Prerequisite - Thermodynamics/ Propulsion Review of Fundamentals/ Ideal Turbojet Performance/ Component Performance/ Non Ideal Cycle Analysis/ Ideal Turbofan Performance/ Non Ideal Turbofan cycle Analysis/ Matching and Off Design/ Turbomachine 2D/ Turbomachine 3D/ Non Ideal Turbomachine 2D/ Axial Flow Compressors Off Design Performance

1. Aeropropulsion
Unit
Fuel Injection
2005 - 2010
International School of Engineering, Chulalongkorn University
Regular Program and International Double Degree Program, Kasetsart University
Assist. Prof. Anurak Atthasit, Ph.D.

2. Aeropropulsion
Unit
2
A. ATTHASIT
Kasetsart University
Topics
1.Solid and Fluid Fuels
2.Liquid and Flame
3.Jet Fuel
4.Liquid Fuel Atomization
5.Fuel Injecter

3. Aeropropulsion
Unit
3
A. ATTHASIT
Kasetsart University
Type of Fuels – Solid Fuels
Solid fuels
Coal classification
Anthracite: hard and geologically the oldest
Bituminous
Lignite: soft coal and the youngest
Further classification: semi- anthracite, semi-bituminous, and sub-bituminous
Chemical properties
Chemical constituents: carbon, hydrogen, oxygen, sulphur

4. Aeropropulsion
Unit
4
A. ATTHASIT
Kasetsart University
Solid Fuels (Physical Properties)
Physical properties Heating or calorific value (GCV) Moisture content Volatile matter Ash
Parameter
Lignite
(Dry Basis)
Indian Coal
Indonesian Coal
South African Coal
GCV (kCal/kg)
4,500
4,000
5,500
6,000
Heating or calorific value

5. Aeropropulsion
Unit
5
A. ATTHASIT
Kasetsart University
Liquid Fuels – Calorific Value
Calorific value
• Heat or energy produced
• Gross calorific value (GCV): vapour is fully condensed
• Net calorific value (NCV): water is not fully condensed
Fuel Oil Gross Calorific Value (kCal/kg) Kerosene 11,100 Diesel Oil 10,800 L.D.O 10,700 Furnace Oil 10,500 LSHS 10,600

6. Aeropropulsion
Unit
6
A. ATTHASIT
Kasetsart University
Liquid Fuels Vs Solid Fuels
Four advantages of liquid fuels over solid fuels…
1 Liquid fuels have moderate ignition temperature. 2 Liquid fuels are easy to transport. 3 Liquid fuels have high calorific value 4 Liquid fuels do not leave any residue on burning.

7. Aeropropulsion
Unit
Kasetsart University A. ATTHASIT 7
Distillation Column
Furnace
Crude
Kerosene
Gases +Tops + Naphtha
Light Gasoil
Heavy Gasoil
Long Residue

8. Aeropropulsion
Unit
8
A. ATTHASIT
Kasetsart University
Liquid Fuel Classification
1. Light Petroleum Distillates (LPD)
2. Gasoline
3. Medium Petroleum Distillates (MPD)
4. Kerosene
5. Heavy Petroleum Distillates (HPD)
6. Miscellaneous

9. Aeropropulsion
Unit
9
A. ATTHASIT
Kasetsart University
Liquid Fuel Classification
Light Petroleum Distillates Produced by distilling crude oil. From C4 thru C11 range of hydrocarbons. Representatives: petroleum ether, cigarette lighter fluid, some camping fuels and solvents. Gasoline Refined petroleum mixture of the C4 thru C12 range. Produced from crude oil using ‘cracking and reforming’. All brands / grades of automotive gasoline fit within this.

10. Aeropropulsion
Unit
10
A. ATTHASIT
Kasetsart University
Liquid Fuel Classification
Medium Petroleum Distillates Produced by distilling crude oil. From C8 thru C12 range of hydrocarbons. Representatives: paint thinners, mineral spirits, dry cleaning solvents and charcoal starter containing mineral spirits. Kerosene Produced by distilling crude oil. From the C9 thru C16 range of hydrocarbons. Representatives: kerosene, jet fuel, and lamp oils.

11. Aeropropulsion
Unit
11
A. ATTHASIT
Kasetsart University
Liquid Fuel Classification
Heavy Petroleum Distillates Produced by distilling crude oil. From C10 thru C23 range of hydrocarbons. Representatives: diesel, lamp / home heating oils. Miscellaneous Produced by collecting - recombining certain fractions of distilled crude oil. From a wide range of hydrocarbons. Representatives: brush cleaners, thinning agents, strippers, products for home, auto-industrial use.

