Alternative Fuels Notes | EduRev

: Alternative Fuels Notes | EduRev

 Page 1


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_1.htm[6/15/2012 3:10:54 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
The Lecture Contains:
ALTERNATE FUELS
Properties of Alternative Fuels
Alcohols: Methanol and Ethanol
Natural Gas
Effect of Natural Gas on Emissions
Liquefied Petroleum Gas
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 2


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_1.htm[6/15/2012 3:10:54 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
The Lecture Contains:
ALTERNATE FUELS
Properties of Alternative Fuels
Alcohols: Methanol and Ethanol
Natural Gas
Effect of Natural Gas on Emissions
Liquefied Petroleum Gas
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
ALTERNATE FUELS
Most important alternative fuel candidates are: ethanol, methanol, natural gas, liquefied petroleum gas
(LPG), vegetable oil esters commonly called as ‘biodiesel’ and hydrogen  High petroleum prices during
1980’s provided motivation for development programmes for use of ethyl alcohol produced from agricultural
products  as motor fuel in countries like Brazil. During the same period, clean burning properties of
methanol and its easy production from natural gas led to technological development activities on methanol
in the USA. Methanol being liquid it is better suited than natural gas for storage on-board of vehicles.
However, due to its toxicity and its corrosive nature towards fuel system materials, interest in methanol as
automotive fuel has gone down although a number of demonstration fuel cell vehicles (FCV) using
methanol have been developed. Presently, natural gas and biodiesel have attracted maximum attention of
the governments, vehicle manufacturers and fuel suppliers. Hydrogen is considered as an alternative
transport fuel in the long term especially for the fuel cell powered vehicles. .
Properties of Alternative Fuels
Some of the key properties of the main alternative fuel candidates are compared in Table 8.13 with those
of conventional petroleum fuels. Key properties to be considered for :
Combustion and Performance: Heat of combustion, heat content of stoichiometric mixture, octane
number (SI engine) , cetane number (CI engine), boiling point ( esp., cold start), flammability limits
Emissions: Chemical composition and nature, adiabatic flame temperature
Storage and Handling: Boiling point, volumetric energy density, vapour pressure, flammability limits
Keeping the above in view the main alternative fuels are being discussed below
                        Table 8.13
Properties of Various Fuels for
Vehicles
Property Gasoline Diesel Methanol Ethanol Natural
gas
Propane DME RME Hydrogen
Mol.wt. ˜110 ˜195 32.04 46.07 ˜18.7 44.10 46.1 ˜ 300 2.015
 Specific
gravity
0.72-0.78 0.82-
0.88
0.796 0.794 0.72 0.51
liquefied
0.67
liquid
0.882 0.090
LHV, MJ/kg 44.0 42.5 19.9 26.8 50.0 46.3 28.4 37.7 120
Heat of
vaporization
,kJ/kg
305 250 1110 904 509 426 410 
at 20º
C
  
Boiling point,
ºC
30-215 180-
370
65 78 -160 -43 -24.9 330-
340
-253
RON
(MON)
90-98
(80-90)
- 112
(91)
111
(92)
120-130
(120-
130)
112
(97)
- - 106
Cetane
number
- 45-55 - - - - >55 51-52 -
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 3


