Notes on Automobile Component Design.pptx

CHAPTER ONE
FUELS AND ITS CHEMICAL REACTION IN
COMBUSTION
Source : Popular Mechanics
3/11/2024 RLK 1

Contents
1.1 Fuel structure and composition
1.2 Properties of fuel
1.3 Chemical reactions in fuel combustion
1.4 Combustible mixture and products of combustion
1.5 Heating value of fuel and mixture
1.6 Heat capacity of charge and combustion products
3/11/2024 RLK 2

CLASSIFICATION
Fuels can be generally classified into two factors:
On the basis of their fuels state:
• Solid Fuels
• Liquid Fuels
• Gaseous Fuels
On the basis of their occurrence:
• Natural Fuels
• Artificial Fuels
3/11/2024 RLK 3

Natural Fuel Artificial Fuels
Solid Fuels
Wood,
Coal,
Oil Shale
Tanbark, Bagasse, Straw,
Charcoal,
Coal,Briquettes
CLASSIFICATION
Source : Globe.net
3/11/2024 RLK 4

Solid Fuels
Advantages:
• Easier transportation and storage.
• Low production cost.
• Moderate ignition temperature.
Disadvantages:
• Large portion of energy is wasted.
• Cost of handling is high and
controlling is also hard.
• Ash content is high & burn with
clinker formation.
Source: The Economist Time
3/11/2024 RLK 5

Natural
Fuel
Artificial Fuels
Liquid Fuels
Petroleum Oils from distillation of
petroleum,
Coal Tar,
Shale-Oil,
Alcohols, etc.
CLASSIFICATION
Source: 123RF
3/11/2024 RLK 6

Liquid Fuels Advantages:
• Higher calorific value per unit mass.
• Burn without ash, clinkers, etc.
• Controlling the combustion is easier.
• Transportation easier through pipes and stored
indefinitely without loss.
• Loss of energy is comparatively lower.
• Require less furnace space for combustion.
Disadvantages:
• Cost of liquid fuel is much higher compared to solid fuel.
• Storage methods are costlier.
• Greater risk of fire hazards.
• Special burning equipment required for more efficient
combustion.
Source: Liquidfuel.net
3/11/2024 RLK 7

Natural
Fuel
Artificial Fuels
Gaseous Fuels
Natural Gas Coal gas, Producer Gas,
Water Gas, Hydrogen,
Acetylene, Oil Gas
Blast Furnace Gas,
CLASSIFICATION
3/11/2024 RLK 8

Gaseous Fuels Advantages:
• Transportation through pipes is easy.
• Sparking combustion is really easy.
• They have a higher heat content.
• Clean after use.
• Do not require any special burner technology.
Disadvantages:
• Large storage tanks required.
• As they are highly inflammable, the chance for
fire hazards are extremely high and strict
safety measures need to be followed.
Source: AP News
3/11/2024 RLK 9

Structure of Hydrocarbon
Paraffins
• also known as alkanes,
• the general
formula CnH2n+2,
where n is the number of
carbon atoms.
3/11/2024 RLK 10

 Olefins
• Olefins are unsaturated
compounds
• formula of CnH2n.
3/11/2024 RLK 11

 Naphthenes
• also known as cycloalkanes,
• are saturated hydrocarbons
• at least one ring of carbon
atoms.
• They have the general
formula CnH2n
3/11/2024 RLK 12

 Aromatics
• The aromatic compounds
or arenes
• general formula of
CnH2n−6
where n is the number of
atoms present and m is the
number of rings.
3/11/2024 RLK 13

Isomerism
1.Structural Isomers
• Chain Isomers
• Chain isomers are
made up of two or
more carbon or other
compounds
• same molecular
formula
• different atomic
arrangements, or
branches
3/11/2024 RLK 15

2. Functional group isomers
• have the same molecular
formula,
• but different functional
groups on the chain.
• For instance, ethyl alcohol
and dimethyl ether have the
same chemical formula, but
different functional groups,
which are circled in blue.
3/11/2024 RLK 16
Isomerism

3.Positional isomers
• are constitutional isomers
that have the same carbon
skeleton
• the same functional groups
but differ from each other
in the location of the
functional groups on or in
the carbon chain
3/11/2024 RLK 17
Isomerism

