Large hydrodynamic thrust bearing: Comparison of the calculations and measurements

Hydrodynamic thrust bearings, used to carry axial loads in heavily loaded shafts of water power plants hydro turbines, can reach outer diameters even exceeding 5 m. In such large objects scale effect could be observed. According to this, allowable bearing specific load assuring safe operation of the bearings has to be decreased, which increases thrust bearing dimensions. This effect is caused by excessive thermal deflections of bearing pads, which significantly change oil gap geometry, and in consequence, decreases bearing load-carrying ability. Design of hydrodynamic thrust bearing of large dimensions seems to be a demanding engineering challenge, and additional difficulty comes from limited possibilities of experimental testing of these systems due to high costs. Theoretical investigations, carried out with the use of specially developed computer models, remain a feasible alternative for experimental research. But the accuracy of the models is not often directly validated, because of the lack of appropriate experimental data coming from large objects. In this paper, results of calculations carried out for a large hydrodynamic thrust bearing are shown and compared to measurement data obtained at bearing commissioning stage. Pad temperatures profile sliding surface, oil pressure in hydrodynamic gap and film geometry are compared to the measured values. According to the presented comparisons, some conclusions are drawn with respect to the accuracy of models used to predict large thrust bearing performance.