COMMON RAIL FUEL INJECTION COMMON RAIL FUEL INJECTION SYSTEMSYSTEM

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Demand On Modern Diesel Engine Demand On Modern Diesel Engine Development Development

Low fuel consumptionLow fuel consumption

Low pollutant emissionsLow pollutant emissions

Quiet running enginesQuiet running engines

Improved engine performanceImproved engine performance

Common rail fuel injection system and its Common rail fuel injection system and its functionfunction

Provide the diesel engine with fuelProvide the diesel engine with fuel Generate the high pressure needed for fuel Generate the high pressure needed for fuel

injection and distribute the fuel to the injection and distribute the fuel to the

individual cylindersindividual cylinders Inject precisely correct amount of fuel at Inject precisely correct amount of fuel at

exactly the right moment in time.exactly the right moment in time. In contrast to other injection system Common In contrast to other injection system Common

rail fuel injection system is an accumulator rail fuel injection system is an accumulator injection system.injection system.

How does a CR system function?How does a CR system function?

Sub functions of a CRFI system

Low pressure c ircuit H igh pressure c ircuit ECU w ith sensors

COM M ON RAIL FUEL INJECTION SYSTEM

Low –pressure circuit comprises of:Low –pressure circuit comprises of:Fuel tank ,Pre-supply pump, Fuel filter, And the Fuel tank ,Pre-supply pump, Fuel filter, And the

respective connection lines.respective connection lines.

The Common Rail Sub functionsThe Common Rail Sub functions

Low –pressure circuitLow –pressure circuit

The low –pressure circuit is responsible for The low –pressure circuit is responsible for transporting the fuel to the high –pressure circuittransporting the fuel to the high –pressure circuit

High –pressure circuit comprises:High –pressure circuit comprises:

High – pressure pump with pressure – control valve High – pressure pump with pressure – control valve

The high – pressure accumulator (Rail )with the rail –The high – pressure accumulator (Rail )with the rail –pressure sensorpressure sensor

Injectors, and Injectors, and

The respective high – pressure connection lines.The respective high – pressure connection lines.

The Common Rail Sub functionsThe Common Rail Sub functions

The high – pressure circuitThe high – pressure circuit

It is the responsibility of the highIt is the responsibility of the high

pressure circuit to generate a constantpressure circuit to generate a constant

unvarying high pressure in the highunvarying high pressure in the high

pressure accumulator (the rail) and topressure accumulator (the rail) and to

inject the fuel through the injectors intoinject the fuel through the injectors into

the engine’s combustion chambers.the engine’s combustion chambers.

ECU and sensorsECU and sensorsThe common rail ECU evaluates the signals from the The common rail ECU evaluates the signals from the

following sensors.following sensors. Crankshaft – speed sensor, Camshaft sensor,Crankshaft – speed sensor, Camshaft sensor, Accelerator-pedal travel sensorAccelerator-pedal travel sensor

The Common Rail Sub functionsThe Common Rail Sub functions

The common rail ECU evaluates the signals from the The common rail ECU evaluates the signals from the following sensors:following sensors:

Boost – pressure sensor, Air temperature sensor,Boost – pressure sensor, Air temperature sensor,

Air – mass meter, and Rail pressure sensor.Air – mass meter, and Rail pressure sensor.

The Common Rail Sub functionsThe Common Rail Sub functions

The Common Rail Sub functionsThe Common Rail Sub functions

ECU and sensorsECU and sensors

The sensor are responsible for measuring important The sensor are responsible for measuring important physical quantities. The ECU calculates injected fuel physical quantities. The ECU calculates injected fuel quantity, start of injection, duration of injection, and quantity, start of injection, duration of injection, and rate of discharge curve, as well supervises the correct rate of discharge curve, as well supervises the correct functioning of the injection system as a whole.functioning of the injection system as a whole.

PRE SUPPLY PUMPPRE SUPPLY PUMP

Transports fuel from the fuel tank to the high pressure Transports fuel from the fuel tank to the high pressure pump.pump.

An electric fuel pump is used for this purpose in the An electric fuel pump is used for this purpose in the CRFIS.CRFIS.

When the electric fuel pump is switched off, the supply When the electric fuel pump is switched off, the supply of fuel is interrupted and the engine stops.of fuel is interrupted and the engine stops.

COMMON RAIL FUEL INJECTION SYSTEMCOMMON RAIL FUEL INJECTION SYSTEM

DESIGNDESIGN

PRE SUPPLY PUMPPRE SUPPLY PUMP

The electric fuel pump comprises of:The electric fuel pump comprises of:

1.Electric Motor1.Electric Motor

2.Roller-Cell Pump2.Roller-Cell Pump

3.Non Return Valve3.Non Return Valve

The roller cell is The roller cell is driven by an electric driven by an electric motor.motor.

Its rotor is mounted Its rotor is mounted eccentrically and eccentrically and provided with slots provided with slots in which movable in which movable rollers are free to rollers are free to travel.travel.

PRE SUPPLY PUMPPRE SUPPLY PUMP

The rollers are forced The rollers are forced against the base plate against the base plate by rotation and by fuel by rotation and by fuel pressure .pressure .

The fuel is The fuel is transported to the transported to the outlet openings on the outlet openings on the pump’s pressure side.pump’s pressure side.

