Experimental Analysis of the Start-Up Torque of a Mildly Loaded Foil Thrust Bearing1

Abstract

The paper deals with the experimental analysis of the torque and of the lift-off velocity of a foil thrust bearing. The geometric characteristics of the foil thrust bearing follow the design recently proposed by Dykas et al. (2009, “Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications,” ASME J. Eng. Gas Turbines Power, 131(1), p. 012301-1). A dedicated test rig was developed and enables the measurement of the speed, the torque, and temperatures under the foils. The measurements underlined the importance of managing heat transfer in a foil thrust bearing. Results are presented for mild static loads ranging from 5 to 60 N and rotation speeds comprised between 20 and 35 krpm. The value of the start-up torque was validated by comparisons with results obtained with a rapid camera.

Preliminary experimental study on static loading characteristics of multi-decked protuberant foil thrust bearing

“…Bearing stiffness measurement is the basis in the selection of bearing clearance, preload, etc. Franck Balducchi experimentally investigated the static stiffness and the start-up torque of a foil thrust bearing with a mild static load ranging from 5 N to 60 N and rotational speed from 20 krpm to 35 krpm (Balducchi, et al, 2013). Hooshang Heshmat et al analyzed bump geometry parameters and load distribution profile effect on bearing stiffness; they also found that Coulomb friction and higher stiffness could be realized by increasing friction coefficient between top foil and bumps (Ku and Heshmat, 1992;Ku and Heshmat, 1993).…”

Development and Application of Integrated Aerodynamic Protuberant Foil Journal and Thrust Bearing in Turboexpander

“…When the preload on the thrust bearing is larger than a certain value, the torque at expansion wheel could not overcome the start-up friction torque [34]. Furthermore, during start-up and speed-down transient processes, friction torque of the foil thrust bearing increases linearly with rotor speed and bearing load.…”

Performance characteristics of gas-lubricated bump-type foil thrust bearing

“…It is important to mention that the analysis of the dynamic force coefficients is performed after neglecting the centrifugal force effects in equation (6); the reason behind this decision will be explained later in details. After that, equations (14) to (16) are substituted into equation (6) and by collecting terms of the same order…”