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ALL ú ú C01 Page 6 ú Mar 15/96
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
HIGH PRESSURE TURBINE CLEARANCE CONTROL SYSTEM -
________________________________________________ DESCRIPTION AND OPERATION
_________________________
1. General_______
A. The high pressure turbine clearance control (HPTCC) system, which consists of a hydraulic actuated valve and connecting tubing to the main engine control (MEC), uses high pressure compressor (HPC) bleed air from the 5th- and 9th-stages to obtain maximum steady-state HPT performance and to minimize exhaust gas temperature (EGT) transient overshoot during throttle bursts.
B. Air selection is determined by fuel pressure signals from the MEC. The bleed air is ducted from the valve to a manifold surrounding the HPT shroud. The temperature of the air controls the thermal expansion of the shroud support structure to optimize the shrouds' relative clearance to the HPT blade tips.
2. High Pressure Turbine Clearance Control Valve (Fig. 1)_____________________________________________
A. The HPTCC valve is located on the right side of the engine just below the horizontal split-line of the high pressure compressor (HPC) case. The combination of valve positions in the MEC and the clearance control valve can result in any of the following three (open or closed) combinations of airflow to the HPT shroud area: 5th-stage airflow only, 5th- and 9th-stage airflow mixture or 9th-stage airflow only.
B. 5th-stage air is extracted from the forward 5th-stage manifold of the HPC stator case at the point where the HPTCC valve mounts. 9th-stage air is extracted from the combustion case through a port adjacent to one of the fuel nozzle ports and routed forward through an external tube to the HPTCC valve.
3. Operation (Fig. 2)_________
A. Cooling air from the HPTCC valve flows through a manifold and enters two ports near the aft flange of the combustion case. The air circulates around an impingement manifold, moves through the manifold and impinges on the support for the HPT shrouds.
B. This air acts on the shroud support to control the expansion rate of the support and therefore controls the clearance between the HPT blades and HPT shroud. The cooling air then flows through passageways towards the aft end of the support and joins 5th-stage cooling air entering the 1st-stage LPT nozzle.
C. After engine start-up and with the engine at low idle power setting, the airflow to the HPT shroud is from the HPC 9th-stage bleed. When the throttle is advanced or retarded to change the core engine speed (N2), the airflow is regulated to maintain optimum HPT shroud to blade tip clearance. The airflow selection for various steady-state power settings is approximately as follows:
(1)
Idle Power - 9th-stage air
(2)
Cruise Power - 5th-stage air
(3)
Climb Power - 5th- and 9th-stage air mixture
(4)
Take-off Power - 9th-stage air
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ALL ú ú C01 Page 1 ú Nov 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
SEEA
5TH-STAGE HPC
BLEED AIR PORT 9TH-STAGE HPC BLEED AIR TUBE
RIGHT VSV ACTUATOR SEAL AND SHROUD DRAIN
HPT CLEARANCE CONTROL VALVE
HPT CLEARANCE CONTROL VALVE DRAIN AND RIGHT VSV ACTUATOR SEAL AND SHROUD DRAIN
TC2
TC1 ACTUATOR VALVE RODS
HPT SHROUD
PCR
MANIFOLD AIR
TUBE
FUEL TUBES
FWDFROM MEC
A
High Pressure Turbine (HPT) Clearance Control Valve Location
Figure 1
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75-24-00
ALL ú ú C01 Page 2 ú Nov 15/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
G-M56-MM-0085(1)-00-B 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737-300 400 500 AMM 飞机维护手册 空气 AIR(6)