PRE SUPPLY PUMPPRE SUPPLY PUMP

Gear type fuel pumpGear type fuel pump The drive gear The drive gear

wheel is driven by wheel is driven by the engine .the engine .

Delivery quantity is Delivery quantity is directly directly proportional to proportional to engine speed .engine speed .

Shut off is by means Shut off is by means of an of an electromagnet..electromagnet..

PRE SUPPLY PUMPPRE SUPPLY PUMPvariantsvariants

High- pressure pumpHigh- pressure pump

The pump plunger moves downwards The pump plunger moves downwards The inlet valve opens The inlet valve opens The fuel is drawn in to the pumping element The fuel is drawn in to the pumping element

chamber(suction stroke)chamber(suction stroke)

At BDC, the inlet valve closes At BDC, the inlet valve closes The fuel in the chamber can be compressed by The fuel in the chamber can be compressed by

the upward moving plunger.the upward moving plunger.

High- pressure pumpHigh- pressure pump

An electromagnet is An electromagnet is used for pumping used for pumping element switch-off.element switch-off.

High- pressure pumpHigh- pressure pump

High- pressure accumulator (Rail)High- pressure accumulator (Rail)Store fuelStore fuel

Prevent pressure fluctuationsPrevent pressure fluctuations

Rail is a forged-steel tube.Rail is a forged-steel tube.

ID is approx.. 10mmID is approx.. 10mm

Length is between 280 and 600mmLength is between 280 and 600mm

The volume must be “ as small as The volume must be “ as small as possible, as large as necessary”possible, as large as necessary”

High- pressure accumulator (Rail)High- pressure accumulator (Rail)

Pressure-control valve (DRV)Pressure-control valve (DRV)

Responsible for Responsible for maintaining the maintaining the pressure in the pressure in the rail at a rail at a constant level.constant level.

Rail-pressure sensor (RDS)Rail-pressure sensor (RDS)

Measures the Measures the pressure in the railpressure in the rail

inputs the information inputs the information to the ECUto the ECU

RDS should RDS should provide provide extremely extremely precise precise measured measured values.values.

RDS is mounted RDS is mounted directly on the directly on the rail.rail.

InjectorInjectorInjects exactly the correct amount of fuel in Injects exactly the correct amount of fuel in to the combustion chamber at precisely to the combustion chamber at precisely the right moment in timethe right moment in time

The injector is equipped with:The injector is equipped with:

2/2 electromagnetic servo valve2/2 electromagnetic servo valve

NozzleNozzle

Valve control chamberValve control chamber

Return lineReturn line

InjectorInjector

The essential forces for correct functioning are:The essential forces for correct functioning are: Nozzle-spring forceNozzle-spring force Valve spring forceValve spring force Electromagnet forceElectromagnet force Force due to the pressure in the valve-control Force due to the pressure in the valve-control

chamber chamber Force due to the pressure in the nozzle needleForce due to the pressure in the nozzle needle

InjectorInjector

ECU with sensorsECU with sensors

Common Rail is an EDC controlled injection Common Rail is an EDC controlled injection systemsystem

The ECU controls & monitors the complete The ECU controls & monitors the complete injection processinjection process

The sensors delivers all the measured values The sensors delivers all the measured values which are required in the processwhich are required in the process

Summary

Components of CRFIS are:Components of CRFIS are: Pre-supply pumpPre-supply pump High-pressure High-pressure

pumppump High-pressure High-pressure

accumulator(rail)accumulator(rail) Pressure-control Pressure-control valvevalve

Rail-pressure Rail-pressure sensorsensor

InjectorsInjectors

ECU with sensorsECU with sensors

COMMON RAIL FUEL INJECTION COMMON RAIL FUEL INJECTION SYSTEMSYSTEM

COMMON RAIL FUEL INJECTION SYSTEMCOMMON RAIL FUEL INJECTION SYSTEM

SUMMARSUMMAR1.The basic functional groups of the common rail are : low 1.The basic functional groups of the common rail are : low

– pressure circuit , high – pressure circuit ECU and – pressure circuit , high – pressure circuit ECU and sensors.sensors.

2.In the low – pressure circuit, the fuel is cleaned by a filter 2.In the low – pressure circuit, the fuel is cleaned by a filter and then transported to the high – pressure circuitand then transported to the high – pressure circuit

COMMON RAIL FUEL INJECTION SYSTEMCOMMON RAIL FUEL INJECTION SYSTEM

SUMMARYSUMMARY3.In the high – pressure circuit , the maximum 3.In the high – pressure circuit , the maximum

pressure of 1,350 bar is generated in the high – pressure of 1,350 bar is generated in the high – pressure accumulator (Rail).pressure accumulator (Rail).

The pressure is maintained at a constant The pressure is maintained at a constant level , and the fuel is taken from the rail every level , and the fuel is taken from the rail every time an injection takes place.time an injection takes place.

4.The ECU controls and monitors the complete 4.The ECU controls and monitors the complete injection system. Using the signals from the injection system. Using the signals from the sensors, the ECU calculates all the values for sensors, the ECU calculates all the values for the injection process and triggers the the injection process and triggers the components in high-pressure circuit (pressure – components in high-pressure circuit (pressure – control valve, injectors). control valve, injectors).