1. UNIT-IV
ALTERNATE FUELS

2. TOPICS
Need for alternate fuels – alcohols, vegetable
oils, bio-diesel, bio-gas, natural gas, liquefied
petroleum gas and hydrogen – manufacturing,
storage and safety properties – engine
modifications and emissions – performance,
combustion and emission characteristics of SI
and CI engines.

3. NEED FOR ALTERNATE FUELS
 Conventional fuels are going to run out
One day, our sources for traditional fuels including petroleum
would be depleted. Owing to the fact that these fuels are typically
not renewable
 To reduce pollution
The use of alternative fuels considerably decreases harmful
exhaust emissions (such as carbon dioxide, carbon monoxide,
particulate matter and sulfur dioxide) as well as ozone-producing
emissions.
 To protect against global warming
According to a commonly accepted scientific theory, burning fossil
fuels was causing temperatures to rise in the earth’s atmosphere
(global warming).

4. NEED FOR ALTERNATE FUELS
 To save money
Alternative fuels can be less expensive to use not just in terms of
the fuel itself but also in terms of a longer service life. This in turn
means savings for the long term.
 Can reuse waste
Biofuels, bio products, and bio power provide modern and fresh
relevance to the old belief that trash for one person is a treasure for
another. That’s good news considering that Americans produce in
excess of 236 million tons of waste each year.
 More choices
People are different. Each person has his own requirements,
opinions, and preferences.
One great thing about alternative fuels and the corresponding
vehicles that run on them is that there is something to suit any
lifestyle.

5. NEED FOR ALTERNATE FUELS
 You’ll be helping the farmers
The use of biofuels that depend on crops produced and processed
locally help to support farmers for their dedicated and hard labor.
Biodiesel and ethanol cooperatives are a result of the great
outmoded farmer cooperatives that assist with returning power to
the hands of the people.
 Can frequently be produced domestically
Often, alternative fuels can be developed domestically, utilizing a
country’s resources and thereby strengthening the economy.

6. NEED FOR ALTERNATE FUELS
 Fuel economy
Vehicles driven on hydrogen fuel cells and diesel are more
economical with respect to fuel compared to an equivalent gasoline
vehicle.
 Meeting Current Global Energy Demand;
 Alternative fuels are receiving attention because of the following
reasons:
 Alternative fuels are mostly produced from domestic resources that
reduce the energy dependence. Use of locally available resources for
fuel purposes can reduce crude oil import bill.
 Most of the alternative fuels, for example, alcohols, biodiesel can be
produced from biomass resources and agricultural wastes and
electricity for battery operated vehicles can be produced from solar
and fuel cells.

7. Parameters are to be considered while deciding the alternative fuel
 The fuel should have high volumetric and mass energy density.
 Ease of transportation from production site to delivery points.
 Long-storage life of fuel, minimum handling, and distribution
problems.
 Environmental compatibility: While using alternative fuel, the engine
performance is expected to improve significantly with regard to
regulated emissions and unregulated emissions.
 Manufacturer’s warranty: The alternative fuel must guarantee the
lifetime of the equipment; its reliability and operational capability are
not modified.
 Investment cost: Additional investment on an existing engine must be
small to ensure that the operation is competitive with petroleum fuel.

8. ALCOHOLS
 Alcohol is an attractive alternative fuel because it can be obtained
from a number of sources, both natural and manufactured. There are
two kinds of alcohol. They are:
Methanol (or) Methyl alcohol (CH3OH)
Ethanol (or) Ethyl alcohol (C2H5OH)

9. METHANOL AS ALTERNATIVE FUEL
• Methanol is one of the most promising substitute for petroleum
fuels. It can be produced from a wide range of available raw materials
like coal, lignite and municipal solid wastes.
• Pure methanol and mixtures of methanol and gasoline (petrol) in
various percentages have been extensively tested in several engines
and vehicles.
• The most common mixtures are M85 (85% Methanol and 15%
gasoline) andM10 (10% methanol and 90% gasoline).

10. METHANOL AS ALTERNATIVE FUEL
 Production of Methanol from Lignite or Coal
 A schematic diagram for producing methanol from lignite or coal is
shown infigure 4.1
 Pulvarized coal is fed into gasifier where oxygen is supplied and
combustiontakes place.
 Synthesis gas which consists of CO and H2 is produced due to
combustion ofcoal.
 All H2S and most of the CO2 are removed by passing amine solution.
 The carbon monoxide (CO) reacts with hydrogen and produces
methanol.
• CO + 2 H2 → CH3OH
 The raw methanol is then purified to remove water.

