1. Design of Port Fuel Injection System
P M V Subbarao
Professor
Mechanical Engineering Department
Means to Achieve Required Spray Quality.…...

2. Instability of Fluid Ligament in Ambient Air

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

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

5. Frequency diagram for Size of droplets
D is the droplet diameter and
N is the normalized number
distribution.

6. Physical & Mathematical Conditions
The following physical and mathematical conditions must be obeyed:
The sum of all probabilities must be unity:
(ii) the instantaneous mass flow of sprayed liquid must be equal to the mass of all droplets produced per unit time:
where n is the total number of droplets produced per unit
time and mL is the liquid mass flux.

7. Physical Models for Spray Characterization
Entropy of a group of droplets:
where S is the information entropy, the name used when the information concept is applied to problems in physics and engineering.
In this equation K is a constant and Pi is the probability of the occurrence of a certain result, in terms of number fraction.
Maximum feasible entropy corresponding to physical conditions will decide the droplet distribution.

8. Simplified Engineering fuel Evaporation model
The comprehensive fuel spray model predicts individual motions of liquid fuel droplets and evaporation of each droplet.
It also includes a more detailed treatment of in-cylinder evaporation.
In a simplified engineering model a representative diameter for the entire group is defined to compute evaporation rate.
Equivalent diameter of same number of uniformly sized droplets having same total surface area.

9. Sauter Mean Diameter Introducing the definition of SMD:
where dnozz is the nozzle diameter,
μf , μg are the fuel and gas dynamic viscosity, respectively,
Re the Reynolds number and
We the Weber number.

10. Anatomy of Electronic Fuel Injector
Solenoid Magnet

11. Force applied by the Solenoid on the Rod
Final Magnetic Energy of the field
Initial Magnetic Energy of the field
Change in energy

12. New Chapter in Fluid Mechanics
Arbitrary pulsating Micro pipe flows
Fully developed axisymmetric pulsating
laminar pipe flow

13. Transient Response of Injector

14. Gasoline Fuel Sprays in Port

15. Injector Capacity : Maximum Fuel Flow Rate
Flow rate is the most important factor to consider when selecting a fuel injector.
EFI tunes are written for a specific injector flow rate and, generally, the fuel injector should match this.
The flow rate is a measure of how much fuel an injector will spray at a 100% duty cycle (wide open) at a specific base fuel pressure.
Most fuel injector flow ratings are measured at a base fuel pressure of 3 bar and is about 10.5 cc/minute.
It is possible to use a different injector size than the fueling map was written for by changing the fuel pressure.

17. Sizing of Injector
While fuel injectors are rated at a 100% duty cycle, it is common practice to size the fuel injectors based on a 80% duty cycle.
Since the flow rate is measured at a static fuel pressure on a new injector, and does not take into account the opening and closing of the injector, the 80% duty cycle maximum gives a factor of safety to account for actual driving conditions and a reduction in flow rate caused by deposits.
This factor of safety is important because a lean fuel mixture will result in excessive heat and can potentially lead to engine damage.

18. Control of Mass Flow Through an EFI
The mass flow through an EFI is selected based on three main factors.
Engine rpm,
Throttle position, and
Oxygen remaining within the exhaust.
The distributor triggering contacts relay the engine speed to the Electronic Control Unit (ECU).
The load on the engine is taken from the intake air pressure sensor.
These factors influence how long the injectors remain on for.