Overview
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Introduction
Principle
Working
Features
Scope for further development
Conclusion
Introduction
 The country among other things has
seen an enormous development in
engines used in cars also.
 The Diesel engines have also
undergone a sea change from the
time Rudolf Diesel invented it way
back in 1892.
 Today Common Rail Direct Injection
(CRDI) is the order of the day.
CRDI Engine
Principle
 Unlike in conventional diesel engines,
the fuel is fed into the common tube or
rail and high pressure is maintained.
 This allows fuel to combine with air
much more efficiently.
 It features high-pressure fuel rail
feeding individual solenoid valves as
opposed to low-pressure fuel pump
feeding injectors.
Layout of a CRDI Engine
The Common Rail Sub functions
 Low –pressure circuit comprises of:
Fuel tank ,Pre-supply pump, Fuel filter, And the
respective connection lines.
Low –pressure circuit
The low –pressure circuit is responsible for
transporting the fuel to the high –pressure
circuit
The Common Rail Sub functions
High –pressure circuit comprises:
 High – pressure pump with pressure – control
valve
 The high – pressure accumulator (Rail )with the
rail –pressure sensor
 Injectors, and
 The respective high – pressure connection lines.
The high – pressure circuit
It is the responsibility of the high
pressure circuit to generate a
constant
unvarying high pressure in the high
pressure accumulator (the rail) and
to
inject the fuel through the injectors
into
the engine’s combustion chambers.
The Common Rail Sub functions
ECU and sensors
The common rail ECU evaluates the signals from
the following sensors.
Crankshaft – speed sensor, Camshaft sensor,
Accelerator-pedal travel sensor
The Common Rail Sub functions
The common rail ECU evaluates the signals from
the following sensors:
Boost – pressure sensor, Air temperature
sensor,
Air – mass meter,
and
Rail pressure
sensor.
The Common Rail Sub functions
ECU and sensors
The sensor are responsible for measuring
important physical quantities. The ECU
calculates injected fuel quantity, start of
injection, duration of injection, and rate of
discharge curve, as well supervises the correct
functioning of the injection system as a whole.
COMMON RAIL FUEL INJECTION SYSTEM
DESIGN
PRE SUPPLY PUMP
 Transports fuel from the fuel tank to the high
pressure pump.
 An electric fuel pump is used for this purpose
in the CRFIS.
 When the electric fuel pump is switched off,
the supply of fuel is interrupted and the engine
stops.
PRE SUPPLY PUMP
The electric fuel pump comprises of:
1.Electric Motor
2.Roller-Cell Pump
3.Non Return Valve
PRE SUPPLY PUMP
 The roller cell is
driven by an
electric motor.
 Its rotor is
mounted
eccentrically and
provided with
slots in which
movable rollers
are free to
PRE SUPPLY PUMP
 The rollers are
forced against the
base plate by
rotation and by
fuel pressure .
 The fuel is
transported to the
outlet openings on
the pump’s
PRE SUPPLY PUMP
variants
 Gear type fuel
pump
 The drive gear wheel
is driven by the
engine .
 Delivery quantity is
directly proportional
to engine speed .
 Shut off is by means
of an electromagnet..
High- pressure pump
 The pump plunger moves downwards
 The inlet valve opens
 The fuel is drawn in to the pumping
element chamber(suction stroke)
High- pressure pump
 At BDC, the inlet valve closes
 The fuel in the chamber can be
compressed by the upward moving
plunger.
High- pressure pump
 An electromagnet
is used for
pumping element
switch-off.
High- pressure accumulator (Rail)
 Store fuel
 Prevent pressure fluctuations
High- pressure accumulator (Rail)
 Rail is a forged-steel tube.
 ID is approx.. 10mm
 Length is between 280 and 600mm
The volume must be “ as small as
possible, as large as necessary”
Pressure-control valve (DRV)
 Responsible
for
maintaining
the pressure
in the rail at
a constant
level.
