Computational and Experimental Investigations on Biodiesel Combustion Process




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De Montfort University


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Peer reviewed


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.





Research Institute