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_1.htm[6/15/2012 3:10:54 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
The Lecture Contains:
ALTERNATE FUELS
Properties of Alternative Fuels
Alcohols: Methanol and Ethanol
Natural Gas
Effect of Natural Gas on Emissions
Liquefied Petroleum Gas
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
ALTERNATE FUELS
Most important alternative fuel candidates are: ethanol, methanol, natural gas, liquefied petroleum gas
(LPG), vegetable oil esters commonly called as ‘biodiesel’ and hydrogen  High petroleum prices during
1980’s provided motivation for development programmes for use of ethyl alcohol produced from agricultural
products  as motor fuel in countries like Brazil. During the same period, clean burning properties of
methanol and its easy production from natural gas led to technological development activities on methanol
in the USA. Methanol being liquid it is better suited than natural gas for storage on-board of vehicles.
However, due to its toxicity and its corrosive nature towards fuel system materials, interest in methanol as
automotive fuel has gone down although a number of demonstration fuel cell vehicles (FCV) using
methanol have been developed. Presently, natural gas and biodiesel have attracted maximum attention of
the governments, vehicle manufacturers and fuel suppliers. Hydrogen is considered as an alternative
transport fuel in the long term especially for the fuel cell powered vehicles. .
Properties of Alternative Fuels
Some of the key properties of the main alternative fuel candidates are compared in Table 8.13 with those
of conventional petroleum fuels. Key properties to be considered for :
Combustion and Performance: Heat of combustion, heat content of stoichiometric mixture, octane
number (SI engine) , cetane number (CI engine), boiling point ( esp., cold start), flammability limits
Emissions: Chemical composition and nature, adiabatic flame temperature
Storage and Handling: Boiling point, volumetric energy density, vapour pressure, flammability limits
Keeping the above in view the main alternative fuels are being discussed below
                        Table 8.13
Properties of Various Fuels for
Vehicles
Property Gasoline Diesel Methanol Ethanol Natural
gas
Propane DME RME Hydrogen
Mol.wt. ˜110 ˜195 32.04 46.07 ˜18.7 44.10 46.1 ˜ 300 2.015
 Specific
gravity
0.72-0.78 0.82-
0.88
0.796 0.794 0.72 0.51
liquefied
0.67
liquid
0.882 0.090
LHV, MJ/kg 44.0 42.5 19.9 26.8 50.0 46.3 28.4 37.7 120
Heat of
vaporization
,kJ/kg
305 250 1110 904 509 426 410 
at 20º
C
  
Boiling point,
ºC
30-215 180-
370
65 78 -160 -43 -24.9 330-
340
-253
RON
(MON)
90-98
(80-90)
- 112
(91)
111
(92)
120-130
(120-
130)
112
(97)
- - 106
Cetane
number
- 45-55 - - - - >55 51-52 -
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
Stoichiometric 
A/F ratio,
mass
14.7 15.0 6.43 8.94 17.12 15.58 9.0 11.2 34.13
LHV of stoich.
mixture,
MJ/m3
3.50 - 3.14 3.28 3.10 3.38  2.88
Adiabatic
flame
temperature
(K)
2266 2151 2197 2227 2268  2383
Stoichiometric
CO2
emissions,
g/MJ fuel
71.9 75.4 69.0 71.2 54.9 64.5 69.0 75.5 0
LHV= Lower heating value
 
 
Page 4


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_1.htm[6/15/2012 3:10:54 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
The Lecture Contains:
ALTERNATE FUELS
Properties of Alternative Fuels
Alcohols: Methanol and Ethanol
Natural Gas
Effect of Natural Gas on Emissions
Liquefied Petroleum Gas
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
ALTERNATE FUELS
Most important alternative fuel candidates are: ethanol, methanol, natural gas, liquefied petroleum gas
(LPG), vegetable oil esters commonly called as ‘biodiesel’ and hydrogen  High petroleum prices during
1980’s provided motivation for development programmes for use of ethyl alcohol produced from agricultural
products  as motor fuel in countries like Brazil. During the same period, clean burning properties of
methanol and its easy production from natural gas led to technological development activities on methanol
in the USA. Methanol being liquid it is better suited than natural gas for storage on-board of vehicles.
However, due to its toxicity and its corrosive nature towards fuel system materials, interest in methanol as
automotive fuel has gone down although a number of demonstration fuel cell vehicles (FCV) using
methanol have been developed. Presently, natural gas and biodiesel have attracted maximum attention of
the governments, vehicle manufacturers and fuel suppliers. Hydrogen is considered as an alternative
transport fuel in the long term especially for the fuel cell powered vehicles. .
Properties of Alternative Fuels
Some of the key properties of the main alternative fuel candidates are compared in Table 8.13 with those
of conventional petroleum fuels. Key properties to be considered for :
Combustion and Performance: Heat of combustion, heat content of stoichiometric mixture, octane
number (SI engine) , cetane number (CI engine), boiling point ( esp., cold start), flammability limits
Emissions: Chemical composition and nature, adiabatic flame temperature
Storage and Handling: Boiling point, volumetric energy density, vapour pressure, flammability limits
Keeping the above in view the main alternative fuels are being discussed below
                        Table 8.13
Properties of Various Fuels for
Vehicles
Property Gasoline Diesel Methanol Ethanol Natural
gas
Propane DME RME Hydrogen
Mol.wt. ˜110 ˜195 32.04 46.07 ˜18.7 44.10 46.1 ˜ 300 2.015
 Specific
gravity
0.72-0.78 0.82-
0.88
0.796 0.794 0.72 0.51
liquefied
0.67
liquid
0.882 0.090
LHV, MJ/kg 44.0 42.5 19.9 26.8 50.0 46.3 28.4 37.7 120
Heat of
vaporization
,kJ/kg
305 250 1110 904 509 426 410 
at 20º
C
  
