Third Assistant Engineer Gas Turbine System (Coast Guard Questions)

Front 1

The thermal energy added to the gas as it flows through the combustion section has what effect on the gas?

Back 1

Increase volume

Front 2

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

Back 2

Speed of the process

Front 3

The Brayton cycle is a series of events best described by which of the following statements?

Back 3

Intake, compression, combustion, expansion, exhaust

Hint 3

Suck, squeeze, bang, blow (basically)

Front 4

Why is a gas turbine considered to operate on the Brayton cycle?

Back 4

Combustion occurs with now increase in pressure

Front 5

In a twin-spool turbine, secondary air is most essential for cooling in what section?

Back 5

HP turbine

Front 6

Which of the following statements is true regarding centrifugal compressors?

Back 6

The centrifugal compressor is frequently used on small, low pressure turbines.

Front 7

A centrifugal compressor assembly consist the following.

Back 7

A rotating impeller and a stationary diffuser.

Front 8

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

Back 8

Changes at each separate component.

Front 9

What is the disadvantage of using a dual-entry centrifugal compressor compared to a single-entry centrifugal compressor?

Back 9

The dual-entry compressor utilizes a more complicated inlet ducting.

Front 10

When working on gas turbine synthetic lube oil, which of the following safety measures should be observed?

Back 10

Multiple: wash area thoroughly, avoid skin contact. Avoid prolonged inhaling of vapors. Wear eye protection and gloves.

Hint 10

All the above

Front 11

When working in or around intake areas, what precautions should be taken?

Back 11

Multiple: remove all loose objects, inspect intake for cleanliness, account for all tools and equipment.

Hint 11

All the above

Front 12

On the GE LM2500 gas turbine, magnetic pickups are utilized for what purpose?

Back 12

Multiple: determining gas generator speed, calculating engine torque, determining power turbine speed

Hint 12

All the above

Front 13

In a gad turbine propulsion installation, the typical control system is designed to perform which three functions?

Back 13

Operational control, safety control, and monitoring

Front 14

How is thermal energy that is added to a substance stored?

Back 14

In the form of internal energy

Front 15

Rankine is the temperature scale that corresponds to which of the following?

Back 15

Absolute reading of a measured temperature in degrees Fahrenheit

Front 16

Which term refers to thermal energy in transition?

Back 16

Heat

Front 17

Kelvin is the absolute temperature scale that corresponds to which of the following?

Back 17

Absolute reading of a measured temperature in degrees Celsius

Front 18

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

Back 18

Adiabatic

Front 19

What is the definition of absolute temperature?

Back 19

Temperature measured with the reference to the theoretical temperature at which all molecular motion stops

Front 20

What is the purpose of the spring in a lip-type oil seal?

Back 20

To keep th neoprene snugly fit around the shaft

Front 21

What type of air seal is used in the combustor and turbine mid-frame of a gas turbine?

Back 21

Fishmouth

Front 22

What type of seal is used in the gearbox of a gas turbine engine?

Back 22

Carbon ring

Front 23

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

Back 23

Labyrinth-honeycomb

Front 24

What prevents objects smaller than 1/4 inch from entering LM2500 gas turbine?

Back 24

FOD screens

Front 25

What is true concerning the fuel oil ignition system of the gas turbine?

Back 25

The igniter's will de-energize once the gas turbine exceeds a preset RPM

Front 26

How is the HP turbine rotor of the LM2500 gas turbine cooled?

Back 26

By continuous flow of compressor discharge air

Front 27

Where are the carbon dioxide nozzles located on LM2500 enclosure?

Back 27

On the cross beam under the compressor front frame

Front 28

What is the primary purpose of the diffuser and distributor on LM2500?

Back 28

To provide uniform air flow to the combustor

Front 29

How many shock mounts are used to secure the LM2500 enclosure to the ships foundation?

Back 29

32

Front 30

The gas generator section of the LM2500 is composed of the following EXECPT?

Back 30

Six stage LP turbine

Front 31

The struts of the GE LM2500 compressor front frame provide passages for all of the following mediums except?

Back 31

Fuel oil

Front 32

What type of combustor is used by the LM2500?

Back 32

Annular

Front 33

In comparing a centrifical type to an axial type compressor which of the following statements is true?

Back 33

Centrifugal compressors have a higher compression ratio per stage than an axial flow compressor

Front 34

The two basic types of compressors used in gas turbine engines are which of the following?

Back 34

Centrifugal and axial

Front 35

Rotation of the controllable pitch propeller (CPP) blades is achieved through axial movement of what component in the hub body assembly

Back 35

The crosshead

Front 36

The fuel system of a gas turbine engine provides all except which of the following??

