PAGE CRDi System
ABSTRACT
Compared with petrol, diesel is the lower quality product of
petroleum family. Diesel particles are larger and heavier than
petrol, thus more difficult to pulverize. Imperfect pulverization
leads to more unburnt particles, hence more pollutant, lower fuel
efficiency
and less power.
Common-rail technology is intended to improve the pulverization
process. Conventional direct injection diesel engines must
repeatedly generate fuel pressure for each injection. But in the
CRDI engines the pressure is built up independently of the
injection sequence and remains permanently available in the fuel
line. CRDI system that uses an ion sensor to provide real-time
combustion data for each cylinder. The common rail upstream of the
cylinders acts as an accumulator, distributing the fuel to the
injectors at a constant pressure of up to 1600 bar. Here high-speed
solenoid valves, regulated by the electronic engine management,
separately control the injection timing and the amount of fuel
injected for each cylinder as a function of the cylinder's actual
need.
In other words, pressure generation and fuel injection are
independent of each other. This is an important advantage of
common-rail injection over conventional fuel injection systems as
CRDI increases the controllability of the individual injection
processes and further refines fuel atomization, saving fuel and
reducing emissions. Fuel economy of 25 to 35 % is obtained over a
standard diesel engine and a substantial noise reduction is
achieved due to a more synchronized timing operation. The principle
of CRDi is also used in petrol engines as dealt with the GDI
(Gasoline Direct Injection) , which removes to a great extent the
draw backs of the conventional carburetors and the MPFI
systems.
1.INTRODUCTION CRDi stands for Common Rail Direct Injection
meaning, direct injection of the fuel into the cylinders of a
diesel engine via a single, common line, called the common rail
which is connected to all the fuel injectors.Whereas ordinary
diesel direct fuel-injection systems have to build up pressure anew
for each and every injection cycle, the new common rail (line)
engines maintain constant pressure regardless of the injection
sequence. This pressure then remains permanently available
throughout the fuel line. The engine's electronic timing regulates
injection pressure according to engine speed and load. The
electronic control unit (ECU) modifies injection pressure precisely
and as needed, based on data obtained from sensors on the cam and
crankshafts. In other words, compression and injection occur
independently of each other. This technique allows fuel to be
injected as needed, saving fuel and lowering emissions.
Fig. 1More accurately measured and timed mixture spray in the
combustion chamber significantly reducing unburned fuel gives CRDi
the potential to meet future emission guidelines such as Euro V.
CRDi engines are now being used in almost all Mercedes-Benz,
Toyota, Hyundai, Ford and many other diesel automobiles. 2.
PRINCIPLE OF CRDi IN GASOLINE ENGINES.Gasoline or petrol engines
were using carburetors for supply of air-fuel mixture before the
introduction of MPFI system .but even now carburetors are in use
for its simplicity and low cost. Now a days the new technology
named Gasoline Direct Injection (GDI) is in use for petrol engines.
The GDI is using the principle of CRDi system. Now let us examine
the various factors that lead to introduction of GDI technology.
2.1.The fall of carburettor.
For most of the existence of the internal combustion engine, the
carburetor has been the device that supplied fuel to the engine. On
many other machines, such as lawnmowers and chainsaws, it still is.
But as the automobile evolved, the carburetor got more and more
complicated trying to handle all of the operating requirements. For
instance, to handle some of these tasks, carburetors had five
different circuits:
2.1.1 : Main circuit Provides just enough fuel for
fuel-efficient cruising
2.1.2 : Idle circuit Provides just enough fuel to keep the
engine idling
2.1.3 : Accelerator pump Provides an extra burst of fuel when
the accelerator pedal is first depressed, reducing hesitation
before the engine speeds up
2.1.4 : Power enrichmentProvides extra fuel when the car is
going up a hill or
circuit towing a trailer
2.1.5 : ChokeProvides extra fuel when the engine is cold so that
it will start effortlessly
In order to meet stricter emissions requirements, catalytic
converters were introduced. Very careful control of the air-to-fuel
ratio was required for the catalytic converter to be effective.
Oxygen sensors monitor the amount of oxygen in the exhaust, and the
engine control unit (ECU) uses this information to adjust the
air-to-fuel ratio in real-time. This is called closed loop
controlit was not feasible to achieve this control with
carburetors. There was a brief period of electrically controlled
carburetors before fuel injection systems took over, but these
electrical carburetors were even more complicated than the purely
mechanical ones.