4. Metamerism
• This type of isomerism arises due
to the presence of different alkyl
chains on each side of the
functional group.
• It is a rare type of isomerism and is
generally limited to molecules that
contain a divalent atom (such as
sulfur or oxygen), surrounded by
alkyl groups.
3/11/2024 RLK 18
Isomerism

Fractional Distillation
3/11/2024 RLK 19

Names of fractions at
the different
condensation
Number of C atoms in the
hydrocarbon molecule
fraction
The approximate
boiling range in °C
of the fraction
Fuel Gas, LPG, refinery
gas
C 1 to 4 <25°C
Gasoline – petrol C 5 to 7 25 to 75°C
Naphtha C 6 to 10 75 to 190°C
Paraffin, kerosene C 10 to 16 190 to 250°C
Diesel oil, gas oil C 14 to 20 250 to 350°C
3/11/2024 RLK 20

1.1 Fuel structure and composition
Crude oil is composed of elements,
which are mainly
• hydrogen (about 13% by weight)
• carbon (about 85%)
• nitrogen (about 0.5%),
• sulfur (0.5%),
• oxygen (1%), and
• metals such as iron, nickel, and copper
(less than 0.1%)
Figure 1 Crude oil
Source :RESOURCE LIBRARY
3/11/2024 RLK 21

• According to weight hydrocarbon, Composition of crude is
Hydrocarbon Average Range
Paraffins 30% 15 to 60%
Naphthenes 49% 30 to 60%
Aromatics 15% 3 to 30%
Asphaltics 6% Remainder
3/11/2024 RLK 22

Gasoline
• The composition of gasolines varies widely, depending on
the crude oils used,
the refinery processes available,
 the overall balance of product demand,
and the product specifications.
• The typical composition of gasoline hydrocarbons (% volume) is as
follows: 4-8% alkanes; 2-5% alkenes; 25-40% isoalkanes; 3-7%
cycloalkanes; l-4% cycloalkenes; and 20-50% total aromatics (0.5-
2.5% benzene) (IARC 1989).
3/11/2024 RLK 23

Diesel
• Diesel is composed of about 75% saturated hydrocarbons (primarily
paraffins including n, iso, and cycloparaffins), and 25% aromatic
hydrocarbons (including naphthalenes and alkylbenzenes).
• The average chemical formula for common diesel fuel is C12H23,
• ranging from approx. C10H20 to C15H28.
3/11/2024 RLK 24

Kerosene
• Chemically, kerosene is a mixture of hydrocarbons.
• The chemical composition depends on its source, but it usually
consists of about 10 different hydrocarbons, each containing 10 to
16 carbon atoms per molecule.
• The main constituents are saturated straight-chain and branched-
chain paraffins, as well as ring-shaped cycloparaffins (also known as
naphthenes).
• Kerosene is less volatile than gasoline.
3/11/2024 RLK 25

Cracking
• Cracking is the name given to
breaking up large hydrocarbon
molecules into smaller and more
useful bits.
• This is achieved by using high
pressures and temperatures
without a catalyst, or lower
temperatures and pressures in the
presence of a catalyst.
• The source of the large
hydrocarbon molecules is often the
naphtha fraction or the gas oil
fraction from the fractional
distillation of crude oil (petroleum).
3/11/2024 RLK 26

• These fractions are obtained from
the distillation process as liquids,
but are re-vaporized before
cracking.
• There is not any single unique
reaction happening in the cracker.
• The hydrocarbon molecules are
broken up in a fairly random way to
produce mixtures of smaller
hydrocarbons, some of which have
carbon-carbon double bonds.
3/11/2024 RLK 27

Cracking History
• The first thermal cracking process for breaking up large nonvolatile
hydrocarbons into gasoline came into use in 1913; it was invented by
William Merriam Burton, a chemist who worked for the Standard Oil
Company (Indiana),
• In the 1920s, French chemist Eugène Houdry improved the cracking
process with catalysts to obtain a higher-octane product. His process was
introduced in 1936 by the Socony-Vacuum Oil Company (later Mobil Oil
Corporation)
• Catalytic cracking was itself improved in the 1940s with the use of fluidized
or moving beds of powdered catalyst.
• During the 1950s, as demand for automobile and jet fuel increased,
hydrocracking was applied to petroleum refining. This process employs
hydrogen gas to improve the hydrogen-carbon ratio in the cracked
molecules and to arrive at a broader range of end products, such as gasoline,
kerosene (used in jet fuel), and diesel fuel.
3/11/2024 RLK 28

