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

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 Fuel metering The mixing of appropriate amount of fuel with the

incoming air which is to be supplied to the enginecylinders is known as fuel metering

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 emissionrequirements, excess air is the obvious diluent

Result of excess air:

Gasoline Engines have traditionally operatedlean (∅ < 1)

4

Equivalence ratio variation vs intake mass flow rate

5

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

6

Carburetor

A device in an internal-combustion enginefor mixing air with a fine spray of liquid fuel

Work on Bernoulli's Principle

Uses the venturi mechanism for metering offuel with air

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8

Changes required in carburetor The main metering system

An idle system

An enrichment system

An accelerator pump

A choke

9

Electronic Fuel Injection System

Electronic Fuel Injection uses various enginesensors and control module to regulate fuelquantity 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

General circuit for EFI12

Fuel delivery system

Electrical Fuel Pump

Pressure Regulator

Fuel Injector

Injector Pulse Width

13

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 infront of intake valve

14

15

Throttle Body Injection System

Also called central body injection system

Uses single injector mounted in throttle body

Fuel is sprayed into intake air entering themanifold

16

Flow pass throttle plate

Purpose of throttle body?

What is throttle plate?

Where is it located?

17

Throttle Plate Design Requirement

Low air flow resistance

Good distribution of air and fuel between cylinders

Runner and branch length

Sufficient heating

18

Problem # 01

Conventional spark-ignition engine operating with gasoline

SI will not run smoothly (due to incomplete combustion) withan equivalence ratio leaner than about ∅= 0.8

Desirable to extend the smooth operating limit of the engine toleaner equivalence ratios so that at part-throttle operation(with intake pressure less than 1 atmosphere) the pumpingwork is reduced

Leaner than normal operation can be achieved by addinghydrogen gas (H2) to the mixture in the intake system

The addition of H2 makes the fuel-air mixture easier to burn

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Solution Balanced chemical equation

H2 + C8H18 + 13(O2 +3.773N2) = 8CO2 + 10H20 + 41.5N2

Air fuel ratio𝐴

𝐹=𝑚𝑎

𝑚𝑓= 15.4

Brake Power

𝑏𝑃 =2𝜋𝑁𝑇

60000= 29kW

Mechanical Efficiency

𝜂 =𝑏𝑃

𝑖𝑃= 50.05𝑘𝑊

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Continued…

Indicated mean effective pressure

𝑖𝑃 =𝑃𝑖 𝑥 𝐿𝐴𝑁𝐾

60000= 486.34𝑘𝑝𝑎

𝑝𝑖 − 𝑝𝑒 = 𝑖𝑚𝑒𝑝 = 476.24kpa

𝑝𝑖 + 𝑝𝑒 = 1 − 𝜂𝑓 𝑖𝑚𝑒𝑝 = 285

By solving both equations:𝑝𝑖 = 380.99𝑘𝑝𝑎𝑝𝑒 = −95.25𝑘𝑝𝑎

Pumping Pressure𝑃𝑢𝑚𝑝𝑖𝑛𝑔 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 𝑝𝑖 − 𝑝𝑒 = 476.24𝑘𝑝𝑎

𝜂 =𝑏𝑃

𝑖𝑃 + 𝑟𝑚𝑒𝑓 + 𝑏𝑚𝑒𝑓= 39.25

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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

Problem # 02 The flame propagation environment under typical engine

condition

Engine specification:

N=1500 rpm; intake pressure=38kpa; λ =1; ignition= 30degree BTC; Bore = 86 mm; Stroke = 86 mm; con-rod to boreratio = 1.58; Clearance vol.=58.77 cc

Plot the following quantities as a function of the mass burnedfraction

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

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Solution

Displaced Volume

𝑉𝑑 =𝜋

4𝐷2𝑙 = 500cc

Total Volume𝑉𝑡 = 𝑉𝑐 + 𝑉𝑑 = 558.77cc

Mass of mixture𝑚 = 32 + 4∅ 1 − 2𝜀 + 28.16𝜓

Assumption: Octane Fuel

Mass of mixture (Modified)𝑚 = 138.2 + 9.12∅ = 147.32kg

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Continued…

Unburned gas temperature𝑇𝑢𝑇𝑜

= (𝑝

𝑝𝑜)𝛾𝑢−1𝛾𝑢

Burned gas temperature

𝑇𝑏 =𝑅𝑢𝑅𝑏

𝑇𝑢 +𝑝𝑉 −𝑚𝑅𝑢𝑇𝑢

𝑚𝑅𝑏𝑥𝑏

Mass fraction burned

𝑥𝑏 =𝑝𝑉 − 𝑝𝑜𝑉0 + 𝛾𝑏 − 1 𝑊 + 𝑄 + 𝛾𝑏−𝛾𝑢 𝑚𝑐𝑣,𝑢(𝑇𝑢 − 𝑇𝑜)

𝑚[ 𝛾𝑏 − 1 ℎ𝑓,𝑢 − ℎ𝑓,𝑏 + (𝛾𝑏 − 𝛾𝑢)𝑐𝑣,𝑢𝑇𝑢

Volume change 𝑝𝑉

𝑚= 𝑥𝑏𝑅𝑏𝑇𝑏 + (1 − 𝑥𝑏)𝑅𝑢𝑇𝑢

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26

Results27

28

0

100

200

300

400

500

600

700

800

-30 -20 -10 0 10 20 30 40 50 60

Tem

pera

ture

Crank Angle

Crank Angle vs Temperature of the mass burned and

Unburned

Tu Tb

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

Mass

Fra

ctio

n B

urn

ed

Crank Angle

Crank Angle vs Mass Fraction Burned

Mass fraction burned

Continued…

Flame Velocity

𝑆𝐿 = 𝑆𝐿,0(𝑇𝑢𝑇𝑜)𝛼(

𝑝

𝑝𝑜)𝛽

Where𝑆𝐿,0 = 𝐵𝑚 + 𝐵∅(∅ − ∅𝑚)

2

𝛼𝑔 = 2.4 − 0.217∅3.51

𝛽𝑔 = −0.357 + 0.14∅2.77

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For Laminar Flame Velocity31

Results32

33

0

5

10

15

20

25

30

35

40

-30 -20 -10 0 10 20 30 40 50 60

Mass

Fra

ctio

n B

urn

ed

Crank Angle

Crank Angle vs Flame Expansion Velocity

Flame Velocity

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

0

100

200

300

400

500

600

700

800

0.0547 0.1047 0.1547 0.2047 0.2547

Tem

pera

ture

Mass fraction burned

Mass fraction burned and Temperature of the

mass burned and unburned

Tu Tb

36

0

5

10

15

20

25

30

35

40

0.0547 0.1047 0.1547 0.2047 0.2547

Flam

e e

xp

an

sio

n v

elo

city

Mass fraction burned

Mass fraction burned vs Flame Expansion Velocity

Flame Velocity

37