DOC AIRBUS | AMM A320FPOWER SECTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The power section of the Auxiliary Power Unit (APU) supplies shaft power to drive:
** ON A/C NOT FOR ALL The power section of the Auxiliary Power Unit (APU) supplies shaft power to drive:
- a load compressor,
- an accessory gearbox,
- an electrical generator.
- a single-stage centrifugal compressor,
- a two-stage axial flow turbine,
- a reverse-flow, annular combustion-chamber.
Power SectionA. Single-Stage Centrifugal Compressor
The compressor section includes:
The compressor section includes:
- a single-stage, 7,5 : 1 pressure ratio, machined titanium, centrifugal impeller,
- single-stage, radial-flow, diffuser vanes,
- axial de-swirl vanes.
B. Reverse-Flow Annular Combustion-Chamber
The compressor discharge air cools the reverse-flow annular combustion-chamber. The annular combustion-chamber surrounds the turbine hub containment.
The compressor discharge air cools the reverse-flow annular combustion-chamber. The annular combustion-chamber surrounds the turbine hub containment.
C. Two-Stage Axial-Flow Turbine
The two-stage, axial-flow turbine includes:
The two-stage, axial-flow turbine includes:
- a cooled first stage nozzle,
- inserted first stage rotor blades,
- an uncooled second stage stator,
- a dual alloy second stage rotor,
- an annular exhaust diffuser.
3. Operation
The Fuel Control Unit (FCU), and the Electronic Control Box (ECB) 59KD, control the optimal fuel flow. This is necessary for the operation of the APU.
To start the APU, air moves through the plenum chamber to the compressor of the power section. It then passes into the primary zone of the reverse-flow annular combustion-chamber. The atomizers spray fuel into the combustion-chamber where it is mixed with the air and ignited. Additional air enters through holes along the combustion chamber. This additional air helps to contain the flame envelope, prevent torching of the combustion-chamber walls and complete the combustion process. The hot gas discharges from the combustion chamber and flows through the two-stage axial-flow turbine. The hot gas expands across the turbine where its energy is converted to mechanical power. This power is used to drive the:
- power section compressor,
- load compressor,
- gearbox,
- accessories for the APU operation.
A logic program in the ECB 59KD prevents engine compressor surge. The flow of fuel is limited to do this as a function of inlet temperature, inlet pressure and speed.
The Fuel Control Unit (FCU), and the Electronic Control Box (ECB) 59KD, control the optimal fuel flow. This is necessary for the operation of the APU.
To start the APU, air moves through the plenum chamber to the compressor of the power section. It then passes into the primary zone of the reverse-flow annular combustion-chamber. The atomizers spray fuel into the combustion-chamber where it is mixed with the air and ignited. Additional air enters through holes along the combustion chamber. This additional air helps to contain the flame envelope, prevent torching of the combustion-chamber walls and complete the combustion process. The hot gas discharges from the combustion chamber and flows through the two-stage axial-flow turbine. The hot gas expands across the turbine where its energy is converted to mechanical power. This power is used to drive the:
- power section compressor,
- load compressor,
- gearbox,
- accessories for the APU operation.
A logic program in the ECB 59KD prevents engine compressor surge. The flow of fuel is limited to do this as a function of inlet temperature, inlet pressure and speed.