Boiling point,
ºC
30-215 180-
370
65 78 -160 -43 -24.9 330-
340
-253
RON
(MON)
90-98
(80-90)
- 112
(91)
111
(92)
120-130
(120-
130)
112
(97)
- - 106
Cetane
number
- 45-55 - - - - >55 51-52 -
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
Stoichiometric 
A/F ratio,
mass
14.7 15.0 6.43 8.94 17.12 15.58 9.0 11.2 34.13
LHV of stoich.
mixture,
MJ/m3
3.50 - 3.14 3.28 3.10 3.38  2.88
Adiabatic
flame
temperature
(K)
2266 2151 2197 2227 2268  2383
Stoichiometric
CO2
emissions,
g/MJ fuel
71.9 75.4 69.0 71.2 54.9 64.5 69.0 75.5 0
LHV= Lower heating value
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_3.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
contd...
Example 8.1: 
Calculate energy content of 1 m
3
 of stoichiometric mixture of methane with air at 1 atmosphere
pressure (101 kPa) and 298 K. LHV of methane is 50 Mj/kg.
Solution:
Stoichiometric mixture composition of methane is given by
Total moles of fuel-air mixture = 1 + 2 x 4.76 = 10.52
Energy content of mixture consisting of 1 kmol of methane: 
            = mol wt x LHV  
= 16 x 50 = 800 MJ
 Volume of stoichiometric mixture consisting 1 kmol of methane
Energy content per unit volume of stoichiometric mixture = 800/258.07 = 3.10 MJ/m
3
               
Ans.
Alcohols: Methanol and Ethanol
Methanol at present is produced mostly from natural gas although both methanol and ethanol can be
produced from renewable sources.  Methanol may be produced near the natural gas field and it being
liquid can be more easily handled and transported over long distances compared to natural gas.
Ethanol is produced almost entirely from the renewable agriculture sources by fermentation of sugar,
grains, tapioca etc.
Alcohols in engines may be used as:
Low concentration ( 5 to 10% by volume) blends in gasoline
Neat alcohol or high level ( 85% by volume) blends
Neat ethanol (95% ethanol + 5% water) and anhydrous ethanol blended up to 20% in gasoline have
been widely used in Brazil during 1980’s. In the USA, use of ethanol was promoted due to agricultural
surplus for blending in the reformulated gasoline as oxygenate. Use of 5 to 10% ethanol as a
blending component in gasoline is permitted in Europe and India.    Now, ethanol is the preferred
oxygenate replacing MTBE. As mentioned earlier, methanol due to its toxicity is not permitted any
more for blending into gasoline. The 10 percent ethanol-gasoline blends used in the USA are
commonly referred as ‘Gasohol’. Key features of alcohols as motor fuel are;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 5


