U.S.C.G. Merchant Marine Exam Assistant Engineer – Limited ...Q612 Gas Turbine Plants U.S.C.G....

National Maritime Center Serving Our Nation’s Mariners

U.S.C.G. Merchant Marine Exam

Assistant Engineer – Limited

Q612 Gas Turbine Plants

(Sample Examination)

Page 1 of 24 Q612 Gas Turbine Plants

8/21/2019

Q612 Gas Turbine Plants U.S.C.G. Merchant Marine Exam Assistant Engineer-Limited Illustrations: 8

Choose the best answer to the following Multiple Choice Questions.

1. The gas generating sections of marine gas turbine engines are based on which of the following?

o (A) Free piston engines. o (B) Radial piston engines. o (C) Oil-fired auxiliary boilers. • (D) Aircraft jet engines.

If choice D is selected set score to 1.

2. In a gas turbine, the air charge is permitted to be compressed adiabatically by what factor, process, or condition?

o (A) Low-compression ratio o (B) Rapid heat transfer • (C) Speed of the process o (D) Interstage cooling

If choice C is selected set score to 1.

3. An open cycle gas turbine engine is best described by which of the following statements?

o (A) Energy is added externally. o (B) Energy is neither created nor destroyed and the cycle is therefore perpetual. o (C) Working fluids are taken in, transformed, and then recuperated. • (D) Working fluids are taken in, transformed, and then discarded.


4. Why is the cycle efficiency higher in the intercooled-recuperated cycle as compared to a simple cycle gas turbine? Illustration GT-0026

o (A) The intercooler serves to increase the required high-pressure compressor power while the recuperator utilizes waste heat from the exhaust to decrease turbine inlet temperature.

o (B) The intercooler serves to increase the required high-pressure compressor power while the recuperator utilizes waste heat from the exhaust to increase turbine inlet temperature.

o (C) The intercooler serves to reduce the required high-pressure compressor power while the recuperator utilizes waste heat from the exhaust to decrease turbine inlet temperature.

• (D) The intercooler serves to reduce the required high-pressure compressor power while the recuperator utilizes waste heat from the exhaust to decrease required fuel to achieve the turbine inlet temperature.



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5. The acronym MFC represents which of the following?

• (A) Main fuel control. o (B) Manifold fuel control. o (C) Midframe compressor. o (D) Maritime fuel congress.

If choice A is selected set score to 1.

6. The acronym FOD stands for which of the following?

• (A) Foreign object damage. o (B) Fuel oil discharge. o (C) Flow offset design. o (D) Fuel override demand.


7. Power is defined as which of the following?

o (A) The rate of applying a force. • (B) The rate of doing work. o (C) Force applied through a distance. o (D) Work performed through a distance.

If choice B is selected set score to 1.

8. Mechanical work is defined as which of the following?

o (A) A measurement in pounds per square inch. • (B) A force acting through a distance. o (C) Rate of doing work. o (D) Distance traveled over time.


9. What is the term given to a process that occurs without a loss or gain of heat?

o (A) Endothermic. • (B) Adiabatic o (C) Exothermic. o (D) Isothermal



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10. Thermal energy is the only form of energy that can be added to or removed from a substance. How is thermal energy that is added to a substance stored?

o (A) In the form of potential kinetic energy. • (B) In the form of internal energy. o (C) In the form of mechanical energy. o (D) In the form of heat.


11. Under standard atmospheric conditions, 208.7 PSIG converts to approximately what in absolute pressure?

o (A) 214.7 PSIA o (B) 104.7 PSIA o (C) 194.0 PSIA • (D) 223.4 PSIA


12. A temperature of 69.5 degrees Fahrenheit converts to approximately what temperature in degrees Rankine?

• (A) 529.5 degrees R. o (B) 590.5 degrees R. o (C) 203.5 degrees R. o (D) 342.5 degrees R.


13. A centrifugal compressor assembly consists of which of the following?

o (A) Stationary vanes and rotating blades. o (B) Rotating pistons and stationary liners. o (C) A stationary impeller and a rotating diffuser. • (D) A rotating impeller and a stationary diffuser.


