R **ON A/C 001-003, 051-099, 401-499,
4. Component Description
_____________________
(Ref. Fig. 002)
A. Variable Inlet Guide-Vane (IGV) The IGV assembly has 14 IGVs. They are installed radially at the load compressor inlet.
B. The IGV Actuator The IGV actuator is the hydromechanical servomechanism which controls the opening angle of the IGVs. To adjust the correct IGV angle, the IGV actuator moves the IGV assembly geartrain. It uses the high pressure fuel supplied from the Fuel Control Unit (FCU) (Ref. 49-32-00) as the hydraulic power source. The ECB monitors the IGV actuator operation. The IGV actuator has the subsequent primary components:
-
the Hydraulic Actuator,
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the Electrohydraulic Servovalve (EHSV),
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the Linear Variable Differential-Transducer (LVDT).
C. Load Compressor Inlet Temperature Sensor (T2) The T2 sensor is a single element thermocouple which measures the air temperature just behind the inlet guide vanes. It is installed in the load compressor. The ECB receives the signal from the T2 sensor and uses this signal for the control of the fuel schedul, the IGVs and the surge control system.
D. Load Compressor Discharge Temperature Sensor (T5) The T5 sensor is a single element thermocouple which measures the air temperature in the APU bleed duct. The ECB receives the signal from the T2 sensor and uses this signal for the control of the fuel schedul and the IGVs.
5. Operation/Control and Indication
________________________________ The adjustable IGVs control the load compressor airflow (output) for the necessary input to the aircraft system (Ref. 49-51-00). The aircraft system transmits a demand signal to the Electronic Control Box (ECB) 59KD to give the necessary IGV control. During the APU start sequence, when the APU speed is less than 40%, the servo input current is zero. This keeps the hydraulic (fuel) servo actuator at the fully extended position and the IGVs closed (0 degrees). This makes sure that:
-there is minimum airflow through the compressor,
-during acceleration, the shaft load on the APU engine is kept to a minimum.
IGV - Actuator Figure 002
R EFF : 001-003, 051-099, 401-499, Page 549-23-00 Config-1 Aug 01/05
CES
Above 75% rpm the position of the IGVs is 22 degrees.
LOAD COMPRESSOR - DESCRIPTION AND OPERATION
___________________________________________
1.
General
_______ The single-stage load compressor is driven directly from the power section. It supplies compressed air (bleed air) to the aircraft pneumatic system.
2.
Component Location
__________________
(Ref. Fig. 001)
-------------------------------------------------------------------------------FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA | | | | DOOR | REF.
-------------------------------------------------------------------------------LOAD COMPRESSOR INLET TEMP. SNSR 316 316AR 49-23-15 ACTUATOR - INLET GUIDE VANE 316 316AR 49-23-51
3.
System Description
__________________ The machined titanium single-stage centrifugal impeller is attached to the single main shaft of the engine. A curvic coupling transmits the drive torque from the engine to the centrifugal impeller. The load compressor bearing cavities are kept dry to prevent oil churning and prevent seal leakage. The load compressor bearing cavities drain into the gearbox. Two air bufferred main shaft seals are used to seal the load compressor bearing cavities. The bellows carbon face seal is used to provide the lowest air leakage to minimise oil consumption. This face seal is air buffered with air from the secondary flow system. This maintains a positive differential across the seal under all operating conditions. The bellows carbon face seal along with the buffer air system has high reliability in preventing oil in the bleed system even with a worn seal. An oil leak witness drain is located aft of the seal to collect any oil leakage. This prevents oil in the bleed system and indicates a degraded seal performance. To aid in long seal life and prevent coking the seal rotor is cooled with oil from the hydraulic mount discharge.
4.
Component Description
_____________________
(Ref. Fig. 002)
A. Variable Inlet Guide-Vane (IGV) The IGV assembly has 16 IGVs. They are installed radially at the load compressor inlet.
B. The IGV Actuator The IGV actuator is the hydromechanical servo mechanism which controls the opening angle of the IGVs. The IGVA consists of:-
-
a two stage hydraulic servo control valve,
-
a power piston,
R EFF : 001-049, 101-105, 107-107, 151-199, 49-23-00Page 1 201-210, Config-2 Aug 01/05 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：A320飛機維護手冊 AMM 機載輔助動力 AIRBORNE AUXILIARY POWER3(108)
