Fuel Injection in the Spark Ignition Engine
-
Upload
anand-kumar -
Category
Documents
-
view
222 -
download
0
Transcript of Fuel Injection in the Spark Ignition Engine
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
1/22
FUEL INJECTION IN
SPARK IGNITION ENGINE
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
2/22
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
3/22
Merits of Fuel Injection in the SI
Engine
Absence of Venturi No Restriction in
Air Flow/Higher Vol.
Eff./Torque/Power
Hot Spots for Preheating cold air
eliminated/Denser air enters
Manifold Branch Pipes Not concerned
with Mixture Preparation (MPI)
Better Acceleration Response (MPI)
Fuel Atomization Generally Improved
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
4/22
Merits (Continued)
Use of Greater Valve Overlap
Use of Sensors to Monitor OperatingParameters/Gives Accurate Matching
of Air/fuel Requirements: ImprovesPower, Reduces fuel consumptionand Emissions
Precise in Metering Fuel in Ports Precise Fuel Distribution Between
Cylinders (MPI)
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
5/22
Merits (Continued)
Fuel Transportation in Manifold not
required (MPI) so no Wall Wetting
Fuel Surge During Fast Cornering or
Heavy Braking Eliminated
Adaptable and Suitable For
Supercharging (SPI and MPI)
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
6/22
Limitations of Petrol Injection
High Initial Cost/High Replacement Cost
Increased Care and Attention/More
Servicing Problems
Requires Special Servicing Equipment toDiagnose Faults and Failures
Special Knowledge of Mechanical and
Electrical Systems Needed to Diagnoseand Rectify Faults
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
7/22
Limitations of Petrol Injection
(Continued)
Injection Equipment Complicated,
Delicate to Handle and Impossible to
Service by Roadside Service Units
Contain More Mechanical and
Electrical Components Which May Go
Wrong
Increased Hydraulic and Mechanical
Noise Due to Pumping and Metering
of Fuel
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
8/22
Limitations of Petrol Injection
(Continued)
Very Careful Filtration Needed Due toFine Tolerances of Metering andDischarging Components
More Electrical/Mechanical PowerNeeded to Drive Fuel Pump and/orInjection Devices
More Fuel Pumping/Injection Equip-ment and Pipe Plumbing Required-May be Awkwardly Placed and Bulky
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
9/22
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
10/22
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
11/22
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
12/22
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
13/22
Indirect Injection
Also Called Manifold Injection orSingle Point Injection (SPI) or ThrottleBody Injection (TBI)
Injector Usually Upstream FromThrottle (Air Intake Side) or In SomeCases Placed on the Opposite Side
Pressures are Low
2 to 6 Bar. MaybeInjected Irrespective of Intake Process
Cost Would be Low
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
14/22
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
15/22
Semi-direct Injection
Also Called Port Injection or IndirectMultipoint Injection (IMPI) or SimplyMulti-point Injection (MPI)
Injectors Positioned in Each InductionManifold Branch Just in Front of InletPort
Injection at Low Pressure (2-6 Bar) Need Not Be Synchronized With
Engine Induction Cycle
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
16/22
Direct Cylinder Injection
Also Called Direct Multi-pointInjection (DMPI) or Gasoline DirectInjection (GDI)
Injection May be During Intake orCompression Process
Increased Turbulence Required
To Compensate For Shorter PermittedTime For Injection/Atomization/MixingInjection Pressure Must Be Higher
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
17/22
Major Features With Petrol
Injection
There is Separate Air and Fuel
Metering
Fuel Metering is Precise
Under All Engine OperatingConditions
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
18/22
Methods of Discharging Fuel Into
Air
1. CONTINUOUS INJECTION
Injector Nozzle and Valve arePermanently Open While Engine is
OperatingAmount of Fuel Discharged as aSpray is Controlled by
a. Varying Metering Orifice, orb. Varying Fuel Discharge Pressure, or
c. Both
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
19/22
Comparing Pulsed and
Continuous Injection
Assume Engine Operates Between 750(Idling) and 7500 rev/min (Max. Speed)
(1:10 ratio)
In Continuous Fuel Injection:
Fuel Flow has to vary by a Factor of 1:50by Volume using Variable Area Orifice
Injection Pressure has to Vary by aFactor of 1:2500 using Fixed Orifice
Or a Combination of Both Variables
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
20/22
Types of Injection For MPI
1. Timed Injection
Start of Fuel Delivery For Each CylinderOccurs at the Same Angular Point in
Engine Cycle
Could be 60 or 90Deg. ATDC of Induction Stroke ofEach Cyl.
2. Non-timed InjectionAll Injectors Programmed to Discharge
Fuel at Same Time. Each Piston Willbe on a Different Part of the Cycle
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
21/22
Operation
Injection System Must SenseChanges to Influencing Parameters
Pass Information to a Coordinating
System (Microprocessor orComputer)
Which In Turn Integrates Individual
Signals and Interprets FuelRequirements
Then Signals Injector to Open andClose
-
7/29/2019 Fuel Injection in the Spark Ignition Engine
22/22
Controlling Parameters to Sense(Some of the Parameters)
1. Engine Speed
2. Amount of Inlet Air (Engine Load)
3. Throttle Position
4. Air Temperature5. Coolant Temperature
6. Altitude
7. Cranking Speed
8. Exhaust Oxygen Concentration
9. Battery Voltage