091cgdi seminar[1]

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Seminar On

Gasoline DirectInjection

BIJESH P8th SEM MECHANICAL


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Contents:

Introduction Transition of fuel supply

Major Objectives of the GDI engine

The difference between new GDI andcurrent MPI

Basic technical features of GDI Engine

Operation Major characteristics of the GDI engine

Achievements in GDI

Disadvantage


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INTRODUCTION

In internal combustion engines, gasoline direct

injection is a variant of fuel injection employed inmodern two- and four- stroke petrol engines. Thepetrol/gasoline is highly pressurised, and injected via acommon rail fuel line directly into the combustion

chamber of each cylinder, as opposed to conventionalmulti-point fuel injection that happens in the intaketract, or cylinder port.


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Transition of fuel supply


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Major Objectives of the GDIengine

Ultra-low fuel consumption that betters that of evendiesel engines

Superior power to conventional MPI engines

WHY NOT CARBURETTOR?

Carburetor has following disadvantages

Vapour lockPerfect air/fuel mixture cannot be obtained

Lack of throttle responseLow volumetric efficiencyMechanical deviceCompromises on emission


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Why The GDI ?

Lower Fuel Consumption and More OutputImproved Volumetric EfficiencyVery efficient intake and relatively high

compression ratio deliver both highperformance and responseLower octane requirementMore precise air-fuel ratio controlMore rapid startingReduced CO2 emissionsImproved transient response.

Advantages of GDI Engines are:


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In two-stroke engines

The benefits of direct injection are even

more pronounced in two-stroke engines,because it eliminates much of the pollutionthey cause. In conventional two-strokes, theexhaust and intake ports are both open atthe same time, at the bottom of the pistonstroke. A large portion of the fuel/airmixture entering the cylinder from thecrankcase through the intake ports goesdirectly out, unburned, through the exhaustport. With direct injection, only air comesfrom the crankcase, and fuel is not injected

until the piston rises and all ports are closed


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The difference between newGDI and current MPI

In MPI or Multi-Point Injection, the fuel isinjected to each intake portIn MPI engines there are limits to fuel

supply response and the combustioncontrol because the fuel mixes with airbefore entering the cylinder.In GDI, gasoline is directly injected into

the cylinder as in a diesel engineThe injection timings are preciselycontrolled to match load conditions.


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Basic technical features of GDIEngine The Upright Straight Intake Port.

The Curved-top Piston.

The High Pressure Fuel Pump.

The High Pressure Swirl Injector.


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Operation Fuel is delivered to the fuel rail by the

high-pressure pump A closed control loop comprising the fuel

pressure sensor, pressure control valveand electronic control unit controls thepressure of the hydraulic systemindividually for all operating points.

The Electronic control unit coordinates the

different torque parameters according tothe position of the accelerator pedal andundertakes the necessary control actionsin the engine.


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Diagram


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Major characteristics of the GDIengine

1. Ultra-lean Combustion Mode

Under most normal driving conditions,up to speeds of 120km/h, the GDI engine

operates in ultra-lean combustion mode forless fuel consumption. In this mode, fuelinjection occurs at the latter stage of thecompression stroke and ignition occurs at anultra-lean air-fuel ratio of 30 to 40


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2. Superior Output ModeWhen the GDI engine is operating with higher

loads or at higher speeds, fuel injection takesplace during the intake stroke. This optimizescombustion by ensuring a homogeneous, coolerair-fuel mixture that minimized the possibility ofengine knocking.


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3. In-cylinder Airflow

The GDI

engine

has

upright


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Newly developed high-pressure swirl

injectors provide the ideal spray pattern tomatch each engine operational modes. And

at the same time by applying highly swirlingmotion to the entire fuel spray, they enablesufficient fuel atomization that is mandatoryfor the GDI even with a relatively low fuel

pressure of 50kg/cm2


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Combustion ChamberThe curved-top piston controls the shape ofthe air-fuel mixture as well as the airflow

inside the combustion chamber, and has animportant role in maintaining a compact airfuel mixture. The mixture, which is injectedlate in the compression stroke, is carried

toward the spark plug before it can disperse.


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Realization of lower fuelconsumption

Fuel Consumption during

IdlingThe GDI engine maintains stable combustion even atlow idle speeds. Moreover, it offers greater flexibilityin setting the idle speed.Compared to conventional engines, its fuel

consumption during idling is 40% less.


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Fuel Consumption during CruisingDriveAt 40km/h, for example, the GDI engine uses 35% less

fuel than a comparably sized conventional engine


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Output

Compared to conventional engines, the GDI engineprovides better volumetric efficiency. The uprightstraight intake ports enable smoother air intake. Andthe vaporization of fuel, which occurs in the cylinderat a late stage of the compression stroke, cools theair for better volumetric efficiency.

Improved Volumetric

Efficiency

Increase Compress on


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Increase Compress onRatioThe cooling of air inside the cylinder by the

vaporization of fuel minimizes engineknocking. This allows a high compressionratio of 12, and thus improve combustionefficiency.


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Achievements Engine performance

Compared to conventional MPI engines of acomparable size, the GDI engine provides approximately10% greater output and torque at all speeds.


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Vehicle Acceleration

In high-output mode, the GDI engine provides outstanding

acceleration.The following chart compares the performance of the GDI enginewith a conventional MPI engine


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Disadvantage

Complexity and Cost :

Direct injection systems are more expensiveto build because their components must be

more rugged -- they handle fuel atsignificantly higher pressures than indirectinjection systems and the injectorsthemselves must be able to withstand theheat and pressure of combustion inside the

cylinder.


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Conclusion

Gasoline direct injection (GDI) enginetechnology has received considerableattention over the last few years as away to significantly improve fuel

efficiency without making a majorshift away from conventional internalcombustion technology. In manyrespects, GDI technology represents

a further step in the natural evolutionof gasoline engine fueling systems.


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References

1. Internal Combustion Engines By: Anand VDomkundwar.2. Internal Combustion Engines By: Mathur &

Sharma.

3. www.howstuffworks.com4. www.mitsubishi-np.in5. www.autoworld.com6. Wikipedia.org

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