DOC AIRBUS | AMM A320FDISTRIBUTION - DESCRIPTION AND OPERATION
** 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 :
Engine Fuel System - Schematic- a fuel supply line
- an engine 2-stage pump and filter assembly
- an engine oil/fuel heat exchanger described in 79-20-00
- a servo fuel heater
- an hydromechanical unit described in 73-20-00
- an IDG oil cooler
- a fuel return valve system
- a burner staging valve
- a fuel manifold
- 20 fuel nozzles (16 standard and 4 pilot nozzles).
2. Component Description
A. Plumbing
(1) Fuel Supply Line
The fuel supply line is connected to the hydraulic junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the pump. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
The fuel supply line is connected to the hydraulic junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the pump. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
(2) Fuel Return Line
The fuel return line is connected to the fluid junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the fuel return valve. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
The fuel return line is connected to the fluid junction box attached on the left side of the pylon in the fan compartment. It is routed along the left fan case side down to the fuel return valve. All the brackets and tubing are built in 321 stainless steel and are fire-proof.
B. Fuel Pump and Filter Assembly
(1) General
(a) The fuel pump pressurizes and circulates the fuel in the fuel system.
The tank fuel pumps deliver the fuel supply up to the engine fuel pump inlet. The fuel then enters the low pressure (LP) stage of the fuel pump. After initial pressurization, the fuel is delivered to the main oil/fuel heat exchanger. There it cools the engine oil.
The tank fuel pumps deliver the fuel supply up to the engine fuel pump inlet. The fuel then enters the low pressure (LP) stage of the fuel pump. After initial pressurization, the fuel is delivered to the main oil/fuel heat exchanger. There it cools the engine oil.
(b) On discharge from the heat exchanger, the fuel flows back to the pump.
It passes through a disposable filter before undergoing a second pressure increase in the high pressure (HP) stage of the pump. The fuel then enters the wash filter where it is divided into a filtered and unfiltered flow. The unfiltered flow bypasses the filter and enters the hydromechanical fuel unit (HMU). The filtered flow goes through the servo fuel heater and then into the HMU. This flow is sufficiently hot to prevent jamming of the HMU servo-mechanisms due to ice particles.
It passes through a disposable filter before undergoing a second pressure increase in the high pressure (HP) stage of the pump. The fuel then enters the wash filter where it is divided into a filtered and unfiltered flow. The unfiltered flow bypasses the filter and enters the hydromechanical fuel unit (HMU). The filtered flow goes through the servo fuel heater and then into the HMU. This flow is sufficiently hot to prevent jamming of the HMU servo-mechanisms due to ice particles.
(c) The returning fuel bypassed from the HMU is tapped to feed the Integrated Drive Generator (IDG) oil cooler. There it cools the oil coming from the engine IDG. The fuel returns then to the pump upstream of the filter, between the LP and HP fuel pump stages. The fuel returns via a port located on the oil/fuel heat exchanger.
(d) If the filters or heat exchanger become clogged :
- a number of bypass valves are provided to prevent excessive pressure build-ups.
(e) The fuel pump and HMU are mounted as a unit. This unit is located on the accessory gearbox (AGB) (aft face on the left side of the horizontal drive shaft housing, aft looking forward).
(2) Functional Description
(a) Fuel pump drive system
The fuel pump drive system consists of the following :
The fuel pump drive system consists of the following :
1 A main drive shaft, driven by the AGB which, in turn, drives the HP stage drive spur gear. The main drive shaft has a shear neck to protect the AGB from any excessive torque in the fuel pump drive.
2 A LP stage drive shaft, driven by the HP stage drive spur gear, providing drive for :
a The LP stage via a hollow shaft.
b The HMU via the HMU drive shaft. The LP pump drive shaft has a shear neck :
- to protect the HMU from LP stage failures
- to maintain proper engine operation even in case of total failure (seizing) of the LP stage.
(b) Fuel pump LP stage
1 General
The LP stage of the fuel pump is of the centrifugal type. It delivers a boost pressure to the HP stage to avoid pump cavitation. The LP stage general characteristics at takeoff power are as follows :
The LP stage of the fuel pump is of the centrifugal type. It delivers a boost pressure to the HP stage to avoid pump cavitation. The LP stage general characteristics at takeoff power are as follows :
a Boost (LP) stage pressure rise: 165 psi (1138 kPa).
b Speed rating : 6250 RPM.
a The fuel pump LH stage consists of :
- an impeller supported by 2 plain bearings provided with swirl ramps,
- an inducer having helical grooves and a scroll.
b The fuel discharged from the boost pumps :
- enters the fuel pump LP stage,
- leaves the pump under pressure,
- flows to the main oil/fuel heat exchanger
- and controls the fuel return valve.