At first, carburetors were replaced with throttle body fuel
injection systems (also known as single point or central fuel
injection systems) that incorporated electrically controlled
fuel-injector valves into the throttle body. These were almost a
bolt-in replacement for the carburetor, so the automakers didn't
have to make any drastic changes to their engine designs.
Gradually, as new engines were designed, throttle body fuel
injection was replaced by multi-port fuel injection (also known as
port, multi-point or sequential fuel injection). These systems have
a fuel injector for each cylinder, usually located so that they
spray right at the intake valve. These systems provide more
accurate fuel metering and quicker response.3.DIRECT INJECTION
SYSTEMS.Direct injection means injecting the fuel directly into the
cylinder instead of premixing it with air in separate intake ports.
That allows for controlling combustion and emissions more
precisely, but demands advanced enginemanagement technologies.
Fig. 3.1Unlike petrol engines, diesel engines dont need ignition
system. Due to the inherent property of diesel, combustion will be
automatically effective under a certain pressure and temperature
combination during the compression phase of Otto cycle. Normally
this requires a high compression ratio around 22 : 1 for normally
aspirated engines. A strong thus heavy block and head is required
to cope with the pressure. Therefore diesel engines are always much
heavier than petrol equivalent.
The lack of ignition system simplifies repair and maintenance,
the absence of throttle also help. The output of a diesel engine is
controlled simply by the amount of fuel injected. This makes the
injection system very decisive to fuel economy. Even without direct
injection, diesel inherently delivers superior fuel economy because
of leaner mixture of fuel and air. Unlike petrol, it can combust
under very lean mixture. This inevitably reduces power output but
under light load or partial load where power is not much an
important consideration, its superior fuel economy shines. Another
explanation for the inferior power output is the extra high
compression ratio. On one hand the high pressure and the heavy
pistons prevent it from revving as high as petrol engine (most
diesel engine deliver peak power at lower than 4500 rpm.), on the
other hand the long stroke dimension required by high compression
ratio favors torque instead of power. This is why diesel engines
always low on power but strong on torque.
Fig. 3.2To solve this problem, diesel makers prefer to add
turbocharger. It is a device to input extra air into the cylinder
while intake to boost up the power output of the engine.
Turbochargers top end power suits the torque curve of diesel very
much, unlike petrol. Therefore turbocharged diesel engines output
similar power to a petrol engine with similar capacity, while
delivering superior low end torque and fuel economy.4.COMMON RAIL
DIRECT INJECTION: FEATURES:
Fig4.1Simply explained, common rail refers to the single fuel
injection line on the CRDi engines. Whereas conventional direct
injection diesel engines must repeatedly generate fuel pressure for
each injection, in CRDi engines the pressure is built up
independently of the injection sequence and remains permanently
available in the fuel line.
In the CRDi system developed jointly by Mercedes-Benz and Bosch,
the electronic engine management system continually adjusts the
peak fuel pressure according to engine speed and throttle position.
Sensor data from the camshaft and crankshaft provide the foundation
for the electronic control unit to adapt the injection pressure
precisely to demand.
Common Rail Direct Injection is different from the conventional
Diesel engines. Without being introduced to an antechamber the fuel
is supplied directly to a common rail from where it is injected
directly onto the pistons which ensures the onset of the combustion
in
the whole fuel mixture at the same time. There is no glow plug
since the injection pressure is high. The fact that there is no
glow plug lowers the maintenance costs and the fuel
consumption.
Compared with petrol, diesel is the lower quality fuel from
petroleum family. Diesel particles are larger and heavier than
petrol, thus more difficult to pulverize. Imperfect pulverization
leads to more unburned particles, hence more pollutant, lower fuel
efficiency and less power. Common-rail technology is intended to
improve the pulverization process.
To improve pulverization, the fuel must be injected at a very
high pressure, so high that normal fuel injectors cannot achieve
it.
In common-rail system, the fuel pressure is implemented by a
very strong pump instead of fuel injectors. The high-pressure fuel
is fed to individual fuel injectors via a common rigid pipe (hence
the name of "common-rail").
In the current first generation design, the pipe withstands
pressures as high as 1,600 bar or 20,000 psi. Fuel always remains
under such pressure even in stand-by state. Therefore whenever the
injector (which acts as a valve rather than a pressure generator)
opens, the high-pressure fuel can be injected into combustion
chamber quickly. As a result, not only pulverization is improved by
the higher fuel pressure, but the duration of fuel injection can be
shortened and the timing can be more precisely controlled. Precise
timing reduces the characteristic Diesel Knock common to all diesel
engines, direct injection or not.
