091cgdi seminar[1]
TRANSCRIPT
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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