3 LP stage lubrication system
The fuel tapped from the scroll at the discharge of the LP stage lubricate the LP stage rotating parts. The lubricated elements are :
The fuel tapped from the scroll at the discharge of the LP stage lubricate the LP stage rotating parts. The lubricated elements are :
- the front and rear bearings
- the LP pump drive shaft splines
- the HMU drive shaft splines
(c) Fuel pump HP stage
1 General
a The fuel pump HP stage converts mechanical energy into hydraulic power required to supply :
- the fuel nozzles
- the HMU servos
- the variable bleed valve (VBV) and variable stator vane (VSV) hydromechanical systems.
b The HP stage hydraulic power is supplied by a positive displacement (gear-type) pump. For a given number of revolutions, the pump delivers a constant fuel flow regardless of the discharge pressure.
A pressure relief valve connected in parallel with the HP pump protects the pump.
A pressure relief valve connected in parallel with the HP pump protects the pump.
c The HP stage general characteristics at takeoff power are as follows :
- discharge pressure : 1000 psi (6895 kPa) maximum
- speed rating : 6250 RPM
- fuel flow : 59 US gal/min. or 223 liter/mn (13380 l/h).
2 Functional Description
The HP fuel pump consists of 2 gearshafts. Each gearshaft is supported by 2 plain bearings ; one is stationary and the other self-aligning.
The filtered fuel enters the HP stage and, after pressurization, is delivered to the HMU. Should an overpressure occur (discharge pressure higher or equal to 1050 psi (7240 kPa), a valve bypasses the fuel toward the HP stage inlet.
The HP fuel pump consists of 2 gearshafts. Each gearshaft is supported by 2 plain bearings ; one is stationary and the other self-aligning.
The filtered fuel enters the HP stage and, after pressurization, is delivered to the HMU. Should an overpressure occur (discharge pressure higher or equal to 1050 psi (7240 kPa), a valve bypasses the fuel toward the HP stage inlet.
3 HP stage lubrication system
The fuel used to lubricate the LP stage items, lubricates also the HP stage rotating parts.
The lubricated elements are :
The fuel used to lubricate the LP stage items, lubricates also the HP stage rotating parts.
The lubricated elements are :
- the HP stage bearings, and
- the thrust ring.
(d) Fuel filter
1 General
This fuel filter is located between the main oil/fuel heat exchanger and fuel pump HP stage. It protects the HMU from particles in suspension in the fuel. The filter disposable cartridge is designed to retain foreign material. The cartridge is periodically replaced and removed. The cartridge is discarded.
This fuel filter is located between the main oil/fuel heat exchanger and fuel pump HP stage. It protects the HMU from particles in suspension in the fuel. The filter disposable cartridge is designed to retain foreign material. The cartridge is periodically replaced and removed. The cartridge is discarded.
2 Functional description
The fuel filter consists of a filter cartridge and a pressure relief valve. The filter cartridge is installed in a cavity on the pump body.
The fuel circulates from the outside to the inside of the filter cartridge. The cartridge has a filtering capability of 32 microns absolute. In case of a clogged filter, a pressure relief valve bypasses the fuel to the HP stage.
Tappings on pump housing enable transmission of the differential pressure across the fuel filter to the fuel differential pressure switch. This pressure switch supplies a clogging indication to the cockpit (Ref. AMM D/O 73-30-00-00).
The fuel filter consists of a filter cartridge and a pressure relief valve. The filter cartridge is installed in a cavity on the pump body.
The fuel circulates from the outside to the inside of the filter cartridge. The cartridge has a filtering capability of 32 microns absolute. In case of a clogged filter, a pressure relief valve bypasses the fuel to the HP stage.
Tappings on pump housing enable transmission of the differential pressure across the fuel filter to the fuel differential pressure switch. This pressure switch supplies a clogging indication to the cockpit (Ref. AMM D/O 73-30-00-00).
(e) Wash flow filter
1 General
The wash flow filter is located at the HP stage discharge. It catches the particles in suspension remaining in the fuel supplying the HMU servos.