Back 36

Acts as a cooling medium for lube oil cooler

Front 37

Gas turbine fuel manifold pressure is established by which of the following actions?

Back 37

Rotating the gas generator

Front 38

Before combustion can occur, the combustion air must be delivered to the composer at a high pressure and low velocity. High Velocity low-pressure air is converted to high pressure, low velocity air at what part of the centrifugal type compressor?

Back 38

Diffuser

Front 39

In a centrifugal compressor which component reduces the velocity and increases the static pressure of air?

Back 39

Diffuser

Front 40

Which of the following wrenches should not be used while working on a gas turbine?

Back 40

Adjustable

Front 41

Which of the following instruments is designed to help you when performing an internal inspection of a gas turbine engine?

Back 41

Borescope

Front 42

The only hand tools that should be used on gas turbine engines are chrome plated, nickel plated, or which of the following?

Back 42

Unplated

Front 43

Wrenches that are recommended for use on a gas turbine engine should be plated with which of the following elements?

Back 43

Nickel

Front 44

Provisions for avoiding the buildup of ice on the intake air surfaces of a gas turbine plant can be found where?

Back 44

In the inlet duct frame at the inlet to the engine. In the exhaust and intake ducting.

Front 45

The divergent area of the exhaust duct aids in what process?

Back 45

Increasing the volume of exhaust gases

Front 46

How's the clutch attached and engaged?

Back 46

Clutch engages automatically when input shaft flange is rotating faster than the output assembly

Front 47

The term lockout on the Synchro self-shifting (SSS) clutch system means that the

Back 47

SSS clutch will not engage

Front 48

How do you manually lock out an SSS clutch?

Back 48

Using the special wrench provided

Front 49

Which of the following statements is true about the lockout control on a Synchro self shifting clutch?

Back 49

Permits operation of the GTE without the rotation of the main reduction gear

Front 50

When the engine fuel valves are de-energized, the remaining fuel left in the system is recirculated back to which of the following?

Back 50

Fuel pump inlet

Front 51

What is the primary function of the main fuel control on the GE LM 2500 gas turbine engine?

Back 51

To control stator vane angle and GG speed

Front 52

For the GE LM 2500 gas turbine the 9th stage bleed air is used for which of the following?

Back 52

Power turbine Cooling

Front 53

For the GE LM 2500 gas turbine engine the 13th stage bleed air is used for which of the following?

Back 53

High pressure turbine 2nd stage nozzle cooling

Front 54

In order to get a ready indication for a normal start with a GE LM 2500 gas turbine engine what permissions must be met?

Back 54

Multiple: bleed air valves must be closed, GG speed must be less than 1200 RPM and all engine trips reset, fuel supply pressure must be greater than 8 PSIG

Hint 54

All the above

Front 55

For the GE LM 2500 gas turbine engine the HP turbine 2nd stage are cool by which of the following?

Back 55

13 stage compressor air

Front 56

For the GE LM 2500 gas turbine engine the HP turbine first stage nozzle vanes are cooled by which of the following?

Back 56

16th stage compressor air

Front 57

For the GE LM 2500 gas turbine engine the HP turbine 2nd stage blades are cooled by convection, with the cooling air being discharged where?

Back 57

Blade tips

Front 58

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

Back 58

Bolted or welded

Front 59

To keep the exit pressures relatively constant across an HP turbine blade which type of construction is generally utilized

Back 59

Impluse-Reaction

Front 60

HP turbine blades are generally caused by which of the following methods?

Back 60

Compressed air entering the root and exiting the tip

Front 61

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

Back 61

Fir-tree design

Front 62

"Standard Day" conditions, are defined by the ISO by which of the following?

Back 62

29.92 in HG @ 15 deg C

14.69 psi @ 59 deg F

Front 63

In the ignition system of a gas turbine engine how is Optimum spark achieved?

Back 63

Concentration of Maximum energy and minimum time

Front 64

What is the power source for the ignition Exciter of a gas turbine engine?

Back 64

Ships 115 volt AC system

Front 65

What is the most common type of spark ignitor used on a gas turbine engine?

Back 65

Annular gap

Front 66

On a propulsion marine gas turbine, full power temperature becomes excessive what action should the operator take?

Back 66

Reduce power to stay within limits

Hint 66

Speed change

Front 67

If the lube oil scavenger temperature exceeds 300 degrees Fahrenheit on the gas turbine engine and reducing power does not bring the temperature within limits the operator should do which of the following?

Back 67

Shut down the engine and troubleshoot

Front 68

Accelerometers are generally used on gas turbine engines to sense which of the following?

Back 68

High-frequency vibration

Front 69

Displacement, velocity and acceleration describe three types which of the following?

Back 69

Vibration sensors