The combustion process of liquid conventional and biofuels depend on
factors ranging from the thermophysicochemical properties associated
with such fuels to the combustion infrastructure used to burn them.
A third class of fuels commonly referred to as surrogate fuels can be
obtained by mixing conventional and biofuels. It is thought that the
existence of oxygen atoms in biofuels play a crucial role in the way
they burn in a stream of air, in
uencing not only the e ciency of the
combustion process of such class of fuels but also the emissions. The
mechanisms through which the existing oxygen atoms in
uence the
combustion process of biofuels (and its surrogates) are still debatable
and unestablished.
This thesis sheds light on the points mentioned in the paragraph
above. Extensive computational and experimental work was done
to elucidate the combustion process of conventional, surrogate and
biofuels. Some of the reaction mechanisms used in modelling the
current reactive
ow simulation are already tested while others were
developed during the course of this work.
The computational results have shown good agreement with the available
experimental data. One of the most important observations and
ndings reported in this work was that when comprehensive reaction
models were used, the injected fuels burned at a slower rate compared
to the situation when reduced models were employed. While
such comprehensive models predicted better
ame structure and far
better by-products compared to the existing experimental results, it
has also led to di erences in some parameters, especially the temperature
eld. The computational prediction has also shown that biodiesel
produces a marginally higher rate of COx compared to diesel which
was also observed experimentally using a Compression Ignition Engine
(CIE). Having said so, the experimental work also showed that surrogate
fuels perform far better than pure diesel and biodiesel in CIE)
in terms of emissions. The experimental work further addressed some
phyisical and spectral analysis of diesel, biodiesel and nine blends as
well as assessing the performance of a combination of these fuels in
a compression ignition engine. The results are in line with what has
reported in the literature but also sheds light on important features
related to surrogate fuels and explain better the expected structure
of such blends which may in
uence the way they burn under di erent
environments.
With regards to the harmfull emissions of the combustion of liquid
fuels, biodiesel was found to produce harmful emissions in a lower
quantity compared to conventional diesel which is in line with the
ndings of many experimental data. The computational ndings have
also predicted less energy content and temperature range for biofuels
of order 10-15% which is also in agreement with many experimental
ndings cited in the literature
