(b)
Close the shroud latches.
S 417-014
(12) Close the APU cowl door:
(a)
Disconnect the door support rods.
(b)
Put the door support rods in the clips on the APU cowl door.
(c)
Close the APU cowl door.
(d)
Close the latches for the APU cowl door.
S 867-011
(13) Set the circuit breaker and the switch:
(a)
Remove the DO-NOT-CLOSE tag and close this circuit breaker: 1) E3-3 Electrical Shelf, APU Control Unit
(b)
Remove the DO-NOT-OPERATE tag from the APU master switch on the P5 forward overhead panel.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
APU ENGINE - DESCRIPTION AND OPERATION
______________________________________
1. General
_______
A. The APU engine supplies the bleed air for pneumatic power and the shaft power to turn the APU electrical generator. The APU engine is a gas turbine. The APU engine has a compressor section, turbine section and gearbox section.
B. Static air or ram air comes in the compressor plenum. An impeller compresses the air and sends it to the turbine plenum. From the turbine plenum, the compressed air goes into the combustion chamber. In the combustion chamber, the air is mixed with fuel. A spark from the igniter plug supplies the ignition of the fuel-air mixture. The gases from combustion flow to the turbine. The energy from the combustion causes the turbine wheel to turn and make mechanical power. The mechanical power turns the compressor and the APU electrical generator. When it is necessary, the turbine plenum supplies the bleed air for pneumatic power.
2. Compressor Section (Fig. 1)
__________________
A. The compressor section is the source of the compressed air for the turbine. The compressor section has a two-stage compressor and the compressor plenum. The compressor is a centrifugal compressor. The two compressor stages are connected by crossover ducts. One impeller and one diffuser make a compressor stage. The first-stage impeller is a double-entry impeller. It has two impellers that are back-to-back. The second-stage impeller is a single-entry impeller. Both of these impellers have a common shaft. The shaft is installed on two bearings that are pressure lubricated. The gearbox end of the shaft connects with a quill shaft in the gearbox. Seals keep the lubrication system isolated from the turbine gases.
3. Turbine Section (Fig. 1)
_______________
A. The turbine section burns the air-fuel mixture and supplies the mechanical power from the combustion. The turbine section has a turbine wheel, torus assembly, nozzle assembly, turbine plenum, and combustion chamber. The turbine wheel is a radial-type wheel. The turbine wheel connects to the shaft that turns the compressor impellers. The turbine plenum gets the compressed air from the compressor impellers. Also, the turbine plenum is a heat shield for the aft end of the APU. The torus assembly connects with the aft end of the combustion chamber. The torus assembly moves the combustion gases to the nozzle assembly. The nozzle assembly moves the combustion gases from the torus assembly to the turbine wheel. A single combustion chamber is made with the inner part of the turbine plenum and torus assembly. The combustion chamber has a combustion liner and cap. The combustion chamber liner supplies the combustion area. The combustion chamber liner has holes to control the location and rate of combustion. The igniter plug and fuel atomizer are installed on the cap of the combustion chamber.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
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