| dc.description.abstract | Cape Chestnut oil was procured from Naromoru in central Kenya and processed to
biodiesel through transesterification in this study. The purpose of this study was to
identify the physical properties and characteristics of Cape chestnut biofuel, assess the
engine emissions as influenced by the fuel and optimize its performance characteristics.
Properties of biodiesel were determined and compared with those of diesel No 2 fuel.
Engine tests were done on the biodiesel blends to evaluate their performance and
emissions characteristics.
The evaluation of engine performance was in terms of Brake Specific Fuel Consumption
(BSFC), Brake Horse Power (BHP) and Thermal Efficiency (TE). The engine
performance was evaluated at a constant engine speed of 1500 RPM on various loads.
The engine was initially run on diesel to establish the reference performance
characteristics before running on biodiesel blends. Engine tests were subsequently
carried out using biodiesel blends. The average brake specific fuel consumption of B100
from the tests carried out was higher than that of diesel by 35.5%. The biodiesel was
blended with diesel volumetrically to 80% (B80), 50% (B50), 20% (B20) and 5% (B5)
the percentage being the volume of biodiesel in the blended fuel and B100 being 100%
biodiesel.
Engine run on the diesel fuel had the lowest BSFC followed closely by B5 whose BSFC
was found to be 7.3% higher than that of No. 2 diesel. The other blends also showed
lower BSFC as compared to neat biodiesel (B100). Blending increased the BSFC of the
blended fuel in proportion to the amount of biodiesel in the blend.
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The tests carried out showed that brake thermal efficiency for B100 was lower than that
of diesel by 20.3% while that of B5 was 7.6% lower and reduced with the increase of the
amount of biodiesel in the blend. The other blends thermal efficiencies were 11.3%,
14.4% and 10.4% for B20, B50 and B80 respectively.
Engine emissions were evaluated in terms of the concentrations of Sulphur Dioxide
(SO2), Nitrogen Dioxide (NO2), Nitrogen Monoxide (NO) and Particulate Matter in the
engine exhaust emission gases. During the engine tests gas emissions were monitored.
The concentration of SO2 for biodiesel blends was shown to increase as the volume of
diesel increased. Concentration of SO2 in B100 was found to be 92.7% lower than that
of No. 2 diesel fuel while that of B20 was 24.7% lower and it decreased with the increase
of biodiesel in the blend. The results showed that the NO concentration for B100 to be
15.5% higher than that of No. 2 diesel and it increased as the amount of the biodiesel in
the blends was increased. The results evaluated found that the concentration of NO2
increased with increased volume of biodiesel in the blend with B100 having an increase
of NO2 concentration of 15% higher than diesel. Particulate matter of less than 10 μm
diameter (PM10) for diesel was found to be 72% of the total collected from all the test
fuels as compared to that of biodiesel blends at 28%.
The study established that the performance characteristics of Cape Chestnut biodiesel
and its blends with diesel were slightly lower as compared to No. 2 diesel. The emissions
evaluated in this study established that the biodiesel and its blends had lower
particulate matter emissions than diesel. Thus the biodiesel is a less pollutant and hence
friendly to the environment. The study concluded that Cape Chestnut biodiesel blends
containing up to 20% biodiesel can be used in an unmodified diesel engine since their
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performance (11.3% thermal efficiency lower than that of biodiesel) and emission
characteristics were very similar to that of diesel with reduced toxic gas emissions.
The graphs plotted for the performance characteristics showed clearly that the
optimum operating range for all the fuels tested was 9-10 Kw (BHP).
The results of the study recommended the use of B20 biodiesel blend which has a higher
performance characteristics than neat biodiesel but lower emissions as compared to
diesel which is good for our environment.
Key Words: Biodiesel, Transesterification, Emissions, Brake Specific Fuel
Consumption, Brake Horse Power, Thermal Efficiency, Performance. | en_US |
