Mechanical Theory 2 Flashcards
Define working fluid
Any gas or liquid that can do work by expansion or flow, or can be compressed or made to flow
What’s a turbine
A bladed spool designed to rotate when acted on by a working fluid
Define compressor
A bladed spool designed to do work on a fluid when rotated
What’s the function of a gas turbine
Gas turbines convert heat energy into rotary motion for ships propulsion
Advantages of a gas turbine
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
Describe the air intake filter
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
Integrated electric propulsion used on
IEP
Type 45
Combination of diesel electric and gas (CODLAG) used on
Type 23
What does the splitter or silencer do
Splits up the air flow stream reducing noise and buffeting
What does the stone guard do
Prevents large/ coarse particles of debris from entering the gas turbine
What does the transition duct do
Provides a smooth change from square cross section air flow to circular cross section air flow
What does the cascade bend do
Directs air safely through a 90 degree bend without causing any turbulence to already smoothed out air flow
What does the engine intake flare do
Seals the engine intake from the rest of the module and houses the water wash ring used for cleaning the engine
What is the function Module ventilation vent flaps
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
Module ventilation is ventilated by
Bernoulli’s theorum
Process of module ventilation
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
Gas turbine cycle
Induction Compression Combustion Power Exhaust
Primary air (15%) is used for
Helps to atomise the fuel and provides air for the initial combustion
Secondary air (10%) is used for
To ensure complete combustion of the fuel
Tertiary air (75%) is used for
Becomes the working fluid
What is used as lubrication on gas turbines
OX22
What are magnetic chips
Collect ferrous debris and are inspected every 24 running hours, debris is always measured
Gas turbine safety devices
Hand trip Fire detectors Power turbine entry temperature Partial overspeed lp/hp governors Vibration monitors PT overspeed Safety interlocks
Hazards for gas turbines
Igniters
Noise