11. METHANOL AS ALTERNATIVE FUEL
 Production of Methanol from Lignite or Coal

12. METHANOL AS ALTERNATIVE FUEL
Methanol from Municipal Solid Wastes

13. METHANOL AS ALTERNATIVE FUEL
Performance of Methanol
Figure shows the performance of petrol, diesel and methanol
engines. It shows that pure methanol engine has about 20%
greater output compared to that of the standard petrol engine.
This is due to the higher compression ratio and more efficient
thermodynamic process of methanol engines.

14. METHANOL AS ALTERNATIVE FUEL
 Thermal efficiency Vs fuel air ratio

15. ETHANOL AS ALTERNATIVE FUEL
 Ethanol has been used as alternative fuel for many years in various
regions of the world. Brazil is probably the leading user, wherein the
early 1990s, 5 million vehicles operated on fuels that were 95%
ethanol. For a number of years gasohol (Mixture of 90% gasoline and
10% ethanol) has been available at service stations in the United
States. The most common mixtures are E85 (85% ethanol and 15%
gasoline)and E10 (10% ethanol and 90% gasoline

16. ETHANOL AS ALTERNATIVE FUEL
Production of Ethanol
Ethanol can be produced from sugar or grain. In contrast with
methanol production, the process does not require extreme
temperature and pressure. Hence very small unit is needed to
produce ethanol. Production of Ethanol from grains

17. Production of Ethanol from sugarcane
 A schematic diagram of producing ethanol is shown in figure 4.10
 Production of ethanol from sugarcane requires simple processes since
the fermentable sugar is obtained directly from the sugarcane.
 The sugarcane is first cut and ground, and the cane juice is extracted.
 This sugarcane juice is then fermented with yeast to produce raw
ethanol.
 Ethanol is produced by fermentation of carbohydrates by the Gay
Lussac relation.
ETHANOL AS ALTERNATIVE FUEL

18. ETHANOL AS ALTERNATIVE FUEL
Production of Ethanol from sugarcane

19. ETHANOL AS ALTERNATIVE FUEL
Performance of Ethanol
 Figure 4.11 shows the performance of petrol and ethanol engines
which is based on mean effective pressure. It is observed that the
mean effective pressure of ethanol is greater than petrol.

20. COMPARISON ON PROPERTIES OF ALCOHOLS
(METHANOL AND ETHANOL) AND GASOLINE
(PETROL)
Air Fuel Ratio:
The alcohol molecule contains fixed oxygen. So, the quantity of air
required for combustion of the alcohol is considerably lower than that
required for petrol.
Calorific Value:
Because of the fixed oxygen, the calorific value of alcohol is lower than
that of petrol. To produce equal amount of energy more than double the
weight of methanol is needed when compared to petrol and 65% greater
weight of ethanol is required when compared to petrol.

22. COMPARISON OF ETHANOL AND METHANOL
• It can be seen from the property tables that most of the properties
of ethanol and methanol resembles with each other with hardly change
of 10%.
• Ethanol is superior to methanol since it has wide ignition limit,
higher calorific value, and high cetane number compared with
methanol. So, ethanol is widely used as S.I engine fuel in many
countries.

23. ALCOHOL IN C.I. ENGINES (DIESEL ENGINES)
 C.I. engines can use alcohol fuel with minimum modifications to
their fuel delivery systems. But alcohols are unsuitable for diesel
engines for the following reasons.
 The cetane number of alcohol fuel is very low, which prevents their
ignition bycompression.
 Alcohol fuels having low lubricating qualities, which cause trouble
in injectionpumps and nozzles.
 Alcohol is much corrosive.

24. ALCOHOL-GASOLINE FUEL BLENDS
 Alcohols cannot be used directly as fuels in automobile engines
except methanol in racing cars. But it can be used as blend with
gasoline. Some common alcohol - gasoline fuel blends are:
 E85 (85% ethanol and 15% gasoline)
 E10 (10% ethanol and 90% gasoline)
 M85 (85% methanol and 15% gasoline)
 M10 (10% methanol and 90% gasoline)

25. ADVANTAGES OF ALCOHOL (METHANOL AND
ETHANOL)
 Higher thermal efficiency.
 Higher volumetric efficiency.
 Good internal cooling.
 The alcohols can also be blended with gasoline (petrol) to form the
gasol (80%petrol and 20% alcohol) and it is widely used in USA.
 Sulphur content in the fuel is low.
 Less overall emission when compared with gasoline.