Benefited by the precise timing, common-rail injection system
can introduce a "post-combustion", which injects small amount of
fuel during the expansion phase thus creating small scale
combustion after the normal combustion takes place. This further
eliminates the unburned particles and also increases the exhaust
flow temperature thus reducing the pre-heat time of the catalytic
converter. In short, "post-combustion" cuts pollutants. The drive
torque and pulsation inside the high-pressure lines are minimal,
since the pump supplies only as much fuel as the engine actually
requires. The high-pressure injectors are available with different
nozzles for different spray configurations. Swirler nozzle to
produce a cone-shaped spray and a slit nozzle for a fan-shaped
spray.
Fig 4.2The new common-rail engine (in addition to other
improvements) cuts fuel consumption by 20%, doubles torque at low
engine speeds and increases power by 25%. It also brings a
significant reduction in the noise and vibrations of conventional
diesel engines. In emission, greenhouse gases (CO2) is reduced by
20%. At a constant level of NOx, carbon monoxide (CO) emissions are
reduced by 40%, unburnt hydrocarbons (HC) by 50%, and particle
emissions by 60%.
CRDI principle not only lowers fuel consumption and emissions
possible; it also offers improved comfort and is quieter than
modern pre-combustion engines. Common-rail engines are thus clearly
superior to ordinary motors using either direct or indirect
fuel-injection systems.
This division of labor necessitates a special chamber to
maintain the high injection pressure of up to 1,600 bar. That is
where the common fuel line (rail) comes in. It is connected to the
injection nozzles (injectors) at the end of which are rapid
solenoid valves to take care of the timing and amount of the
injection.
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. When the timing shuts the
solenoid valves, fuel injection ends immediately.
With the state-of-the-art common-rail direct fuel injection used
an ideal compromise can be attained between economy, torque, ride
comfort and long life.
4.1The Injector:A fuel injector is nothing but an electronically
controlled valve. It is supplied with pressurized fuel by the fuel
pump, and it is capable of opening and closing many times per
second. When the injector is energized, an electromagnet moves a
plunger that opens the valve, allowing the pressurized fuel to
squirt out through a tiny nozzle. The nozzle is designed to atomize
the fuel -- to make as fine a mist as possible so that it can burn
easily. The amount of fuel supplied to the engine is determined by
the amount of time the fuel injector stays open. This is called the
pulse width, and it is controlled by the ECU. The injectors are
mounted in the intake manifold so that they spray fuel directly at
the intake valves. A pipe called the fuel rail supplies pressurized
fuel to all of the injectors. Each injector is complete and
self-contained with nozzle, hydraulic intensifier, and electronic
digital valve. At the end of each injector, a rapid-acting solenoid
valve adjusts both the injection timing and the amount of fuel
injected. A microcomputer controls each valve's opening and closing
sequence.
valve
Fig 4.1.14.2 Spiral-Shaped Intake Port For Optimum Swirl: The
aluminum cylinder head for the CRDI engines is a new development.
Among its distinguishing features are two spiral-shaped intake
ports. One serves as a swirl port while the other serves as a
charge port. Both ports are paired with the symmetrical combustion
chamber, rapidly swirling the intake air before it enters the
cylinders. The result is an optimum mixture, especially under
partial throttle. The newly-designed injector nozzles (injectors)
located in the middle of the cylinders provide for even
distribution of fuel inside the combustion chambers
4.3 Integrated Port For Exhaust Gas Recycling:Another novelty is
the integrated port for exhaust gas recycling (EGR) in the cylinder
head. Whereas older diesel engines lead exhaust gases outside
around the engine the new CRDi engines are incorporated with a cast
port for the direct injection motor which conducts the gases within
the cylinder head itself. The exhaust gases recirculate directly
from the exhaust side to the intake side. There are three
advantages to this system. For one, it eliminates external pipes
which are subject to vibration. Then, integrating EGR into the
cylinder head means that part of the exhaust heat is transferred to
the coolant, resulting in quicker engine warm-up. Finally, this new
technique allows cooler exhaust gases and that means better
combustion.
4.4 Precise Timing Courtesy Air Flow Metering:The hot-film mass
air-flow meter is located in front of the turbocharger's compressor
permitting an exact analysis of the air-mass that is being taken
in. This mass will alter depending on temperature or atmospheric
pressure. Due to this metering system, the microcomputer that
controls engine timing receives precise data. It is thus able to
regulate exhaust-gas recycling according to engine load and speed
in the interest of lowering nitrous oxide and particle
emissions.
