Gas Turbines Flashcards
What is the definition of compressor stall
Stall is the breakdown of the laminar air flow over the compressor blades and results from incorrect velocity within the compressor stage
Three examples of compressor stall
Slow acceleration - especially on startup
Unusual noise from the engine or intake
Rapid rise in turbine inlet temperature
Fluctuations in spool speed
How do we control the inlet air velocity
Compressor air bleed valves
Multi spool engines
Variable angle inlet guide vanes
What is the definition of creep
A phenomena where a piece of material will lengthen over use
Caused by heat and centrifugal force
What are the effects of blade creep
Critical clearances of blade length may not meet and result in high speed contact resulting in catastrophic failure
What tests are done on gas turbine oil
Appearance
Water content
Total alkalinity number
Viscosity
Elemental oil analysis
What is wet motor
Rotation of the engine with fuel and no flame
Prove on engine fuel system
When is wet motoring done
Check for fuel leaks
Setting to work fuel system auxiliaries
Priming on engine fuel system
Setting to work new or replacement engines
What are the responsibilities of the gas turbine allocation authority GTAA
Ensure close control of the gas turbine charge units pool nesersary for adequate exchange
Management of of certain GTCU spares
Provide liaison with operational, maintenance, store, and foreign navies
Why are hourly based inspections done
To assess the condition of the engine and components throughout working life
And ensure replacements are done to avoid catastrophic failures
What is a basin trial
Full machinery and systems check alongside with strict limitations of delivered power
What is a large repair trial
Elements of propulsion performance trial
What is post upkeep trial
Full package of bring alive trials including
Harbour, SATs and safety/ readiness checks
What is propulsion preference assessment
Authorised full power for a timed period in order to get S346 readings to compare with previous assessments
What is the purpose of the alignment indicator
Initial set up occurs when the module is installed
Ship must be on a straight course, in calm conditions and module must be at full power for 30 minutes