Thermal cracking
• High temperatures (typically in the range of 450°C to 750°C) and
pressures (up to about 70 atmospheres)
• Used to break the large hydrocarbons into smaller ones.
• Thermal cracking gives mixtures of products containing high
proportions of hydrocarbons with double bonds - alkenes.
• carbon-carbon bonds are broken so that each carbon atom ends up
with a single electron. In other words, free radicals are formed.
3/11/2024 RLK 29

Catalytic cracking
• Modern cracking uses zeolites as the catalyst.
• temperature of about 500°C and moderately low pressures.
• These are complex aluminosilicates, and are large lattices of
aluminium, silicon and oxygen atoms carrying a negative charge.
• The zeolites used in catalytic cracking are chosen to give high
percentages of hydrocarbons with between 5 and 10 carbon atoms -
particularly useful for petrol (gasoline). It also produces high
proportions of branched alkanes and aromatic hydrocarbons like
benzene.
3/11/2024 RLK 30

Alkylation
• Process of producing a high-octane number gasoline
component(alkylate) by combining light olefins with iso-butane in the
presence of a strongly acid catalyst
• Mineral acid such as sulfuric acid and hydro-fluoric acid are used
commonly but these have been replaced by solid acid catalyst.
• Alkylation produces a mixture of high-octane number branch chain
paraffins with low sensitivity and can be a valuabale component when
MON is limiting specification point.
3/11/2024 RLK 32

• Olefins used in the mixture are usually derived from catalytic cracking
units and are normally
• The reaction takes place are complex
• The product is iso-octane (2,2,4 trimethylpentane), which has, by
definition, a RON and a MON of 100.
3/11/2024 RLK 33

Isomerization
• This is a process for converting straight chain paraffins to branch
chain and used to provide iso-butane feed for alkylation process
• Simply to convert the realatively low-octane number quality of
staright paraffins to a more valuable branch chain molecules.
• Catalyst used paltinium or zeolite
• Separating unchanged staright paraffins
• Sulfur free to avoid catalyst poisoining
3/11/2024 RLK 34

Polymerization
• In this process light olefins such as propene and butenes are reacted
together to give heavier olefins, which ahs a good octane quality
• Catalyst used is phosphoric acid on keiselguhr.
• The product is 100% olefinic
• Relatively poor MON compared to RON
3/11/2024 RLK 35

Finishing Processes
Produced gasoline and diesel are unstable
Contains hydrogen sulfide, mercaptants(thiols), cresylic acids and
nepthenic acid
Other acid materials coming from alkylation
Treatments
• Causatic Washing
• Merox Treating
• Hydrosulfurization
3/11/2024 RLK 36

Properties of fuel
1. Density ()
• density is strongly influenced by temperature
• the quality standards state the determination
of density at 15 °C.
• The density of the fuel also affects the quality
of atomization and combustion.
• density affects the fuel mass that reaches the
combustion chamber, and thus the energy
content of the fuel dose, altering the fuel/air
ratio and the engine’s power.
Source: SPL
3/11/2024 RLK 37

Density
• Fuel density directly affects fuel performance.
• some of the engine properties, such as cetane number, heating value
and viscosity are strongly connected to density.
Storage
• As diesel engine fuel systems (the pump and the injectors) meter the
fuel by volume, modification of the Knowing the density is also
necessary in the manufacturing, storage, transportation and
distribution process of biodiesel as it is an important parameter to be
taken into account in the design of these processes.
3/11/2024 RLK 38

viscosity The viscosity of liquid fuels is their
property to resist the relative movement
tendency of their composing layers due
to intermolecular attraction forces
(viscosity is the reverse of fluidity).
Viscosity influences
• the ease of starting the engine,
• the spray quality,
• the size of the particles (drops),
• the penetration of the injected jet and
the quality of the fuel-air mixture
combustion (Canakci, 2009).
Source: newbhu.ec.in
3/11/2024 RLK 39