The compressed air from the turbocharger then flows through the
intercooler which cools it down to 70 degrees centigrade. Since
cool air has less volume than warm air, more air is taken inside
the combustion chamber, thus amplifying the effect of the
turbocharger. In the subordinate mixing chamber, fresh air and
exhaust gas mingle in a computer-determined ratio to match engine
load at the moment. The mixing chamber is outfitted with a special
exhaust-gas recycling valve and a butterfly valve controlled by a
electro-pneumatic converter. The throttle increases the pressure
gradient between the intake and outlet sides, thus increasing the
recycled exhaust gases' effect on performance
4.5 Swirl-Control Valves In The Intake Manifolds:Pneumatically
guided swirl valves in the intake system help bring the fuel-air
mixture to a high swirl rate at low rpm. This leads to efficient
combustion and high torque. At high rpm the swirl is reduced and
this in turn improves power output.
On the way to the combustion chambers the compressed fresh air
mixed with exhaust gases passes through swing manifolds. The intake
area just before the cylinder head is single-channel, later
becoming dual-channel. These two channels have different tasks. One
acts as a spiral channel, swirling the mixture while the other
serves as a charge channel which closes with the aid of
electro-pneumatically activated valves under partial-load
operation. The advantage of this arrangement is that de-energizing
increases the rate of swirl in the cylinders so that combustion
produces less particle emissions than older direct-injection
engines.
4.6 Multiple Pilot Injection And Post Injection:The high
combustion pressure of up to 145 bar (2130 psi) and the rate at
which this pressure rises during the combustion process normally
produce higher noise levels in direct injection engines than in
their pre-chamber (indirect injection) counterparts. However, the
CRDi system employs a piece of technical wizardry known as pilot
injection' to overcome this problem: A few nanoseconds before the
main fuel injection, a small amount of diesel is injected into the
cylinder and ignites, thereby establishing the combustion process
and setting the ideal conditions for the main combustion process.
Consequently, the fuel ignites faster with the result that the rise
in pressure and temperature is less sudden.
The system utilizes multiple pilot injections - small doses of
fuel made prior to the main injection of fuel in each cylinder's
firing, which help to smooth the sharp combustion character of the
diesel engine to gasoline-like smoothness. The end effect, however,
is not only a reduction in combustion noise but also a reduction in
nitrogen oxide (NOx) emissions.
Post injection is a similarly small dose of fuel injected after
the main injection. Common rail technology's potential to lower
particulate emissions is profound in this area. The small post
injection is inserted with precise timing at the moment that is
ideal for lower particulate discharge.
Other methods to reduce noise are providing special cover for
the cylinder head and the intercooler, and bracing on the oil pan,
the timing-gear case and crankcase. The bottom line is that the
noise produced by the new CRDI engines is lower than for comparable
pre-combustion engines.
4.7 Powerful Microcomputer:The new direct-injection motors are
regulated by a powerful microcomputer linked via CAN (Controller
Area Network) data bus to other control devices on board. These
devices exchange data. The engine's electrical controls are a
central element of the common rail system because regulation of
injection pressure and control of the solenoid valves for each
cylinder - both indispensable for variable control of the motor -
would be unthinkable without them.
This electronic engine management network is a critical element
of the common rail system because only the speed and spontaneity of
electronics can ensure immediate pressure injection adjustment and
cylinder-specific control of the injector solenoid valves.4.8
Newly-Developed Catalytic Converters With Zeolith Coating: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.
Emissions conform for the German "D3" norms which are 50 percent
tighter than the maximum values prescribed in the EURO-2
guidelines. A new coating for the catalytic converters consisting
of platinum, aluminum oxide and Zeolith crystals has been devised
that besides oxidizing hydrocarbons and carbon monoxide, also
converters diminish nitrous oxide. The converter near the engine is
equipped with a bypass channel via which a residual amount of
hydrocarbons are passed on to the emission control devices on the
underbody.
4.9 High Rigidity Cylinder Block And Dual Mass FlywheelTo
complement the new-generation common-rail system's unprecedented
smoothness and low noise several enhancements have been added to
its structure. Cylinder- block rigidity is increased by ribs in the
water jacket and the crankshaft bearing cap is integrated into the
lower block to greatly reduce engine vibration. A dual-mass
flywheel is fitted to the engines to compensate for the harmonic
effect of diesel engine on the powertrain elements, eliminating the
characteristic rattle often associated with diesels.
