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Diesel fuel requires sufficient lubricity to prevent excessive wear in fuel injection equipment. The processes for removing sulfur from diesel fuel also eliminate compounds that are responsible for its lubricating properties. This phenomenon is counterbalanced by employing lubricity additives to restore fuel lubricity to an acceptable level. The aim of this study was to compare the two different laboratory methods for testing lubricity. The two methods were the EN 590 standard method high frequency reciprocating rig (HFRR) and a less utilized method scuffing load ball-on-cylinder lubricity evaluator (SLBOCLE). Two different commercial lubricity additives were used. In addition, rapeseed methyl ester (RME) was used for lubricity purposes in the same way as the additives. To study the possible effect of the base fuel, the tests were performed with fossil diesel fuel, paraffinic diesel (Hydrotreated vegetable oil, HVO), and a blend of these.

Fuel spray mixing has been analyzed numerically in a single-cylinder optical research engine with a flat piston top. In the study, a narrow spray angle has been used to align the sprays towards the piston top. Fuel spray mass flow rate has been simulated with 1-D code in order to have reliable boundary condition for the CFD simulations. Different start of fuel injections were tested as well as three charge air pressures and two initial mixture temperatures. Quantitative analysis was performed for the evaporation rates, mixture homogeneity at top dead center, and for the local air-fuel ratios. One of the observations of this study was that there exists an optimum start of fuel injection when the rate of spray evaporation and the mixture homogeneity are considered.