26. DISADVANTAGES OF ALCOHOL
 Alcohol is much corrosive than gasoline (petrol). So, special metals
should beused for the engine part to avoid corrosion.
 Poor cold weather starting characteristics due to low vapour pressure
andevaporation.
 Ignition characteristics are poor.
 Since alcohols have invisible flames, it is dangerous to handle
 Vapour lock in fuel delivery systems.
 Energy content of the alcohol is low. So, almost twice the amount
of alcoholcompared to gasoline is required to give the same energy.

27. VEGETABLE OILS AS DIESEL FUELS
 Vegetable oils have two broad classifications:
 Edible oils (sunflower, soy bean, palm oil, etc.)
 Non-edible oils (jatropha, karanji, rubber seed oil, etc.).
 Edible type oils are mainly used for food purposes whereas
nonedible oils are used for food purposes.

28. Pyrolysis
.✓ Pyrolysis is a promising method for the production of
environmentally friendly liquid fuels. It is the chemical reaction
caused by the application of thermal energy in the absence of air.
Vegetable oils and animal fats can be pyrolyzed.
✓ Pyrolysis process takes place at higher temperatures of about 250–
400ºC and at higher heating rates. Heating of vegetable oils breaks the
bigger molecules into smaller molecules and a wide range of HC are
formed.

29. .✓ The pyrolyzed products can be divided into gaseous, liquid fractions
consisting of paraffins, olefins and naphthenes, and solid residue.
✓ The pyrolyzed vegetable oils contain acceptable amounts of sulfur,
water, and sediment and give acceptable copper corrosion values but
unacceptable ash, carbon residue, and pour point.
✓ The pyrolyzed vegetable oils contain acceptable amounts of sulfur,
water, and sediment and give acceptable copper corrosion values but
unacceptable ash, carbon residue, and pour point.

30. Table - Physical and Chemical properties of test
methods

31. Advantages of Vegetable Oils
 Vegetable oils can be used as substitute fuel for diesel engine
application.
 Use of vegetable oil for fuel purposes reduces the import of costly
petroleum andimproves the economy of agricultural countries.
 They are biodegradable and nontoxic.
 Vegetable oils are of low aromatics and low sulfur content and hence
reduce theparticulate matter emissions.
 They have a reasonable cetane number and hence possesses less
knockingtendency.

32. Disadvantages of using vegetable oil as C.I. Engine
fuel
1. The high viscosity of vegetable oils leads to pumping and
atomization problemsin the normal diesel fuel injection systems.
2. High carbon residue causes heavy smoke emission and carbon
deposition on the injection nozzle tips and in the combustion
chamber.
3. There are also problems of incompatibility with engine lubricants.
4. The poor volatility makes the vegetable oil difficult to vaporize and
ignite. This leads to thermal cracking resulting in the heavy smoke
emission and carbon deposits in the combustion chamber. This

33. BIO-DIESEL
• This is an alternative to standard diesel fuel. This is made from
biological sources instead of petroleum. It is made from plant oils or
animal food. Pure bio-diesel is referred by B100 standard diesel is
usually mixed with biodiesel. 80% of standard diesel is mixed with
20% of bio-diesel. This blended bio-diesel is referred by B20.
• National Bio-diesel Board, the technical definition of bio- diesel is
"a fuel comprised at mono-alkyl esters of long chain, fatty acids
derived from vegetable oils or animal fats, designated B100, and
meeting the requirements of ASTMD6751".

35. Biodiesel Production
 Vegetable oil reacts with alcohol (typically methanol or ethanol) in the
presence of catalyst produced biodiesel. Biodiesel production process
consists of three steps; namely,
Conversion of triglycerides (TG) to diglycerides and one
ester molecule
Followed by the conversion of diglycerides (DG) into
monoglycerides (MG) and one ester molecule
Monoglycerides into glycerol and one ester molecule
catalyst

36. Advantages
 It also safer and non-toxic.
 It has higher flag point than conventional diesel oil.
 It can be easily stored and transported.
 It can be also used as engine lubrication assistant.
 It increases the engine life due to less deposit.
 It has lesser emissions. The below table gives average emission of
biodiesel andcomposed diesel fuel.

