Alternative Fuels (contd.) Notes | EduRev

: Alternative Fuels (contd.) Notes | EduRev

 Page 1


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_1.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
The Lecture Contains:
BIODIESEL
Biodiesel Production – Esterification of Oils
Properties of Biodiesel
Emissions
Hydrogen
Greenhouse Gas Emissions with Alternative Fuels
Questions
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 2


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_1.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
The Lecture Contains:
BIODIESEL
Biodiesel Production – Esterification of Oils
Properties of Biodiesel
Emissions
Hydrogen
Greenhouse Gas Emissions with Alternative Fuels
Questions
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_2.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
BIODIESEL
In a 1912 speech, Rudolf Diesel said, "the use of vegetable oils for engine fuels may seem
insignificant today, but such oils may become, in the course of time, as important as petroleum and
the coal - tar products of the present time". The revival of biodiesel derived from vegetable oils started
as a result of agricultural surplus in some European countries and under Kyoto protocol the need of
reducing greenhouse gas CO
2
 emissions.  
Biodiesel is a renewable fuel that is produced from a variety of edible and non-edible vegetable oils
and animal fats. 
The term “biodiesel” is commonly used for methyl or ethyl esters of the fatty acids in natural oils and
fats, which meet the fuel quality requirements of compression-ignition engines.
Straight vegetable oils (SVO) are not considered as biodiesel. The straight vegetable oils have a very
high viscosity that makes flow of these oils difficult even at room temperatures.  Moreover, presence
of glycerine in the vegetable oil causes formation of heavy carbon deposits on the injector nozzle
holes that results in poor and unacceptable performance and emissions from the engine even within a
few hours of operation.
Biodiesel Production – Esterification of Oils
Biodiesel is produced by reacting vegetable oils or animal fats with an alcohol such as methanol or
ethanol in presence of a catalyst to yield mono-alkyl esters. The overall reaction is given in Fig. 8.6.
 Glycerol is obtained as a by-product.
Figure
8.6:
Esterification reaction for vegetable oils and
fats.’
Properties of Biodiesel
A variety of vegetable oils such as soybean, rapeseed, safflower, jatropha-curcas, palm, and
cottonseed oils have been used for production of biodiesel.  Waste edible oils left after frying/cooking
 operation etc., have also been converted to biodiesel for study of their performance. The biodiesel
are also known as fatty acid methyl esters [FAME]. Recently non-edible oil produced from jatropha-
curcas seeds has gained interest in India as this plant can be easily grown on wastelands. The
properties of methyl esters of rapeseed and jatropha oils are given in Table 8.18.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 3


