Energy losses in the spring-supported thrust bearings used in many large hydroelectric generator units were estimated to be small compared to the rate of energy (power) generation but, nevertheless, commercially significant. The purpose of thepresent study was examine the influence of oil viscosity on power loss. Experiments were performed using a test facility containing a thrust bearing of 1.2 m outer diameter and both power loss and temperature rise were measured for oils of ISO grade 32,46 and 68, all at various oil pot temperatures. Power loss and temperature rise decreased as the viscosity of the oil in the oil pot decreased. Minimum oil film thicknesses were predicted with numerical analysis using a specialized software package(GENMAT). The accuracy of this calculation was supported by the good agreement between the temperature rise predicted by numerical analysis and the experimentally determined values. Provided film thickness were adequate to avoid any danger of wiping (10 - 15μm), the present study showed clearly that significant energy savings could be realized in the large spring-supported thrust bearings and associated guide bearings by lowering oil viscosities.
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