4.10 Unique Intake And Exhaust Ports:The CRDi engine uses an
aluminium cylinder head with two spiral intake ports, one for
swirling the fuel/air mixture and the other for filling the
combustion chamber.
Both ports are tuned to the symmetrically shaped combustion
chambers and are designed to set the air into rapid swirling motion
even before it reaches the cylinders. This ensures an optimal
fuel/air mixture, especially in the part throttle range.
Inside the combustion chambers, newly developed injectors are
positioned in the middle of the cylinder to promote uniform fuel
distribution.
Another new feature of the CRDi engine is the integration of a
port in the cylinder head for the exhaust gas recirculation (EGR)
system. In most diesel engines this system is routed around the
outside of the engine but in the CRDI system an EGR port has been
cast into the cylinder head to channel gas from the exhaust side of
the engine to the intake side.
This design has three distinct benefits: It dispenses with
external EGR lines, transfers exhaust heat to the coolant for
quicker engine warm-up, and at the same time cools exhaust gases to
further enhance combustion.4.11 Reduced Noise Levels:Diesel engines
are known to be noisy. But the introduction of the CRDi engines has
made many attributes of the old Diesel engines have become
something of the past. One of these is noise. The noisy side of the
old Diesel engines which was a cause of inconvenience has given way
largely to a quietness in the CRDi technology, because many
functions executed by mechanical systems in the old Diesel engines
are carried out electronically in the CRDi technology. This in turn
enables the engine to run with much less noise. Moreover the
carrying out of the injection via multiple injections instead of
single is one of the causes which ensures the quietness of the
engine. In the CRDi technology it is ensured that all the parts of
the engine work in harmony, thereby minimizing the engine noise.
Besides that, a high efficiency is achieved now even at low engine
speeds. If the unequalled noise insulation is added to this it is
almost impossible to hear any engine noise, especially inside the
car.
5 CRDi FUTURE TRENDS :5.1 Ulra-High Pressure Common Rail
Injection:Newer CRDi engines feature maximum pressures of 1800 bar.
This pressure is up to 33% higher than that of first-generation
systems, many of which are in the 1600-bar range. This technology
generates an ideal swirl in the combustion chamber which, coupled
with the common-rail injectors superior fuel-spray pattern and
optimized piston head design, allows the air/fuel mixture to form a
perfect vertical vortex resulting in uniform combustion and greatly
reduced NOx (nitrogen oxide) emissions. The system realizes high
output and torque, superb fuel economy, emissions low enough to
achieve Euro Stage IV designation and noise levels the same as a
gasoline engines. In particular, exhaust emissions and Nox are
reduced by some 50% over the current generation of diesel
engines.
5.2 CRDi And Particle Filter:Particle emission is always the
biggest problem of diesel engines. While diesel engines emit
considerably less pollutant CO and Nox as well as green house gas
CO2, the only shortcoming is excessive level of particles. These
particles are mainly composed of carbon and hydrocarbons. They lead
to dark smoke and smog which is very crucial to air quality of
urban area, if not to the ecology system of our planet.
Basically, particle filter is a porous silicon carbide unit;
comprising passageways which has a property of easily trapping and
retaining particles from the exhaust gas flow. Before the filter
surface is fully occupied, these carbon / hydrocarbon particles
should be burnt up, becoming CO2 and water and leave the filter
accompany with exhaust gas flow. The process is called
regeneration.
Fig 5.2.1Normally regeneration takes place at 550 C. However,
the main problem is: this temperature is not obtainable under
normal conditions. Normally the temperature varies between 150 and
200C when the driving in town, as the exhaust gas is not in full
flow.
The new common-rail injection technology helps solving this
problem. By its high-pressure, precise injection during a very
short period, the common-rail system can introduce a
"post-combustion" by injecting small amount of fuel during
expansion phase. This increases the exhaust flow temperature to
around 350C.
Then, a specially designed oxidizing catalyst converter locating
near the entrance of the particle filter unit will combust the
remaining unburnt fuel come from the "post-combustion". This raises
the temperature further to 450 C.
The last 100C required is fulfilled by adding an addictive
called Eolys to the fuel. Eolys lowers the operating temperature of
particle burning to 450 C, now regeneration occurs. The
liquid-state additive is store in a small tank and added to the
fuel by pump. The PF unit needs to be cleaned up every 80,000 km by
high-pressure water, to get rid of the deposits resulting from the
additive.