Fuel viscosity has both an upper and a lower limit.
The fuel with a too low viscosity
• provides a very fine spray,
• the drops having a very low mass and speed.
This leads to insufficient penetration and the formation of black smoke specific to
combustion in the absence of oxygen (near the injector) (Băţaga, 2003).
A too viscous biodiesel leads to the formation of too big drops,
• which will penetrate to the wall opposite to the injector.
• The cylinder surface being cold, it will interrupt the combustion reaction and blue
smoke will form (intermediate combustion product consisting of aldehydes and acids
with pungent odor) (Băţaga, 2003) .
3/11/2024 RLK 40

Flash Point
• Flash point is the minimum
temperature of liquid to give
enough vapor to form combustible
mixture with air.
• If the flash point of the fuel is less
than the ambient temperature
then this condition is best for the
engine.
Source: NAST
3/11/2024 RLK 41

Pour point
• The Pour Point is the temperature at
which the paraffin in the fuel has
crystallized to the point where the fuel
gels and becomes resistant to flow.
3/11/2024 RLK 43

• It has many implications,
especially within engines,
• it can be used to determine
what temperature ranges the oil,
or petroleum, can be used in.
• It will also give a good indication
of the temperature at which the
oil will become too viscous that
it will prevent the engine from
starting
3/11/2024 RLK 44

Reid Vapor Pressure
3/11/2024 RLK 45

Fractional Distillation
Source: ASTM D86
3/11/2024 RLK 46

Gasoline Aviation Oil
Kerosene Diesel
Source: BS4
Distillation recovery as per ASTM D86
3/11/2024 RLK 47

Cetane Number
• Cetane Number is a measure of
the ignition quality of a diesel
fuel.
• Cetane number is actually a
measure of a fuel's ignition
delay.
• This is the time period between
the start of injection and start of
combustion (ignition) for the
fuel.
3/11/2024 RLK 48

Ignition delay and cetane number
3/11/2024 RLK 49

• In a particular diesel engine, higher Cetane fuels will have shorter ignition
delay periods than lower Cetane fuels.
• Fuel Cetane number strongly affects the ignition delay and combustion
phasing of this single injection mode of low-temperature premixed diesel
combustion
• One of the reasons for forming exhaust pollutants is insufficient combustion
in the engine cylinder.
• Fuel properties also play a significant role to increase or decrease exhaust
pollutants. Various investigations clearly reported that Cetane number (CN)
affects exhaust emissions..
• Fuels with a high CN have a very short ignition delay time; that is, ignition
occurs in a very brief interval of time after injection begins.
• Conversely, the longer the ignition delay time the lower the CN.
3/11/2024 RLK 51

Cetane Index
• ADTM D4737 provide the four variable equation presented in equation 1
• CI = 45.2 + (0.0892) (T10 N) + (0.131 + (0.901) (B)) (T50 N) + (0.0523- (0.420)(B))
(T90 N ) +(0.00049)((T10N)² – (T90N)²) + (107) (B) + (60) (B²) ………………(1) [16]
• Where:
• CI = Calculated Cetane Index by use of four variable equation,
• D = Density at 15ºC, g/cm³
• DN = D-0.85
• B = (exp[ ((-3.5) (DN)) – 1
• T10 N = T10-215
• T50 N = T50-260
• T90 N = T90-310
• T10= Distillation temperature (⁰C) corresponding to 10% (V/V) recovery
3/11/2024 RLK 52

Cetane Index
• ASTM D976 provide 2 variable equation which is presented in
equation 2
• CCI = 454.74 – 1641.416 D + 774.74 D²– 0.554 T50 + 97.803 (log
T50)² ……………. (2) [17]
• Where
• CCI = Calculated Cetane index
• D = Density at 15ºC, g/cm³
• T50 = mid-boiling temperature, ⁰C
3/11/2024 RLK 53

Octane Number
3/11/2024 RLK 54

Sulphur • The amount of sulphur in the fuel oil
depends mainly on the source of the
crude oil and to a lesser extent on the
refining process.
• The normal sulfur content for the
residual fuel oil (furnace oil) is in the
order of 2-4 %.
• The main disadvantage of sulphur is the
risk of corrosion by sulphuric acid
formed during and after combustion,
and condensing in cool parts of the
chimney or stack, air pre heater and
economizer.
3/11/2024 RLK 57

