29 Junet Babu CRDi 3
-
Upload
jaiveer-yadav -
Category
Documents
-
view
219 -
download
0
Transcript of 29 Junet Babu CRDi 3
-
7/27/2019 29 Junet Babu CRDi 3
1/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering1
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 foreach 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 injectionpressure 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 loweringemissions.
Fig. 1
More 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.
-
7/27/2019 29 Junet Babu CRDi 3
2/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering2
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 simplicityand 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 usexamine 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 lawnmowersand 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 idling2.1.3 : Accelerator pump Provides an extra burst of fuel when the accelerator pedal is
first depressed, reducing hesitation before the engine
speeds up2.1.4 : Power enrichment Provides extra fuel when the car is going up a hill or
circuit towing a trailer
2.1.5 : Choke Provides 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 beeffective. 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.
-
7/27/2019 29 Junet Babu CRDi 3
3/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering3
At first, carburetors were replaced with throttle body fuel injection systems (also knownas 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 enginedesigns.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 sprayright at the intake valve. These systems provide more accurate fuel metering and quicker
response.
-
7/27/2019 29 Junet Babu CRDi 3
4/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering4
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 emissionsmore precisely, but demands advanced engine
management technologies.
Fig. 3.1
Unlike petrol engines, diesel engines dont need ignition system. Due to the inherentproperty 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 strongthus 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 directinjection, 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.
-
7/27/2019 29 Junet Babu CRDi 3
5/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering5
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 petrolengine (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. 3.2
To 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.
-
7/27/2019 29 Junet Babu CRDi 3
6/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering6
4.COMMON RAIL DIRECT INJECTION: FEATURES:
Fig4.1
Simply explained, common rail refers to the single fuel injection line on the CRDiengines. 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 enginespeed 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.
-
7/27/2019 29 Junet Babu CRDi 3
7/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering7
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 fromwhere 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 thefuel consumption.
Compared with petrol, diesel is the lower quality fuel from petroleum family. Dieselparticles 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 thatnormal 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 commonrigid pipe (hence the name of "common-rail").
In the current first generation design, the pipe withstands pressures as high as 1,600 baror 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, thehigh-pressure fuel can be injected into combustion chamber quickly. As a result, not onlypulverization 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 creatingsmall 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. Thedrive 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 toproduce a cone-shaped spray and a slit nozzle for a fan-shaped spray.
-
7/27/2019 29 Junet Babu CRDi 3
8/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering8
Fig 4.2
The 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. Inemission, 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-railengines 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 injectionpressure 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.
-
7/27/2019 29 Junet Babu CRDi 3
9/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering9
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 amountof 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 4.1.1
-
7/27/2019 29 Junet Babu CRDi 3
10/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering10
4.2 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 portwhile 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-designedinjector 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 newCRDi engines are incorporated with a cast port for the direct injection motor whichconducts 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, themicrocomputer 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
-
7/27/2019 29 Junet Babu CRDi 3
11/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering11
4.5 Swirl-Control Valves In The Intake Manifolds:
Pneumatically guided swirl valves in the intake system help bring the fuel-air mixture toa 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 exhaustgases 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 chargechannel 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 olderdirect-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 indirect 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, asmall 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 combustioncharacter 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. Thesmall 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 bottomline is that the noise produced by the new CRDI engines is lower than for comparablepre-combustion engines
.
-
7/27/2019 29 Junet Babu CRDi 3
12/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering12
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 thecommon 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 solenoidvalves.
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 themotor 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 beendevised 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 controldevices on the underbody.
4.9 High Rigidity Cylinder Block And Dual Mass Flywheel
To 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 intothe 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.
-
7/27/2019 29 Junet Babu CRDi 3
13/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering13
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 intakeside.
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 mademany attributes of the old Diesel engines have become something of the past. One ofthese 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 outelectronically 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, therebyminimizing 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.
-
7/27/2019 29 Junet Babu CRDi 3
14/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering14
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 withthe 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 EuroStage 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 onlyshortcoming 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 whichhas a property of easily trapping and retaining particles from the exhaust gas flow. Beforethe 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.
-
7/27/2019 29 Junet Babu CRDi 3
15/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering15
Fig 5.2.1
Normally regeneration takes place at 550 C. However, the main problem is: this
temperature is not obtainable under normal conditions. Normally the temperature variesbetween 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.
-
7/27/2019 29 Junet Babu CRDi 3
16/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering16
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 significantbecause an open-loop system cannot accurately compensate for factors such as wear,
manufacturing tolerances in the fuel injectors, or for variations in temperature and fuelquality. 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 productionsystems. High-speed, common-rail direct-injection diesel engines are theoretically
capable of excellent performance, economy, and emissions, but to achieve this they willrequire a much higher level of control than is possible with today's technology. Withclosed-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 startsby 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 ismeasured by the engine control module (ECM) and processed to provide a signal that isproportional 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 quitepronounced, 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, andfuel 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 thelocation 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.
-
7/27/2019 29 Junet Babu CRDi 3
17/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering17
To reduce audible noise and NOx, a current production high-pressure common-railsystem 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 enginedesigners 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 furtherreduction 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.
-
7/27/2019 29 Junet Babu CRDi 3
18/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering18
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 petrolengines(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 thistechnology cant be employed to ordinary engines.
-
7/27/2019 29 Junet Babu CRDi 3
19/20
CRDi System
Sree Narayana Gurukulam College Of Engineering Department of Mechanical Engineering19
REFERENCES
1. Automotive Mechanics by S Srinivasan.
2. I C Engines By M.L.Malthur & Sharma.
3. I C Engines By V . Ganesan.
4. Automotive Engines by S Srinivasan.
5. www.autoweb.com.au
6. www.mazda.co.nz
7. www.toyota.ee/eng/technology
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
13.www.mercedes-benz.com/e/innovation/rd/forschung_cdi.htm
14.www.mitsubishi-motors.co.jp/inter/technology/GDI/page1.html
15.www.ukcar.com/sframe.htm?/features/tech/Engine/diesel/cr.htm
16.www.daimlerchrysler.com/specials/detroit02/mercedes-benz_g-class_e.htm
-
7/27/2019 29 Junet Babu CRDi 3
20/20
CRDi System