Tilting pad thrust bearings are the key components in hydropower units. As the thrust loads increase with the unit capacities of the hydro turbines, many thrust bearings failed due to rub-impacts between the collar and pads. Some plants have to be shut down for up to one month to repair the damaged pads which has lead to enormous economic losses. The lubrication processes of thrust bearings are quite complex involving fluid-thermal-structural interactions between the pad, the collar, the oil film and the oil surrounding the pad. This paper reviews the bearing mechanism including the thermal-elastic deformation, the transient and dynamic characteristics, the bidirectional thrust bearing, as well as the various prediction methods on the lubrication performance. At last, an overview of some special designs including the covered materials, supporting system and hydrostatic jacking system to improve the thrust lubrication was briefly presented.

A review on the large tilting pad thrust bearings in the hydropower units

Polymer-based additives such as poly isobutylene are blended with lubricating oil to enhance the lubricating performance of the base oil. The Rabinowitsch fluid model effectively describes the infl...

Performance of hydrostatic circular thrust pad bearing operating with Rabinowitsch fluid model

The pressure distribution in an aerostatic bearing has an important effect on the performance of the associated mechanical equipment. To more accurately predict performance, a new dynamic modeling ...

A novel dynamic modeling method for aerostatic spindle based on pressure distribution

Reynolds equation is solved using finite difference method (FDM) on the surface of the tilting pad to find the pressure distribution in the lubricant oil film. Different pressure profiles with grid independence are described. The present work evaluates pressure at various locations after performing a thorough grid refinement. In recent similar works, this aspect has not been addressed. However, present study shows that it can have significant effect on the pressure profile. Results of a sector shaped pad are presented and it is shown that the maximum average value of pressure is 12% (approximately) greater than the previous results. Grid independence occurs after 24 × 24 grids. A parameter "ψ" has been proposed to provide convenient indicator of obtaining grid independent results. ψ = |(P refinedgrid - P Refrence-grid)/P refinedgrid|, ψ ≤ e, where "e" can be fixed to a convenient value and a constant minimum film thickness value of 75 μm is used in present study. This important parameter is highlighted in the present work; the location of the peak pressure zone in terms of (r, θ) coordinates is getting shifted by changing the grid size which will help the designer and experimentalist to conveniently determine the position of pressure measurement probe.

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D.V. Srikanth

Papers

Determination of a large tilting pad thrust bearing angular stiffness