Pumped storage power plants play an important role in contemporary power systems producing electricity during peaks of demand and utilizing a surplus of energy production in low-demand periods for storing energy in water reservoirs. Their use is important nowadays in cooperation with wind power farms. The most typical units in pumped storage power plants are vertical shaft Francis-type pump-turbines. A characteristic feature of these setups is bidirectional operation, with one direction of rotation in generating mode and the opposite direction in pumping mode when the unit is powered by electricity from the grid, pumping water to the upper reservoir. Pumped storage power plants are usually built as large objects and the machines installed typically exceed a power of 100 MW.
In vertical shaft machines an important role is played by a thrust bearing, which accommodates vertical forces of the weight of the rotating parts, as well as hydraulic forces acting on a turbine runner. The fluid film thrust bearings in these machines are, in most cases, of the tilting pad type. Operation of such bearings is bidirectional, so the bearing pads have to be supported symmetrically, which is unfavourable for their performance according to the literature results [
1,
2], yet their specific load is quite high for the sake of minimising power losses. On the other hand, it is an established fact that, because of the scale effect of thermoelastic deformations in thrust bearings [
3], the large diameter bearings must be designed in a way that minimises pad deformations. Therefore, the large thrust bearings of pumped storage power plants should be considered critical machine components, with special care in the design and operation. The special care in design and operation is also reflected by numerous publications over the years, comprising demonstrations of achievements of particular bearing design modifications, such as double layer bearing, described and tested in [
4]. Detailed theoretical calculations of bearing properties were presented with the use of more and more sophisticated models including heat exchange between the pads and at the pads’ surroundings, like the code Marmac1, described in [
5]. An important modification of the bearings contributing to minimized thermal deformations were also the bearings with a polymer lining of the pad surface studied in numerous publications, e.g., [
6]. Additionally, a common design feature of hydrostatic jacking, meant to improve bearing operation in transient states, was an object of research and the results were, for example, discussed in [
7]. The codes used for bearing calculations are quite sophisticated, seeming to take into account all effects significant for bearing performance, such as deformations, lubricant properties as a function of temperature and pressure, oil mixing between the pads, heat exchange, etc. [
8,
9,
10]. However, the accuracy of these codes is not clear, as there are few papers comparing theoretical and experimental results for large bearings. These examples are the results of the testing of a large bearing in a special unique test rig reported by Yuan et al. [
11]. Other published results of comparisons between calculations and field data were presented by Dąbrowski and Wasilczuk [
12], where the object was a hydrogenerator bearing with a system of compensation of thermal deflections; by Wodtke et al. [
13], where the results of one of the largest thrust bearings in the world, installed in the Itaipu power plant were presented, and the method utilized was FSI (fluid structure interaction) combining a CFD (computational fluid dynamics) solution for a fluid film with a FEM (finite element method) solution for a solid structure. Huang et al. [
14] published a detailed comparison between the experimental results obtained in a special test rig on a bidirectional bearing and numerical predictions. The comparison showed quite good overall agreement on the oil film thickness, pressure, and temperature. The calculation method was a combination of FDM (finite difference method) and FEM.
uang Th A relative shortage of direct comparisons between calculations and field data of large thrust bearings is quite understandable, bearing in mind the difficulty in gathering detailed test results for large bearings. Due to many operational problems in pump turbines of one Polish power plant, an extensive program of field tests on thrust bearings has been carried out, aimed at improving bearing reliability [
15,
16]. Data presented in this paper comprises standard hydrodynamic operation and a special hybrid regime. The hybrid regime, when the hydrostatic system was activated during steady state operation, was only used for testing. The data enables one to see trends of changes of various parameters, and compare the hybrid and hydrodynamic regimes. They can also be used by other researchers for comparing their theoretical predictions to measurement data.