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Mechanical Theory 2 > Mechanical Theory 2 > Flashcards

Mechanical Theory 2 Flashcards

1
Q

Define working fluid

A

Any gas or liquid that can do work by expansion or flow, or can be compressed or made to flow

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2
Q

What’s a turbine

A

A bladed spool designed to rotate when acted on by a working fluid

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3
Q

Define compressor

A

A bladed spool designed to do work on a fluid when rotated

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4
Q

What’s the function of a gas turbine

A

Gas turbines convert heat energy into rotary motion for ships propulsion

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5
Q

Advantages of a gas turbine

A

Allows the ship to get underway quickly

Ease of operation and emphasis on remote control

High power to weight ratio

Minimum ship borne maintenance

Lower man power requirement

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6
Q

Describe the air intake filter

A

Spray eliminator used to remove water by changing direction of air

Knit mesh filter
Removes particle matter

Water separation water drains into a trough which ensures a water seal across the bottom of the filters

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7
Q

Integrated electric propulsion used on

IEP

A

Type 45

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8
Q

Combination of diesel electric and gas (CODLAG) used on

A

Type 23

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9
Q

What does the splitter or silencer do

A

Splits up the air flow stream reducing noise and buffeting

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10
Q

What does the stone guard do

A

Prevents large/ coarse particles of debris from entering the gas turbine

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11
Q

What does the transition duct do

A

Provides a smooth change from square cross section air flow to circular cross section air flow

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12
Q

What does the cascade bend do

A

Directs air safely through a 90 degree bend without causing any turbulence to already smoothed out air flow

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13
Q

What does the engine intake flare do

A

Seals the engine intake from the rest of the module and houses the water wash ring used for cleaning the engine

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14
Q

What is the function Module ventilation vent flaps

A

Module vent flaps isolate the module in event of an emergency

When the engine is running flaps are open to allow airflow to cool the module and expel exhaust fumes

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15
Q

Module ventilation is ventilated by

A

Bernoulli’s theorum

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16
Q

Process of module ventilation

A

Air is drawn into the module because of the depressed formed at the other end

Air circulates the module keeping it cool

A depression of air is formed (Bernoullis Theorum)

Vent flaps are open

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17
Q

Gas turbine cycle

A 
Induction
Compression
Combustion 
Power 
Exhaust
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18
Q

Primary air (15%) is used for

A

Helps to atomise the fuel and provides air for the initial combustion

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19
Q

Secondary air (10%) is used for

A

To ensure complete combustion of the fuel

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20
Q

Tertiary air (75%) is used for

A

Becomes the working fluid

21
Q

What is used as lubrication on gas turbines

A

OX22

22
Q

What are magnetic chips

A

Collect ferrous debris and are inspected every 24 running hours, debris is always measured

23
Q

Gas turbine safety devices

A 
Hand trip 
Fire detectors
Power turbine entry temperature 
Partial overspeed
lp/hp governors 
Vibration monitors 
PT overspeed 
Safety interlocks
24
Q

Hazards for gas turbines

A

Igniters

Noise

25
Q

What fire extinguishers are fitted to gas turbines

A

BCF

BTM

26
Q

What are the hourly checks used on a running gas turbine

A

Pressure and temperatures
Oil levels
Any excessive/unusual noise
Any leaks

27
Q

When will a wet motor be done

A

Prove the fuel system after maintenance

Bleed any air from/prime the fuel system

28
Q

What does a dry motor do

A

Used to purge fuel abs explosive gases from the combustion chamber

29
Q

When will you do a dry motor

A

After a failed or aborted start
After a wet motor cycle
To enable water washing

30
Q

What is water washing

A

Is carried out to prevent the build up of debris and fouling on the compressor blades.

31
Q

Define straight cut/ spur gear teeth

A

Single tooth contact, only suitable for low speed low torque applications

32
Q

Define helical gear teeth

A

Angled teeth more teeth in contact making gear stronger and quieter

33
Q

Define double helical gear teeth

A

Made up of 2 helical gears back to back angle cuts In opposite directions cancels out any thrust

34
Q

Explain worm and wheel

A

Is used on non parallel axis, wheel is straight cut gear.Very large gear reductions are possible giving it a high torque

35
Q

How would you change direction of gears

A

Add a 3rd gear

36
Q

What does a Plummer block do

A

Plummer blocks are used to support the weight of the shaft within the ship without absorbing any thrust

37
Q

What does a bulkhead gland do

A

Maintains water right integrity as the shaft passes through compartments without absorbing any thrust

38
Q

What does a stern seal do

A

Maintains a water tight seal as the shaft passes through the ships hull

39
Q

What does the A brackets do

A

Take no thrust but support the weight of the propellor shaft lubricated by sea water

40
Q

What are the 2 types of propellor

A

Fixed blade

Controllable pitch propellor

41
Q

What is a fixed blade propellor

A

Blade angle cannot be changed

42
Q

How do we embark fuel

A 
Ras
Road bowser/tanker
Jetty storage tanks 
Lighter barge
Fixed jetty pipeline
43
Q

What is a displacement tank

A

A fuel tank that will contain some salt water that act as fuel storage only ever filled to 90%

44
Q

What is a undisplaced tank

A

A tank that only holds fuel

45
Q

What is a centrifuge

A

Seperates oil and water from fuel using centrifugal force

46
Q

What do we test fuel for

A

Water
Dirt
Surfactants

47
Q

Fuel system hazards

A

Fire and explosion
Toxicity
Dermatitis
Pollution

48
Q

What’s the flow of fuel from a tanker to ship engines

A 
Tanker 
Filling trunk 
Manifold 
Displaced tanks 
Centrifuge 
Undisplaced tanks
Fuel transfer pump
Service tank
Fuel boost pump
Fuel boost ringmain

Mechanical Theory 2 (1 decks)

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