Abstract
Due to the increasing consumption of fuels in heavy industries, especially in road transportation, significant efforts are being made to increase the market participation of renewable fuels, including ethanol. In diesel engines, however, ethanol cannot be used as a pure fuel, primarily due to its very low cetane number and lubricity. For this reason, greater attention is being paid to blended fuels containing diesel and varying percentages of ethanol. Tests of lubricating properties carried out in accordance with the standard HFRR (high frequency reciprocating rig) method for ethanol–diesel fuel blends have long durations, which leads to ethanol evaporation and changes in the composition of the tested fuel sample under elevated temperatures. Therefore, this study presents an alternative lubricity assessment criterion based on the measurement of the scuffing load with a four-ball machine. Lubricity tests of blends of typical diesel fuel and ethanol, with ethanol volume fractions up to 14% (v/v), were conducted using a four-ball machine with a continuous increase of the load force of the friction node. In this method the lubrication criterion was the scuffing load of the tribosystem. The obtained results provided insights into the influence of the addition of ethanol to diesel fuel on lubricating properties, while limiting the ethanol evaporation process. The results also showed that an increase in the fraction of ethanol up to 14% (v/v) in diesel fuel resulted in a decrease in the scuffing load and a corresponding deterioration in the lubricating properties of the diesel–ethanol blend. For an ethanol volume fraction of 6–14%, the changes in the scuffing load were smaller than in ethanol volume fractions of 0–6%.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
Due primarily to its very low cetane number, i.e., a very low propensity for self-ignition, as shown in [23,24,25,26,27,28], ethanol cannot be used as a pure fuel in diesel engines
Additional samples included blends of standard diesel fuel with ethanol volume fractions ranging from 2% to 14%
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It has been shown that the dominant wear observed in the HFRR method is delamination and adhesive wear [32,52] To address this challenge, this work proposes another lubricity assessment criterion, based on the measurement of the scuffing load with a four-ball machine, which, in the case of diesel–ethanol blends, reflects the ability to create a boundary lubricating layer. This work proposes another lubricity assessment criterion, based on the measurement of the scuffing load with a four-ball machine, which, in the case of diesel–ethanol blends, reflects the ability to create a boundary lubricating layer This result is possible due to the specificity of the test, which is characterized by a short duration.
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