12. Aeropropulsion
Unit
12
A. ATTHASIT
Kasetsart University
Liquid and Flame

13. Aeropropulsion
Unit
13
A. ATTHASIT
Kasetsart University
Properties of Flammable Liquids
The vapor of a flammable liquid ignites and causes fire or explosion – not the liquid itself. The flammability of a liquid depends on its physical properties:
•Vapor Pressure
•Flash Point
•Limits of Flammability
•Vapor Density

14. Aeropropulsion
Unit
14
A. ATTHASIT
Kasetsart University
Vapor Pressure
•Vapor pressure is a measure of how fast a liquid evaporates.
• The higher the vapor pressure the more rapidly the liquid will evaporate.
• Vapor pressure goes up and down with the temperature of the liquid.

15. Aeropropulsion
Unit
15
A. ATTHASIT
Kasetsart University
What is Flash Point?
•Flash point is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid.
•The lower the flash point, the easier it is to ignite the material. For example, gasoline has a flash point of -40 degrees C (-40 F) and is more flammable than ethylene glycol (antifreeze) which has a flash point of 111 degrees C (232 F).

16. Aeropropulsion
Unit
Kasetsart University A. ATTHASIT 16
What Is Ignition Point?
•The minimum temperature at
which a substance will
continue to burn without
additional application of
external heat. Also called
kindling point.
•Liquid •Flash
Point
•Ignition
Temp
•Gasoline -43oC 280oC to
456oC
•Kerosene 38oC 210oC

17. Aeropropulsion
Unit
17
A. ATTHASIT
Kasetsart University
Limits of Flammability
•The limits of flammability is the range that a mixture of air and vapor is flammable.
• Mixtures can be too lean (not enough vapor) or too rich (too much vapor) to ignite and burn.
LEL – “lower explosive limit” UEL – “upper explosive limit”
Example

18. Aeropropulsion
Unit
18
A. ATTHASIT
Kasetsart University
Flammable Physical Relationships
A flammable liquid in its liquid state will not burn. It only will ignite when it vaporizes into a gaseous state. All flammable liquids give off vapors that can ignite and burn when an ignition source i.e., lighted cigarette or spark.

19. Aeropropulsion
Unit
19
A. ATTHASIT
Kasetsart University
Jet Fuel

20. Aeropropulsion
Unit
20
A. ATTHASIT
Kasetsart University
Jet Fuel – Civil Jet Fuels
JET A-1
It is produced to a stringent internationally agreed standard, has a flash point above 38°C (100°F) and a freeze point maximum of -47°C. It is widely available outside the U.S.A. Jet A- 1 meets the requirements of British specification DEF STAN 91-91 (Jet A-1)
JET A
Jet A is a similar kerosene type of fuel, normally only available in the U.S.A. It has the same flash point as Jet A-1 but a higher freeze point maximum (-40°C).
JET B
Jet B is a distillate covering the naphtha and kerosene fractions. It can be used as an alternative to Jet A-1 but because it is more difficult to handle (higher flammability), there is only significant demand in very cold climates where its better cold weather performance is important. In Canada it is supplied against the Canadian Specification CAN/CGSB 3.23

21. Aeropropulsion
Unit
21
A. ATTHASIT
Kasetsart University
Jet Fuel – Military Jet Fuels
JP-4 JP-4 is the military equivalent of Jet B with the addition of corrosion inhibitor and anti-icing additives; it meets the requirements of the U.S. Military Specification MIL-DTL-5624U and also meets the requirements of the British Specification DEF STAN 91-88 AVTAG/FSII. JP-5 JP-5 is a high flash point kerosene meeting the requirements of the U.S. Military Specification MIL-DTL-5624U Grade JP-5. JP-5 also meets the requirements of the British Specification DEF STAN 91-86 AVCAT/FSII. JP-8 JP-8 is the military equivalent of Jet A-1 with the addition of corrosion inhibitor and anti- icing additives; it meets the requirements of the U.S. Military Specification MIL-DTL- 83133E. JP-8 also meets the requirements of the British Specification DEF STAN 91-87 AVTUR/FSII. NATO Code F-34.

