Experimental studies for the thermo-physiochemical properties of Biodiesel and its blends and the performance of such fuels in a Compression Ignition Engine

An experimental work was conducted to obtain an insight on the variation of fundamental thermo-physiochemical properties for a range of mixtures of red Diesel (referred to here as D100), and Biodiesel (referred to here as B100) and the performance of such blends in a Compression Ignition Engine (CIE). The results for some specific properties such as density and viscosity; water content, pour and cloud points for D100, B100 and blended fuels (referred to here as B10-B90, the numbers indicate the percentage of Biodiesel in the blend), strongly indicate that the resultant mixture is an ideal solution and display a linear increase with increasing the B100 percentage in the blend. The cetane number showed a linear variation between B10-B80 but high value for B90 and B100. Sulphur content decreases continuously with increasing the Biodiesel percentages in the blend while the acid content increases with increasing B100 ratio. All these results carries no controversial issues with previous related studies. The FTIR data obtained using gas analyser has shown that D100, B100 and fuels blends include a range of sub-hydrocarbons with Alkanes (=C-H) compounds as the main hydrocarbon. All Biodiesel blends has shown significant existence of Aldehydes (-C=O) and Ketones (-C=Ost). Nitro-compounds (-NO2) exist in almost all fuels while Alcohols, ethers, acids and esters (-C-O-) are mainly associated with B100 and its blends. Allowing more time for B100 and its blends, the FTIR data strongly indicate that chemical composition changes and water contents increases in B100 and its blends leading to instability issues. Using D100, B100 and 3 blends, mainly B25, B50 and B75 in a Diesel (CIE), the results showed that D100 releases higher rate of energy as expected compared to B100 and its blends. However the results showed that the blends burn more efficiently in the CIE used with the blend B75 producing the best engine efficiency and reasonably low fuel consumption. The emission data showed that the B100 and its blends produce less unburned hydrocarbon, CO, CO2 and NOx emission compared to D100. The better thermal and emission performance of the blends is most likely due to their balanced chemical composition as revealed by the FTIR spectra. The current work also indicates that blended fuels with higher ratio of B100 are recommended to use in CIEs to ensure efficient combustion.