This presentation was prepared by Mechanical Engineers during their final year in their Internal Combustion Engine program offered at University of Engineering and Technology Lahore.

1. SI engine fuel metering and
manifold phenomenon
Presented by:
Usama Naveed 2013-ME-329
Shahzaib Ilyas 2013-ME-333
Waqar Saeed 2013-ME-339
Hamza Saleemi 2013-ME-340
Hamza Iqbal 2013-ME-341
Presented to:
Dr. Shahid Imran
1

2. Contents
 Fuel Metering
 SI Engine Maintenance Requirement
 Carburetor
 Working Animation of Carburetor
 Changes required in Carburetor
 Electronic Fuel Injection System
 General circuit for EFI
 Multi-port fuel injection system
 Throttle Body Injection System
 Fuel flow throttle plate
 Throttle plate design requirement
 Problems
2

3. 3
Fuel metering
 The mixing of appropriate amount of fuel with the
incoming air which is to be supplied to the engine
cylinders is known as fuel metering

4. SI engine mixture requirements
 Most gasolines have (A/F)stich in the range 14.4 - 14.7
 Typical value for (A/F) for SI engine = 14.6
 In the absence of strict engine NOx emission
requirements, excess air is the obvious diluent
 Result of excess air:
Gasoline Engines have traditionally operated
lean (∅ < 1)
4

5. Equivalence ratio variation vs intake
mass flow rate
5

6. Recycled exhaust (EGR) schedule
as a function of intake flow rate
6

7. Carburetor
A device in an internal-combustion engine
for mixing air with a fine spray of liquid fuel
Work on Bernoulli's Principle
Uses the venturi mechanism for metering of
fuel with air
7

8. 8

9. Changes required in carburetor
 The main metering system
 An idle system
 An enrichment system
 An accelerator pump
 A choke
9

10. Electronic Fuel Injection System
 Electronic Fuel Injection uses various engine
sensors and control module to regulate fuel
quantity for proper metering of fuel with air
 EFI consists of
1. Sensor system
2. Fuel delivery system
3. Air induction system
4. Computer control system
10

11. 11

12. General circuit for EFI12

13. Fuel delivery system
 Electrical Fuel Pump
 Pressure Regulator
 Fuel Injector
 Injector Pulse Width
13

14. Multi-port fuel injection system
 Uses multiple injectors for fuel injection
 One injector is located in each manifold runner
 ECU controls injectors by pulsing their current
 Injectors spray fuel directly into intake port in
front of intake valve
14

15. 15

16. Throttle Body Injection System
 Also called central body injection system
 Uses single injector mounted in throttle body
 Fuel is sprayed into intake air entering the
manifold
16

17. Flow pass throttle plate
 Purpose of throttle body?
 What is throttle plate?
 Where is it located?
17

18. Throttle Plate Design Requirement
 Low air flow resistance
 Good distribution of air and fuel between cylinders
 Runner and branch length
 Sufficient heating
18

19. Problem # 01
 Conventional spark-ignition engine operating with gasoline
 SI will not run smoothly (due to incomplete combustion) with
an equivalence ratio leaner than about ∅= 0.8
 Desirable to extend the smooth operating limit of the engine to
leaner equivalence ratios so that at part-throttle operation
(with intake pressure less than 1 atmosphere) the pumping
work is reduced
 Leaner than normal operation can be achieved by adding
hydrogen gas (H2) to the mixture in the intake system
 The addition of H2 makes the fuel-air mixture easier to burn
19

20. Solution
 Balanced chemical equation
H2 + C8H18 + 13(O2 +3.773N2) = 8CO2 + 10H20 +
41.5N2
 Air fuel ratio
𝐴
𝐹
=
𝑚 𝑎
𝑚 𝑓
= 15.4
 Brake Power
𝑏𝑃 =
2𝜋𝑁𝑇
60000
= 29kW
 Mechanical Efficiency
𝜂 =
𝑏𝑃
𝑖𝑃
= 50.05𝑘𝑊
20

21. Continued…
 Indicated mean effective pressure
𝑖𝑃 =
𝑃𝑖 𝑥 𝐿𝐴𝑁𝐾
60000
= 486.34𝑘𝑝𝑎
𝑝𝑖 − 𝑝𝑒 = 𝑖𝑚𝑒𝑝 = 476.24kpa
𝑝𝑖 + 𝑝𝑒 = 1 − 𝜂 𝑓 𝑖𝑚𝑒𝑝 = 285
 By solving both equations:
𝑝𝑖 = 380.99𝑘𝑝𝑎
𝑝𝑒 = −95.25𝑘𝑝𝑎
 Pumping Pressure
𝑃𝑢𝑚𝑝𝑖𝑛𝑔 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 𝑝𝑖 − 𝑝𝑒 = 476.24𝑘𝑝𝑎
𝜂 =
𝑏𝑃
𝑖𝑃 + 𝑟𝑚𝑒𝑓 + 𝑏𝑚𝑒𝑓
= 39.25
21

