Turbines Flashcards
When do igniters stop operating?
Once flame is established
What is the function of a gas turbine?
To convert heat energy into rotary motion for ship propulsion
In mechanical terms (component ‘a’ is bolted to component ‘b’ etc), where does the transmission system begin ?
At the power turbine
What lubricating oil is commonly used in RN gas turbines?
OX22
Name 5 trips and safety devices that you would find on a gas turbine.
- Fire detector
- Hand Trip
- Partial overspeed
- Vibration monitor
- LP/HP Governors
What is the largest ratio that can be sensibly achieved on single gear reduction?
15:1
How often are FL cut-ins carried out?
Every 24Hrs
What is the purpose of water washing?
To remove fowling deposits such as dust & carbon, from the compressor blades
In relation to the fuel system what is the max fill level for displaced tanks?
90%
In relation to the fuel system what is the max level for undisplaced tanks?
95%
In relation to the fuel system the Max interface for water reaction test as above?
2%
Name the components that are used to support the weight of the shaft, outside of the hull.
- Intermediate A Bracket
- Main A Bracket
Name the gas turbines used in the navy
- Spey on type 23’s
- WR21 on 45’s
What does IEP mean?
Integrated Electric Propulsion
What does CODLAG mean?
Combination of Diesel Electric and Gas
What are the 5 Advantages of Gas turbines?
- Get underway quickly
- Ease of operation (emphasis on remote control)
- High power/weight ratio
- Minimum shipboard maintenance
- Low manpower requirement
What is the purpose or air intake filters?
to Stop water, dirt and debris from the air entering the intake trunking.
What does the splitter/silencer do?
- Smooths out airflow (removes turbulence)
- reduces noise
What is a stone guard?
Its a wire mesh that prevents large particles of debris from entering turbine
What does the Transition duct do?
Turns square airflow into circular without creating turbulence
What does the cascade bend do?
Directs the air smoothly through 90 degrees.
What is the Engine intake flare?
It seals the engine intake from the rest of the module and houses the water wash ring.
Name the 5 parts of the operating cycle of a Gas turbine.
ICCPE
- Induction
- Compression
- Combustion
- Power
- Exhaust
What is Bernoulli’s principle?
pressure decreases when the flow speed increases
What is a ‘Mag chip’ and what does it do?
they are small magnets, fitted to the oil system to collect debris.
they are inspected every 24hrs not to be cleaned, the debris is monitored
After use igniters must not …..
Touched for at least 5 minutes to allow stored energy to be discharged
What running checks are carried out hourly on a running engine?
- Pressure & temperature
- Oil levels
- Noise & Vibration
- Leaks
What is Waterwashing?
The procedure used to remove deposits from the compressor blades
What is PX24?
It is an inhibiting fluid, sprayed into the engine to remove moisture and protect the engine.
What is partial overspeed used for?
It reduces speed if propeller comes out of water
What do Governors do?
Control speed
GAS TURBINE AIR FLOW
Describe Primary air..
15 %
For initial combustion
Describe Secondary air..
10%
Ensures fuel is fully burnt
Describe tertiary air…
75%
Heated by combustion process, becomes working air in the turbines
Describe Igniter…
2000 Volts on initial starting then it is deenergized as it is no longer needed
describe LP/HP Compressors..
LP comp is attached to LP turbine,
HP comp is attached to HP turbine
the shaft runs within a shaft and the turbines turn the compressors
Describe the Induction process
Air gets drawn in, enters LP compressor which increases the pressure using rotating blades
What is the 1st stage of a 3 stage filter?
Spray eliminator
Air gets drawn through a torturous path, which removes moisture.
What is the 2nd stage of air filter?
Knitmesh
criss cross fabric that collects particles
What is the 3rd stage of air filters?
another torturous path where all water is removed
What is the manometric leg?
the water is collected in a trough at the bottom of the filters, where the water level is maintained by the manometric leg.
Stops unfiltered air entering system
What is partial overspeed for?
Reduces speed if propeller comes out of water
What is Power turbine over-speed?
if turbine speed reaches 110% the HPSOC (High pressure shut off cock)
will stop engine
Describe wet motoring & when is it done?
- Fuel on
- Turn engine
- fuse removed
- ignitors off
- After maintenance & vent air from system
Describe Dry motoring & when is it done?
- Turn engine over
- No fuel
- No ignitors
- After wet motoring, after combustion to get rid unburnt fuel & so washing routines can be done
Describe Water washing & when is it done?
- WR21 150 running hours
- Spey 100 hours or 2 months
- When performance deteriorates
- Removes fouling from compressor blades
- Done after cooling period of 30 mins
What is inhibiting done for?
to protect engine from corrosion if it is shut down for a period of time.
PX24
What are the 4 Inhibiting warnings?
- PX24 is flammable
- no smoking
- ensure engine room vents are running
- ensure engine ignitors are removed
