Page 409 - Advances in Eco-Fuels for a Sustainable Environment

Engine modification for alternative fuels usage in diesel engine 363

produced need not sustain for long time. Whereas, fire point is the minimum temper-
ature at which vapor of the fuel steadily burns at least for five seconds once ignited.
Flash point and fire point are the property that directly signifies whether the fuel is
safely transportable; it is not related to engine performance.

13.2.5.2 Cloud point and pour point
The cloud and pour points of the biodiesel and diesel fuel are tested by cloud and pour
point apparatus, according to ASTM D97 and ASTM D2500 standards. Cloud point is
the minimum temperature at which the first crystal formation starts. Pour point is the
minimum temperature below which a liquid loses its flow characteristics. A freezer
that can cool below 0°C is used, where temperature is decreased in steps of 3°C until
a cloud or haze or wax crystal is formed at the bottom of the test tube. The temperature
at which the cloud forms is called the cloud point. After the cloud point, the temper-
ature is reduced in steps of 1°C until the temperature at which the fuel loses its flow
characteristics or stops moving. The cloud and pour point property are significant for
the fuel when they have to be used in cold regions.

13.2.5.3 Viscosity
The Brookfield viscometer model DV3T was used to measure the dynamic viscosity
of the tested fuels. The test is usually carried by a 16mL sample to be taken in the
cylindrical cup for viscosity measurement. The sample is poured into a spindle and
cylindrical cup-type arrangement in which the sample is continuously subjected to
shear stress. According to the ASTM D445 standard, the temperature of testing fuel
was maintained at 40 °C by using the water bath arrangement. Viscosity is defined as
the resistance offered by one layer to another while in motion. Viscosity is an impor-
tant property for any fuel that runs in the engine. Pure biodiesel has maximum viscos-
ity because of increases of density and fatty acid content. According to the ASTM
D445, the kinematic viscosity should be in the range of 1.9–6cSt. If the kinematic
viscosity of any fuel is <1.9cSt, the fuel will leak from the fuel injector and pump.
If it is >6cSt, then the nozzle opening pressure should be increased through engine
modification.

13.2.5.4 Calorific value
The Bomb Calorimeter (Model-IKA C2000) was used to measure the cross calorific
value of the solid and liquid samples. It is a constant-volume type calorimeter that
measures the heat of a particular reaction or measures the calorific value of the fuels.
Bomb calorimeters are built in such a way that they can withstand the large pressure
produced within the calorimeter due to the reaction or burning of fuel. The electrical
energy is used as an ignition source for the burning of testing fuels, and the heating
filament is made up of tungsten materials. In the bomb calorimeter, I g of the sample
was taken in the crucible and was electrically ignited to burn with the presence of pure
oxygen. During the combustion, heat was released and a rise in temperature was