14. While air is being compressed in a centrifugal flow gas turbine, what happens to the direction of air flow?

o (A) Changes only once from inlet to outlet. o (B) Changes only at the compressor inlet. o (C) Changes only at the compressor discharge. • (D) Changes at each separate component.



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15. An axial compressor basically consists of which of the following?

• (A) Stationary vanes and rotating blades.o (B) A rotating impeller and a stationary diffuser.o (C) Rotating pistons and stationary liners.o (D) A stationary impeller and a rotating diffuser.


16. Which of the following is the main advantage of a split-axial compressor case?

• (A) Easier to repair and inspect.o (B) Cheaper to manufacture.o (C) Simpler to disassemble.o (D) Stronger construction.


17. What is the term used to describe the stationary vanes preceding the first stage of anaxial compressor?

• (A) Inlet guide vanes.o (B) Variable inlet vanes.o (C) Variable stator vanes.o (D) First stage stator vanes.


18. Two functions of the compressor stator vanes include which of the following?

• (A) Direct air flow to each rotor stage at the correct angle and deliver air to the combustor at thecorrect velocity and pressure.

o (B) Direct air flow to rotor blades at the correct angle and are shaped to produce a velocityincrease and maintain a constant pressure.

o (C) Direct air flow to rotor blades at the correct angle and are shaped to maintain a constantvelocity and produce a pressure increase.

o (D) Direct air flow to rotor blades at the correct angle and are shaped to cause a velocity increaseand a pressure decrease.


19. What is a compressor midspan shroud?

o (A) The center of a two-piece rotor blade.• (B) A brace built into the middle of a rotor blade for damping.o (C) A support for the tips of the stator blades.o (D) A method of securing stator blades.



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Q612 Gas Turbine Plants U.S.C.G. Merchant Marine Exam Assistant Engineer-Limited Illustrations: 8 20. Which of the following statements is true concerning axial compressor disk-type rotors?

o (A) Rotor consists of rings that are flanged to fit one against the other. o (B) Rotor is only suitable for low-speed compressors. • (C) Rotor discs are shrunk fit onto a steel shaft. o (D) Rotor discs are held together by through bolts.


21. In a gas turbine engine, the majority of the energy is added to the working fluid in which of the following components?

o (A) Power turbine. o (B) Compressor. • (C) Combustor. o (D) High-pressure turbine.


22. The three most common types of combustors used in gas turbine engines are which of the following?

o (A) can, derivative, and can-derivative. o (B) can, vortex, and can-vortex. o (C) can, angular, and can-angular. • (D) can, annular, and can-annular.


23. A turbine stage is represented by which of the following components and in which order?

o (A) Two sets of stationary vanes, one set of rotating blades. o (B) One set of rotating vanes, one set of stationary blades. o (C) One set of rotating blades, one set of stationary vanes. • (D) One set of stationary vanes, one set of rotating blades.


24. The turbine nozzles convert heat and pressure energy to velocity energy by means of which of the following?

o (A) Divergent process. o (B) Convergent-Divergent process. o (C) Deflection process. • (D) Convergent process.



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25. The turbine nozzle blades convert the combustion gases heat and pressure energy into what form ofenergy?

o (A) Chemicalo (B) Thermalo (C) Electrical• (D) Kinetic


26. The circle of turbine stationary vanes that convert pressure and thermal energy to velocity energyand direct the combustion gases in the direction of turbine wheel rotation is referred to as what?

o (A) Rotor assembly.o (B) Diffuser assembly.o (C) Compressor assembly.• (D) Nozzle assembly.


27. Which of the following designs is the most satisfactory method for attaching turbine blades to therotor disk?

o (A) Retaining ring design.• (B) Fir-tree design.o (C) Pinning design.o (D) Locking tab design.


28. Turbine disks are commonly attached to the shaft by which of the following methods?

o (A) Locking tabs or retaining rings.o (B) Pinned or locking tabs.• (C) Bolted or welded.o (D) Riveted or pinned.


