Increasing strict regulation on the sulfur content of diesel fuels results in decreases the lubricity of these fuels. The lubricity of the fuel is an indication of the amount of wear or scarring that occurs between two metal parts covered with the fuel as they come in contact with each other. Low lubricity fuel may cause high wear and scarring and high lubricity fuel may provide reduced wear and longer component life. Previous studies have shown that alkyl esters of triglycerides derived from vegetable oils have increased diesel fuel lubricity at concentration of less than 1%. The major objective of this study was to analyze the effectiveness of indigenous non-edible feedstocks such as jatropha (Jatropha curcas) as an additive in petroleum based diesel fuels. Jatropha oil, and its alky esters (methyl and ethyl ester) and oil-ester blends with diesel were tested as an additive to enhance the lubricity of diesel fuels. In case of fuels, the lubricating behavior is associated with boundary film-forming properties. The analysis was carried out by using ASTM 6079-4 test method using High Frequency Reciprocating Rig (HFRR model D1377) as an analytical tool. The coefficient of friction and wear was observed higher for the low lubricity diesel fuel (LLDF) and it decreases with the addition of additive dose of oil, methyl and ethyl ester of jatropha. It may be due to the better lubricating behavior of non-edible based oil and ester compare to LLDF. During the HFRR test 2±0.20 ml of fluid sample under test is placed in reservoir which is maintained at a specified temperature of 60±2 °C. The HFRR test uses a vertically mounted steel ball to apply force to a horizontally mounted stationary steel disk with an applied load (200±1 g). The test ball is oscillated at a fixed frequency (50 ± 1 Hz) with a fixed stroke length (1 ± 0.02 mm) while the disk is fully immersed in the fluid reservoir. The whole test rig was placed in the humidity cabin with transparent enclosure. The test was kept for 75 minutes and the wear scar on the ball was measured by electronic microscope. It is believed that the high concentration of the particular fatty acid in oil and alkyl ester could be responsible for enhancing the lubricity and subsequent lower wear scar.

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