DOC AIRBUS | AMM A320FDISTRIBUTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The engine fuel supply distribution system mainly consists of:
** ON A/C NOT FOR ALL The engine fuel supply distribution system mainly consists of:
Fuel System Schematic- a fuel supply line
- an engine 2-stage pump High Pressure/Low Pressure (HP/LP),
- a fuel filter,
- an engine Fuel Cooled Oil Cooler (FCOC),
- a Fuel Metering Unit (FMU),
- an Integrated Drive Generator (IDG) Fuel Cooled Oil Cooler (FCOC),
- a fuel diverter and return (to tank) valve,
- a fuel flowmeter,
- a Fuel Distribution Valve (FDV),
- 20 fuel nozzles.
2. Fuel Manifold and Fuel Tubes
The fuel manifold and fuel tubes consist of several single wall tubes which carry fuel between components in the fuel system. Fuel supplied to the fuel nozzles is carried by a large tube from the FMU to the fuel distribution valve. At the fuel distribution valve the fuel supply is split and carried to twenty fuel nozzles by ten manifolds. Each fuel manifold feeds two fuel nozzles. Fuel pressure for actuating various valves is supplied by small tubes from the FMU mounted on the fuel pump.
All the brackets and tubing are fireproof.
** ON A/C NOT FOR ALL The fuel manifold and fuel tubes consist of several single wall tubes which carry fuel between components in the fuel system. Fuel supplied to the fuel nozzles is carried by a large tube from the FMU to the fuel distribution valve. At the fuel distribution valve the fuel supply is split and carried to twenty fuel nozzles by ten manifolds. Each fuel manifold feeds two fuel nozzles. Fuel pressure for actuating various valves is supplied by small tubes from the FMU mounted on the fuel pump.
All the brackets and tubing are fireproof.
3. Fuel Pump
A. General
The Low Pressure/High Pressure (LP/HP) fuel pumps are housed in a single pump unit which is driven by a common gearbox output shaft. A LP stage and a HP stage provide fuel at the flows and pressures required for the operation of the hydromechanical components and for combustion in the burner.
The unit consists of a LP centrifugal boost stage which feeds an HP single stage, two gear pump. The housing has a provision for the installation of the FMU.
Fuel from the aircraft tanks flows to the LP stage of the engine fuel pumps, through the aircraft fuel pumps.
The LP pump is designed to provide fuel to the HP gear stage with the aircraft pumps inoperative. After passing through the LP boost stage, the fuel flows through the fuel filter to the HP gear stage. A coarse mesh strainer is provided at the inlet to the HP gear stage. This stage is protected from overpressure by a relief valve. Excess flow from the gear stage pump is recirculated through the FMU bypass loop to the low pressure side of the pump.
The Low Pressure/High Pressure (LP/HP) fuel pumps are housed in a single pump unit which is driven by a common gearbox output shaft. A LP stage and a HP stage provide fuel at the flows and pressures required for the operation of the hydromechanical components and for combustion in the burner.
The unit consists of a LP centrifugal boost stage which feeds an HP single stage, two gear pump. The housing has a provision for the installation of the FMU.
Fuel from the aircraft tanks flows to the LP stage of the engine fuel pumps, through the aircraft fuel pumps.
The LP pump is designed to provide fuel to the HP gear stage with the aircraft pumps inoperative. After passing through the LP boost stage, the fuel flows through the fuel filter to the HP gear stage. A coarse mesh strainer is provided at the inlet to the HP gear stage. This stage is protected from overpressure by a relief valve. Excess flow from the gear stage pump is recirculated through the FMU bypass loop to the low pressure side of the pump.
B. Description
The LP/HP fuel pump is installed on the rear face of the accessory gearbox. It is attached with an adapter housing and driven by an input shaft which has a shear section.
The low pressure stage is a shrouded radial flow centrifugal impeller with an axial inducer.
The HP pump is a two gear type. Its drive gear is attached to the drive shaft and this turns the driven gear.
These are input shaft, which is connected by external spline to the internal spline of the drive gear. The journals of the drive and driven gear are held by "stationary" and "floating" set of matched bearings.
The centrifugal pumping element has the impeller/inducer installed on the drive shaft.
The pump has four ports:
The LP/HP fuel pump is installed on the rear face of the accessory gearbox. It is attached with an adapter housing and driven by an input shaft which has a shear section.
The low pressure stage is a shrouded radial flow centrifugal impeller with an axial inducer.
The HP pump is a two gear type. Its drive gear is attached to the drive shaft and this turns the driven gear.
These are input shaft, which is connected by external spline to the internal spline of the drive gear. The journals of the drive and driven gear are held by "stationary" and "floating" set of matched bearings.
