15.6 Flashcards
(24 cards)
How much energy does a turbine absorb for exhaust gasses
60 to 70%
What are the two types of turbine
Radial flow
Axial flow
Radial flow turbine
Only one stage
Small airflow and very inefficient
Older
Axial flow turbine
Allows much more air flow then a radial turbine
Modern aircraft
What is an impulse turbine blade
Inlet nozzle guid vanes are convergent ducts to reduce static pressure to harvest energy
The pressure drops in the fixed guide vanes
What is a reaction type turbine blade
Inlet nozzle guide vanes direct flow without changing pressure
Pressure is reduced on rotating nozzles
What is the combination that makes up a turbine blade
Combination of impulse and reaction
Blade is half and half
The root is impulse
How is a turbine blade made
Cast as a single crystal
How is a turbine blade cooled
Air comes in through a hole in the bottom of the blade and comes out of blades via small holes
Also can have a ceramic coating
What turbine blades are shrouded
Low pressure turbine blades
What are the advantages and disadvantages of a Shrouded blade
Advantages
Helps reduce vibration
More effective at stopping airflow creep up the blades
Disadvantages
Limits turbine speeds
What is a disk know as when all the turbine blades are attached to it
Turbine wheel
How does cooling are travel into the turbine wheel and what compressor does the air come form
HP bleed are goes through holes in the disk and goes to bottom of baled
How is the turbine wheel connected to the shaft
Welded of bolted
When the spline fits into the coupling device the turbine wheel is?
Married to the compressor
What is the most common way of attaching turbine blades
Firtree
Latched against wheel with stops
What makes up a stage on a turbine
Nozzle guid vane and rotor
What is a stator known as in a turbine
Nozzle guide vane
Turbine inlet guide vane
Nozzle diaphragm
What do all turbine vanes have
Inner and outer shrouds
How are vanes attached to turbines
Welded of riveted in position
What is creep
Elongation if blades due to heat bending and centrifugal forces
Are cracks allowed on disk and what is used to see them
No cracks allowed
Use penetrating die to see them
Is pitting or marks allowed on turbine blades
Yes they can be blended out
What does a stress rupture crack on the leading edge of a turbine blade show
Overheat
