Effect of presence of lifting pocket on the THD performance of a large tilting-pad thrust bearing

Abstract

Hydrostatic assistance is a commonly used method to improve limited load carrying ability of tiltingpad thrust bearings during transient states of operation of vertical shaft hydro-generators. Despite of special hydraulic equipment (as pumps, valves, etc.), it also requires manufacturing of special recesses/pockets at pad sliding surfaces, into which oil is injected under high pressure. It allows to lift the rotor before start-up of the machine and form a hydrostatic film between pads and collar. There is a quite wide variety of geometry of recesses (shape, depth, and size) met in practical large bearing applications. The presence of a hydrostatic pocket (usually located in the sliding surface above the pivot area, where thin film, high oil pressure and temperature are observed) affects bearing performance under hydrodynamic operation.In theoretical researches, there is an almost common practice not to include hydrostatic recess in thermohydrodynamic (THD) or thermoelastohydrodynamic (TEHD) analysis. This is probably due to the problems with obtaining solution for oil film geometry with pocket, the order of magnitude of the pocket depths being larger than gap thickness. In this paper, an attempt was taken to study the effect of lifting pocket on THD performance of a large tilting-pad thrust bearing of Itaipu power plant. Bearing performance was evaluated including recess shape for several cases of its depth. The results show that hydrostatic recess changes calculated bearing properties quite significantly, especially in vicinity of the pocket.

Measured and Predicted Operating Characteristics of a Tilting-Pad Journal Bearing with Jacking-Oil Device at Hydrostatic, Hybrid, and Hydrodynamic Operation

“…[16] for a setup for investigations of journal test bearings the test section is depicted in Figure 1a. The test shaft (1) is supported by two fluid-film journal bearings (2,3). The test bearing (4) is mounted in a test bearing housing (5).…”

“…If the number of starts is reduced to once a day this value increases to 2.5 MPa. Design parameters of different hydrostatic jacking systems for thrust bearings from literature are 2 of 15 listed in [2]. Several publications investigate operation of hybrid journal bearings building up a combined hydrostatic and hydrodynamic pressure, e.g., [3].…”

Nonlinear dynamic analysis of low viscosity fluid-lubricated tilting-pad journal bearing for different design parameters

“…With good stability on rotor systems, tilting-pad journal bearings (TPJBs) have been widely applied in large-scale rotating machineries, such as steam turbines, gas turbines, and nuclear reactor coolant pumps. The representative research of tilting-pad thrust bearings focuses on the effects of surface roughness [1] and lifting pockets [2] on bearing performance. Water has been gradually used as the journal bearing lubricant in ship stern shafts, hydraulic turbines, and water pumps instead of oil.…”

Effects of the dimple geometry on the isothermal performance of a hydrodynamic textured tilting-pad thrust bearing

“…In 2014, Satish et al [15] investigated the influence of dimple geometry on fully textured hybrid thrust pad bearing and operating with non-Newtonian lubricant. By using the Finite Element Method, the simulated results indicate that the values of load carrying capacity, frictional power loss, maximum pressure and fluid film stiffness coefficient are significantly affected by the behavior of lubricant.…”