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_1.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
The Lecture Contains:
BIODIESEL
Biodiesel Production – Esterification of Oils
Properties of Biodiesel
Emissions
Hydrogen
Greenhouse Gas Emissions with Alternative Fuels
Questions
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_2.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
BIODIESEL
In a 1912 speech, Rudolf Diesel said, "the use of vegetable oils for engine fuels may seem
insignificant today, but such oils may become, in the course of time, as important as petroleum and
the coal - tar products of the present time". The revival of biodiesel derived from vegetable oils started
as a result of agricultural surplus in some European countries and under Kyoto protocol the need of
reducing greenhouse gas CO
2
 emissions.  
Biodiesel is a renewable fuel that is produced from a variety of edible and non-edible vegetable oils
and animal fats. 
The term “biodiesel” is commonly used for methyl or ethyl esters of the fatty acids in natural oils and
fats, which meet the fuel quality requirements of compression-ignition engines.
Straight vegetable oils (SVO) are not considered as biodiesel. The straight vegetable oils have a very
high viscosity that makes flow of these oils difficult even at room temperatures.  Moreover, presence
of glycerine in the vegetable oil causes formation of heavy carbon deposits on the injector nozzle
holes that results in poor and unacceptable performance and emissions from the engine even within a
few hours of operation.
Biodiesel Production – Esterification of Oils
Biodiesel is produced by reacting vegetable oils or animal fats with an alcohol such as methanol or
ethanol in presence of a catalyst to yield mono-alkyl esters. The overall reaction is given in Fig. 8.6.
 Glycerol is obtained as a by-product.
Figure
8.6:
Esterification reaction for vegetable oils and
fats.’
Properties of Biodiesel
A variety of vegetable oils such as soybean, rapeseed, safflower, jatropha-curcas, palm, and
cottonseed oils have been used for production of biodiesel.  Waste edible oils left after frying/cooking
 operation etc., have also been converted to biodiesel for study of their performance. The biodiesel
are also known as fatty acid methyl esters [FAME]. Recently non-edible oil produced from jatropha-
curcas seeds has gained interest in India as this plant can be easily grown on wastelands. The
properties of methyl esters of rapeseed and jatropha oils are given in Table 8.18.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_3.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
                                       Table 8.18
Properties of Biodiesel Derived from Some
Vegetable Oils
Properties Rapeseed
methyl ester
Jatropha
methyl
ester
Molecular weight
Hydrogen/carbon ratio, m/m
Oxygen content, % m/m
Relative density @ 15° C
Kinematic viscosity @ 40° C, mm2/s
Cetane number
Lower heat of combustion, MJ/kg
Sulphur content, %m/m
˜300
0.15
9-11
0.882
4.57
51.6
37.7
<0.002
˜293
0.157
10.9
0.88
4.4
57.1
38.45
< 0.020
The vegetable oil esters are practically free of sulphur and have a high cetane number ranging from
46 to 60 depending upon the feedstock. Due to presence of oxygen, biodiesels have a lower calorific
value than the diesel fuels. European specifications for biodiesel or fatty acid methyl esters (FAME),
EN 14214 have been issued in 2003.
Emissions
The influence of biodiesel on emissions varies depending on the type of biodiesel (soybean,
rapeseed, or animal fats) and on the type of conventional diesel to which the biodiesel is added due
to differences in their chemical composition and properties. The average effects of blending of
biodiesel in diesel fuel on CO, HC, NO
x
 and PM emissions compared to diesel as base fuel are
shown in Fig.8.7.The Table 8.19 gives change in emissions with 20 % blend of biodiesel in diesel and
100% biodiesel compared to diesel alone. These show the average of the trends observed in a
number of investigations.
Use of biodiesel results in reduction of CO, HC and PM, but slight increase in NO
x
 emissions is
obtained.
Reduction in CO emissions is attributed to presence of oxygen in the fuel molecule.
A slight increase in NO
x
 emissions results perhaps due to advancement of dynamic injection
timing with biodiesel. The methyl esters have a lower compressibility, which results in
advancement of dynamic injection timing with biodiesel compared to diesel.
Lower SOF with biodiesel and advanced injection timing also results in lower PM emissions.
Volumetric fuel consumption with biodiesel is higher than diesel due to its lower heating value.
An increase of 10-11 % in fuel consumption compared to diesel may be expected when
comparing their heating values. An increase in volumetric fuel consumption by 0.9-2.1% with
20% blends has been obtained.
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 4


