LP Compressor Airflow Control System

EngineIAE

The airflow control system includes:

(1) An LPC bleed-slave actuator

(2) An LPC bleed-master actuator

(3) Two bleed-valve actuating rods

(4) A booster bleed valve and actuating mechanism The airflow control system automatically operates to control the air bled from the LP compressor.The two actuators are mechanically attached to each actuating rod and, the bleed-valve and actuating mechanism. The two actuators are connected hydraulically and operate together by command and feedback signals from/ to the EEC.

  • The two actuators are hydraulically connected units which operate together.
  • The two bleed-valve actuating rods connect each actuator fork end to the synchronizing ring. The force to move the synchronizing and its linkage through the actuating rods, is supplied from the two actuators.
  • The master actuator gives an accurate control in relation to an electrical input signal (command signal) from the EEC. The master actuator also gives an electrical output signal (the positions of the actuator piston fork end) to an electrical input signal (command signal) from the EEC. The master actuator also gives an electrical output signal (the positions of the actuator piston fork end) to the EEC.

Slave Actuator

Master Actuator


A portion of fan air passes into the 3-stage booster and enters the core by a converging duct formed by the fan frame. This duct is provided with Booster Stage Bleed Valves (BSBV).

At low LP spool speeds the booster provides more air than the core engine can utilize. To match the booster discharge airflow to the core engine requirements at low speed, excess air is bled off through booster stage bleed valves (BSBV) into the fan discharge air stream. At higher engine speeds the BSBV are closed so that all the booster discharge (primary air flow) enters the core engine.

The bleed valve mechanism is supported by the intermediate structure and the outer ring of the stage 2.5 vanes.Two actuating rods which are each motivated by actuators impart a circumferential and axial motion to the valve ring via 2 power arms. 8 arms are synchronized by valve ring itself and set axial position of valve ring uniformly.

The ring valve opens during the engine start and other scheduled flight operations. This permits some of the LP compressor airflow (which normally go into the HP compressor) to go through the fan airstream. The bleed valves are closed during takeoff and cruise operations.

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