Biodiesel is considered as a renewable biofuel-based substitute for fossil diesel as the properties of biodiesel are similar to those of normal diesel fuel. However, biodiesel has some properties which a negative effect on engine combustion. Binary and ternary fuel blends (blends of biodiesels with the opposite properties) are the best environmentally friendly alternative in compression ignition engines. In this paper, the effects of binary and ternary blends of tomato, papaya, and apricot seed biodiesels on the energy and exergy balance as well as emissions on a compression ignition diesel engine were experimentally and theoretically investigated. The obtained results reveal that the maximum and minimum exergy efficiency are related to the biodiesel of tomatopapaya blend at about 29.63% and pure diesel at about 28.46% respectively. Also, the obtained results show that, compared to the tomato biodiesel-diesel blend, using the binary blends decreases the percentage of heat loss exergy by 5.5% and 3.3% on average for tomato-papaya biodiesel -diesel and tomato-apricot biodiesel-diesel, respectively. The results address that the energy percentage of exhaust emissions at the speed of maximum torque and maximum power averaged 30% while this fraction for exergy was about 13%. The emission results show that the minimum oxygen monoxide emissions, which is 0.3% less than that of diesel, is related to the tomato-apricot-papaya biodiesel-diesel ternary blend.

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