

41. The turbine extracts energy from hot gases.
42. It drives the compressor and accessories.
43. A turbine consists of rotor blades and stator vanes.
44. The stator guides gas flow onto rotor blades.
45. The high-pressure turbine drives the compressor.
46. The low-pressure turbine drives the fan or propeller.
47. Turbine blades are made of nickel-based superalloys.
48. Blade cooling prevents overheating.
49. Cooling air passes through internal passages and holes.
50. Blade creep occurs from long-term high temperatures.

6. Exhaust and Thrust

51. The exhaust system directs gases rearward efficiently.
52. Thrust is created by high-velocity gas exiting the nozzle.
53. Convergent nozzles are used on subsonic engines.
54. Convergent-divergent nozzles are used for supersonic speeds.
55. Afterburners add fuel to the exhaust for extra thrust.
56. Thrust reversers help decelerate the aircraft after landing.
57. Reversers operate hydraulically or pneumatically.
58. Bucket, cascade, and clamshell are main types of reversers.
59. Reverse thrust should not be used in flight.
60. EGT (Exhaust Gas Temperature) is an important performance indicator.

7. Engine Starting and Ignition

61. Starting provides rotation for initial air compression.
62. Air turbine starters are common in large engines.
63. Electrical starters are used on small turbine engines.
64. Ignition systems provide spark for combustion start.
65. Two igniters are used for reliability and redundancy.
66. Igniters use high-voltage discharge.
67. Ignition is required during start and for relight.
68. Exciters store and discharge energy to igniters.
69. After engine self-sustains, the starter disengages.
70. Starter cutout occurs automatically after light-up.

8. Engine Control Systems

71. Engine thrust is controlled by fuel flow.
72. The fuel control unit (FCU) meters correct fuel quantity.
73. FADEC stands for Full Authority Digital Engine Control.
74. FADEC controls fuel and engine parameters electronically.
75. FADEC removes mechanical control cables.
76. Manual reversion may be used in older systems.
77. Power levers command thrust setting to FADEC.
78. Engine control prevents over-speed and over-temperature.
79. EPR (Engine Pressure Ratio) indicates engine thrust.
80. N1 and N2 show compressor spool speeds.

9. Lubrication and Fuel Systems

81. The oil system lubricates and cools engine bearings.
82. Dry sump systems are common in turbine engines.
83. Scavenge pumps return oil to the tank.
84. Filters remove dirt and metal particles.
85. Chip detectors signal metal contamination.
86. Oil coolers maintain correct temperature.
87. The fuel system delivers fuel from tanks to combustion.
88. Boost pumps supply fuel to the engine pumps.
89. Fuel filters remove contaminants.
90. The FCU meters fuel according to throttle position and conditions.

10. Fire Protection, Performance, and Maintenance

91. Fire detection systems use continuous loops or thermal sensors.
92. Overheat detection warns of rising temperature before fire.
93. Fire extinguishing systems use Halon or clean agents.
94. Engine performance is measured by EPR, N1, and fuel flow.
95. Specific fuel consumption defines fuel efficiency.
96. Vibration monitoring detects rotor imbalance.
97. Engine trend monitoring helps predict maintenance needs.
98. Borescope inspection checks internal parts.
99. Engine removal is required for major overhauls.
100. Proper maintenance ensures reliability, safety, and efficiency.

 

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