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_1.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
The Lecture Contains:
BIODIESEL
Biodiesel Production – Esterification of Oils
Properties of Biodiesel
Emissions
Hydrogen
Greenhouse Gas Emissions with Alternative Fuels
Questions
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_2.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
BIODIESEL
In a 1912 speech, Rudolf Diesel said, "the use of vegetable oils for engine fuels may seem
insignificant today, but such oils may become, in the course of time, as important as petroleum and
the coal - tar products of the present time". The revival of biodiesel derived from vegetable oils started
as a result of agricultural surplus in some European countries and under Kyoto protocol the need of
reducing greenhouse gas CO
2
 emissions.  
Biodiesel is a renewable fuel that is produced from a variety of edible and non-edible vegetable oils
and animal fats. 
The term “biodiesel” is commonly used for methyl or ethyl esters of the fatty acids in natural oils and
fats, which meet the fuel quality requirements of compression-ignition engines.
Straight vegetable oils (SVO) are not considered as biodiesel. The straight vegetable oils have a very
high viscosity that makes flow of these oils difficult even at room temperatures.  Moreover, presence
of glycerine in the vegetable oil causes formation of heavy carbon deposits on the injector nozzle
holes that results in poor and unacceptable performance and emissions from the engine even within a
few hours of operation.
Biodiesel Production – Esterification of Oils
Biodiesel is produced by reacting vegetable oils or animal fats with an alcohol such as methanol or
ethanol in presence of a catalyst to yield mono-alkyl esters. The overall reaction is given in Fig. 8.6.
 Glycerol is obtained as a by-product.
Figure
8.6:
Esterification reaction for vegetable oils and
fats.’
Properties of Biodiesel
A variety of vegetable oils such as soybean, rapeseed, safflower, jatropha-curcas, palm, and
cottonseed oils have been used for production of biodiesel.  Waste edible oils left after frying/cooking
 operation etc., have also been converted to biodiesel for study of their performance. The biodiesel
are also known as fatty acid methyl esters [FAME]. Recently non-edible oil produced from jatropha-
curcas seeds has gained interest in India as this plant can be easily grown on wastelands. The
properties of methyl esters of rapeseed and jatropha oils are given in Table 8.18.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_3.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
                                       Table 8.18
Properties of Biodiesel Derived from Some
Vegetable Oils
Properties Rapeseed
methyl ester
Jatropha
methyl
ester
Molecular weight
Hydrogen/carbon ratio, m/m
Oxygen content, % m/m
Relative density @ 15° C
Kinematic viscosity @ 40° C, mm2/s
Cetane number
Lower heat of combustion, MJ/kg
Sulphur content, %m/m
˜300
0.15
9-11
0.882
4.57
51.6
37.7
<0.002
˜293
0.157
10.9
0.88
4.4
57.1
38.45
< 0.020
The vegetable oil esters are practically free of sulphur and have a high cetane number ranging from
46 to 60 depending upon the feedstock. Due to presence of oxygen, biodiesels have a lower calorific
value than the diesel fuels. European specifications for biodiesel or fatty acid methyl esters (FAME),
EN 14214 have been issued in 2003.
Emissions
The influence of biodiesel on emissions varies depending on the type of biodiesel (soybean,
rapeseed, or animal fats) and on the type of conventional diesel to which the biodiesel is added due
to differences in their chemical composition and properties. The average effects of blending of
biodiesel in diesel fuel on CO, HC, NO
x
 and PM emissions compared to diesel as base fuel are
shown in Fig.8.7.The Table 8.19 gives change in emissions with 20 % blend of biodiesel in diesel and
100% biodiesel compared to diesel alone. These show the average of the trends observed in a
number of investigations.
Use of biodiesel results in reduction of CO, HC and PM, but slight increase in NO
x
 emissions is
obtained.
Reduction in CO emissions is attributed to presence of oxygen in the fuel molecule.
A slight increase in NO
x
 emissions results perhaps due to advancement of dynamic injection
timing with biodiesel. The methyl esters have a lower compressibility, which results in
advancement of dynamic injection timing with biodiesel compared to diesel.
Lower SOF with biodiesel and advanced injection timing also results in lower PM emissions.
Volumetric fuel consumption with biodiesel is higher than diesel due to its lower heating value.
An increase of 10-11 % in fuel consumption compared to diesel may be expected when
comparing their heating values. An increase in volumetric fuel consumption by 0.9-2.1% with
20% blends has been obtained.
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_3.htm[6/15/2012 3:11:13 PM]
Figure
8.7:
Average effect  on  diesel engine emissions resulting from 
addition of biodiesel in diesel fuels
                                                                           Table 8.19
Average reduction in emissions with use of biodiesel and 20% biodiesel
blends compared to diesel alone
Emission B100 B20
HC
CO
PM
NOx
PAH
Sulphates
- 93
- 50
- 30
+13
- 80
- 100
-30
-20
-22
+2
-13
-20
 
