Gas Turbines

Question 1

What does CODLAG stand for

Answer 1

Combination of diesel electric and gas

Question 2

What are the turbines called and what ship are they on

Answer 2

There are 2 spey engines on the type 23

Question 3

What are the advantages of a gas turbine

Answer 3

To get underway quickly
Ease of operation with the emphasis on remote control
High power/weight ratio
Minimum shipboard maintenance
Low manpower requirement

Question 4

What does the 3 stage filtration do

Answer 4

Filters sea sprey and dirt

Question 5

What does the stone guard do

Answer 5

Prevents large coarse particles of debris from entering

Question 6

What are the 3 stages of a 3 stage filtration system

And what do they do

Answer 6

Sprey eliminator which removes water from the air
Knitmesh filter which removes particulate matter
Water seperation where water drains into a trough creating a water seal accross the bottom of the filters

Question 7

What does a splitter/silencer do

Answer 7

Reduces air noise and buffering

Question 8

What does the transition duct do

Answer 8

It turns the square trunking in to a round pipe smoothly

Question 9

What does the cascade bend do

Answer 9

Directs the air smoothly at a 90 degree angle without causing turbulence

Question 10

What does iep stand for

Answer 10

Intergrated electric propulsion

Question 11

Explain how the module ventilation works

Answer 11

1. The depression of air from rushing exhaust gases is created. Bernoulis principle
2. Vent flaps remain open when running only shut to help extinguish a fire
3. Air circulates around the module
4. Air is drawn in because of the depression on the other end

Question 12

What are the 5 phases of a gas turbine

Answer 12

Induction
Compression
Combustion
Power
Exhaust

Question 13

What happens during the LP/HP compressors

Answer 13

Air is drawn in and gradually gets compressed as the gaps between the blades get smaller.
Compressed to 1/20

Question 14

What happens during the combustion cans

Answer 14

Air is drawn in to aid the burning fuel and get heated up to create the working force

Question 15

What do the HP/LP turbines do

Answer 15

They use the moving air (working force) to turn the LP/HP compressors

Question 16

What is the purpose of the power turbine

Answer 16

The remaining energy of hot air passes through the turbine creating rotary force turning the shaft to gearbox

Question 17

What are the 3 names and percentages of the air entering the combustion can

Answer 17

Primary air 15%
Secondary air 10%
Tertiary air 75%

Question 18

Explain primary, secondary and tertiary air

Answer 18

Primary air helps atomise the fuel and provides air for the initial combustion

Secondary air ensures complete combustion and provides a layer of air between the fuel and flame tube

Tertiary air is heated up by the cobustion process causing rise in pressure and becomes the working fluid.

Question 19

What needs lubricating in the gas turbines

Answer 19

Shaft bearings need lubricating using OX22 lubricating oil using a scavenge system with magnetic chip detectors

Question 20

what is the function of the gas turbine

Answer 20

is to convert heat energy into rotary motion for ships propulsion

Question 21

what is the purpose of the engine intake flair

Answer 21

seals the engine intake from the rest of the module and houses the water wash rings

Question 22

what are the magnetic chip detector and how often are they checked

Answer 22

fitted into the scavenge system to collect ferrous debris, give an early indication of engine wear, checked every 24 hours of running time and the debris is not to be removed but to be measured and logged.

Question 23

list the safety devises fitted to a gas turbine

Answer 23

power turbine overspeed
safety interlocks
hand trip
fire detectors
power turbine entry temperature
partial overspeed safety 
LP/HP compressor governor
vibration monitor

Question 24

explain how the power turbine overspeed works

Answer 24

if speed reaches 110 percent of safe limit the high pressure shut off cock will stop the engine by isolating its fuel supply