29. Which of the following is an advantage of a single-shaft gas turbine engine compared to a split-shaftgas turbine engine?

o (A) Better fuel economyo (B) Lower starting torque• (C) Fewer moving partso (D) Reversible



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30. What type of air seal is used in the sump and turbine areas of a gas turbine engine?

o (A) Pneumatic carbon ringo (B) Lip-type• (C) Labyrinth-Honeycombo (D) Fishmouth


31. What type of air seal is used in the combustor and turbine midframe of a gas turbine?

o (A) Pneumatic carbon ringo (B) Lip-typeo (C) Labyrinth-Honeycomb• (D) Fishmouth


32. What type of engine starter motor is commonly found on the marine gas turbine shown in theillustration? Illustration GT-0006

o (A) AC synchronous motor• (B) Hydraulic motoro (C) DC series wound electric motoro (D) AC induction motor


33. Accelerating the compressor to the self-sustaining speed of the engine is the function of which of thefollowing components?

o (A) PT shaft• (B) Startero (C) Mechanical drive shafto (D) Compressor extension shaft


34. In the ignition system of a gas turbine engine, how is optimum spark achieved?

o (A) Concentration of minimum energy in maximum timeo (B) Concentration of minimum energy in minimum timeo (C) Concentration of maximum energy in maximum time• (D) Concentration of maximum energy in minimum time



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35. The electrostatic vent fog precipitator removes oil mist from which of the following areas?

o (A) Gas turbine engineo (B) Lube oil storage tank• (C) Main reduction gearo (D) Synchronous self-shifting clutch


36. How is the lube oil supplied to each bearing in a gas turbine engine controlled?

• (A) Calibrated orifice.o (B) Flow divider.o (C) Lube oil pump.o (D) Regulating valve.


37. The main lubrication system utilized by the gas turbine engine shown in the illustration is whattype? Illustration GT-0017

o (A) Wet sump• (B) Dry sumpo (C) Oil mist recovery sumpo (D) Common drain sump


38. As shown in the illustration, what is the purpose of pressurizing the main bearing lube oil sumps on atypical marine gas turbine? Illustration GT-0023

o (A) Assists in cooling the lube oil.o (B) Provides uniform lube oil distribution around the bearing.o (C) Increases lube oil penetration.• (D) Minimizes oil leakage from the rotor shaft.


39. Air used to cool the combustion liners and turbine components is referred to as which of thefollowing?

• (A) Secondary air.o (B) Control air.o (C) Primary air.o (D) None of the above.



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40. The fuel oil system of a gas turbine engine provides all EXCEPT which of the following?

• (A) Acts as a cooling medium for the lube oil coolero (B) Provides accurately metered fuel for combustiono (C) Controls the angle of the variable stator vaneso (D) Acts as a hydraulic medium to actuate the fuel control


41. How is the clutch shown in the attached illustration engaged? Illustration GT-0018

o (A) Pneumatic pressure from the compressor engages the clutch.• (B) Clutch engages automatically when input shaft flange is rotating faster than the output

assembly.o (C) Clutch engages automatically once the output assembly begins rotating.o (D) Clutch is engaged manually prior to start up.


42. Which of the following statements is true about the "lockout control" on a synchronous self-shifting(SSS) clutch?

o (A) The mechanism is incorporated into the input assembly of the clutch.o (B) It is an automatically operated control.• (C) Permits operation of the GTE without the rotation of the main reduction gear.o (D) None of the above.


43. What type of main reduction gear arrangement prevents independent axial and rotational movementof the pinions?

o (A) Unlocked train• (B) Locked traino (C) Independent suspensiono (D) Hydraulic suspension


44. What feature is commonly used on articulated reduction gear arrangements for the correction ofmisalignment between the 1st reduction gear and the 2nd reduction pinions?

• (A) Quill shafts.o (B) Torsion pads.o (C) Fixed block pads.o (D) Locked train shims.



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45. What is the purpose of the Controllable-Pitch Propeller (CPP) hydraulic oil power system?

o (A) Supplies low-pressure oil for both pitch control and stern tube sealing.o (B) Supplies high-pressure oil for both propeller blade actuation and stern tube sealing.• (C) Supplies high-pressure oil for blade actuation and control oil for propeller pitch control.o (D) Supplies low-pressure oil for propeller blade actuation and control oil for propeller pitch

control.