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_1.htm[6/15/2012 3:10:54 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
The Lecture Contains:
ALTERNATE FUELS
Properties of Alternative Fuels
Alcohols: Methanol and Ethanol
Natural Gas
Effect of Natural Gas on Emissions
Liquefied Petroleum Gas
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
ALTERNATE FUELS
Most important alternative fuel candidates are: ethanol, methanol, natural gas, liquefied petroleum gas
(LPG), vegetable oil esters commonly called as ‘biodiesel’ and hydrogen  High petroleum prices during
1980’s provided motivation for development programmes for use of ethyl alcohol produced from agricultural
products  as motor fuel in countries like Brazil. During the same period, clean burning properties of
methanol and its easy production from natural gas led to technological development activities on methanol
in the USA. Methanol being liquid it is better suited than natural gas for storage on-board of vehicles.
However, due to its toxicity and its corrosive nature towards fuel system materials, interest in methanol as
automotive fuel has gone down although a number of demonstration fuel cell vehicles (FCV) using
methanol have been developed. Presently, natural gas and biodiesel have attracted maximum attention of
the governments, vehicle manufacturers and fuel suppliers. Hydrogen is considered as an alternative
transport fuel in the long term especially for the fuel cell powered vehicles. .
Properties of Alternative Fuels
Some of the key properties of the main alternative fuel candidates are compared in Table 8.13 with those
of conventional petroleum fuels. Key properties to be considered for :
Combustion and Performance: Heat of combustion, heat content of stoichiometric mixture, octane
number (SI engine) , cetane number (CI engine), boiling point ( esp., cold start), flammability limits
Emissions: Chemical composition and nature, adiabatic flame temperature
Storage and Handling: Boiling point, volumetric energy density, vapour pressure, flammability limits
Keeping the above in view the main alternative fuels are being discussed below
                        Table 8.13
Properties of Various Fuels for
Vehicles
Property Gasoline Diesel Methanol Ethanol Natural
gas
Propane DME RME Hydrogen
Mol.wt. ˜110 ˜195 32.04 46.07 ˜18.7 44.10 46.1 ˜ 300 2.015
 Specific
gravity
0.72-0.78 0.82-
0.88
0.796 0.794 0.72 0.51
liquefied
0.67
liquid
0.882 0.090
LHV, MJ/kg 44.0 42.5 19.9 26.8 50.0 46.3 28.4 37.7 120
Heat of
vaporization
,kJ/kg
305 250 1110 904 509 426 410 
at 20º
C
  
Boiling point,
ºC
30-215 180-
370
65 78 -160 -43 -24.9 330-
340
-253
RON
(MON)
90-98
(80-90)
- 112
(91)
111
(92)
120-130
(120-
130)
112
(97)
- - 106
Cetane
number
- 45-55 - - - - >55 51-52 -
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_2.htm[6/15/2012 3:10:55 PM]
Stoichiometric 
A/F ratio,
mass
14.7 15.0 6.43 8.94 17.12 15.58 9.0 11.2 34.13
LHV of stoich.
mixture,
MJ/m3
3.50 - 3.14 3.28 3.10 3.38  2.88
Adiabatic
flame
temperature
(K)
2266 2151 2197 2227 2268  2383
Stoichiometric
CO2
emissions,
g/MJ fuel
71.9 75.4 69.0 71.2 54.9 64.5 69.0 75.5 0
LHV= Lower heating value
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_3.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
contd...
Example 8.1: 
Calculate energy content of 1 m
3
 of stoichiometric mixture of methane with air at 1 atmosphere
pressure (101 kPa) and 298 K. LHV of methane is 50 Mj/kg.
Solution:
Stoichiometric mixture composition of methane is given by
Total moles of fuel-air mixture = 1 + 2 x 4.76 = 10.52
Energy content of mixture consisting of 1 kmol of methane: 
            = mol wt x LHV  
= 16 x 50 = 800 MJ
 Volume of stoichiometric mixture consisting 1 kmol of methane
Energy content per unit volume of stoichiometric mixture = 800/258.07 = 3.10 MJ/m
3
               
