The influence of sea water in oil emulsion on bearing performance

Abstract The lubricant in the bearings of ships can be easily polluted by sea water. Too much sea water may deteriorate the bearing performance and result in catastrophic failure; therefore, the lubricant should be changed regularly to prevent this. It is important to investigate the effect of adding sea water to mineral oil on the tribological performance of these bearings. In the present study, different amounts of sea water of 1, 2, and 3 per cent (by mass) were mixed with a typical mineral oil with a viscosity of 46 mm2/s at 40 °C and tested in 12 identical journal bearings under different operation conditions of rotational speed and load. For each case, the temperature within the oil film, the loci of the shaft centre, the power consumption, and the viscosity of the emulsion were measured. In parallel to these measurements, a CFD simulation was performed for the test bearings to estimate the friction force and load capacity. The experimental measurements and the computational predictions were compared. A maximum amount of sea water that can be tole-rated in the mineral oil was established for the normal working conditions of the journal bearing.

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