DOC AIRBUS | AMM A320FHPT ACTIVE CLEARANCE CONTROL SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. General
The High Pressure Turbine (HPT) clearance control system of the engine uses High Pressure Compressor (HPC) bleed air from stages 5 and 9. This system is used to obtain maximum steady-state HPT performance and to minimize Exhaust Gas Temperature (EGT) transient overshoot during throttle bursts. Air selection is determined by fuel pressure signals from the Hydromechanical Unit (HMU).The bleed air is ducted from the valve to a manifold surrounding the HPT shroud.
The temperature of the air controls the HPT shrouds clearance relative to the HPT blade tips.
** ON A/C NOT FOR ALL The High Pressure Turbine (HPT) clearance control system of the engine uses High Pressure Compressor (HPC) bleed air from stages 5 and 9. This system is used to obtain maximum steady-state HPT performance and to minimize Exhaust Gas Temperature (EGT) transient overshoot during throttle bursts. Air selection is determined by fuel pressure signals from the Hydromechanical Unit (HMU).The bleed air is ducted from the valve to a manifold surrounding the HPT shroud.
HPTCC - SchematicThe temperature of the air controls the HPT shrouds clearance relative to the HPT blade tips.
2. Description
The clearance control system supplies HPC bleed air from the 5th and 9th stage air to the HPT shroud support to control the thermal expansion of the shroud support structure. The bleed air is modulated by the Electronic Control Unit (ECU) in response to the shroud temperature sensed by the Turbine Clearance Control (TCC) sensor.
On engine start the HPTCC valve ports 9th stage air to unload the compressor and enhance engine acceleration. At ground idle power setting, the air flow to the HPT shroud is essentially from the HPC stage 9 bleed. When the throttle is advanced or retarded to change the core engine speed, the air flow is regulated to maintain the optimum HPT shroud to blade tip clearance.
When the engine is shut down, the hydraulic actuator valve rod is retracted to the start position.
** ON A/C NOT FOR ALL The clearance control system supplies HPC bleed air from the 5th and 9th stage air to the HPT shroud support to control the thermal expansion of the shroud support structure. The bleed air is modulated by the Electronic Control Unit (ECU) in response to the shroud temperature sensed by the Turbine Clearance Control (TCC) sensor.
On engine start the HPTCC valve ports 9th stage air to unload the compressor and enhance engine acceleration. At ground idle power setting, the air flow to the HPT shroud is essentially from the HPC stage 9 bleed. When the throttle is advanced or retarded to change the core engine speed, the air flow is regulated to maintain the optimum HPT shroud to blade tip clearance.
When the engine is shut down, the hydraulic actuator valve rod is retracted to the start position.
3. HPT Clearance Valve
The high pressure turbine clearance control valve is a three-way valve with two inlet ports, 5th and 9th stage, and two outlet ports. One outlet port provides a start bleed function and through the other outlet port flows a mixture of 5th and 9th stage air to the turbine case. The valve consists of an outer housing, two metering plates, an axial moving contoured piston, and an integral fuel powered actuator with dual independent transducers for position feedback. The piston and the metering plates constitute variable orifices that achieve the proper mix of 5th and 9th stage air.
The high pressure turbine clearance control valve is a three-way valve with two inlet ports, 5th and 9th stage, and two outlet ports. One outlet port provides a start bleed function and through the other outlet port flows a mixture of 5th and 9th stage air to the turbine case. The valve consists of an outer housing, two metering plates, an axial moving contoured piston, and an integral fuel powered actuator with dual independent transducers for position feedback. The piston and the metering plates constitute variable orifices that achieve the proper mix of 5th and 9th stage air.