The centrifugal pumping element has the impeller/inducer installed on the drive shaft.
The pump has four ports:
- gear pump inlet port,
- gear pump discharge port,
- booster pump inlet port,
- booster pump discharge port.
C. Operation
Fuel goes into the booster pump inlet port and flows through the centrifugal pumping element. There, the impeller/inducer sends the fuel to the external FCOC. The fuel returns through the external filter.
The fuel goes through the gearpump element which sends the fuel through the pump discharge port to the FMU.
The gearpump element sends the fuel through the discharge port which has the relief valve. The valve set to limit gear discharge pressure increase to 1365 psi (94 bar) differential at fuel pump flow. The relief valve sends fuel back to the inlet side of the gear pump element.
Fuel goes into the booster pump inlet port and flows through the centrifugal pumping element. There, the impeller/inducer sends the fuel to the external FCOC. The fuel returns through the external filter.
The fuel goes through the gearpump element which sends the fuel through the pump discharge port to the FMU.
The gearpump element sends the fuel through the discharge port which has the relief valve. The valve set to limit gear discharge pressure increase to 1365 psi (94 bar) differential at fuel pump flow. The relief valve sends fuel back to the inlet side of the gear pump element.
4. Fuel Filter
NOTE: A 40 micron fuel filter provides the main filtration for the fuel system.
A. Description
(1) The fuel filter element is a low pressure filter which removes all contamination from fuel to go through it.
(2) The filter element is installed in the lower housing of a Fuel Cooled Oil Cooler (FCOC). The FCOC includes the following components:
(a) A filter cap which has a pressure plate to keep the filter element in position once installed.
(b) A filter bypass valve to let the fuel go around the filter element when it becomes clogged.
The filter cap of the FCOC also includes a fuel drain plug to drain the fuel for maintenance purposes.
The filter cap of the FCOC also includes a fuel drain plug to drain the fuel for maintenance purposes.
B. Operation
(1) The fuel from the FCOC goes through the filter element into the high pressure gear element of an LP/HP fuel pump.
(2) The filter bypass valve keeps a pressure drop across the filter element to a maximum of 17 psi (1.17 bar) differential. If the pressure drop is higher than the maximum limit, the bypass valve will start to open and let the fuel go around the filter element.
A. General
The fuel nozzles receive fuel from the fuel manifolds. The fuel nozzles mix the fuel with air, and send the mixture into the combustion chamber in a controlled pattern.
The fuel nozzles receive fuel from the fuel manifolds. The fuel nozzles mix the fuel with air, and send the mixture into the combustion chamber in a controlled pattern.
B. Description/Operation
There are 20 fuel nozzles equally spaced around the diffuser case assembly. The fuel nozzles are installed through the wall of the case, and each nozzle is held in position by three bolts.
The fuel nozzles carry the fuel through a single orifice.
The fuel is vaporized by high-velocity air as it enters the combustion chamber. The fuel nozzle forms the atomized mixture of fuel and air into the correct pattern for satisfactory combustion.
The design of the fuel nozzle results in fast vaporization of the fuel through the full range of operation.
The high-velocity flow of fuel prevents formation of coke on areas where fuel touches metal. Heatshields installed also prevent formation of coke.
There are 20 fuel nozzles equally spaced around the diffuser case assembly. The fuel nozzles are installed through the wall of the case, and each nozzle is held in position by three bolts.
The fuel nozzles carry the fuel through a single orifice.
The fuel is vaporized by high-velocity air as it enters the combustion chamber. The fuel nozzle forms the atomized mixture of fuel and air into the correct pattern for satisfactory combustion.
The design of the fuel nozzle results in fast vaporization of the fuel through the full range of operation.
The high-velocity flow of fuel prevents formation of coke on areas where fuel touches metal. Heatshields installed also prevent formation of coke.
6. Fuel Diverter and Return Valve
A. General
The Fuel Diverter and Return Valve (FD and RV) is a primary unit in the Heat Management System (HMS) of the engine. The FD and RV has two valves in one body. They are a Fuel Diverter Valve (FDV) and a Fuel Return Valve (FRV).
The FDV operates to change the direction of the FMU spill flow to:
The Fuel Diverter and Return Valve (FD and RV) is a primary unit in the Heat Management System (HMS) of the engine. The FD and RV has two valves in one body. They are a Fuel Diverter Valve (FDV) and a Fuel Return Valve (FRV).
The FDV operates to change the direction of the FMU spill flow to:
- The Fuel Cooled Oil Cooler (FCOC) or,
- the fuel filter (element) inlet or,
- the IDG FCOC.
B. Description
The fuel diverter and return valve is installed on the FCOC.