 
Page 5


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_1.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
The Lecture Contains:
BIODIESEL
Biodiesel Production – Esterification of Oils
Properties of Biodiesel
Emissions
Hydrogen
Greenhouse Gas Emissions with Alternative Fuels
Questions
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_2.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
BIODIESEL
In a 1912 speech, Rudolf Diesel said, "the use of vegetable oils for engine fuels may seem
insignificant today, but such oils may become, in the course of time, as important as petroleum and
the coal - tar products of the present time". The revival of biodiesel derived from vegetable oils started
as a result of agricultural surplus in some European countries and under Kyoto protocol the need of
reducing greenhouse gas CO
2
 emissions.  
Biodiesel is a renewable fuel that is produced from a variety of edible and non-edible vegetable oils
and animal fats. 
The term “biodiesel” is commonly used for methyl or ethyl esters of the fatty acids in natural oils and
fats, which meet the fuel quality requirements of compression-ignition engines.
Straight vegetable oils (SVO) are not considered as biodiesel. The straight vegetable oils have a very
high viscosity that makes flow of these oils difficult even at room temperatures.  Moreover, presence
of glycerine in the vegetable oil causes formation of heavy carbon deposits on the injector nozzle
holes that results in poor and unacceptable performance and emissions from the engine even within a
few hours of operation.
Biodiesel Production – Esterification of Oils
Biodiesel is produced by reacting vegetable oils or animal fats with an alcohol such as methanol or
ethanol in presence of a catalyst to yield mono-alkyl esters. The overall reaction is given in Fig. 8.6.
 Glycerol is obtained as a by-product.
Figure
8.6:
Esterification reaction for vegetable oils and
fats.’
Properties of Biodiesel
A variety of vegetable oils such as soybean, rapeseed, safflower, jatropha-curcas, palm, and
cottonseed oils have been used for production of biodiesel.  Waste edible oils left after frying/cooking
 operation etc., have also been converted to biodiesel for study of their performance. The biodiesel
are also known as fatty acid methyl esters [FAME]. Recently non-edible oil produced from jatropha-
curcas seeds has gained interest in India as this plant can be easily grown on wastelands. The
properties of methyl esters of rapeseed and jatropha oils are given in Table 8.18.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_3.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
                                       Table 8.18
Properties of Biodiesel Derived from Some
Vegetable Oils
Properties Rapeseed
methyl ester
Jatropha
methyl
ester
Molecular weight
Hydrogen/carbon ratio, m/m
Oxygen content, % m/m
Relative density @ 15° C
Kinematic viscosity @ 40° C, mm2/s
Cetane number
Lower heat of combustion, MJ/kg
Sulphur content, %m/m
˜300
0.15
9-11
0.882
4.57
51.6
37.7
<0.002
˜293
0.157
10.9
0.88
4.4
57.1
38.45
< 0.020
The vegetable oil esters are practically free of sulphur and have a high cetane number ranging from
46 to 60 depending upon the feedstock. Due to presence of oxygen, biodiesels have a lower calorific
value than the diesel fuels. European specifications for biodiesel or fatty acid methyl esters (FAME),
EN 14214 have been issued in 2003.
Emissions
The influence of biodiesel on emissions varies depending on the type of biodiesel (soybean,
rapeseed, or animal fats) and on the type of conventional diesel to which the biodiesel is added due
to differences in their chemical composition and properties. The average effects of blending of
biodiesel in diesel fuel on CO, HC, NO
x
 and PM emissions compared to diesel as base fuel are
shown in Fig.8.7.The Table 8.19 gives change in emissions with 20 % blend of biodiesel in diesel and
100% biodiesel compared to diesel alone. These show the average of the trends observed in a
number of investigations.
Use of biodiesel results in reduction of CO, HC and PM, but slight increase in NO
x
 emissions is
obtained.
Reduction in CO emissions is attributed to presence of oxygen in the fuel molecule.
A slight increase in NO
x
 emissions results perhaps due to advancement of dynamic injection
timing with biodiesel. The methyl esters have a lower compressibility, which results in
advancement of dynamic injection timing with biodiesel compared to diesel.
Lower SOF with biodiesel and advanced injection timing also results in lower PM emissions.
Volumetric fuel consumption with biodiesel is higher than diesel due to its lower heating value.
An increase of 10-11 % in fuel consumption compared to diesel may be expected when
comparing their heating values. An increase in volumetric fuel consumption by 0.9-2.1% with
20% blends has been obtained.
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_3.htm[6/15/2012 3:11:13 PM]
Figure
8.7:
Average effect  on  diesel engine emissions resulting from 
addition of biodiesel in diesel fuels
                                                                           Table 8.19
Average reduction in emissions with use of biodiesel and 20% biodiesel
blends compared to diesel alone
Emission B100 B20
HC
CO
PM
NOx
PAH
Sulphates
- 93
- 50
- 30
+13
- 80
- 100
-30
-20
-22
+2
-13
-20
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture40/40_4.htm[6/15/2012 3:11:13 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 40:Alternative Fuels (contd.)
 
