Abstract
The performance of a 118-kW tractor fuelled by pure biodiesel was monitored during a long-term field experiment with approximately 800 h of engine function. The objective was to demonstrate that B100, a pure biodiesel fuel, is a viable alternative to traditional diesel oil in terms of long-term mechanical reliability. A bench test on the new engine, performed by attaching a test stand to the power take-off of the tractor, showed an expected reduction in power (-9%) and torque (-7%) and an increase in specific consumption (+13%) when biodiesel was used as a complete substitute to diesel oil. Furthermore, with the same setup, the exhaust gas had a Bosch smoke index equal to 50% of the value for the same engine fuelled with diesel oil. After these initial tests, the tractor was set up for normal field operations, in which both the engine curves and lubricant quality were periodically monitored. These surveys indicated no significant reduction in engine performance; however, the lubricant was consequently diluted and contaminated by biodiesel, which caused the lubricant properties to considerably worsen. However, on the basis of the chemical-physical analysis, reducing the oil change interval from 200 h (manufacturer's indications for the engine when operating with diesel oil) to 100 h would compensate for this progressive quality decline. At the end of the trials, the engine was disassembled to check the condition of its components; wear and lacquer-like coating phenomena were observed, and their levels were acceptable. The obtained results demonstrated that B100 can effectively substitute for diesel oil in a standard compression-ignition engine: the power change is not perceptible during normal operation of a tractor, and no particular problem will arise in the engine during its life if the lubricant is changed every 100 h.