5.3 CRDi And Closed-Loop Control Injection:One feature of
diesel-engine management had been holding back diesel's technical
advance: the lack of true, closed-loop control of the injection
system. This is significant because an open-loop system cannot
accurately compensate for factors such as wear, manufacturing
tolerances in the fuel injectors, or for variations in temperature
and fuel quality. Gasoline-injection systems have been closed loop
for years, and many of the advances in power, refinement, economy,
and emissions seen today have been possible because of the
real-time feedback that this provides.
Its solution to this problem is an all-new common-rail,
direct-injection system that uses an ion sensor to provide
real-time combustion data for each cylinder. It is said to provide
closed-loop control at a cost that will be roughly equivalent to
today's best production systems. High-speed, common-rail
direct-injection diesel engines are theoretically capable of
excellent performance, economy, and emissions, but to achieve this
they will require a much higher level of control than is possible
with today's technology. With closed-loop systems and ion-sensing
technology, the potential of diesel engines for automotive
applications can be unlocked.
The ion-sensing system creates an electrical field in the region
where combustion starts by introducing a positive dc voltage at the
tip of the glow plug. The field attracts the negatively charged
particles created during combustion, producing a small current from
the sensor to the piston and cylinder walls, which provide a
ground. The current is measured by the engine control module (ECM)
and processed to provide a signal that is proportional to the
applied sensor voltage and to the level of ionization in the
vicinity of the sensor. The difference in ionization before and
after the start of combustion is quite pronounced, allowing the
ion-sensing system to provide precise start-of-combustion (SOC)
data that can be compared with a table of required SOC timings held
by the ECM. The fuel control strategy can therefore be changed from
open loop to closed loop, allowing the desired SOC to be maintained
for all engine speeds, loads, temperatures, and fuel qualities; and
to accommodate production tolerances and wear in each injector.
Because the sensing function is combined with the glow plug, no
engine modifications are required, and the sensor is in a near
ideal location. One significant feature of the location is that
soot build-up, which can reduce the resistance between the sensor
and ground, can be easily detected and burnt off through a simple,
automated routine.
To reduce audible noise and NOx, a current production
high-pressure common-rail system will typically inject a pilot
pulse of around 3-5 mm3 of fuel before the main injection event.
Pilot injection can reduce noise by 3-5 dB, but too large a pulse
will compromise fuel consumption and emissions. Existing technology
can reduce the pilot injection volume to around 1-2 mm3 but only at
low injection pressures. Most engine designers would prefer higher
pressures because this allows cylinders to be fueled more quickly
and for the spray pattern to be improved, leading to increased
torque and less smoke.
Closed-loop system allows a pilot volume of around 0.5-1.0 mm3
under high pressures using standard injectors, and is said to
reduce particulates by around 10-20%. The precise volume of the
pilot injection can be balanced between cylinders, leading to a
further reduction in noise. The adaptively learned injector
calibrations can also be applied to post-injection pulses, which
provide a more complete combustion. 2-3% improvement in fuel
consumption can be achieved compared with today's high-pressure
systems by incorporating closed loop control.6.CONCLUTION The
seminar that I had taken is CRDi system from which we reached to
the conclusion that CRDi technology revolutionized diesel engines
and also petrol engines(by introduction of GDI technology).
By introduction of CRDi a lot of advantages are obtained ,some
of them are More power is developed.
Increased fuel efficiency.
Reduced noise.
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.
More pulverization of fuel is obtained.
A very high injection pressure can be achieved.
The powerful microcomputer make the whole system more
perfect.
It doubles the torque at lower engine speeds.
The main disadvantage is that this technology increase the cost
of the engine.Also this technology cant be employed to ordinary
engines.REFERENCES
1. Automotive Mechanics by S Srinivasan.
2. I C Engines By M.L.Malthur & Sharma.
3. I C Engines By V . Ganesan.
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www.mazda.co.nz
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8. www.tpgi.com.au/ozway/page4.html
9. www.sae.org/automag/techbriefs_11-99/06.htm
10. www.auto.howstuffworks.com/fuel-injection.htm
11. www.scoop.co.nz/mason/stories/HL0102/S00052.htm
12. www.autozine.kyul.net/technical_school/engine/diesel.htm
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www.mitsubishi-motors.co.jp/inter/technology/GDI/page1.html
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www.ukcar.com/sframe.htm?/features/tech/Engine/diesel/cr.htm
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