22. Aeropropulsion
Unit
22
A. ATTHASIT
Kasetsart University
Aviation Fuel Additives
1. Anti-knock additives reduce the tendency of gasoline to detonate.
2. Anti-oxidants prevent the formation of gum deposits on fuel system components caused by oxidation of the fuel in storage and also inhibit the formation of peroxide compounds in certain jet fuels.
3. Static dissipater additives reduce the hazardous effects of static electricity generated by movement of fuel through modern high flow-rate fuel transfer systems (e.g. aircraft and fuelling equipment).
4. Corrosion inhibitors protect ferrous metals in fuel handling systems, such as pipelines and fuel storage tanks, from corrosion.
5. Fuel System Icing Inhibitors (Anti-icing additives) reduce the freezing point of water precipitated from jet fuels due to cooling at high altitudes and prevent the formation of ice crystals which restrict the flow of fuel to the engine.
6. Biocide additives are sometimes used to combat microbiological growths in jet fuel.
7. Thermal Stability Improver additives are sometimes used in military JP-8 fuel, to produce a grade referred to as JP-8+100, to inhibit deposit formation in the high temperature areas of the aircraft fuel system.

23. Aeropropulsion
Unit
23
A. ATTHASIT
Kasetsart University
Liquid Fuel Atomization

24. Aeropropulsion
Unit
24
A. ATTHASIT
Kasetsart University
Basic Processes in Atomization
Fuel stream is broken up into shreds and ligaments
Large drops and globules produced in primary atomization are further disintegrated into smaller droplets
Secondary Atomization

25. Aeropropulsion
Unit
25
A. ATTHASIT
Kasetsart University
Processes in Atomization
Secondary atomization:
Large blobs produce small droplets
Final size distribution
Primary atomization:
Jet breaks up into liquid ligaments and blobs

26. Aeropropulsion
Unit
26
A. ATTHASIT
Kasetsart University
Spray Characteristics
Characteristics of fuel spray: droplet velocities and drop size distributions
Characteristics of fuel spray: affected by
• Geometry of the atomizer
• Properties of the gaseous medium into which the fuel stream is discharged
• Physical properties of the fuel itself

27. Aeropropulsion
Unit
27
A. ATTHASIT
Kasetsart University
Mechanism of Jet and Sheet Breakup
•Small disturbances at injector exit promote the formation of waves that eventually lead to-disintegration into ligaments and then drops.
•The relative velocity between air and fuel will be lower, resulting in larger drops.
•An increase in fuel viscosity is always accompanied by an increase in mean drop size.

28. Aeropropulsion
Unit
28
A. ATTHASIT
Kasetsart University
Breakup of Fuel Jets
Jet issues from orifice
Oscillation of jet causes formation of neck
Neck thins
Neck breaks due to surface tension
‘Satellite drop’
Drop becomes spherical

29. Aeropropulsion
Unit
Kasetsart University A. ATTHASIT 29
Breakup of Fuel Jets – Rayleigh Instability
According to Rayleigh, the growth
of small disturbances leads to
breakup when the fastest growing
disturbance attains a wavelength λopt
of 4.51d, where d is the initial jet
diameter.
Cylinder of length 4.51d becomes a spherical drop:
2 3 4.51d d D
4 6
 
  D  1.89d

30. Aeropropulsion
Unit
Kasetsart University A. ATTHASIT 30
Rayleigh Instability Modification
Weber extended Rayleigh’s work to include the effect of viscosity on the
disintegration of jets into drops:
0.5
opt   4.44d(13Oh )
The Ohnesorge number, Oh , is a dimensionless number that relates the
viscous and surface tension force.
Oh
L



μ is the liquid viscosity
ρ is the liquid density
σ is the surface tension
L is the characteristic length scale (typically- drop diameter)
The Ohnesorge number for a 3 mm diameter rain drop is typically ~0.002. Larger
Ohnesorge numbers indicate a more influence of the viscosity .

31. Aeropropulsion
Unit
31
A. ATTHASIT
Kasetsart University
Modes of Atomization
Low velocities: oscillations causes the jet to disintegrate into drops (Rayleigh mechanism of breakup). Drop diameters ~ 2 jet diameter.
Increase in jet velocity: interaction between the jet and the air reduces the optimum wavelength for jet breakup  smaller drop size, drop diameters ~ jet diameter.
Further increase in jet velocity: unstable growth of small waves in droplets  satellite creation.
High jet velocities: atomization occurs rapidly, mean drop diameters are less than 80 μm.
Mode 1-3: dependent on fuel viscosity, ambient air density, and initial jet diameter
Mode 4: corresponds to prompt atomization, and drop sizes are strongly dependent on surface tension

32. Aeropropulsion
Unit
32
A. ATTHASIT
Kasetsart University
Breakup of Fuel Sheets
Most atomizers discharge the fuel in the form of a conical sheet.
If the relative velocity between the fuel sheet and the surrounding air is fairly low, a wave motion is generated on the sheet which causes rings of fuel to break away from its leading edge.