Foreign materials retained by the filter are removed by the fuel flow supplying the HMU metering system.
The wash flow filter is located at the HP stage discharge. It catches the particles in suspension remaining in the fuel supplying the HMU servos.
Foreign materials retained by the filter are removed by the fuel flow supplying the HMU metering system.
2 Functional description
The wash flow filter is incorporated with the pump housing. It consists of a filtering element and a pressure relief valve. Should the filter clog, a pressure relief valve bypasses the fuel to the HMU servos fuel supply. The wash flow filter has a filtering capability of 65 microns absolute.
The wash flow filter is incorporated with the pump housing. It consists of a filtering element and a pressure relief valve. Should the filter clog, a pressure relief valve bypasses the fuel to the HMU servos fuel supply. The wash flow filter has a filtering capability of 65 microns absolute.
C. Servo Fuel Heater
(1) General
(a) The servo fuel heater raises the temperature. This prevents ice from entering the control servos inside the hydromechanical fuel unit (HMU).
(b) The servo fuel heater is mounted on the aft section of the main oil/fuel heat exchanger located on the accessory gearbox (AGB) aft face, between the oil tank and the fuel pump/HMU package.
(2) Description and Operation
The servo fuel heater consists of :
The oil :
Heat exchange between oil and fuel occurs by conduction and convection inside the unit. The 2 fluids circulate in the servo fuel heater through separate flowpaths.
The oil initially lubricates and cools the engine sumps.
Then it enters the servo fuel heater, giving off heat to the fuel from the wash flow filter. The heated fuel then flows to the internal HMU servos.
The servo fuel heater consists of :
- a housing with a heat exchanger core inside
- a cover.
The oil :
- enters the heater through one flange of the housing
- circulates around the core tubes, and
- leaves through the opposite flange of the housing.
- one corresponding to the normal circuit
- the other is used if clogging of the main oil/fuel heat exchanger restricts oil circulation beyond acceptable limits.
Heat exchange between oil and fuel occurs by conduction and convection inside the unit. The 2 fluids circulate in the servo fuel heater through separate flowpaths.
The oil initially lubricates and cools the engine sumps.
Then it enters the servo fuel heater, giving off heat to the fuel from the wash flow filter. The heated fuel then flows to the internal HMU servos.
NOTE: There is no fuel anti-clogging valve in the servo fuel heater system.
D. IDG Oil Cooler Assembly
(a) The Integrated Drive Generator (IDG) oil cooler is designed to transfer heat to the fuel from the oil, utilising the main engine oil.
The IDG oil cooler is located forward of the AGB at 5.30 o'clock position, aft looking forward. Adapting brackets attach it under the fan inlet case, with its end cover pointing rearwards.
The IDG oil cooler is located forward of the AGB at 5.30 o'clock position, aft looking forward. Adapting brackets attach it under the fan inlet case, with its end cover pointing rearwards.
(2) Description
The IDG oil cooler consists of a cast aluminium alloy cylindrical case, closed at one end, open and flanged at the other end.
At the open flanged end of the case, positioned radially to the bore is a square "oil inlet" mounting port facing outwards. In line with the "oil inlet pad" and at the closed end of the cylinder is situated the square oil outlet mounting pad. Opposite the oil side ports there are two square fuel ports. The mounting port that is closest to the open end of the cylinder is the "fuel inlet" port, the lower is the "fuel outlet" port. Incorporated into the cylinder are four cast mounting lugs, positioned close to each port. Between the upper mounting lugs which are near to the open end of the cylinder are two bores which are designed to accept the bobbins. Opposite the fuel out bobbin bore is positioned the oil drain boss. Below the two lower mounting lugs towards the closed end of the cylinder is positioned the fuel pressure relief valve.
The oil cooler is made up of the following elements:
The IDG oil cooler consists of a cast aluminium alloy cylindrical case, closed at one end, open and flanged at the other end.
At the open flanged end of the case, positioned radially to the bore is a square "oil inlet" mounting port facing outwards. In line with the "oil inlet pad" and at the closed end of the cylinder is situated the square oil outlet mounting pad. Opposite the oil side ports there are two square fuel ports. The mounting port that is closest to the open end of the cylinder is the "fuel inlet" port, the lower is the "fuel outlet" port. Incorporated into the cylinder are four cast mounting lugs, positioned close to each port. Between the upper mounting lugs which are near to the open end of the cylinder are two bores which are designed to accept the bobbins. Opposite the fuel out bobbin bore is positioned the oil drain boss. Below the two lower mounting lugs towards the closed end of the cylinder is positioned the fuel pressure relief valve.
