DOC AIRBUS | AMM A320FHIGH PRESSURE TURBINE (HPT) - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. High Pressure Turbine (HPT)
(1) The HPT module changes some of the high temperature and high velocity gas energy into torque. The 1st stage turbine vanes point the gases out of the combustion chamber at an efficient angle which turns the HPT.
(2) The HPT module is a rotor system with two stages and 44 blades in each of the rotors. The rotor system is housed by the HPT case which contains the 26 Blade Outer Air Seals (BOAS) for each stage. Cool air flows through holes in the BOAS and into the gaspath. The HPT case is the containment structure for the turbine rotors and functions as structural support to the diffuser case and also houses the Turbine Intermediate Case (TIC).
High Pressure Turbine (HPT) ModuleA. The HPT is to the rear of the diffuser case.
(1) The HPT case holds the TIC at the rear of the turbines.
B. The HPT uses the gas pressure from the High Pressure Compressor (HPC) with the increased fuel energy from the combustion chamber to turn a two-stage turbine.
(1) The torque of this turbine turns the HPC through the HPC shaft.
(2) The HPT and HPC turn clockwise while the Low Pressure Compressor (LPC) and Low Pressure Turbine (LPT) turn counterclockwise for increased efficiency.
C. A 1st stage seal at the front of the HPT assembly and a 2nd stage seal at the rear of the assembly have knife-edge seals which turn against sealing rings to control air leakage.
(1) These 1st and 2nd stage seals have counterweight flanges to make it possible to correct the unbalance of the HPT assembly.
D. There are 44 blades in each of the HPT 1st and 2nd stage hubs, which have a controlled clearance with HPT case seals at their tips.
(1) The seals are in segments that let them move as a result of temperature changes.
E. An Active Clearance Control (ACC) system uses fan air manifolds around the outer HPT case to change blade tip clearances.
(1) When necessary (for example during climb or cruise operation), fan discharge air in the manifold applied against the HPT case outer rails makes the case cooler and decreases the inner diameter of the 1st and 2nd stage seal segments. This decreases the 1st and 2nd stage blade tip clearances and increases the efficiency of the turbine.
(2) The HPT 1st stage blades are kept at the lowest temperature possible with diffuser area air from around the combustion chamber.
(3) This air flows through the cooling air duct and into the openings in the hub and blade roots and from there into the blade airfoils.