33. Aeropropulsion
Unit
33
A. ATTHASIT
Kasetsart University
Breakup of Fuel Sheets - Airblast
Air blast atomizers: one or more high-velocity air streams (usually swirling) impinge on a slow-moving, conical sheet of fuel.

34. Aeropropulsion
Unit
34
A. ATTHASIT
Kasetsart University
Breakup of Fuel Sheets – Pressure Swirl Atomizer
Pressure-swirl atomizers: the relative velocity required for atomization is achieved by injecting the conical sheet of fuel at high velocity into slow-moving air or gas.
The ambient pressure is varied (from the left to right): 1, 5, 20 bar. The increased ambient pressure leads to the appearance of the periodic structures on the penetrating spray.
Fachgebiet Strömungslehre und Aerodynamik – spray research group

35. Aeropropulsion
Unit
35
A. ATTHASIT
Kasetsart University
Prompt Atomization
Breakup take place very rapidly: the jet or sheet has no time to develop a wavy structure, but is immediately torn into fragments by its vigorous interaction with the surrounding air.
Drop sizes are largely independent of the initial fuel dimension (jet diameter or sheet thickness) and independent of viscosity.
Rapid and violent disruption of the fuel

36. Aeropropulsion
Unit
36
A. ATTHASIT
Kasetsart University
Classical or Prompt - Weber numbers
The Weber Number is a dimensionless value useful for analyzing fluid flows where there is an interface between two different fluids.
The Weber Number is the ratio between the inertial force and the surface tension force, and can be expressed as
We = ρ v2 l / σ
where
We = Weber number (dimensionless)
ρ = density of fluid (kg/m3, lb/ft3)
v = velocity of fluid (m/s, ft/s)
l = characteristic length (m, ft)
σ = surface tension (dyne/cm)
Since the Weber Number represents an index of the inertial force to the surface tension force acting on a fluid element, it can be useful analyzing thin films flows and the formation of droplets and bubbles.

37. Aeropropulsion
Unit
Kasetsart University A. ATTHASIT 37
Classical or Prompt - Weber numbers
2 v D
We



Low We  low atomizing pressures or low atomizing air velocities
 Classical mechanism is dominant
High We  high atomizing pressures or high atomizing air velocities
 Prompt mechanism is dominant

38. Aeropropulsion
Unit
38
A. ATTHASIT
Kasetsart University
Atomizer Requirements
1.Ability to provide good atomization over a wide range of fuel flow rates.
2.Rapid response to changes in fuel flow rate.
3.Freedom from flow instabilities.
4.Low power requirements
5.Capability for scaling, to provide design flexibility.
6.Low cost, light weight, ease of maintenance, and ease of removal for servicing.
7.Low susceptibility to damage during manufacture and installation.
8.Low susceptibility to blockage by contaminants in the fuel and to carbon buildup on the nozzle face.
9.Low susceptibility to gum formation by heat soakage.
10.Uniform radial and circumferential fuel distribution.

39. Aeropropulsion
Unit
39
A. ATTHASIT
Kasetsart University
Pressure Atomizers - Principal
Pressure atomizers rely on the conversion of pressure into kinetic energy to achieve a high relative velocity between the fuel and the surrounding air or gas

40. Aeropropulsion
Unit
40
A. ATTHASIT
Kasetsart University
Pressure Atomizers
Pressure Atomizers
Plain Orifice
Dual-Orifice

41. Aeropropulsion
Unit
41
A. ATTHASIT
Kasetsart University
Rotary Atomizers
Advantages: cheapness and simplicity, only a low-pressure fuel pump is needed. Disadvantages: poor high-altitude relighting performance (non optimized igniter-plug location because of the long flow path), slow response to changes in fuel flow.
Ideally suited for small engines: high rotational speeds >350 rps.

42. Aeropropulsion
Unit
42
A. ATTHASIT
Kasetsart University
Airblast Atomizers
Airblast atomizers have many advantages over pressure atomizers, especially in their application to combustion systems operating at high pressures.
-They require lower fuel pump pressures and produce a finer spray.
-Ensures thorough mixing of air and fuel, ensuing the combustion process in characterized by very low soot formation and a blue flame of low luminosity.
-Wide range of aircraft, marine and industrial gas turbines.

43. Aeropropulsion
Unit
Kasetsart University A. ATTHASIT 43
Conclusion
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2
1
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2
1
1
*
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2
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1
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2
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1
2
1
1
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2
1
1
2
1
2
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2
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1
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T
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M
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T
M
T
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0
0 t
dA d du
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udu dP
dh dh udu
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a
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d
A dA
u du
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T
A
u

dx
2
dP
P 
Cabin Crew!
Prepare for
take-off!