15.6 turbine section Flashcards
what is the sole purpose of the gas generator
to absorb approximately 60% to 70% of the total pressure energy from the exhaust gases
what are the two different types of turbine on gas turbine engine
radial flow turbine
axial flow turbine
what kind of stage is a radial flow turbine
a single-stage turbine
where are radial flow turbine only used on
small gas turbines such as the APU
what is the advantage of radial airflow turbine
they have a simple design and easy to manufacture
where are axial flow turbines mainly used
modern gas turbine engines
what is an advantage of axial flow turbine
they allow the very high airflow required to create the high thrust of modern engines
what are the three classifications of turbine blades
- impulse configuration
- reaction configuration
- reaction-impulse configuration
in the impulse configuration, where dos the total pressure drop across each stage happen
at the fix nozzle guide vanes
with the reaction configuration, the fix nozzle guide vanes are designed to alter what
the gas flow direction without changing the pressure
when the turbine blades are installed onto the disc, what does the disc become
the turbine wheel
what allows the attachment of the turbine blades onto the disc
a series of grooves and notches
what is the most common type of turbine blade root
fir tree
what does the peening application require
a small notch to be grounded in the edge of the blade fir tree root before the blade installation
where are the turbine inlet nozzle vanes located
directly aft of the combustion chamber and immediately forward of the turbine wheel
why must the turbine inlet temperature be controlled
because damage can occur to the turbine inlet vanes if not controlled
how may pitting caused by FOD be blended
by stoning or polishing
what is deformation of a turbine blade be caused by
over temperature
what do stress rupture cracks usually appear as
minute hairline cracks
what absorbs heat from the turbine blades by conduction
the turbine rim
why is a sufficient clearance exist between the blade root and the notch
to permit movement of the turbine blade when the disc is cold
how is the attachment of the turbine shaft to the compressor rotor hub
it is usually accomplished by a spline cut on the forward end of the shaft
what is the second purpose of the turbine inlet nozzle
to deflect the gases to a specific angle in the direction of turbine rotation
what does the turbine inlet nozzle assembly consist of
an inner shroud and an outer shroud between which the nozzle vanes are fixed
what is done on nozzle vanes to allow for thermal expansion
either the inner or outer shroud ring is cut into segments
what is used to inspect the turbine blades for stress rupture cracks and deformation of the leading edge
strong light and a magnifying glass
when might the leading edge not be completely straight and of uniform thickness
where repairs by blending has been done
what promotes creep in turbine blades
the extreme temperature
