60
Alternative Fuels for Transportation
Biodiesel specification ensures that at viscosity upper limit, fuel will flow
readily during cold starting. Higher viscosity of fuel leads to poor atomization, incomplete combustion, and increases carbon deposits. Moreover,
higher viscosity fuel needs higher pumping power also. Fuels with lower
viscosity leaks past the plunger through the clearance between plunger and
barrel during fuel compression.
3.4.4 Density
Density is mass of the substances occupying unit volume at 15ºC. Density
of fuel is evaluated as per ASTM D4052. Hydrometers are used to evaluate
the density of liquids. Biodiesel is slightly higher than conventional diesel.
Diesel engine injectors normally operate on a volume metering system. If
the fuel is of higher density, a large mass of fuel is injected and hence more
power and emissions.
3.4.5 Cetane Number
Cetane number of fuel is a measure of the ignition performance of diesel fuel
obtained by comparing it to the reference fuels in a standardized engine test;
that is, cooperative fuel research (CFR) cetane engine, as per ASTM D613
test method. The higher cetane number in fuel is better in its ignition properties. The cetane number affects engine parameters like combustion, stability, drivability, smoke, noise, and emissions. Cetane number of biodiesel
is higher than that of diesel. Adequate cetane number is required for good
engine performance. High cetane number ensures good cold start properties
and minimizes the formation of white smoke.
The cetane number of biodiesel depends on the feedstock used for the
biodiesel production. Cetane number of biodiesel decrease with an increase
in unsaturation (oleic and linolenic) and increases with an increase in chain
length. Esters of saturated fatty acids such as palmitic and stearic acids have
higher cetane numbers.
3.4.6 Distillation Characteristics
Biodiesel does not contain any highly volatile components, hence it evaporates at higher temperatures. Biodiesel components have very close boiling
points. Boiling point of biodiesel generally ranges from 330–360ºC.
3.4.7 Cold Filter Plugging Point
Cold filter plugging point (CFPP) is the temperatures at which a fuel will
cause a fuel filter to plug due to fuel components that have begun to crystallize or gel. CFPP of biodiesel is determined as per EN 116 test method. CFPP
reflects the cold weather performance of the fuel. At lower temperatures fuel
Alternative Fuels for Transportation
Biodiesel specification ensures that at viscosity upper limit, fuel will flow
readily during cold starting. Higher viscosity of fuel leads to poor atomization, incomplete combustion, and increases carbon deposits. Moreover,
higher viscosity fuel needs higher pumping power also. Fuels with lower
viscosity leaks past the plunger through the clearance between plunger and
barrel during fuel compression.
3.4.4 Density
Density is mass of the substances occupying unit volume at 15ºC. Density
of fuel is evaluated as per ASTM D4052. Hydrometers are used to evaluate
the density of liquids. Biodiesel is slightly higher than conventional diesel.
Diesel engine injectors normally operate on a volume metering system. If
the fuel is of higher density, a large mass of fuel is injected and hence more
power and emissions.
3.4.5 Cetane Number
Cetane number of fuel is a measure of the ignition performance of diesel fuel
obtained by comparing it to the reference fuels in a standardized engine test;
that is, cooperative fuel research (CFR) cetane engine, as per ASTM D613
test method. The higher cetane number in fuel is better in its ignition properties. The cetane number affects engine parameters like combustion, stability, drivability, smoke, noise, and emissions. Cetane number of biodiesel
is higher than that of diesel. Adequate cetane number is required for good
engine performance. High cetane number ensures good cold start properties
and minimizes the formation of white smoke.
The cetane number of biodiesel depends on the feedstock used for the
biodiesel production. Cetane number of biodiesel decrease with an increase
in unsaturation (oleic and linolenic) and increases with an increase in chain
length. Esters of saturated fatty acids such as palmitic and stearic acids have
higher cetane numbers.
3.4.6 Distillation Characteristics
Biodiesel does not contain any highly volatile components, hence it evaporates at higher temperatures. Biodiesel components have very close boiling
points. Boiling point of biodiesel generally ranges from 330–360ºC.
3.4.7 Cold Filter Plugging Point
Cold filter plugging point (CFPP) is the temperatures at which a fuel will
cause a fuel filter to plug due to fuel components that have begun to crystallize or gel. CFPP of biodiesel is determined as per EN 116 test method. CFPP
reflects the cold weather performance of the fuel. At lower temperatures fuel