Portal de Periódicos da CAPES

Load direction effects on measured static and dynamic operating characteristics of tilting pad journal bearings

2005; Taylor & Francis; Volume: 2; Issue: 2 Linguagem: Inglês

10.1080/14484846.2005.11464488

2204-2253

Robert Brechting, Robert J Prior, Ronald D. Flack, Lloyd Barrett,

Adhesion, Friction, and Surface Interactions

AbstractThis paper presents a comparison of the measured dynamic coefficients, and the measured static characteristics for a tilting pad journal bearing operating at different load angles. Load angles of 0°, 18°, 36°, 54° and 72° were tested. The bearing had five pads and the journal diameter was 70mm, with a length to diameter ratio of 0.75. The pivot offset ratio was 0.50, and a nominal radial assembled bearing clearance, cb, of 74.9 μm was used. The rocker-backed pads had nominal radial ground in pad clearances, cp, of 109.2 μm, which yielded a preload factor of 0.314. Most tilting pad bearings are designed to operate with load on-pad or between-pads, although forces generated in the drive train can result in a bearing load in any direction. Measurements were made for two Sommerfeld numbers: 0.332 and 0.796. The test rig used for these studies has been previously documented. Dynamic coefficients were extracted from the test rig by applying sinusoidal and synchronous forces and measuring the resulting journal-to-bearing relative motion. The measured and reported parameters are eccentricity magnitude, attitude angle, and eight linearized dynamic coefficients (non-dimensional principal and cross-coupled stiffness and damping coefficients). The measured data presented in this may be used to assess the rotor dynamic performance of similar applications. The load angle had a moderate influence on operating eccentricity and attitude angle. For the speed and load conditions included herein, the dynamic coefficients were not strongly dependent on load angle. But very importantly the measured results demonstrate the ability of tilting pad journal bearings to satisfactorily operate at off-optimum load angles.Keywords: Tilting pad journal bearingEccentricitydynamic coeffi cientsstability Additional informationNotes on contributorsRobert BrechtingBob Brechting, is a Mechanical Engineer at BP&R Engineering, Inc in Holland, Michigan. He has been with BP&R for two years, where his responsibilities include the design of rotating powder/slush molding machines, high temperature and pressure piping systems as well as various data acquisition and monitoring systems. Bob received his BSME degree from Michigan Technological University in 2000, and earned his MSME in 2002 from the University of Virginia. His research has focused on the experimental determination of static and dynamic properties of tilting pad fluid film bearings under increasing load, speed and thermal effects. He has written and reviewed several papers on experimental fluid film bearing testing, and is a member of ASME and SAE.Robert J PriorRon Flack is a Professor and the past-Chairman of the Mechanical and Aerospace Engineering Department at the University of Virginia. He has twice been a Guest Professor at University of Karlsruhe and was previously an analytical compressor design engineer at Pratt & Whitney Aircraft. He is a former Director of the Rotating Machinery and Controls (ROMAC) Industrial Research Program at UVa and is a former Fulbright Scholar. Ron's research experience and interests include experimental internal flows in turbomachines and fluid film bearings. He is an ASME Fellow and received the 2003 ASME Moody Award. He just published a textbook on Jet Propulsion with Cambridge University Press. Ron is retiring in August 2005 and will become Professor Emeritus.