22. Outcomes22
Rich Mixture Lean Mixture
Low air to fuel ratio High air to fuel ratio
High mechanical efficiency Low mechanical efficiency
High equivalence ratio Low equivalence ratio

23. Problem # 02
 The flame propagation environment under typical engine
condition
 Engine specification:
N=1500 rpm; intake pressure=38kpa; λ =1; ignition= 30
degree BTC; Bore = 86 mm; Stroke = 86 mm; con-rod to bore
ratio = 1.58; Clearance vol.=58.77 cc
 Plot the following quantities as a function of the mass burned
fraction
1. The unburned and burned gas temperatures
2. The laminar flame speed
3. The laminar flame expansion velocity
4. The mass fraction burn
5. The volume of burned gas
23

24. Solution
 Displaced Volume
𝑉𝑑 =
𝜋
4
𝐷2
𝑙 = 500cc
 Total Volume
𝑉𝑡 = 𝑉𝑐 + 𝑉𝑑 = 558.77cc
 Mass of mixture
𝑚 = 32 + 4∅ 1 − 2𝜀 + 28.16𝜓
 Assumption: Octane Fuel
 Mass of mixture (Modified)
𝑚 = 138.2 + 9.12∅ = 147.32kg
24

25. Continued…
 Unburned gas temperature
𝑇𝑢
𝑇𝑜
= (
𝑝
𝑝 𝑜
)
𝛾 𝑢−1
𝛾 𝑢
 Burned gas temperature
𝑇𝑏 =
𝑅 𝑢
𝑅 𝑏
𝑇𝑢 +
𝑝𝑉 − 𝑚𝑅 𝑢 𝑇𝑢
𝑚𝑅 𝑏 𝑥 𝑏
 Mass fraction burned
𝑥 𝑏 =
𝑝𝑉 − 𝑝 𝑜 𝑉0 + 𝛾 𝑏 − 1 𝑊 + 𝑄 + 𝛾 𝑏− 𝛾𝑢 𝑚𝑐 𝑣,𝑢(𝑇𝑢 − 𝑇𝑜)
𝑚[ 𝛾 𝑏 − 1 ℎ 𝑓,𝑢 − ℎ 𝑓,𝑏 + (𝛾 𝑏 − 𝛾𝑢)𝑐 𝑣,𝑢 𝑇𝑢
 Volume change
𝑝𝑉
𝑚
= 𝑥 𝑏 𝑅 𝑏 𝑇𝑏 + (1 − 𝑥 𝑏)𝑅 𝑢 𝑇𝑢
25

26. 26

27. Results27

28. 28
0
100
200
300
400
500
600
700
800
-30 -20 -10 0 10 20 30 40 50 60
Temperature
Crank Angle
Crank Angle vs Temperature of the mass burned and
Unburned
Tu Tb

29. 29
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
-30 -20 -10 0 10 20 30 40 50 60
MassFractionBurned
Crank Angle
Crank Angle vs Mass Fraction Burned
Mass fraction burned

30. Continued…
 Flame Velocity
𝑆 𝐿 = 𝑆 𝐿,0(
𝑇𝑢
𝑇𝑜
) 𝛼(
𝑝
𝑝 𝑜
) 𝛽
Where
𝑆 𝐿,0 = 𝐵 𝑚 + 𝐵∅(∅ − ∅ 𝑚)2
𝛼 𝑔 = 2.4 − 0.217∅3.51
𝛽𝑔 = −0.357 + 0.14∅2.77
30

31. For Laminar Flame Velocity31

32. Results32

33. 33
0
5
10
15
20
25
30
35
40
-30 -20 -10 0 10 20 30 40 50 60
MassFractionBurned
Crank Angle
Crank Angle vs Flame Expansion Velocity
Flame Velocity

34. 34
0
100
200
300
400
500
600
700
800
-30 -20 -10 0 10 20 30 40 50 60
Crank Angle
Comparison between Temperature of the mass
burned, unburned and flame Velocity
Tu Tb Flame Velocity

35. 35
0
100
200
300
400
500
600
700
800
0.0547 0.1047 0.1547 0.2047 0.2547
Temperature
Mass fraction burned
Mass fraction burned and Temperature of the
mass burned and unburned
Tu Tb

36. 36
0
5
10
15
20
25
30
35
40
0.0547 0.1047 0.1547 0.2047 0.2547
Flameexpansionvelocity
Mass fraction burned
Mass fraction burned vs Flame Expansion Velocity
Flame Velocity

37. 37