Tilting pad thrust bearings (TPTBs) control rotor axial placement in rotating machinery, and their main advantages include low drag power loss, simple installation, and low-cost maintenance. The paper details a novel thermo-elasto-hydrodynamic (TEHD) analysis predictive tool for TPTBs that considers a three-dimensional (3D) thermal energy transport equation in the fluid film, coupled with heat conduction equations in the pads, and a generalized Reynolds equation with cross-film viscosity variation. The predicted pressure field and temperature rise are employed in a finite element (FE) structural model to produce 3D elastic deformation fields in the bearing pads. Solutions of the governing equations delivers the operating film thickness, required flowrate, and shear drag power loss, and the pad and lubricant temperature rises as a function of an applied load and shaft speed. To verify the model, predictions of pad subsurface temperature are benchmarked against published test data for a centrally pivoted eight-pad TPTB with 267 mm in outer diameter (OD) operating at 4–13 krpm (maximum surface speed = 175 m/s) and under a specific load ranging from 0.69 to 3.44 MPa. The current TEHD temperature predictions match well the test data with a maximum difference of 4 °C and 11 °C (<10%) at laminar and turbulent flow conditions, receptively. Next, the TEHD predictive tool is used to study the influence of both pad and liner material properties on the performance of a TPTB. The analysis takes a whole steel pad (without a liner or babbitt), a steel pad with a 2-mm-thick babbitt layer (common usage), a steel pad with a 2-mm-thick hard-polymer (polyether ether ketone, e.g., PEEK®) liner, and a pad entirely made of hard-polymer material, whose elastic modulus is just 12.5 GPa, only 6% that of steel. The bare steel pad reveals the poorest performance among all the pads as it produces the smallest fluid film thickness and consumes the largest drag power loss. For laminar flow operations (Reynolds number Re < 580), the babbitted-steel pad operates with the thickest fluid film and the lowest film temperature rise. For turbulent flow conditions Re > 800, the solid hard-polymer pad, however, shows a 23% thicker film than that in the babbitted pad and produces up to 25% lesser drag power loss. In general, the solid hard-polymer TPTB is found to be a good fit for operation at a turbulent flow condition as it shows a lower drag power loss and a larger film thickness; however, its demand for a too large supply flowrate is significant. Predictions for steel pads with various hard-polymer liner and babbitt thicknesses demonstrate that using a hard-polymer liner, instead of white metal, isolates the pad from the fluid film and results in an up to 30 °C (50%) lower temperature rise in the pads than that for a babbitted-steel pad. For operations under a heavy specific load (>3.0 MPa), however, a thick hard-polymer liner extensively deforms and results in a small film thickness.
Self-equalizing tilting pad thrust bearing (TPTB) improves operation reliability by adjusting its pads to accommodate for thrust collar tilt. The paper describes a kinematics model for the equalizing mechanism integrated into an existing thermo-elasto-hydrodynamic (TEHD) analysis tool to deliver load performance predictions for self-equalizing TPTBs. The analysis accounts for the sliding friction forces acting at the contact points of the leveling plates and the rolling friction at their pivots. Further, a Hertz contact analysis model delivers a peak pressure and deformation over the contact area between the leveling plates. Next, the paper presents predictions for an example self-equalizing TPTB operating with a thrust collar static misalignment f = 0.01. The bearing 126 mm in outer diameter has six pads, operates at 4 krpm (26 m/s max. surface speed) and under a specific load/pad ranging from 0.5 to 3.5 MPa. Compared to a non-equalizing TPTB, a self-equalizing TPTB operates with up to 50% larger minimum film thickness and about ½ largest elastic deformation. Friction forces affect the performance of the pad leveling system to reduce the film clearance and increase a pad peak pressure. Predictions from the Hertz contact analysis show a significantly large peak pressure at the contact points of the leveling plates (> 0.9 GPa) when the bearing supports a 3 MPa/pad specific load. The paper stresses the importance of conducting a comprehensive multiple-pad analysis to accurately evaluate the performance and reliable operation of self-equalizing TPTBs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.