Theory2 Flashcards
(49 cards)
Advantages of gas turbines
An ability to underway quickly Ease of operation with the emphasis on remote control High power / weight ratio Minimum shipboard maintenance Low manpower required
What does IEP stand for
Integrated Electric Propulsion
What does CODLAG stand for
Combination of Diesel Electric and Gas
Gas turbine system components
Air intake 3 stage filter system Silencer Stone guard Transition duct Cascade bend Module ventilation Engine intake flare Gas turbine Power tribute Exhaust trunking
What is the purpose of the air intake filters
to remove water, dirt and debris form the air entering the intake trunking
Describe the first stage of filter system
1st stage: Air enters the filter system (called spray eliminators), where the air changes direction due to the baffle plates. The change of direction causes the water held in suspension to drop out. The water will now fall to the water trough. Dry air will continue through to the next stag.
Describe the second stage of the filter system
After the first stage spray eliminator the air passes through a knitmesh filter where any particulate matter is removed.
Describe the final stage in the filter system
A final stage of water separation ensures any residual water in also removed. Air to the engine is now completely water and particulate free
What is the purpose of a Splitter-Silencer
The filtered air passes through the intake trunking to the splitter/silencer.
The filtered air passes over vanes which split up and smooth out the ait flow removing any turbulence, air noise and buffeting.
Turbulence in the air flow massively effects the engines performance.
What is the purpose of the stone guard
The stone guard prevents large particles of debris from entering the gas turbine when maintenance is being carried out.
What is the four strike cycle for a gas turbine
Induction Compression Combustion Power Exhaust
Describe the induction phase in the gas turbine
Induction:
Air from intake system is drawn into the engine
Describe the Low Pressure compression phase
The compression state is divided into Low pressure and High pressure.
Air is drawn in from the intake at atmospheric pressure and enters the LP compressor.
The low Pressure section then increases the pressure of the air using a series pf rotating blades, that have divergent passages within them, that continually moves and compresses the air as it passes the vanes.
Describe the High Pressure compression stroke in the four strike cycle
Air leaves the LP Compressor passes through to a second set of rotating blades known as the High Pressure compressor, which increases the pressure even more, using the same principle of squeezing the air through divergent passages.
By slowing down the air divergent passage we will raise its pressure.
Describe the Combustion phase during the four section phase
The Gas Turbines combustion system is designed to release the max amount of chemical energy from our fuel in the smallest possible space, with the min of losses.
The combustion chambers of the GT mixes the compressed air with atomised fuel, For initial starting of the engine an ignitor housed within the combustion chamber provides a High Tension spark to ignite the air/fuel mixture
What are the three parts of combustion
Primary air: 15% of the air providing air for initial combustion
Secondary air: Makes up 10% of the total air flow. it is used to ensure complete combustion of the fuel and provides a layer of air between the fuel and the flame tube.
Tertiary air: accounts for the remaining 75% of the air flow.
What drives the HP and LP turbines
The hot expanded gasses leaving the combustion chamber
What is the purpose of the HP and LP turbines
To drive the HP and LP compressors respectively. meaning the gas turbine uses hot gasses to produce its own compressed air
What causes the power turbine to move
The remaining energy within the hot gases after it passes through the HP and LP Turbines, will pass through the power turbines causing it to turn
What’s the lubrication used for the Gas turbine
OX22
What’s the name of the gas turbine used on a type 23
Spey
Why are safety devices and trips fitted on a Gas Turbine
They are fitted to protect the engines and personnel from damage or injury should the engine fail to perform
What does the hand trip device do
Activates the HP fuel shut off cock
Command approval must be met before operating this trip
What does the fire detector do
They are fitted to provide indication of high temp/ fire inside the engine module