37. Disadvantages
 NOx emissions will form smoke.
 Although bio-diesel being solvent helps in better lubrication, yet the
loosening deposits from the conventional diesel engine compound
may clog the fuel filter. So, filters should be changed often.
 Cost of the biodiesel is more than the conventional diesel oil.
 Less availability.
 Bio-diesel breaks down rubber components.
 It does not suits all type of engines. In some engines, the reduction in
power occurred at 10%.
 1.1 litres of bio-diesel oil would be equivalent to 1 litre of
conventional diesel oil.

38. NATURAL GAS
• Natural gas, like petroleum comes from underground reserves. It
consists, mainly about 95 percent of methane (CH4). The remaining 5
percent comprises of butane, propane, ethane with small amount of
water vapour. Simple chemical structure of methane makes possible for
complete combustion, releasing lesser emissions.
Two types of natural gas is used as alternative fuel. They are:
 Compressed Natural Gas (CNG)
 Liquefied Natural Gas (LNG)

39. Compressed Natural Gas (CNG)
 Natural gas is compressed and stored in high-pressure cylinders. This
is done for ease transportation storage and automation. Hence it is
called compressed natural gas.
 It requires no additives and its production does not need complicated
refining processes.
 It has very low emissions.

40. Liquefied Natural Gas (LNG)
• LNG means natural gas in liquid form. It is made by refrigerating
natural gas to minus 161°C. It is a clear, colourless, odourless liquid.
During the liquefaction process, natural gas is cooled below its boiling
point removing most of the water vapour, butane, propane, etc., so that
LNG is more than 98 percent of methane (CH4).
• LNG is much more dense than CNG, which means more energy
per unit volume. The implication is the higher vehicle range for the
same size of fuel cylinder.

41. LIQUEFIED PETROLEUM GAS
 Liquefied petroleum gas (LPG), a mixture of propane (C3H8) and
butane (C4H10)gas, is a popular fuel for internal combustion engines.
 It is a nonrenewable fossil fuel that is prepared in a liquid state
under certain conditions.
 This popularity comes from many features of the fuel such as its
high octane number for spark ignited engines, comparable to gasoline
heating value that ensures similar power output.

42. HYDROGEN FUELS
• Hydrogen fuel can be produced from water, a
potentially available raw material. Hydrogen is best
suited for I.C engines since physical delay is almost
zero. So number of automobile manufacturers have
built with prototype or modified engines which
operate on hydrogen fuel.
Properties of Hydrogen Fuel
It has low emission property.
Hydrogen density is low, both when it act as a liquid as well
as gas.
Calorific value is high.

43. Hydrogen Engines
 Hydrogen is a highly reactive fuel which is required to handle in a
great manner. Flash back arresters have to be provided between the
engine and the storage tank to prevent flash back from going to tank.
 Energy density of hydrogen in liquid state is one fourth that of
gasoline. As a gas it has less than one tenth of the density of air. This
makes the storage of hydrogen easier. It can be stored easily in a
cryogenic container when it is in liquid form.

44. Hydrogen injection in spark ignition engine

45. Liquid Hydrogen storage and gaseous
hydrogen injection system

46. Advantages of using hydrogen as a fuel
 High energy content per volume when stored as a liquid. This
increases thevehicle range for a given fuel tank capacity.
 No toxic gas is produced after the reaction.
 Availability of the hydrogen fuel is more.
 It does not pollute the environment.
 Low emission due to less carbon content in the fuel.

47. Disadvantages of using hydrogen as a
fuel
• Low volumetric efficiency.
• Fuel cost is high.
• No possibility of refuel.
• Size of the system is large due to heavy and bulky storage tank.
• Storing as a gas makes the system as more tedious one.
• High NOx emission is due to high flame temperature.

48. Engine Modification System for LPG

49. Engine Modification Using Ethanol

50. PERFORMANCE, COMBUSTION AND
EMISSION CHARACTERISTICS OF SI AND
CI ENGINES USING THE ALTERNATE
FUELS
• Here we are going to compare the gasoline with the
hydrogen fuel.
Comparison of Performance Characteristics
• In analysing the performance characteristics of the
gasoline and hydrogen fuel, we can take the brake
thermal efficiency factor. The brake thermal
efficiency of the hydrogen fuel is more when
compared with gasoline fuel.

51. Comparison of Performance Characteristics

52. Emission of CO

53. Emission of NO

54. Emission of HC

55. Comparison of Combustion Characteristics