The FDV is a two-position selector valve which has two pistons in a sleeve. The two pistons are mechanically connected and make two valve areas which are referred to as valve A and valve B. The FRV has a main valve and a pushing piston in a sleeve. This main valve is a half-area piston-type valve which moves the valve to change the metering port area. The main valve has two valve functions that are referred to as valve C and valve D
The EEC gives the electrical signal to the FDRV to change the position of the valves. The FDRV gives a feedback signal to the EEC to transmit the position of valves in the unit. The fuel flow changes with the position of the valves. Thus, the fuel flow can be controlled through the FDRV and the EEC.
The fuel diverter and return valve is installed on the FCOC.
The FDV is a two-position selector valve which has two pistons in a sleeve. The two pistons are mechanically connected and make two valve areas which are referred to as valve A and valve B. The FRV has a main valve and a pushing piston in a sleeve. This main valve is a half-area piston-type valve which moves the valve to change the metering port area. The main valve has two valve functions that are referred to as valve C and valve D
The EEC gives the electrical signal to the FDRV to change the position of the valves. The FDRV gives a feedback signal to the EEC to transmit the position of valves in the unit. The fuel flow changes with the position of the valves. Thus, the fuel flow can be controlled through the FDRV and the EEC.
C. Operation
(1) General
The FDRV configuration allows four modes of operation according to the electrical signals generated from the EEC (based on fuel and oil temperature measurements transmitted by means of thermocouples).
The FDRV configuration allows four modes of operation according to the electrical signals generated from the EEC (based on fuel and oil temperature measurements transmitted by means of thermocouples).
(2) Fuel return valve
- The EEC operates the dual-wound torque motor to control the servo pressure. This servo fuel pushes the main valve.
- The pressure balance between two sides of the main valve (Valves C and D) gives the direction and the speed of the valve movement.
Then the valve changes the direction of the fuel flow and controls the metering port area.
(3) Fuel diverter valve
- The EEC energizes the solenoid valve to let the servo fuel flow. This servo fuel goes into one side of the piston face in the valve B.
- The servo pressure pushes two pistons (which are the valves A and B) in the same direction. Then these valves change the direction of the fuel flow, and one of these pistons compresses the spring.
- When the solenoid is de-energized, this spring pushes back two pistons.
(There is an orifice to release the servo fuel to the FMU spill port).
And the other one of two pistons pushes the switch assemblies. - The switch assemblies transmit the EEC the valve position when the solenoid is de-energized.
(4) Constant Pressure Valve (CPV)
The CPV makes the servo pressure constant between the HP port and LP port of the FDRV. This servo flow moves each valve in the FDRV.
The CPV makes the servo pressure constant between the HP port and LP port of the FDRV. This servo flow moves each valve in the FDRV.
(5) Failure mode
(a) When the servo pressure becomes zero:
1 The pushing piston comes up to hold the main valve at a mode 5 position.
2 The spring extends to hold the FDV pistons at a mode 5 position.
(b) Other than in (a), the FDRV keeps the mode 5 position in these conditions:
1 The failure of the electrical signal.
2 During the engine stops.
(c) If the IDG FCOC port is clogged in this valve position, relief valve releases the FMU spill flow. This relief valve is in the valve A and it can release the unwanted pressure to the FCOC port.
7. Fuel Distribution Valve
A. General
The FDV subdivides scheduled engine fuel flow from the FMU equally to ten fuel manifolds, each of which in turn feeds two nozzles.
The FDV subdivides scheduled engine fuel flow from the FMU equally to ten fuel manifolds, each of which in turn feeds two nozzles.
B. Description
The fuel distribution valve is installed at the 4:00 o'clock location, at the front flange of the diffuser case.
The fuel distribution valve receives fuel through a fuel line from the FMU. The fuel goes through a 200 micron strainer, and then into ten internal discharge ports. The ten discharge ports are connected to the ten fuel manifolds.
Eight of the ten internal discharge ports in the valve are connected after an engine shutdown. This lets fuel drain from eight of the fuel manifolds, and into the engine through the lowest fuel nozzle.
The two fuel manifolds which remain full help supply fuel for the next engine start.
The fuel distribution valve is installed at the 4:00 o'clock location, at the front flange of the diffuser case.
The fuel distribution valve receives fuel through a fuel line from the FMU. The fuel goes through a 200 micron strainer, and then into ten internal discharge ports. The ten discharge ports are connected to the ten fuel manifolds.
Eight of the ten internal discharge ports in the valve are connected after an engine shutdown. This lets fuel drain from eight of the fuel manifolds, and into the engine through the lowest fuel nozzle.
The two fuel manifolds which remain full help supply fuel for the next engine start.