Session: 03-28-01: Joint Session on Recent Advances in Advanced Materials Processing and Tribology

Paper Number: 95071

95071 - Experimental Investigation of Fixed-Geometry Thrust Bearing Taper Geometry on Critical Operating Parameters 

This paper expands on previous experimental work on the active performance characteristics of fixed geometry hydrodynamic thrust bearings machined to variable thrust pad taper depths. Hydrodynamic thrust bearings work by entraining oil lubrication between a flat rotating runner surface and converging geometry of a thrust pad surface to develop a film of pressurized oil capable of supporting axially oriented thrust loads. The geometry of the thrust pads converging in the direction of relative motion is crucial to the development and preservation of full hydrodynamic lubrication. Reynolds equation governs the behavior of the distribution of oil film pressure across the bearing pad and provides a range of taper slopes predicted to be capable of generating favorable conditions for hydrodynamic lubrication. It is theoretically predicted that subtle changes in taper slope can result in significant variance in bearing performance in terms of minimum oil film thickness, power loss, bearing operating temperature, and oil film pressure distribution. There is yet limited experimental research investigating these effects on fixed geometry hydrodynamic thrust bearings with helical tapers. The present research uses a newly developed three-axis milling center repurposed to serve as a widely capable platform for experimental testing of hydrodynamic thrust bearings. The test rig can apply thrust loads up to 1,250 lbf at rotational speeds up to 8,000 rpm. Five fixed geometry hydrodynamic thrust bearings with eight identical helically tapered thrust pads made of cast aluminum alloy have each been machined such that the depth of their tapered surface at the leading edge is 0.0005”, 0.0010”, 0.0015”, 0.0020”, and 0.0025” with all other geometrical features held constant. The test rig includes an oil conditioning system which supplies a constant flow of ISO 32 motor oil to the test bearing at 40°C. Each bearing is experimentally evaluated according to a test matrix prescribing five static loads at four different speeds. The integrated sensor system includes an eddy current sensor to measure the minimum oil film thickness, a friction torque moment arm with load cell to measure power loss, K-type thermocouples to measure bearing temperature, pressure transducers to measure oil film pressure distribution, and load cells to measure the applied thrust force. The test rig also introduces a novel bearing alignment system used to ensure precise alignment of the bearing and runner during operation based on pressure feedback from individual thrust pads. Results obtained from this experiment are used to compare the effect of taper geometry on active performance of the test bearings considered. Trends in performance observed are related to the trends predicted analytically by the Reynolds equation.

Presenting Author: Collier Fais Ohio University

Presenting Author Biography: Collier Fais is a P.h.D candidate in Mechanical Engineering Dept. at Ohio University

Authors:

Collier Fais Ohio University
Isaiah Yasko Ohio University
Anbara Lutfullaeva Ohio University
Muhammad Ali Ohio University
Rick Walker MIBA Bearings