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Active Clearance Control System Schematic
Figure 002 (SHEET 1)
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Active Clearance Control System Schematic
Figure 002 (SHEET 2)
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Active Clearance Control System Schematic
Figure 002 (SHEET 3)
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Compressor Control Schematic
Figure 003
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(c) Variable Bleed Valve system (VBV)
(Ref. 75-31-00)
(d) Variable Stator Vane system (VSV)
(Ref. 75-32-00)
(4) Indicating
(Ref. 75-41-00)
B. Nacelle Section The nacelle installation is designed to provide cooling and ventilation air for engine accessories mounted along the fan and core casing. The distribution and circulation of the air in the components is such that the temperature limit for specific component is not exceeded.
2. Description
___________ All engine air enters through the engine air inlet cowl, the front mounted fan. After being compressed by the fan, the airflow is divided by the flow splitter in the fan frame into primary and secondary (bypass) airflows. The logics of the air systems controlled by the FADEC are fully described in chapter 73-20-00. Propulsion Airflow System
- Secondary flow Fan air passes through the outlet guide vanes (OGV) and the fan frame struts. Bypass air is discharged through the fan exit nozzle during normal engine functioning and provides the major portion of engine thrust (4/5 of the total airflow of the engine). When the thrust reverser is deployed, the fan exit nozzle is blocked and the bypass air is directed outward at a forward angle through the reverser pivoting doors to provide reverse thrust (Ref. chap. 78-36-00). Some of the fan discharge air may be from the primary airflow through bypass valves located in the fan frame. A small portion of the bypass air is used for core engine compartment cooling and for low pressure turbine cooling and environmental control system cooling through the precooler.
- Primary flow A portion of fan air passes into the 4-stage booster and enters the core by a converging duct formed by the fan frame. This duct is provided with variable bleed valves (VBV). The compressed air enters the combustion chamber and is ignited with the fuel. The exhaust gases flow through the high pressure turbine (HPT) and the low pressure turbine (LPT) and are discharged through the primary jet nozzle.
A. Engine anti-icing Air from 5th stage compressor is used to de-ice inlet cowl in case of icing conditions (Ref. 30-21-00).
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B. Cooling
(Ref. 75-20-00)
(1) Front and Rear Bearing Sump Pressurizing Air
(a) A preferred direction of air circulation is established by means of pressurizing the labyrinth seals. This pressure exceeds the internal pressure of the sump.
(b) The sumps are vented to prevent overpressures in the sump. The air is vented by the center vent tube located inside the LPT shaft.
(2) Cooling Air System
(Ref. 75-25-00)
(a) Heat transfer is primarily attained by convection and conduction. Radiation transfer is confined to the primary zone of the combustion chamber. Core zone is cooled using compressor flow. Fan zone is cooled using ambient air.
(3) Rotor active clearance control system
(Ref. 75-23-00)
(a) The HPC/HPT rotor cooling air consists of booster discharge air that is bled internally and 5th stage HPC air that is modulated by the ECU and introduced externally through a pipe to the number three bearing cavity.
(4) HPTACC system
(Ref. 75-21-00)
(a) Cooling air for the HPT blades is bled from the final stage of high pressure compressor (HPC).
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