DOC AIRBUS | AMM A320FLOW PRESSURE TURBINE (LPT) - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. Low Pressure Turbine (LPT)
(1) The LPT is made of a three-stage rotor, a turbine case assembly, two stator vane stages and an LPT driveshaft. The LPT provides the rotational force for the Low Pressure Compressor (LPC) and the Fan Drive Gearbox (FDG). The energy from the hot combustion gases is changed into torque by the LPT blade and rotor assemblies. There are 84 1st stage, 86 2nd stage and 78 3rd stage solid nickel alloy shrouded blades that have a fir-tree root to attach them to the hub.
LPT ModuleA. Gas flow from the HPT is turned by the Turbine Intermediate Case (TIC) vanes and is changed to torque by the LPT.
(1) The LPT is connected to the Low Pressure Compressor (LPC) through the LPT shaft and uses this torque to turn the LPC.
(2) The LPT and LPC turn counterclockwise as seen from the rear.
(3) The HPT and High Pressure Compressor (HPC) turn clockwise.
B. The LPT has three stages, an LPT 1st and 3rd stage attached to an LPT 2nd stage hub with a single circle of tie bolts.
NOTE: Each compressor and turbine rotor has stages with numbers that start at one. For the LPT the stages are the 1st thru 3rd.
C. Gas leakage at the LPT blade tips is controlled by outer-air seal segments.
(1) These segments keep a controlled clearance with the adjacent blade tip knife-edges.
D. The LPT has an Active Clearance Control (ACC) system.
(1) With this system, a turbine ACC air valve (energized by the Electronic Engine Control (EEC)) controls air from fan bypass and sends it to a panel assembly around the LPT case.
(2) This HPC air from the ACC cooling panels makes the LPT case cooler and decreases its diameter. This decreases the diameter of the outer-air seal segments which causes tighter clearances at the 1st thru 3rd stage blade tips and increased engine efficiency.
E. Gas leakage between the rotor stages is controlled by fin-type inner air seal segments attached to inner seal supports at the LPT 2nd and 3rd stage vane inner feet.
(1) These segments keep a controlled clearance with knife edges on the 1st and 3rd stage turbine rotor flanges.