Ash Content
• The ash value is related to the inorganic material in the fuel oil.
• The ash levels of distillate fuels are negligible.
• Residual fuels have more of the ash-forming constituents.
• These salts may be compounds of sodium, vanadium, calcium,
magnesium, silicon, iron, aluminum, nickel, etc.
• Typically, the ash value is in the range 0.03–0.07%.
• Excessive ash in liquid fuels can cause fouling deposits in the
combustion equipment.
• Ash has erosive effect on the burner tips, causes damage to the
refractories at high temperatures and gives rise to high temperature
corrosion and fouling of equipment’s.
3/11/2024 RLK 58

Carbon Residue
• Carbon residue indicates the tendency of oil to deposit a carbonaceous
solid residue on a hot surface, such as a burner or injection nozzle,
when its vaporisable constituents evaporate.
• Residual oil contain carbon residue ranging from 1 percent or more.
3/11/2024 RLK 59

Diesel Specification
3/11/2024 RLK 61

Petrol Specification
3/11/2024 RLK 62

Petrol Specification
3/11/2024 RLK 63

Chemical reactions in fuel combustion
• Fuel + O2 → CO2 + H2O
• The original substance is called the fuel,
• the source of oxygen is called the oxidizer.
• During combustion, new chemical substances
are created from the fuel and the oxidizer.
These substances are called exhaust.
3/11/2024 RLK 64

• Energy is released in a series of small
explosions (combustion) as fuel reacts
chemically with oxygen from the air.
• A complete combustion reaction occurs
when a fuel reacts quickly with oxygen (O2)
and produces carbon dioxide (CO2)
and water (H2O).
• The general equation for a complete
combustion reaction is:
Fuel + O2 → CO2 + H2O
3/11/2024 RLK 65

3/11/2024 RLK 66
 Combustion Reaction of Gasoline
C8H18 + 12.5O2 8CO2 + 26H2O
 Combustion Reaction of Kerosene
2C12H26 + 37O2 24CO2 + 26H20
 Combustion Reaction of Diesel
C13H28 + 20O2 13CO2 + 14H2O

Types of Combustion
3/11/2024 RLK 67

QUESTION?
• Sometimes the flame on a gas
stove isn’t just blue but has some
yellow or orange in it.
• Why might this occur?
3/11/2024 RLK 68

QUESTION?
• So if you have a bottle of
gasoline (octane) sitting around
and open to the atmosphere
which contains oxygen,
• why doesn’t it just burst into
flames?
3/11/2024 RLK 69

QUESTION?
When sand is poured over
some burning material, the fire
goes off. It is because:
• Ignition temperature is brought
down
• Air Supply is cut off
• Sand is a band conductor of heat
• All of the above
3/11/2024 RLK 70

1] Complete Combustion
• Complete combustion occurs in an
unlimited supply of air, oxygen in
particular.
• complete combustion is also known as
clean combustion.
• Here the hydrocarbon will burn out
completely with the oxygen and leave
only two byproducts, water, and
carbon dioxide.
3/11/2024 RLK 71
Types of Combustion

2. Incomplete combustion
• Incomplete combustion takes place
when the air is in limited supply.
• And as opposed to complete
combustion it is otherwise known as
dirty combustion.
• Due to lack of oxygen, the fuel will not
react completely. This, in turn,
produces carbon monoxide and soot
instead of carbon dioxide.
3/11/2024 RLK 72
Types of Combustion

3. Rapid Combustion
• Rapid energy needs external heat
energy for the reaction to occur.
• The combustion produces a large
amount of heat and light energy and
does so rapidly.
• The combustion will carry on as long
as the fuel is available.
3/11/2024 RLK 73
Types of Combustion

4] Spontaneous Combustion
• As the name suggests the combustion
occurs spontaneously.
• This means that it requires no external
energy for the combustion to start.
• It happens due to self-heating.
• A substance with low-ignition
temperatures gets heated and this heat
is unable to escape.
3/11/2024 RLK 74
Types of Combustion

