DOC AIRBUS | AMM A320FCOMPRESSOR INTERMEDIATE CASE (CIC) - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. Compressor Intermediate Case (CIC)
(1) The CIC functions as the support between the Low Pressure Compressor (LPC) and the High Pressure Compressor (HPC). The case includes nine aerodynamic struts, two primary engine mounts and a redundant engine mount. The CIC also transmits the thrust loads from the engine at two thrust mounts. The module includes a fire containment ring that both supplies protection for the LPC structure from the core nacelle fire zone and functions as a support for the thrust reverser inner cowl.
(2) The CIC also houses the No. 3 bearing compartment. The No. 3 bearing functions as a radial and axial support at the front of the HPC. A pressurized layer of oil supplied to the circumference of the No. 3 bearing assembly support absorbs rotor radial movement and decreases vibration. The compartment includes carbon face seals at the front and rear and labyrinth seals to control the flow of oil and air in the compartment. Forward of the No. 3 bearing is the No. 3 bearing bevel gear which engages a gearbox drive bevel gear to supply torque between the HPC and the angle gearbox.
2. Description of the Compressor Intermediate Case (CIC) Module
Compressor Intermediate Case (CIC) ModuleA. At the front of the gaspath area in the CIC is the LPC exit stator.
(1) This stator turns the air from the LPC and directs it to the HPC.
B. At the rear of the CIC is the HPC inlet case and vane assembly.
(1) This is a variable-vane stator assembly in which the angle of each vane is controlled by an arm at its outer end, attached to a synchronizing ring.
(2) A linkage from this ring connected to an external actuator turns the vanes to an angle which is the best for the engine operation condition.
NOTE: The first three vane stages of the HPC are variable-vane type also. An actuator controlled by both an engine vane control and by signals from the Electronic Engine Control (EEC) causes vane angle movement in the CIC and HPC variable vane stages.
C. At the rear of the CIC is the No. 3 bearing and bevel gear assembly.
(1) The No. 3 bearing is a ball bearing and is the thrust bearing for the HPC which holds the front of the HPC radially and axially.
(2) This bearing has oil-damping features. A pressurized film of oil around the No. 3 bearing support assembly absorbs rotor radial movement and decreases vibration.
D. The No. 3 bearing bevel gear is forward of the No. 3 bearing.
(1) This gear engages a gearbox drive bevel gear and supplies torque from the HPC/HPT through the gearbox drive shaft to the angle gearbox.
E. The No. 3 bearing area uses buffer air to control airflow.
(1) With this type of pressurization, air from the HPC is used to keep internal bearing compartment pressures at the correct level.
(2) The No. 3 bearing front face seal and support assembly at the front of the CIC controls air and oil leakage.
NOTE: The No. 3 bearing front and rear face seals are wet-face carbon seals of a lift-off configuration. Grooves in the faces of the sealing seats push away the carbon seals at high speed, with decreased friction and wear and no increased leakage.
(3) A labyrinth seal around LPC rear hub knife-edges controls airflow into the compartment. The No. 3 bearing front and rear face seals control oil in the bearing compartment.