46. A magnet pickup typically produces what type of signal output?

o (A) high currento (B) pure sine wave• (C) voltage pulseo (D) steady DC voltage


47. Compressor characteristics are normally summarized in the form of which of the following?

o (A) Straight line graph.o (B) Venn diagram.o (C) Spread sheet.• (D) Compressor map.


48. Which of the following is NOT a gas turbine auto shutdown parameter?

o (A) High exhaust gas temperature.o (B) Power turbine over speed.• (C) High compressor discharge pressure.o (D) Module enclosure fire.


49. Wrenches that are recommended for use on gas turbine engines should be plated with which of thefollowing elements?

o (A) Carbon• (B) Nickelo (C) Bronzeo (D) Silver



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Q612 Gas Turbine Plants U.S.C.G. Merchant Marine Exam Assistant Engineer-Limited Illustrations: 8 50. When conducting a borescope inspection, you must be aware of all of the following factors EXCEPT

which?

• (A) The engineer’s experience. o (B) The internal reference points. o (C) The inspection areas and ports. o (D) The limitations of your equipment.


51. Borescope inspection of the combustor section requires which type of light source?

o (A) 150 watt o (B) 500 watt • (C) 1000 watt o (D) All of the above.


52. All clock positions, engine references, and enclosure references apply to viewing the gas turbine engine shown in the illustration, from which of the following locations? Illustration GT-0017

o (A) Right side of the compressor to the left side. o (B) Left side of the power turbine to the right side. • (C) Rear (exhaust end), looking toward the intake end. o (D) Intake end, looking toward the exhaust end.


53. The two main types of compressor stall are known as what?

• (A) Steady state and transient. o (B) Overspeed and overload stall. o (C) Flame out and inlet temperature stall. o (D) Rapid rise and temperature inversion.


54. Compressor surge is caused by which of the following factors?

o (A) Low ambient air temperature. • (B) Interrupted air flow. o (C) Maximum fuel pressure. o (D) Increased demand for secondary air.



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55. Which of the following could cause compressor stall?

o (A) The angle at which the hot gases strike the turbine rotor blades is too high. o (B) The angle at which the air strikes the compressor rotor blades is too low. • (C) The angle at which the air strikes the compressor rotor blades is too high. o (D) Air flow over the lower foil section becomes turbulent and destroys the pressure zone.


56. Where are the carbon dioxide nozzles located in the GE LM2500 gas turbine enclosure?

• (A) On the cross beam under the compressor front frame. o (B) Above and below the combustor section. o (C) On either side of the power turbine. o (D) Above the compressor.


57. How is the HP turbine rotor of the GE LM2500 gas turbine cooled?

• (A) By a continuous flow of compressor discharge air o (B) By synthetic lube oil o (C) By an air to air heat exchanger o (D) By the ship's service sea water cooling system


58. What is the primary purpose of the diffuser and distributor on the GE LM2500 gas turbine?

o (A) To provide uniform air flow to the compressor o (B) To provide even temperature distribution at the compressor • (C) To provide uniform air flow to the combustor o (D) To provide uniform air flow to the turbine


59. As shown in the illustration of a gas turbine fuel oil system, when the engine fuel oil valves are de-energized, the remaining fuel left in the system is recirculated back to which of the following? Illustration GT-0021

o (A) High-pressure relief valve. o (B) Fuel purge manifold. • (C) Fuel pump inlet. o (D) Day tank.



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60. For the GE LM2500 gas turbine shown in the illustration, the 9th stage bleed air is used for which ofthe following? Illustration GT-0017

o (A) Sump pressurization and cooling.o (B) Compressor balance piston cavity pressurization.o (C) High-pressure turbine second stage nozzle cooling.• (D) Power turbine cooling.


61. For the GE LM2500 gas turbine engine shown in the illustration, the HP turbine 1st stage nozzlevanes are cooled by which of the following? Illustration GT-0020

o (A) 8th stage compressor air.o (B) 9th stage compressor air.o (C) 13th stage compressor air.• (D) 16th stage compressor air.