Rail-pressure sensor (RDS)
 Measures the
pressure in the
rail
 inputs the
information to the
ECU
 RDS should provide
extremely precise
measured values.
 RDS is mounted
directly on the rail.
Injector
 Injects exactly the correct amount of
fuel in to the combustion chamber at
precisely the right moment in time
Injector
The injector is equipped with:
 2/2 electromagnetic servo
valve
 Nozzle
 Valve control chamber
 Return line
Injector
The essential forces for correct functioning
are:
 Nozzle-spring force
 Valve spring force
 Electromagnet force
 Force due to the pressure in the valvecontrol chamber
 Force due to the pressure in the nozzle
needle
ECU with sensors
 Common Rail is an EDC controlled
injection system
 The ECU controls & monitors the
complete injection process
 The sensors delivers all the measured
values which are required in the process
COMMON RAIL FUEL INJECTION SYSTEM
Summary
Components of CRFIS
are:
 Pre-supply pump
 High-pressure pump
 High-pressure
accumulator(rail)
 Pressure-control
valve
 Rail-pressure sensor
 Injectors
 ECU with sensors
Working
 Solenoid valves make possible fine
electronic control over the injection time
and amount, and the higher pressure
that the common rail technology makes
available provides better fuel
atomization. In order to lower engine
noise, the engine's electronic control
unit can inject a small amount of diesel
just before the main injection event
("pilot" injection), thus reducing its
explosiveness and vibration, as well as
optimizing injection timing and the
process continues
Features
Direct injector
Spiral-shaped intake port
Integrated port
Air flow metering
Multiple Pilot injection and
Post injection
 Powerful Microcomputer
 Newly-developed catalytic
converters
 Reduced noise levels
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Direct injector
A fuel injector is
nothing but an
electronically
controlled valve.
Spiral-shaped Intake port
Provides optimum
swirl and even
distribution of fuel.
Integrated port
Integrated port is used for exhaust gas
recycling. There are three advantages
to this system
• eliminates external pipes which are
subject to vibration
• quicker engine warm-up
• better combustion.
Air flow metering
 It gives exact analysis of the air-mass
that is being taken in.
 Due to this metering system, the
microcomputer that controls engine
timing receives precise data.
Multiple Pilot injection and
Post injection
 Pilot injections is small doses of fuel
made prior to the main injection which
help to smoothen the sharp combustion
character.
 Post injection is a similarly small dose of
fuel injected after the main injection to
reduce particulates.
Powerful Microcomputer
 The microcomputer regulates the
amount of time the valves stay open
and thus the amount of fuel injected,
depending on operating conditions and
how much output is needed.
Newly-developed catalytic
converters
 Besides electronically-controlled
exhaust-gas recycling which contributes
to lower nitrous oxide emissions, CRDI
engines are equipped with catalytic
converters near the motor and emission
control devices on the underbody. These
vouch for a high degree of efficiency.
Reduced Noise levels
 The Electronic control and multiple
injections reduced noise to a great
extent
Scope for further
development
 Use of different fuels for zero
emissions and better engine
performance
 By using different fuels and cetane
improvers, maximum torque can be
obtained
 Lowering the cost
 Closed-loop control injection with ion
sensing technology
Conclusion
CRDI technology revolutionized diesel
engines. It has changed the way one
looks as diesel cars by providing the
above said advantages.
Advantages
-More power is developed
-Increased fuel efficiency
-More stability
-Pollutants are reduced
-Particulates of exhaust are reduced
-Exhaust gas recirculation is enhanced
-Precise injection timing is obtained
-Pilot and post injection increase the
combustion quality
-The powerful microcomputer makes the
whole system more perfect
Manufacturers of CRDI engine
The car makers refer to their common
rail engines by their own brand
names. Some of them are
BMW's D-engines
Mahindra's CRDe
Tata's DICOR
Honda's i-CTDi
Hyundai-Kia's CRDi etc
References
 International Journal of Automotive
Technology
 Approaches to Automotive Emissions
Control
 Magazines: Auto week, Automobile India