Hydrogen
Interest in hydrogen as a potential alternative automotive fuel has grown due to need of reducing  
greenhouse gas, CO
2
 emissions and to minimize dependence on fossil fuels. Hydrogen can be
produced from a variety of fossil and non-fossil sources. 
Hydrogen is a colourless, odourless and non-toxic gas. It burns with an invisible and smokeless
flame. The combustion products of hydrogen consist of water and some nitrogen oxides. The major
hurdles in the use of hydrogen as a fuel are lack of production, distribution and storage infrastructure.
On board storage of hydrogen is another major challenge.  Hydrogen has very low boiling point (–
253º C) and very low volumetric energy density. 
Volumetric energy density of compressed hydrogen is just one-third of energy density of natural gas.
Liquid hydrogen also has a very low volumetric energy density, which is about one-fourth of gasoline.
 Hydrogen can be stored as compressed gas, as iron, magnesium, titanium or nickel hydride, or in
liquefied form. The liquid, hydride and compressed hydrogen storage methods are compared in Table
8.20 for storing 19 litres of gasoline equivalent in energy. Hydrogen storage space required is at least
10 to 12 times higher than for gasoline.  Storage and fuel weight for hydrides is 27 times and for
compressed H
2
 is 4 to 5 times of gasoline.
                            Table 8.20
Comparison of Hydrogen Storage
Methods
 Gasoline Liquid H
2
Hydride Fe-
Ti (1.2%)
Compressed
H
2
 (70MPa)
Energy (LHV) stored, MJ
Fuel mass, kg
Tank mass, kg
Total Fuel System mass, kg
Volume, l
600
14
6.5
20.5
19
600
5
19
24
178
600 
5
550
555
190
600
5
85
90
227
Combustion characteristics of hydrogen and its impact on emissions are given below;
Hydrogen octane rating is 106 RON making it more suitable for spark-ignited engines.
The laminar flame speed of hydrogen is 3 m/s, about 10 times that of gasoline and methane.
Hydrogen has very wide flammability limits ranging from 5 to 75% by volume (f = 0.07 to 9),
which may lead to pre-ignition and backfiring problems.
Its adiabatic flame temperature is higher by about 110º C compared to gasoline.
 If inducted along with intake air,   the volume of hydrogen is nearly 30% of the stoichiometric
mixture decreasing maximum engine power.
Hydrogen on combustion produces water and there are no emissions of carbon containing
pollutants such as HC, CO and CO
2
 and air toxics.
Trace amounts of HC, CO and CO2 however, may be  emitted as a result of combustion of
lubricating oil leaking into engine cylinder.
NO
x
 is the only pollutant of concern from hydrogen engines. Very low NO
x
 emissions can be
obtained with extremely lean engine operation (f < 0.05) and/or injection of water into intake
manifold or exhaust gas recirculation which in this case consists primarily of water vapours.
 
 
 
 
 
 
 
 
 
 
 
 
 
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