ABSTRACT
A TD 110-TD 115 single cylinder four-stroke compression ignition engine test bed, and incorporated with a hydraulic dynamometer was used to conduct the engine performance analysis to study the influence of marula oil methyl ester (MOME)- diesel fuel(DF) on engine performance The engine performance experiments of DF samples and MOME –DF blended fuel samples; B5 (i.e. 5% MOME and 98% Diesel fuel by volumetric proportion), B10, B15, B20, and B25 were conducted in accordance with standardized SAE practice SAE J1312 procedure for four-stroke compression ignition engines (SAE, 1995). The findings of the tests show that: the brake power reached to a maximum at 2000g engine load, and decreases slightly thereafter for all tested fuel samples. The brake power for B5 and B10 fuel samples were observed to be 0.19% and 0.094% higher than DF(2.315 kW), with B15 fuel sample exhibiting brake power value similar to DF benchmark, this could be attributed to their comparably higher fuel mass flow rate, better fuel oxygenation, and air-fuel mixtures than DF sample; the minimum brake specific fuel consumption (BSFC) values for all tested fuel samples was recorded at the engine load of 2500g, with B5 and B10 fuel samples lower than the DF benchmark (309.10 g/kWh) by 18.7% and 0.16%, thus suggesting a propensity for improved fuel economy on account of their lower fuel consumption patterns, lubricity and higher fuel mass flow rate; the drop in brake specific energy consumption (BSEC) values for B5 (2.75%), B10 (1.95%), B15(1.66%), B20(1.37%), and B25(0.22%) fuel samples were also found to be lower than the DF (13.83MJ/kWhr) benchmark, to further explains the influence of biodiesel proportion in the fuel samples, whose increase lowers the calorific values, air-fuel mixtures, and consequently raises the densities and viscosities of fuel samples with an adverse effect on fuel atomization and combustion. The combined effects of improved fuel combustion and inherent lubricity of fuel blends enabled B5 (2.68%), B10 (1.91%), B15 (1.53), and B20 (1.15%) fuel samples to exhibit higher brake thermal efficiency (BTE) values than B25 (26.1%) and DF (26.1%) samples respectively under similar loading condition. Consequently, the rise in biodiesel proportion in the blends is the culprit for poor fuel atomization and combustion behavior, which in turn serves as a pointer to higher blend viscosities and lower calorific values respectively. It could be seen from foregoing that B5, B10 and B15 MOME-DF blended fuel samples clearly demonstrated superior performance characteristics than conventional diesel fuel, and is therefore suitable for use as fuel, and diesel fuel extender and/or conserver in Nigeria.
