Turbines 1 - Week 5

turbine section elements

case, stator vanes (nozzles), shroud rings, rotor blades

purpose of turbine section

convert kinetic energy of combustion gases into mechanical energy to drive the compressor

a turbine stage consists of

a row of stator vanes followed by a row of rotor blades

two turbine designs

axial flow (most common) & radial inflow

radial inflow uses

apus

radial inflow

combustion gases enter at edges and exit at the center

axial flow

airflow is front to back

first stage of stators directly after combustion are called

nozzle guide vanes

the stator and rotor blades form _____________ ducts

convergent, increase velocity & decrease pressure

in a multiple spool engine the smallest shaft diameter is for the

lowest pressure spool

counter-rotating spools help with

gyroscopic effect, vibrations, aerodynamic efficiencies

stator blades (nozzles) are designed to

direct air at correct angle to turn rotor & increase velocity of air (form convergent duct)

turbine rotor assembly consists of

shaft, disk, blades

turbine and compressor rotors are

dynamically balanced to reduce vibrations

most common blade to hub attachment

fir tree root (radial motion)

what locks blades in axially

welding, lock-tabs, rivets

high speed rotor uses these types of blades

open tip

low speed rotor uses these types of blades

shrouded

turbine rpm is caused by what forces

impulse & reaction

impulse

blades change airflow direction with minimal change in pressure or velocity

reaction

blades form a series of convergent ducts to increase velocity and decrease pressure

impulse-reaction

blade base impulse shaped, blade tip reaction shaped, maintains uniform velocity and pressure drop along blade length

blade cooling allows for

increased turbine service life

blade cooling is needed because

blades exposed to hot combustion gases

stator blades have holes in them for cooling this type of cooling known as

convection or film cooling