1. Artificial Fuel Induction Systems for A SI Engine
P M V Subbarao
Professor
Mechanical Engineering Department
Forced And Controlled Injection of Fuel…...

2. Performance of Bernoulli’s Effect
Cylinder 1
Cylinder 3
Cylinder 2
Cylinder 4

3. Replacement for Carburettor
At first, carburettors were replaced with throttle body fuel injection systems.
They were also known as single point or central fuel injection systems.
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.
Mertis:
Absence of Venturi – No Restriction in Air Flow/Higher Vol. Eff./Torque/Power.
Fuel Atomization Generally Improved.
Better Acceleration Response (MPI).
Drawback: Manifold Branch Pipes are still concerned with Mixture Preparation (MPI)

4. Growth of Artificial Induction in SI Engines
There are both mechanical and electronically controlled injection systems.
First step in this direction was Engines with Single point Fuel Injection.
The fuel-induction systems for current (high percentage) spark-ignition engines inject the fuel.

5. Fuel Injection Strategy : Last decade of 20th century
Gradually new SI engines were designed.
Throttle body fuel injection was replaced by multi-port fuel injection.
This is 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.
Ever increasing rate in the production of fuel injection vehicles lead to decrease in release of the pollutions in nature.

6. Evolution of Fuel Injection Systems for SI Engine
This triggered Numerous researches in optimizing the fuel injection system.
Recognition of the fuel behavior.
Analysis of the process of preparation of mixtures in the inlet port of fuel injection vehicles using MPFI system.

7. Additional Merits of Fuel Injection in Manifolds of SI Engine
Precise in Metering Fuel in Ports
Precise Fuel Distribution Between Cylinders (MPFI).
More precise control of the equivalence ratio.
Helps in achieving better volumetric efficiency
Manifold Branch Pipes Not concerned with Mixture Preparation (MPFI).
Use of Greater Valve Overlap
Hot Spots for Preheating cold air eliminated/Denser air enters
Further improvement in Acceleration Response (MPI)
Use of Sensors to Monitor Operating Parameters/Gives Accurate Matching of Air/fuel Requirements: Improves Power, Reduces fuel consumption and Emissions

8. Essential Knowledge Systems : MPFI
Recognition of the structure and spray pattern.
The time and condition with which the fuel should be sprayed in the port.
Selection of suitable parameters of the spray:
Atomization specification
Spay pattern
Appropriate angles

9. Instability of Fluid Ligament in Ambient Air

10. Kelvin-Helm Holtz Instability

11. Wave Theory of Instability
WAVE theory is based on the temporal Kelvin-Helmholtz instability.
The model assumes a round liquid jet (density ρl ) with an inviscid outer gas phase.
The liquid velocity is assumed to be constant inside the jet and drops to zero at the interface between the liquid and gas phases.
The small disturbance introduced by manifold air flow in an axisymmetric fuel jet grows with time.
The maximum growth rate (Ω ) and the corresponding wavelength Λ decide the value of spray angle.

12. Mean diameter distribution of droplets (micron) in 100 mm downstream and 300 Kpa, 25o C

13. Distribution of droplets velocity (m/s) in 100 mm downstream and 300 Kpa, 25o C

14. Geometrical Features of A Successful Fuel Spray
The maximal deviation of the emerging droplets from the axis, described by the angle .

15. Length of Spray