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M1 > GT construction > Flashcards

GT construction Flashcards

1
Q

Definition of CODLOG?

A

Combination of diesel electric or gas, type 26

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2
Q

Definition of CODLAG?

A

Combination of diesel electric and gas, type 23

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3
Q

Description of CODLAG?

A

Each shaft has its own direct drive SM1A or SM1C and electric motor. They can be run either both or a mixed combination driving twin shafts in any configuration the command desires. Astern power is not available when the gas turbines are clutched into the transmission system

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4
Q

GT on each class of ship?

A

Spey - type 23
MT30 - carrier
WR21 - type 45

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5
Q

Creep is a combination of which stresses?

A

Heat and centrifugal

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6
Q

Definition of IEP?

A

Integrated electric propulsion - type 45

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7
Q

How can we minimise blade creep?

A

Hot starts
Over temperature running
Long periods at high power
Over load the engine

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8
Q

Description of IEP?

A

The system uses 2 x WR21 complex cycle gas turbine alternators and 2 x Wartsila diesel generators. These produce 4160 volts to power the advanced induction motors. Configuration is decided by command depending on fuel remaining and speed required

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9
Q

Maximum output of GTs?

A

Spey SM1A 12.75 MW
Spey SM1C 18.75 MW
WR21 21 MW
MT30 36 MW

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10
Q

Definition of blade creep?

A

The phenomena where a piece of material will lengthen over time

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11
Q

What are the benefits of a single crystal turbine blade?

A

High resistance to creep and fatigue
Very high strength
Excellent mechanical properties
Improved heat resistance
No crystalline grain boundaries

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12
Q

What are the requirements for a turbine blade?

A

Withstand high temperatures
Creep resistance
Low coefficient of expansion
Workable
Corrosion and erosion resistance
Thermal shock resistance
Low cost
Maintain high tensile strength at high temperatures
Oxidation resistant
Compact and light

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13
Q

How do we minimise the possibility of surge and stall?

A

Compressor air bleed valves
Multi-spool engines
Variable inlet guide vanes

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14
Q

What is the function of the LP accumulator?

A

Smooths out fluctuations in the fuel supply pressure

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15
Q

What is the function of the pressurising valve?

A

Meters fuel through the locating pin atomisers on start up and then to main burners

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16
Q

What are the functions of a gas turbine fuel control system?

A

Supply fuel to the burners for starting to running and over its full operating range
Acceleration and deceleration control
Shut off fuel supply under normal and emergency conditions

17
Q

Definition of surge?

A

A complete breakdown of airflow leading to the reverse of flow. This will result in a violent expulsion of previously compressed air back through the intake

18
Q

Contributing factors that lead to surge and stall?

A

Obstruction of air intake system
Rapid acceleration of the compressor
Compressor blade fouling
Malfunction of the compressor bleed valves

19
Q

What are the functions of the HPSOC?

A

Recirculates fuel back to the section side of the pump when closed
Provides positive fuel shut off when engine shutting down
Provides a safe method of tripping the engine manually

20
Q

Definition of stall?

A

A breakdown of laminar airflow over the compressor blades

21
Q

Start operation of a Spey?

A

The air turbine start motor engages via a centrifugal clutch inside the accessory gearbox. Air is supplied from HP air ring main at 275 bar and reduced to 24 bar to the GT inlet valve, it is then reduced further by a dome reducer to a cranking pressure of 3.5 bar. The air start solenoid is energised during the start sequence allowing air to crank the engine up to speed. Once the engine is self sustaining air is shut off by the engine control system which deenergises the air start solenoid valve. The clutch now disengages allowing the air start motor to reduce to idle

22
Q

What fire detection system does the WR21 use?

A

Two shot CO2

23
Q

What fire detection system does the MT30 use?

A

Two shot HI FOG fine water mist and nitrogen system

24
Q

Spey infrared detection system?

A

The system comprises of 3 infrared detectors which are designed to measure radiation heat levels within 2 narrow bands within the module. If any sensor senses a fire condition it will send a signal to the control unit within 25 milliseconds.
When the control unit is set to auto mode the first shot is released due to the operation of metron pyrotechnic cartridges

25
Q

What fire detection system does the Spey use?

A

Two shot BTM HALON 1301

26
Q

When would you carry out an engine inhibit routine?

A

When the GT is shut down for more than 20 days
Every 20 days in tropical climates
Every 40 days in temperate climate

27
Q

When should we carry out a GT water wash routine?

A

Every 250 running hours or 1 month
Returning a GT from an inhibit state to a running condition
Prior to a performance assessment
When the GT is shut down for more than 20 days prior to an inhibit

28
Q

Procedure for a GT inhibit routine?

A

Carry out wash routine followed by dry run
Cool back engine for 30 mins
Full inhibit tank with 1L of PX24
Initiate dry motor cycle
10 seconds after starter engages PX24 is injected into the engine bell mouth from the wash tank until tank is empty

29
Q

Combustion arrangements?

A

Can annular
Annular combustion ring
Radial combustors

30
Q

Methods of fire detection?

A

Heat
Infra red
Detector wire
Operated local or remote

31
Q

Turbine blade manufacture?

A

Conventionally cast
Directionally solidified
Single crystal

32
Q

Purpose of the air intake?

A

Three stage filtration system removes particles, water sand and other contaminates
Stone guard catches any foreign objects which may damage compressor blades

33
Q

Components of the intake system?

A

Separator units facing aft
Plenum chamber
Splitter silencer

34
Q

Typical gas turbine on engine fuel system?

A

Shut off fuel supply under emergency and normal conditions

35
Q

Requirements of the fuel system?

A

Prevent surge rich flame out during acceleration
Prevent over temperature of components
Prevent stall rich flame out during deceleration

36
Q

Components of the fuel system?

A

LP pressure fuel supply - 2 bar
LP accumulator - smooths out fluctuation in fuel supply
LP filter - nominal 10 microns
HP fuel pump - 35-80 bar
Drives
HP filter
Motorised fuel control valve
HPSOC
Pressurising valve

M1 (4 decks)

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