The oil cooler is made up of the following elements:
(a) A case bore
The case bore is precision machined to accommodate the matrix (core). Elastomeric preformed packing fitted between the case, matrix tubeplate and end cover provides the sealed and divided oil flow passages. Elastomeric preformed packing fitted between the case, bobbins and end cover provides the sealed and divided fuel flow passages.
The case bore is precision machined to accommodate the matrix (core). Elastomeric preformed packing fitted between the case, matrix tubeplate and end cover provides the sealed and divided oil flow passages. Elastomeric preformed packing fitted between the case, bobbins and end cover provides the sealed and divided fuel flow passages.
(b) A matrix (core)
The matrix (core) assembly is removable and consists of a number of aluminium alloy dimpled "U" shaped tubes. The tubes are inserted through a series of precision drilled baffle plates, separated by distance pieces over tie-rods. The tubes are mechanically bonded to a forget alloy tubeplate which is profiled to the case and end cover flanges. The matrix (core) tubeplate is located and bolted between the case and end cover flanges. The matrix (core) and case assemblies are designed to direct oil in eight radial flow passes over the fuel filled "U" tubes.
The matrix (core) assembly is removable and consists of a number of aluminium alloy dimpled "U" shaped tubes. The tubes are inserted through a series of precision drilled baffle plates, separated by distance pieces over tie-rods. The tubes are mechanically bonded to a forget alloy tubeplate which is profiled to the case and end cover flanges. The matrix (core) tubeplate is located and bolted between the case and end cover flanges. The matrix (core) and case assemblies are designed to direct oil in eight radial flow passes over the fuel filled "U" tubes.
(c) An end cover
The aluminium alloy end cover has fuel inlet and outlet port bores which accept the bobbins situated side by side. Within the end cover there is an internal dividing rib, sealed with elastomeric preformed packing. When assembled against the matrix (core) tubeplate directs the fuel into and from the matrix, (fuel making two passes).
The aluminium alloy end cover has fuel inlet and outlet port bores which accept the bobbins situated side by side. Within the end cover there is an internal dividing rib, sealed with elastomeric preformed packing. When assembled against the matrix (core) tubeplate directs the fuel into and from the matrix, (fuel making two passes).
(3) Operation
Fuel flows through the matrix (core) tubes (Refer to Fig. 012) in two passes. Should there be a build up of pressure in the system of more than 27 psi (186.2 kpa) on the fuel side, the pressure relief valve will allow the fuel to enter the "fuel inlet" port connection then exit through the "fuel outlet" port connection bypassing the cooler. Warm oil flows across the fuel filled matrix (core) tubes in eight passes to the oil outlet port.
Fuel flows through the matrix (core) tubes (Refer to Fig. 012) in two passes. Should there be a build up of pressure in the system of more than 27 psi (186.2 kpa) on the fuel side, the pressure relief valve will allow the fuel to enter the "fuel inlet" port connection then exit through the "fuel outlet" port connection bypassing the cooler. Warm oil flows across the fuel filled matrix (core) tubes in eight passes to the oil outlet port.
E. Fuel Return Valve Assembly
(a) The purpose of the fuel return valve is to return fuel flow to the tank.
The return fuel flow is controlled at the IDG oil cooler outlet by :
The fuel return valve has a shutoff function from the ENG/MASTER control switch digital signal (cockpit). The signal transits through the Arinc bus and ECU and overrides the engine "oil in" temperature command.
The return fuel flow is controlled at the IDG oil cooler outlet by :
- the engine oil temperature
- the fuel temperature
The fuel return valve has a shutoff function from the ENG/MASTER control switch digital signal (cockpit). The signal transits through the Arinc bus and ECU and overrides the engine "oil in" temperature command.
(2) The fuel return valve is located on the left side of the fan frame (aft loocking forward) beside the oil tank.
(a) The fuel return valve controls 2 flow levels :
1 The first level (approximately 660 pph or 300 kg/h) is controlled by the engine "oil in" temperature when higher than 190°F (88°C). The V1 solenoid valve is energized by the electronic control unit (ECU) (Ref. AMM D/O 73-20-00-00).
