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COOLING - DESCRIPTION AND OPERATION
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1. General
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The power plant cooling system consists of :
- cooling of the nacelle compartments
- cooling of the aircraft and engine accessories
- cooling of engine parts (HPT, HPC, LPT, ECU)
A. Nacelle Compartment Cooling
The nacelle is divided in three major areas
- the engine air inlet
- fan compartment
- core compartment.
The functions of the nacelle compartments are :
(1) Sufficient airflow to offset the effects of engine case heat rejection and engine flange air leakage thereby maintaining an acceptable compartment temperature level.
(2) Cooling of temperature critical components.
(3) Cowling pressure load limiting in the event of pneumatic duct failures.
(4) Ventilation of compartment during engine shutdown.
(5) Ventilation of combustible fluid vapors to preclude fires.
B. Aircraft and Engine Accessories Cooling The nacelle installation is designed to provide cooling and ventilation air for engine accessories mounted on the fan and core casing. The distribution and circulation of the air in the compartments is such that the limit for specific components is not exceeded.
C. Cooling of Engine Parts Different parts of the engine are cooled by air bled from the primary flow (HPTACC, RACSB), secondary flow (LPTACC). A scoop in the air intake cowl enables cooling of the ECU by ram air.
2. Location of Components
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A. Location of High Pressure Turbine Active Clearance Control (HPTACC) System (Ref. Fig. 001) The HPTACC valve is located on the HPC compressor case at 3 o'clock (aft looking forward).
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HPTACC System Location
Figure 001
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B. Location of Low Pressure Turbine Active Clearance Control (LPTACC) System (Ref. Fig. 002)
C. Location of Rotor Active Clearance Control and Start Bleed System(RACSB). (Ref. Fig. 003)
D. Location of ECU cooling system (Ref. Fig. 004)
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LPTACC System Location
Figure 002
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RACSB System Location
Figure 003
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ECU Cooling System Location
Figure 004
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HPT ACTIVE CLEARANCE CONTROL SYSTEM - DESCRIPTION AND OPERATION
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1. General
_______ (Ref. Fig. 001) The engine High Pressure Turbine Active Clearance Control (HPTACC) system uses High Pressure Compressor (HPC) bleed air from stages 4 and 9 to heat or cool the High Pressure Turbine (HPT) shroud support structure. The purpose of the system is to maximize turbine efficiency during cruise and to minimize Exhaust Gas Temperature (EGT) peak during throttle bursts.
2. Description
___________ (Ref. Fig. 002) The HPTACC is a closed loop system based on shroud temperature. The Electronic Control Unit (ECU) first calculates the HPTACC valve position to control the temperature of the shroud to the desired level. Then, the ECU sends an electrical signal to the Hydromechanical Unit (HMU) to move the HPTACC valve. The HPTACC valve is an hydraulic actuator linked with the 4th and the 9th stage butterfly valves which control air flow to the HPT shroud support structure. Two Linear Variable Differential Transformers (LVDT) are connected to the actuator to give valve position feedback to the two thermocouples which are embedded in the HPT shroud support structure and provide temperature feedback to the ECU. On engine start, the HPTACC valve moves to the 9th stage bleed position which unloads the compressor to improve engine acceleration. At and above ground idle, the HPTACC valve position is determined by the closed loop shroud temperature control. When the engine is shut down, the valve extends to a failsafe no air position. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：A320飞机维护手册 AMM AIR 空气(8)
