DOC AIRBUS | AMM A320FLOW PRESSURE COMPRESSOR (LPC) - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. Low Pressure Compressor (LPC)
(1) The LPC is located aft of the Fan Intermediate Case (FIC). The three stage LPC initially compresses the fan air on the path to the core of the engine (primary flow). The LPC rotor is supplied torque by the Low Pressure Turbine (LPT).
(2) The LPC rotor hub is attached to the LPT shaft which connects the LPC to the fan rotor through the fan input coupling and Fan Drive Gearbox (FDG). The FDG lets the LPC turn at a higher speed than the fan rotor for increased efficiency.
(3) At the inlet to the LPC, there is one stage of Variable Inlet Guide Vanes (VIGVs). The remaining part of the LPC has three Integrally Bladed Rotors (IBRs) and two stator stages. To increase the range of operation and to reject dirt from the LPC airstream, there is an annular LPC (stage 2.5) bleed valve at the rear of the LPC.
2. Description of the Low Pressure Compressor (LPC) Module
Low Pressure Compressor ModuleA. The LPC is to the rear of the FIC
(1) This compressor increases the pressure of the gaspath air from the rear of the fan that goes through the LPC inlet vanes in the FIC.
B. The LPT shaft supplies torque to the LPC.
(1) The LPC turns counterclockwise as seen from the rear, and the fan (forward of the LPC) and High Pressure Compressor (HPC) (rear of the LPC) turn clockwise. The result of this is a straighter airflow through the compressor and higher efficiency.
C. The LPC is connected at its front to the fan rotor through the Fan Drive Gear System (FDGS) which is a reduction gear unit.
(1) Because the FDGS lets the fan turn at a lower speed, the LPC is permitted to turn at a higher speed for increased efficiency.
(2) The higher speed makes possible an increased pressure ratio per stage. Because of this, fewer LPC parts are necessary.
D. There is one variable inlet vane stage that is part of the FIC group, followed by three LPC rotor and two LPC stator stages.
(1) The disks and blades of each rotor stage are of the Integral Blade Rotor (IBR) design, in which the blades and disk are one piece.
(2) An LPC rotor hub is attached to the inner diameter of the 2nd stage rotor with tie rods and is connected to the LPT shaft to the rear of the No. 2 bearing.
E. Counterweights are available at the front and rear of the LPC rotor for balance.
NOTE: Compressor stage numbers start at the front of each rotor and stator assembly. There is a fan stage but it has no stage number. The first stage of the LPC is the LPC 1st stage rotor, followed by the 2nd and 3rd stages.