2 The second level (which adds approximately 660 pph or 300 kg/h to the first flow level) is controlled by the IDG oil cooler "fuel out" temperature when higher than 269°F (132°C). The V2 thermostatic valve is controlled by the "fuel out" temperature.
(b) The fuel return valve provides for return fuel temperature limitation.
When the hot fuel is at 260°F (127°C), the fuel return valve mixes :
When the hot fuel is at 260°F (127°C), the fuel return valve mixes :
- a cold fuel flow (from the engine LP fuel pump) with
- the hot fuel flow (calibrated to maintain a temperature of 214°F (100°C) in the return line.
1 440 pph (200 kg/h) cold flow with 600 pph (300 kg/h) hot flow.
2 880 pph (400 kg/h) cold flow with 1320 pph (600 kg/h) hot flow.
3 A signal from the ENG/MASTER control switch to FADEC permits to override the V1 opening signal if :
- engine oil temperature is higher than 200°F (93°C) during :
take off
climb
specific operating conditions (Ref. AMM D/O 73-20-00-00)
4 A hydraulic signal from the HP fuel shutoff valve closes the V1 valve at engine shutdown.
F. Burner Staging Valve
(1) General
The purpose of the Burner Staging Valve (BSV) is to deliver fuel to either all 20 fuel nozzles, or every other fuel nozzle (10 total) as commanded by the ECU. Fuel passes directly through the BSV manifold/mounting bracket to 10 fuel nozzles which are always on when the engine is in operation.
The purpose of the Burner Staging Valve (BSV) is to deliver fuel to either all 20 fuel nozzles, or every other fuel nozzle (10 total) as commanded by the ECU. Fuel passes directly through the BSV manifold/mounting bracket to 10 fuel nozzles which are always on when the engine is in operation.
(2) Description and Operation
The BSV is a poppet type shutoff valve that is opened or closed by fuel pressure (PC or PCR) from the HMU based on ECU logic. The main poppet valve allows metered fuel delivery to the staged manifold and under most conditions is set to the open (unstaged) position. A check valve inside the BSV overrides and/or holds the main poppet valve open to assure that all 20 fuel nozzles are used for takeoff or other high power operations when inlet pressure is high (when P22 reaches 200 to 300 psi). The burner staging valve stages on 10 nozzles when a lower Fuel Air Ratio (FAR) is required by the ECU. This ensures that there is adequate decel capability in the decel schedule. Dual switches in the BSV monitor the position of the valve and transmit a feedback indication to the ECU. The switches are open when the valve is open (unstaged).
After the ECU logic has determined that a lower FAR is required, the BSV is staged to 10 nozzles through the HMU BSV solenoid. If the ECU receives a valid signal from the BSV feedback switches that the BSV did stage, the ECU logic then lowers the FAR in the decel schedule to ensure a constant rate of engine deceleration. In operating conditions where a low FAR is required, the design of the fuel nozzles provides the necessary spray pattern to ensure that the engine will decel properly and that adequate flame out margin is maintained.
The BSV is a poppet type shutoff valve that is opened or closed by fuel pressure (PC or PCR) from the HMU based on ECU logic. The main poppet valve allows metered fuel delivery to the staged manifold and under most conditions is set to the open (unstaged) position. A check valve inside the BSV overrides and/or holds the main poppet valve open to assure that all 20 fuel nozzles are used for takeoff or other high power operations when inlet pressure is high (when P22 reaches 200 to 300 psi). The burner staging valve stages on 10 nozzles when a lower Fuel Air Ratio (FAR) is required by the ECU. This ensures that there is adequate decel capability in the decel schedule. Dual switches in the BSV monitor the position of the valve and transmit a feedback indication to the ECU. The switches are open when the valve is open (unstaged).
After the ECU logic has determined that a lower FAR is required, the BSV is staged to 10 nozzles through the HMU BSV solenoid. If the ECU receives a valid signal from the BSV feedback switches that the BSV did stage, the ECU logic then lowers the FAR in the decel schedule to ensure a constant rate of engine deceleration. In operating conditions where a low FAR is required, the design of the fuel nozzles provides the necessary spray pattern to ensure that the engine will decel properly and that adequate flame out margin is maintained.
G. Fuel Manifold
(1) General
The fuel manifold supplies metered fuel to the twenty fuel nozzles and drains any fuel that may leak from the fuel supply connection lines.
