Engine Bleed Air ( Continue )

ATA36
  1. Bleed Pressure Regulator Valve Control Solenoid
  • The bleed pressure regulator valve control solenoid is installed downstream of the precooler exchanger to control the bleed pressure regulator valve. It includes :
    • a thermostat body assy
    • a solenoid sub-assembly
    • a non-return sub-assembly
  • General operation : The bleed pressure regulator valve control solenoid continuously senses the temperature of the air from the bleed air precooler exchanger of the bleed air system. It also monitors the differential pressure between the upstream side of the bleed pressure regulator valve and the downstream side of the bleed air precooler exchanger.It controls pneumatically the air supply through the bleed air system by closing the bleed pressure regulator valve.
  • Electrical closing function : The pushbutton switches (ENG 1 (2) BLEED) energize/de-energize the solenoid. When the coil of the solenoid sub-assembly is energized, the core moves up and the clapper moves off its seat, under the spring load. This vents the coupling line and causes closure of the bleed pressure regulator valve.
    • NOTE:The bleed pressure regulator valve control solenoid has no direct effect on the HP bleed valve operation. The HP bleed valve also closes because the bleed pressure regulator valve closure vents to ambient the signal pressure in the sense line between the bleed pressure regulator valve and the HP bleed valve.
  • Non-return function : The diaphragm sub-assembly detects a differential pressure between the downstream section of the bleed air precooler exchanger and the upstream section of the bleed pressure regulator valve.When the differential pressure decreases below 0.01 bar (0.145 PSI), the diaphragm sub-assembly opens the solenoid valve.This closes the bleed pressure regulator valve.If the pressure upstream the bleed pressure regulator valve is too high, the relief valve opens to prevent damage to the diaphragm sub-assembly.
  • Final :
    • Bleed pressure regulator valve control solenoid chỉ đóng vai trò đóng ,mở PRV.
    • PRV có thể được Close ,open bằng Electric hoặc Pressure.Nhưng cả 2 trường hợp đều liên quan đến solenoid valve .Bằng electric là khi bấm ON , OFF của ENG Bleed , dẫn đến energize ( de-energize ) solenoid. Bằng áp suất là do chênh áp giữa dòng Downstream của Precooler và Upstream của PRV tác động vào 1 màng Diaphragm , đẩy 1 áp lực làm mở solenoid valve , đẫn đến đóng PRV.
PRV
  • A thermal fuse (7) permits to vent to ambient chamber (5) of the opening/closing subassembly. This causes the valve to close.
  • The microswitch in the valve signals the extreme position (closed) of the butterfly plate.
  • The upstream pressure supplies chamber (1) of the regulator through a jet to control the position of the clapper (2) and maintain constant air pressure in the actuator opening chamber.
  • The regulator calibration can be modified by the secondary stage of the regulator which is pneumatically connected to the Bleed Pressure regulator valve Control Solenoid according to the air temperature sensed downstream to the PCE ( PreCooler Exchanger ) . The air pressure in chamber (3) can vary according to an air leakage controlled by the Bleed Pressure Regulator Valve Control Solenoid. As clapper (2) remains in contact with its seat (4), downstream pressure still supplies the actuator closing chamber despite a reduced pressure air value lower than the nominal regulation threshold.The test intake is used for checking correct valve operation on the ground by directly supplying the regulator.The downstream pressure supplies the actuator closing chamber through distribution clapper (4). Indeed when downstream pressure reaches the value determined by spring preloading.

2. Pressure and Temperature Monitoring

  • Two pressure transducers :7HA & 8HA ( 1 và 2 tương ứng ENG1, ENG2 )
  • one control temperature sensor (CTS) : 6HA ( 1 và 2 tương ứng ENG1, ENG2 )
  • BMC1 (1HA1) and BMC2 (1HA2)

All for monitor the pressure and the temperature of the engine bleed air.

  • the PRESSURE TRANSDUCER 7HA1(2) is used to measure the transferred pressure which is the pressure between the bleed pressure regulator valve and the HP bleed valve. The pressure transducer 7HA1(2) is electrically connected to the BMC 1(2) for monitoring purpose. A sensing line connects the pressure transducer 7HA1(2) to the pneumatic duct downstream of the HP bleed valve.
  • the pressure transducer 8HA1(2) is used to measure the regulated pressure. The pressure transducer 8HA1(2) is connected with a sensing line to the pneumatic duct downstream of the bleed pressure regulator valve. This transducer is electrically connected to the BMC 1(2) for monitoring/indication of the system parameters.
  • A temperature sensor 6HA1(2) is installed downstream of the precooler. It is installed in the elbow of the pneumatic duct in the left (right) pylon. An electrical cable connects the sensor to the BMC.

3. Fan Air Valve Control Thermostat

  • The fan air valve control thermostat is installed downstream of the bleed air precooler exchanger. It controls, through the fan air valve, the engine fan cooling airflow in order to maintain the bleed air temperature to 200 deg.C (392 deg.F) plus or minus 15 deg.C (27 deg.F).
  • The fan air valve control thermostat contains two mains parts:
    • A temperature sensing element
    • A pressure regulator.
  • Regulation : When the temperature downstream of the precooler exchanger is below the required value:
    • the INVAR rod valve remains on its seat
    • no air flows through the pressure regulator
    • the FAV remains closed.
  • When the temperature is over the required value differential expansion between the INVAR rod and the stainless steel sensing tube opens the rod valve causing the venting of the chamber A and thus allowing a pressure signal through the thermostat to the opening chamber of the FAV. Between both values the FAV butterfly has an intermediate position.
  • A thermostat installed downstream of the precooler exchanger senses the hot air temperature and sends to the valve a pressure signal corresponding to precooler cooling air demand. The FAV butterfly takes a position from fully closed to fully open to maintain the temperature value of air bleed within limits.
  • Two microswitches in the valve signal the full open and full closed positions of the butterfly. A thermal fuse installed on the valve body closes the valve if the nacelle temperature reaches 450 plus or minus 25 deg.C (45 deg.F).
  • Final :
    • Connector chỉ để signal vị trí đóng mở của FAV thôi , không có tác dụng j liên quan đến regulate valve.
    • Việc đóng mở FAV chỉ liên quan đến nhiệt độ :
      • Nhiệt độ qua downstream Precooler mà cao trên nngưỡng, probe sẽ mở đường vent buồng A , dẫn đến áp suất khí sẽ chạy thẳng đến FAV giúp mở valve này.
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