Ans.
Alcohols: Methanol and Ethanol
Methanol at present is produced mostly from natural gas although both methanol and ethanol can be
produced from renewable sources.  Methanol may be produced near the natural gas field and it being
liquid can be more easily handled and transported over long distances compared to natural gas.
Ethanol is produced almost entirely from the renewable agriculture sources by fermentation of sugar,
grains, tapioca etc.
Alcohols in engines may be used as:
Low concentration ( 5 to 10% by volume) blends in gasoline
Neat alcohol or high level ( 85% by volume) blends
Neat ethanol (95% ethanol + 5% water) and anhydrous ethanol blended up to 20% in gasoline have
been widely used in Brazil during 1980’s. In the USA, use of ethanol was promoted due to agricultural
surplus for blending in the reformulated gasoline as oxygenate. Use of 5 to 10% ethanol as a
blending component in gasoline is permitted in Europe and India.    Now, ethanol is the preferred
oxygenate replacing MTBE. As mentioned earlier, methanol due to its toxicity is not permitted any
more for blending into gasoline. The 10 percent ethanol-gasoline blends used in the USA are
commonly referred as ‘Gasohol’. Key features of alcohols as motor fuel are;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture39/39_4.htm[6/15/2012 3:10:55 PM]
 Module8:Engine Fuels and Their Effects on Emissions
 Lecture 39:Alternative Fuels
 
contd...
Alcohols are a preferred alternative for SI engines only due to their high octane number. A higher
engine compression ratio could be used to obtain a higher engine thermal efficiency.
Cetane number of methanol and ethanol are close to 5 and 8, respectively.
Direct injection alcohol engine prototypes operating similar to diesel/CI engines have also been
developed using either a positive source of ignition or high dosage of ignition quality improvers (3 to
7% by volume).
Alcohols are not easily miscible in the diesel fuels. To prepare alcohol-diesel blends high amounts of
emulsifiers or solublizers are required.
Heating value of ethanol is approximately 60 percent and that of methanol is only 45 % of gasoline.
The stoichiometric air-fuel ratio due to presence of oxygen in the molecule is much lower than the
gasoline.
The volumetric energy content of stoichiometric mixture (gaseous state) of alcohols and gasoline
however, are not very different. Thus, engine specific power output that may be obtained with
alcohols and gasoline is nearly the same.
The latent heat of vaporization of methanol and ethanol is nearly 4 and 2.7 times, respectively
compared to gasoline. Cold starting performance with neat alcohol is therefore, poor compared to
gasoline.
Flames of neat alcohols in air are not easily visible to the naked eye. Hence, 15% gasoline is mixed
to alcohol for making the flame visible in case of an accidental fire.
A large number of investigations have been carried out with alcohols as engine fuel. Emissions with low
level alcohol blends as well as with neat alcohols have been studied. CO and NO
x
 emissions show no clear
trend although lower flame temperatures with alcohol may result in lower NO
x
 emissions.  With neat alcohol
operation, as the emissions of most of the volatile organic compounds in the exhaust  would consist of
alcohols or  aldehydes only,  the photo-chemical reactivity and the ozone forming potential is lower with
alcohol fuel operation.
The main advantages and disadvantages of alcohols with respect to conventional gasoline and diesel fuels
are summarized in Table 8.14.
                                                                  Table 8.14
Advantages and Disadvantages of Alcohol Motor Fuels Compared to Gasoline
and Diesel
Performance
Parameter
Compared to gasoline and
diesel fuels
Advantages/Disadvantages
Flame temperature Lower Potentially lower NOx emissions and
lower heat losses
Vapour pressure Lower Poor cold starting and warm up
performance, higher 
unburned fuel emissions during
starting/warm up phase
PM emissions
 
Lower Due to clean burning characteristics
PM emissions are   even lower than
the gasoline engines
 
 
 
 
 
 
 
 
 
 
 
 
 
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