5] Explosive Combustion
• Explosive Combustion happens when
the reaction occurs very rapidly.
• The reaction occurs when something
ignites to produce heat, light and
sound energy, the simple way to
describe is it to call it an explosion.
• Some classic examples are firecrackers
or blowing up of dynamite.
3/11/2024 RLK 75
Types of Combustion

Chemical Reaction in combustion
1. When carbon burns in sufficient
quantity of oxygen
2. If sufficient oxygen is not available
3/11/2024 RLK 76

3. If carbon monoxide is burnt further 4. When sulphur burns with oxygen,
3/11/2024 RLK 77

5. When Hydrogen reacts with Oxygen 6. When Methane reacts with oxygen
3/11/2024 RLK 78

7.When Ethene Reacts with Oxygen
3/11/2024 RLK 79

Theoretical or Minimum Air Required for Complete
Combustion
• The theoretical or minimum mass (or volume) of oxygen required for
complete combustion of 1 kg of fuel may be calculated from the
chemical analysis of the fuel.
• In order to obtain maximum amount of heat from a fuel, the adequate
supply of oxygen is very essential for the complete combustion of a
fuel.
3/11/2024 RLK 80

3/11/2024 RLK 81
• 1 kg of carbon requires 8 / 3 kg of oxygen for its complete combustion.
• 1 kg of hydrogen requires 8 kg of oxygen
• 1 kg of sulphur requires 1 kg of oxygen for its complete combustion.
• Total oxygen required for complete combustion of 1 kg of fuel is given
as:
Combustion

3/11/2024 RLK 82
 If some oxygen (say O2 kg) is already present in the fuel, then total
oxygen required for the complete combustion of 1 kg of fuel is:
 The composition of air is taken as:
Nitrogen (N2) = 77% ; Oxygen (O2) = 23% (By Mass)
Nitrogen (N2) = 79%; Oxygen (O2) = 21% (By Volume)
 for obtaining 1 kg of oxygen, amount of air required
Combustion

3/11/2024 RLK 83
Combustion
Theoretical or minimum air required for complete combustion of 1
kg of fuel:

3/11/2024 RLK 84
Average Molar Mass of air

3/11/2024 RLK 85
The atomic / molecular weights are:
Nitrogen: 14.0067 x 2 = 28.0134 g/mol
Oxygen: 15.9994 x 2 = 31.9988 g/mol
Argon: 39.948 g/mol
Carbon dioxide: 44.01 g /mol
Weight of each gas by knowing the percentage
Nitrogen: (78.084 / 100) x 28.0134 = 21.8739 g/mol
Oxygen: (20.946 / 100) x 31.9988 = 6.7025 g/mol
Argon: (0.934 / 100) x 39.948 = 0.373 g/mol
Carbon dioxide: (0.03 / 100) x 44.01 = 0.013203 g/mol
Add all the values we get,
21.8739 + 6.7025 + 0.373 + 0.013203 = 28.96 g / mol. This is the molecular weight
of the air

1.4.4 THE COMBUSTION PROCESS
3/11/2024 RLK 86

3/11/2024 RLK 87

3/11/2024 RLK 88

3/11/2024 RLK 89
In general, the products of combustion include many different species in addition to the major
species (CO2, H2O, N2, O2), and the balance of the stoichiometric equation requires the use of
thermodynamic equilibrium relations. However, assuming that the products contain major species
only (complete combustion) and excess air, the global equation for lean combustion Φ ≤1 is

3/11/2024 RLK 90

Theoretical Air and Air-Fuel Ratio
• The minimum amount of air which will allow the complete combustion of the fuel
is called the Theoretical Air (also referred to as Stoichiometric Air).
• In this case the products do not contain any oxygen.
• If we supply less than theoretical air then the products could include carbon
monoxide (CO), thus it is normal practice to supply more than theoretical air to
prevent this occurrence.
• This Excess Air will result in oxygen appearing in the products.
• The standard measure of the amount of air used in a combustion process is the Air-
Fuel Ratio (AF), defined as follows:
•
3/11/2024 RLK 91

Develop the combustion equation and determine the air-fuel ratio
for the complete combustion of n-Butane (C4H10) with a) theoretical
air, and b) 50% excess air.
3/11/2024 RLK 93

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