62. Large steam drums are not required in the design of a coil-type auxiliary water-tube boiler because__________.

• (A) steam and water are separated in the accumulator (flash chamber)o (B) the heat of combustion is sufficient to remove all moisture from the steamo (C) the volume of steam is small at low pressureso (D) automatic burner cycling controls steam volume and quality


63. The rate of heat transfer in a water-tube auxiliary boiler can be increased by __________.

o (A) operating the boiler at less than normal water level• (B) installing fins on the firesides of water-tubeso (C) increasing the amount of excess air to the burnerso (D) treating the boiler water with chemical oxygen scavengers


64. The boiler shown in the illustration would be classed as __________. Illustration MO-0064

• (A) single-pass, fire-tube, scotch marineo (B) two-pass, scotch marineo (C) forced circulation, coil-typeo (D) two-pass, water-tube



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65. A photoelectric cell installed in an automatically fired auxiliary boiler burner management system__________.

• (A) opens the burner circuit upon sensing a flame failureo (B) detects a flame failure by monitoring radiant heat from glowing refractoryo (C) requires mechanical linkage to secure the burner fuel supplyo (D) must be bypassed at low firing rates


66. Which of the listed sequence of events occurs when an automatic auxiliary boiler is prepurged?

o (A) The damper on the inlet side of the furnace is moved to the open position for a given numberof seconds and then moved to the closed position.

• (B) The damper on the inlet side of the furnace is moved to the open position for a given numberof seconds and then moved to the low fire position.

o (C) The damper is moved to the closed position for a given number of seconds and then movedto the low fire position.

o (D) The damper in the uptakes is moved to the wide open position for a given number of secondsand then moved to the low firing rate position.


67. A variable capacity, pressure atomizing, fuel oil burner functions to __________.

o (A) maintain a constant fuel temperature• (B) provide a wide range of combustiono (C) provide a constant fuel return pressureo (D) maintain smokeless fuel oil atomization


68. When preparing to light off a cold boiler equipped with a return flow fuel oil system, the recirculatingvalve directs the flow of oil __________.

o (A) directly to the fuel oil heater inlet for further warm-upo (B) back to the fuel oil settler for further filtration• (C) back to the suction side of the service pumpo (D) directly to the deep tanks



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69. Which of the following is the advantage of operating a typical closed feedwater system for a marineboiler when compared to an open feedwater system?

o (A) Reduced requirement for condensate purity.o (B) Allows for lower feed pump operating pressures.• (C) Increased capability of removing and controlling dissolved oxygen.o (D) Reduced steam requirement for feedwater heating.


70. The two-element feedwater regulator functions similarly to the three-element feedwater regulator,but does not utilize __________.

o (A) drum pressureo (B) steam flow measuremento (C) water level• (D) feedwater flow measurement



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National Maritime Center

Serving Our Nation’s Mariners

11/1/2018

Adapted for testing purposes only from Gas Turbine Systems Supervisor

NAVEDTRA 14111

Further reproduction prohibited without permission

GT-0006




11/1/2018

Adapted for testing purposes only from Gas Turbine Systems Technician (Electrical)

3/ Gas Turbine Systems Technician (Mechanical) 3, Volume 2

NAVEDTRA 14114


GT-0017




11/1/2018



NAVEDTRA 14113


GT-0018




11/1/2018



NAVEDTRA 14114


GT-0020




11/1/2018



NAVEDTRA 14114


GT-0021




11/1/2018

Adapted for testing purposes only from HUNT, Modern Marine Engineer's Manual, Volume I, 3rd edition

Copyright © 1999 by the Cornell Maritime Press


GT-0023




11/1/2018

Adapted for testing purposes only from WOODYARD, Pounder’s Marine Diesel

Engines and Gas Turbines, 9th Edition

Copyright © 2009 by Elsevier Ltd.


GT-0026




10/19/2018

Adapted for testing purposes only from SHIELDS, Boilers, Types, Characteristics, and Functions

Copyright © 1961 by McGraw-Hill, Inc.

Further reproduction prohibited without permission.

MO-0064


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