The fuel manifold supplies metered fuel to the twenty fuel nozzles and drains any fuel that may leak from the fuel supply connection lines.
(2) Description and Operation
The fuel manifold consists of a manifold supplying fuel to ten fuel nozzles that is unstaged or staged (depending on BSV position), a staged manifold that always supplies fuel to the remaining ten fuel nozzles when the engine is in operation, and a drain manifold. Fuel nozzles on the two fuel manifolds are located in an alternating pattern. Each manifold is divided into two segments joined by connecting nuts at the 6 and 12 o'clock positions.
The fuel supply manifold halves are connected to supply lines from the BSV at the 5 and 6 o'clock positions. Each of the connections has individual drain lines. This fuel supply splitting limits fuel pressure drop across lines and facilitates removal/installation operations.
A drain function is performed at each fuel nozzle connection by a shroud sealed by two o-rings. The shrouds are connected to the main drain manifold by fifteen integral and five removable drain lines. The five removable drain tubes are to facilitate access to borescope ports. A drain line connected to the aircraft drain mast is attached to the drain manifold at the 7 o'clock position.
The fuel manifold consists of a manifold supplying fuel to ten fuel nozzles that is unstaged or staged (depending on BSV position), a staged manifold that always supplies fuel to the remaining ten fuel nozzles when the engine is in operation, and a drain manifold. Fuel nozzles on the two fuel manifolds are located in an alternating pattern. Each manifold is divided into two segments joined by connecting nuts at the 6 and 12 o'clock positions.
The fuel supply manifold halves are connected to supply lines from the BSV at the 5 and 6 o'clock positions. Each of the connections has individual drain lines. This fuel supply splitting limits fuel pressure drop across lines and facilitates removal/installation operations.
A drain function is performed at each fuel nozzle connection by a shroud sealed by two o-rings. The shrouds are connected to the main drain manifold by fifteen integral and five removable drain lines. The five removable drain tubes are to facilitate access to borescope ports. A drain line connected to the aircraft drain mast is attached to the drain manifold at the 7 o'clock position.
H. Fuel Nozzle
(1) General
The fuel nozzles are installed into the combustion case assembly. They are connected to the fuel manifold assembly. The 20 fuel nozzles deliver fuel into the combustor in a spray pattern. This provides good light-off and efficient burning at high power.
Four of the 20 fuel nozzles (positions 7, 8 14 and 15) have a wider primary spray pattern to provide enhanced altitude relight reliability.
The fuel nozzles are installed into the combustion case assembly. They are connected to the fuel manifold assembly. The 20 fuel nozzles deliver fuel into the combustor in a spray pattern. This provides good light-off and efficient burning at high power.
Four of the 20 fuel nozzles (positions 7, 8 14 and 15) have a wider primary spray pattern to provide enhanced altitude relight reliability.
(2) Operation
The fuel nozzles contain both primary and secondary fuel flow passages.
As the engine is started :
This fuel passes through the secondary passage of the nozzle tube and tip.
Then it enters the combustion chamber as an uniform density, cone shaped spray. The cone of the secondary spray is wider than that of the primary, therefore, surrounding the primary spray pattern.
The fuel nozzles contain both primary and secondary fuel flow passages.
As the engine is started :
- the fuel passes through the inlet, and
- accumulates in the portion of nozzle that houses the valves.
- is directed through the check valve
- passes through the primary passage of the nozzle tube and tip,
- enters the combustion chamber as an uniform density spray
This fuel passes through the secondary passage of the nozzle tube and tip.
Then it enters the combustion chamber as an uniform density, cone shaped spray. The cone of the secondary spray is wider than that of the primary, therefore, surrounding the primary spray pattern.
(1) General
The fuel nozzle filter is located just before the injectors. It protects the injectors from particles in suspension in the fuel.
The fuel nozzle filter is located just before the injectors. It protects the injectors from particles in suspension in the fuel.
(2) Functional description
The fuel nozzle filter consists of a filter element and a by-pass valve. The filter element has a filtering capability of 300 microns absolute.
In case of a clogged filter element, the valve by-passes the fuel to the injectors.
The fuel nozzle filter consists of a filter element and a by-pass valve. The filter element has a filtering capability of 300 microns absolute.
In case of a clogged filter element, the valve by-passes the fuel to the injectors.