Abstract

Saturation level of a biodiesel is one of the factors affecting the performance and exhaust gas emissions of a compression ignition engine. This research was conducted to evaluate the engine performance and analyse its exhaust gas using biodiesel binary blends from desert date and baobab seed oils in comparison to petro-diesel. Gas Chromatography Mass Spectrograph was used to determine the saturation level of the biodiesels. The results showed that desert date biodiesel was predominantly (48.5%) unsaturated methyl linoleic while baobab biodiesel was largely (74%) dominated by saturated methyl lauric. The two methyl esters were equally blended by volume and re-blended with petro-diesel from B5 to B30 at an interval of 5%. The performance of the multi-blended fuels in the 86F single cylinder 4 stroke cycle diesel engine test bed coupled with versatile data acquisition system (VDAS) were determined at a constant speed of 2500 rpm with an engine torque between 2Nm to 8Nm. The developed brake power obtained showed that B30 at 8 Nm was (1.511 kW) about 11% above the petro-diesel while B5 has the best value (5.46 bar) of brake mean effective pressure (BMEP) at the torque of 8 Nm. On the other hand, the petro-diesel was observed to produce higher brake thermal efficiency (about 2% above B30) and lower exhaust gas temperature (54% below B25 and B30) at the same engine torque. The values of the brake specific fuel consumption were found to be decreasing with increase in engine torque. At 8 Nm, a significant decrease was observed with B10 and B15 that was 18.5% lower than the petro-diesel at the same condition. At constant torque of 4Nm and a varying engine speeds (1500, 2000 and 2500 rpm) for the emission analysis. Petro-diesel was observed to have the lowest NOx emission (125 ppm) at 2000 rpm but increases with increase in blend ratio. B30 has the highest emission of 411 ppm at 2500 rpm. However, for hydrocarbon, the highest emission of 275 ppm from petro-diesel was obtained at 1500 rpm while B10 has the lowest hydrocarbon at the same speed. The results from the CO and CO2 showed that B30 at 1500 rpm has the lowest CO emission with 6 % lower than the PD but B15 was the lowest in CO2 emission at 2500 rpm.

Key words: Binary Blending, Engine Performance, Desert date, Baobab, Petro-diesel